| blob | c394e5509e2f632d1801c252edbee1bea71beb4a |
1 /* Fold a constant sub-tree into a single node for C-compiler
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
3 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
4 Free Software Foundation, Inc.
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 2, or (at your option) any later
11 version.
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to the Free
20 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
21 02110-1301, USA. */
23 /*@@ This file should be rewritten to use an arbitrary precision
24 @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
25 @@ Perhaps the routines could also be used for bc/dc, and made a lib.
26 @@ The routines that translate from the ap rep should
27 @@ warn if precision et. al. is lost.
28 @@ This would also make life easier when this technology is used
29 @@ for cross-compilers. */
31 /* The entry points in this file are fold, size_int_wide, size_binop
32 and force_fit_type.
34 fold takes a tree as argument and returns a simplified tree.
36 size_binop takes a tree code for an arithmetic operation
37 and two operands that are trees, and produces a tree for the
38 result, assuming the type comes from `sizetype'.
40 size_int takes an integer value, and creates a tree constant
41 with type from `sizetype'.
43 force_fit_type takes a constant, an overflowable flag and prior
44 overflow indicators. It forces the value to fit the type and sets
45 TREE_OVERFLOW and TREE_CONSTANT_OVERFLOW as appropriate. */
63 /* The following constants represent a bit based encoding of GCC's
64 comparison operators. This encoding simplifies transformations
65 on relational comparison operators, such as AND and OR. */
83 };
115 tree);
137 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
138 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
139 and SUM1. Then this yields nonzero if overflow occurred during the
140 addition.
142 Overflow occurs if A and B have the same sign, but A and SUM differ in
143 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
144 sign. */
145 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
146 \f
147 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
148 We do that by representing the two-word integer in 4 words, with only
149 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
150 number. The value of the word is LOWPART + HIGHPART * BASE. */
152 #define LOWPART(x) \
153 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
154 #define HIGHPART(x) \
155 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
156 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
158 /* Unpack a two-word integer into 4 words.
159 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
160 WORDS points to the array of HOST_WIDE_INTs. */
162 static void
164 {
169 }
171 /* Pack an array of 4 words into a two-word integer.
172 WORDS points to the array of words.
173 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
175 static void
178 {
181 }
182 \f
183 /* T is an INT_CST node. OVERFLOWABLE indicates if we are interested
184 in overflow of the value, when >0 we are only interested in signed
185 overflow, for <0 we are interested in any overflow. OVERFLOWED
186 indicates whether overflow has already occurred. CONST_OVERFLOWED
187 indicates whether constant overflow has already occurred. We force
188 T's value to be within range of T's type (by setting to 0 or 1 all
189 the bits outside the type's range). We set TREE_OVERFLOWED if,
190 OVERFLOWED is nonzero,
191 or OVERFLOWABLE is >0 and signed overflow occurs
192 or OVERFLOWABLE is <0 and any overflow occurs
193 We set TREE_CONSTANT_OVERFLOWED if,
194 CONST_OVERFLOWED is nonzero
195 or we set TREE_OVERFLOWED.
196 We return either the original T, or a copy. */
198 tree
201 {
203 HOST_WIDE_INT high;
215 else
217 /* Size types *are* sign extended. */
222 /* First clear all bits that are beyond the type's precision. */
225 ;
228 else
229 {
233 }
240 {
241 /* Sign extend top half? */
245 }
247 {
250 }
251 else
252 {
253 /* Sign extend bottom half? */
255 {
258 }
259 }
261 /* If the value changed, return a new node. */
264 {
270 {
274 }
276 {
279 }
280 }
283 }
284 \f
285 /* Add two doubleword integers with doubleword result.
286 Return nonzero if the operation overflows according to UNSIGNED_P.
287 Each argument is given as two `HOST_WIDE_INT' pieces.
288 One argument is L1 and H1; the other, L2 and H2.
289 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
291 int
296 {
298 HOST_WIDE_INT h;
308 else
310 }
312 /* Negate a doubleword integer with doubleword result.
313 Return nonzero if the operation overflows, assuming it's signed.
314 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
315 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
317 int
320 {
322 {
326 }
327 else
328 {
332 }
333 }
334 \f
335 /* Multiply two doubleword integers with doubleword result.
336 Return nonzero if the operation overflows according to UNSIGNED_P.
337 Each argument is given as two `HOST_WIDE_INT' pieces.
338 One argument is L1 and H1; the other, L2 and H2.
339 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
341 int
346 {
361 {
364 {
366 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
368 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
372 }
374 }
379 /* Unsigned overflow is immediate. */
383 /* Check for signed overflow by calculating the signed representation of the
384 top half of the result; it should agree with the low half's sign bit. */
386 {
389 }
391 {
394 }
396 }
397 \f
398 /* Shift the doubleword integer in L1, H1 left by COUNT places
399 keeping only PREC bits of result.
400 Shift right if COUNT is negative.
401 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
402 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
404 void
408 {
412 {
415 }
421 {
422 /* Shifting by the host word size is undefined according to the
423 ANSI standard, so we must handle this as a special case. */
426 }
428 {
431 }
432 else
433 {
437 }
439 /* Sign extend all bits that are beyond the precision. */
447 ;
449 {
452 }
453 else
454 {
458 }
459 }
461 /* Shift the doubleword integer in L1, H1 right by COUNT places
462 keeping only PREC bits of result. COUNT must be positive.
463 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
464 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
466 void
471 {
474 signmask = (arith
482 {
483 /* Shifting by the host word size is undefined according to the
484 ANSI standard, so we must handle this as a special case. */
487 }
489 {
492 }
493 else
494 {
498 }
500 /* Zero / sign extend all bits that are beyond the precision. */
503 {
506 }
508 ;
510 {
513 }
514 else
515 {
519 }
520 }
521 \f
522 /* Rotate the doubleword integer in L1, H1 left by COUNT places
523 keeping only PREC bits of result.
524 Rotate right if COUNT is negative.
525 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
527 void
531 {
543 }
545 /* Rotate the doubleword integer in L1, H1 left by COUNT places
546 keeping only PREC bits of result. COUNT must be positive.
547 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
549 void
553 {
565 }
566 \f
567 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
568 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
569 CODE is a tree code for a kind of division, one of
570 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
571 or EXACT_DIV_EXPR
572 It controls how the quotient is rounded to an integer.
573 Return nonzero if the operation overflows.
574 UNS nonzero says do unsigned division. */
576 int
579 HOST_WIDE_INT hnum_orig,
581 HOST_WIDE_INT hden_orig,
585 {
601 /* Calculate quotient sign and convert operands to unsigned. */
603 {
605 {
607 /* (minimum integer) / (-1) is the only overflow case. */
611 }
613 {
616 }
617 }
622 /* This unsigned division rounds toward zero. */
625 }
629 /* hden != 0 already checked. */
634 }
644 /* Special code for when the divisor < BASE. */
646 {
647 /* hnum != 0 already checked. */
649 {
653 }
654 }
655 else
656 {
657 /* Full double precision division,
658 with thanks to Don Knuth's "Seminumerical Algorithms". */
662 /* Find the highest nonzero divisor digit. */
665 {
668 }
670 /* Insure that the first digit of the divisor is at least BASE/2.
671 This is required by the quotient digit estimation algorithm. */
678 {
682 }
687 {
692 }
693 }
697 /* Main loop */
699 {
700 /* Guess the next quotient digit, quo_est, by dividing the first
701 two remaining dividend digits by the high order quotient digit.
702 quo_est is never low and is at most 2 high. */
709 else
712 /* Refine quo_est so it's usually correct, and at most one high. */
717 quo_est--;
719 /* Try QUO_EST as the quotient digit, by multiplying the
720 divisor by QUO_EST and subtracting from the remaining dividend.
721 Keep in mind that QUO_EST is the I - 1st digit. */
725 {
731 }
733 /* If quo_est was high by one, then num[i] went negative and
734 we need to correct things. */
736 {
737 quo_est--;
740 {
744 }
747 }
749 /* Store the quotient digit. */
751 }
752 }
756 finish_up:
757 /* If result is negative, make it so. */
761 /* Compute trial remainder: rem = num - (quo * den) */
767 {
776 {
777 /* quo = quo - 1; */
780 }
781 else
788 {
791 }
792 else
798 {
804 /* Get absolute values. */
810 /* If (2 * abs (lrem) >= abs (lden)) */
819 {
821 /* quo = quo - 1; */
824 else
825 /* quo = quo + 1; */
828 }
829 else
831 }
836 }
838 /* Compute true remainder: rem = num - (quo * den) */
843 }
845 /* If ARG2 divides ARG1 with zero remainder, carries out the division
846 of type CODE and returns the quotient.
847 Otherwise returns NULL_TREE. */
849 static tree
851 {
870 }
871 \f
872 /* Return true if the built-in mathematical function specified by CODE
873 is odd, i.e. -f(x) == f(-x). */
875 static bool
877 {
879 {
896 }
898 }
900 /* Check whether we may negate an integer constant T without causing
901 overflow. */
903 bool
905 {
908 tree type;
918 {
923 }
924 else
929 }
931 /* Determine whether an expression T can be cheaply negated using
932 the function negate_expr. */
934 static bool
936 {
937 tree type;
946 {
951 /* Check that -CST will not overflow type. */
965 /* -(A + B) -> (-B) - A. */
970 /* -(A + B) -> (-A) - B. */
974 /* We can't turn -(A-B) into B-A when we honor signed zeros. */
983 /* Fall through. */
992 /* Negate -((double)float) as (double)(-float). */
994 {
998 }
1002 /* Negate -f(x) as f(-x). */
1008 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
1010 {
1016 }
1021 }
1023 }
1025 /* Given T, an expression, return the negation of T. Allow for T to be
1026 null, in which case return null. */
1028 static tree
1030 {
1031 tree type;
1032 tree tem;
1041 {
1052 /* Two's complement FP formats, such as c4x, may overflow. */
1058 {
1067 }
1075 {
1076 /* -(A + B) -> (-B) - A. */
1080 {
1085 }
1087 /* -(A + B) -> (-A) - B. */
1089 {
1094 }
1095 }
1099 /* - (A - B) -> B - A */
1112 /* Fall through. */
1116 {
1129 }
1133 /* Convert -((double)float) into (double)(-float). */
1135 {
1139 }
1143 /* Negate -f(x) as f(-x). */
1146 {
1153 }
1157 /* Optimize -((int)x >> 31) into (unsigned)x >> 31. */
1159 {
1164 {
1171 }
1172 }
1177 }
1181 }
1182 \f
1183 /* Split a tree IN into a constant, literal and variable parts that could be
1184 combined with CODE to make IN. "constant" means an expression with
1185 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1186 commutative arithmetic operation. Store the constant part into *CONP,
1187 the literal in *LITP and return the variable part. If a part isn't
1188 present, set it to null. If the tree does not decompose in this way,
1189 return the entire tree as the variable part and the other parts as null.
1191 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1192 case, we negate an operand that was subtracted. Except if it is a
1193 literal for which we use *MINUS_LITP instead.
1195 If NEGATE_P is true, we are negating all of IN, again except a literal
1196 for which we use *MINUS_LITP instead.
1198 If IN is itself a literal or constant, return it as appropriate.
1200 Note that we do not guarantee that any of the three values will be the
1201 same type as IN, but they will have the same signedness and mode. */
1203 static tree
1206 {
1213 /* Strip any conversions that don't change the machine mode or signedness. */
1220 /* We can associate addition and subtraction together (even
1221 though the C standard doesn't say so) for integers because
1222 the value is not affected. For reals, the value might be
1223 affected, so we can't. */
1226 {
1232 /* First see if either of the operands is a literal, then a constant. */
1243 /* If we haven't dealt with either operand, this is not a case we can
1244 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1249 else
1252 /* Now do any needed negations. */
1259 }
1262 else
1266 {
1273 }
1276 }
1278 /* Re-associate trees split by the above function. T1 and T2 are either
1279 expressions to associate or null. Return the new expression, if any. If
1280 we build an operation, do it in TYPE and with CODE. */
1282 static tree
1284 {
1290 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1291 try to fold this since we will have infinite recursion. But do
1292 deal with any NEGATE_EXPRs. */
1295 {
1297 {
1306 }
1308 {
1311 }
1315 }
1319 }
1320 \f
1321 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1322 to produce a new constant.
1324 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1326 tree
1328 {
1332 HOST_WIDE_INT hi;
1334 HOST_WIDE_INT garbageh;
1335 tree t;
1338 int is_sizetype
1348 {
1364 /* It's unclear from the C standard whether shifts can overflow.
1365 The following code ignores overflow; perhaps a C standard
1366 interpretation ruling is needed. */
1395 /* This is a shortcut for a common special case. */
1400 {
1406 }
1408 /* ... fall through ... */
1412 {
1415 }
1418 {
1421 }
1428 /* This is a shortcut for a common special case. */
1433 {
1438 }
1440 /* ... fall through ... */
1456 else
1462 else
1468 }
1473 {
1474 /* Propagate overflow flags ourselves. */
1477 {
1481 }
1483 {
1486 }
1487 }
1488 else
1496 }
1498 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1499 constant. We assume ARG1 and ARG2 have the same data type, or at least
1500 are the same kind of constant and the same machine mode. Return zero if
1501 combining the constants is not allowed in the current operating mode.
1503 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1505 static tree
1507 {
1508 /* Sanity check for the recursive cases. */
1519 {
1521 REAL_VALUE_TYPE d1;
1522 REAL_VALUE_TYPE d2;
1523 REAL_VALUE_TYPE value;
1524 REAL_VALUE_TYPE result;
1534 /* Don't perform operation if we honor signaling NaNs and
1535 either operand is a NaN. */
1540 /* Don't perform operation if it would raise a division
1541 by zero exception. */
1547 /* If either operand is a NaN, just return it. Otherwise, set up
1548 for floating-point trap; we return an overflow. */
1557 /* Don't constant fold this floating point operation if
1558 the result has overflowed and flag_trapping_math. */
1566 /* Don't constant fold this floating point operation if the
1567 result may dependent upon the run-time rounding mode and
1568 flag_rounding_math is set, or if GCC's software emulation
1569 is unable to accurately represent the result. */
1584 }
1587 {
1596 {
1607 notrunc);
1611 notrunc);
1615 {
1616 tree magsquared
1620 notrunc);
1621 tree t1
1625 notrunc);
1626 tree t2
1630 notrunc);
1637 }
1642 }
1646 }
1649 }
1651 /* Create a size type INT_CST node with NUMBER sign extended. KIND
1652 indicates which particular sizetype to create. */
1654 tree
1656 {
1658 }
1659 \f
1660 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1661 is a tree code. The type of the result is taken from the operands.
1662 Both must be the same type integer type and it must be a size type.
1663 If the operands are constant, so is the result. */
1665 tree
1667 {
1676 /* Handle the special case of two integer constants faster. */
1678 {
1679 /* And some specific cases even faster than that. */
1688 /* Handle general case of two integer constants. */
1690 }
1693 }
1695 /* Given two values, either both of sizetype or both of bitsizetype,
1696 compute the difference between the two values. Return the value
1697 in signed type corresponding to the type of the operands. */
1699 tree
1701 {
1703 tree ctype;
1708 /* If the type is already signed, just do the simple thing. */
1714 /* If either operand is not a constant, do the conversions to the signed
1715 type and subtract. The hardware will do the right thing with any
1716 overflow in the subtraction. */
1721 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1722 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1723 overflow) and negate (which can't either). Special-case a result
1724 of zero while we're here. */
1729 else
1733 }
1734 \f
1735 /* A subroutine of fold_convert_const handling conversions of an
1736 INTEGER_CST to another integer type. */
1738 static tree
1740 {
1741 tree t;
1743 /* Given an integer constant, make new constant with new type,
1744 appropriately sign-extended or truncated. */
1749 /* Don't set the overflow when
1750 converting a pointer */
1759 }
1761 /* A subroutine of fold_convert_const handling conversions a REAL_CST
1762 to an integer type. */
1764 static tree
1766 {
1768 tree t;
1770 /* The following code implements the floating point to integer
1771 conversion rules required by the Java Language Specification,
1772 that IEEE NaNs are mapped to zero and values that overflow
1773 the target precision saturate, i.e. values greater than
1774 INT_MAX are mapped to INT_MAX, and values less than INT_MIN
1775 are mapped to INT_MIN. These semantics are allowed by the
1776 C and C++ standards that simply state that the behavior of
1777 FP-to-integer conversion is unspecified upon overflow. */
1780 REAL_VALUE_TYPE r;
1784 {
1803 }
1805 /* If R is NaN, return zero and show we have an overflow. */
1807 {
1811 }
1813 /* See if R is less than the lower bound or greater than the
1814 upper bound. */
1817 {
1821 {
1825 }
1826 }
1829 {
1832 {
1835 {
1839 }
1840 }
1841 }
1851 }
1853 /* A subroutine of fold_convert_const handling conversions a REAL_CST
1854 to another floating point type. */
1856 static tree
1858 {
1859 REAL_VALUE_TYPE value;
1860 tree t;
1869 }
1871 /* Attempt to fold type conversion operation CODE of expression ARG1 to
1872 type TYPE. If no simplification can be done return NULL_TREE. */
1874 static tree
1876 {
1881 {
1886 }
1888 {
1893 }
1895 }
1897 /* Construct a vector of zero elements of vector type TYPE. */
1899 static tree
1901 {
1912 }
1914 /* Convert expression ARG to type TYPE. Used by the middle-end for
1915 simple conversions in preference to calling the front-end's convert. */
1917 tree
1919 {
1921 tree tem;
1937 {
1942 {
1946 }
1951 {
1954 }
1961 {
1965 }
1967 {
1971 }
1974 {
1990 }
1994 {
2003 {
2007 {
2011 }
2019 }
2023 }
2038 }
2039 }
2040 \f
2041 /* Return false if expr can be assumed not to be an lvalue, true
2042 otherwise. */
2044 static bool
2046 {
2047 /* We only need to wrap lvalue tree codes. */
2049 {
2083 /* Assume the worst for front-end tree codes. */
2087 }
2090 }
2092 /* Return an expr equal to X but certainly not valid as an lvalue. */
2094 tree
2096 {
2097 /* While we are in GIMPLE, NON_LVALUE_EXPR doesn't mean anything to
2098 us. */
2105 }
2107 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2108 Zero means allow extended lvalues. */
2112 /* When pedantic, return an expr equal to X but certainly not valid as a
2113 pedantic lvalue. Otherwise, return X. */
2115 static tree
2117 {
2120 else
2122 }
2123 \f
2124 /* Given a tree comparison code, return the code that is the logical inverse
2125 of the given code. It is not safe to do this for floating-point
2126 comparisons, except for NE_EXPR and EQ_EXPR, so we receive a machine mode
2127 as well: if reversing the comparison is unsafe, return ERROR_MARK. */
2129 enum tree_code
2131 {
2136 {
2167 }
2168 }
2170 /* Similar, but return the comparison that results if the operands are
2171 swapped. This is safe for floating-point. */
2173 enum tree_code
2175 {
2177 {
2203 }
2204 }
2207 /* Convert a comparison tree code from an enum tree_code representation
2208 into a compcode bit-based encoding. This function is the inverse of
2209 compcode_to_comparison. */
2211 static enum comparison_code
2213 {
2215 {
2246 }
2247 }
2249 /* Convert a compcode bit-based encoding of a comparison operator back
2250 to GCC's enum tree_code representation. This function is the
2251 inverse of comparison_to_compcode. */
2253 static enum tree_code
2255 {
2257 {
2288 }
2289 }
2291 /* Return a tree for the comparison which is the combination of
2292 doing the AND or OR (depending on CODE) of the two operations LCODE
2293 and RCODE on the identical operands LL_ARG and LR_ARG. Take into account
2294 the possibility of trapping if the mode has NaNs, and return NULL_TREE
2295 if this makes the transformation invalid. */
2297 tree
2301 {
2308 {
2319 }
2322 {
2323 /* Eliminate unordered comparisons, as well as LTGT and ORD
2324 which are not used unless the mode has NaNs. */
2330 }
2332 {
2333 /* Check that the original operation and the optimized ones will trap
2334 under the same condition. */
2345 /* In a short-circuited boolean expression the LHS might be
2346 such that the RHS, if evaluated, will never trap. For
2347 example, in ORD (x, y) && (x < y), we evaluate the RHS only
2348 if neither x nor y is NaN. (This is a mixed blessing: for
2349 example, the expression above will never trap, hence
2350 optimizing it to x < y would be invalid). */
2355 /* If the comparison was short-circuited, and only the RHS
2356 trapped, we may now generate a spurious trap. */
2361 /* If we changed the conditions that cause a trap, we lose. */
2364 }
2370 else
2373 }
2375 /* Return nonzero if CODE is a tree code that represents a truth value. */
2377 static int
2379 {
2384 }
2385 \f
2386 /* Return nonzero if two operands (typically of the same tree node)
2387 are necessarily equal. If either argument has side-effects this
2388 function returns zero. FLAGS modifies behavior as follows:
2390 If OEP_ONLY_CONST is set, only return nonzero for constants.
2391 This function tests whether the operands are indistinguishable;
2392 it does not test whether they are equal using C's == operation.
2393 The distinction is important for IEEE floating point, because
2394 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2395 (2) two NaNs may be indistinguishable, but NaN!=NaN.
2397 If OEP_ONLY_CONST is unset, a VAR_DECL is considered equal to itself
2398 even though it may hold multiple values during a function.
2399 This is because a GCC tree node guarantees that nothing else is
2400 executed between the evaluation of its "operands" (which may often
2401 be evaluated in arbitrary order). Hence if the operands themselves
2402 don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
2403 same value in each operand/subexpression. Hence leaving OEP_ONLY_CONST
2404 unset means assuming isochronic (or instantaneous) tree equivalence.
2405 Unless comparing arbitrary expression trees, such as from different
2406 statements, this flag can usually be left unset.
2408 If OEP_PURE_SAME is set, then pure functions with identical arguments
2409 are considered the same. It is used when the caller has other ways
2410 to ensure that global memory is unchanged in between. */
2412 int
2414 {
2415 /* If either is ERROR_MARK, they aren't equal. */
2419 /* If both types don't have the same signedness, then we can't consider
2420 them equal. We must check this before the STRIP_NOPS calls
2421 because they may change the signedness of the arguments. */
2425 /* If both types don't have the same precision, then it is not safe
2426 to strip NOPs. */
2434 /* This is needed for conversions and for COMPONENT_REF.
2435 Might as well play it safe and always test this. */
2441 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2442 We don't care about side effects in that case because the SAVE_EXPR
2443 takes care of that for us. In all other cases, two expressions are
2444 equal if they have no side effects. If we have two identical
2445 expressions with side effects that should be treated the same due
2446 to the only side effects being identical SAVE_EXPR's, that will
2447 be detected in the recursive calls below. */
2453 /* Next handle constant cases, those for which we can return 1 even
2454 if ONLY_CONST is set. */
2457 {
2470 {
2480 {
2482 flags))
2486 }
2489 }
2493 flags)
2495 flags));
2508 }
2513 /* Define macros to test an operand from arg0 and arg1 for equality and a
2514 variant that allows null and views null as being different from any
2515 non-null value. In the latter case, if either is null, the both
2516 must be; otherwise, do the normal comparison. */
2517 #define OP_SAME(N) operand_equal_p (TREE_OPERAND (arg0, N), \
2518 TREE_OPERAND (arg1, N), flags)
2520 #define OP_SAME_WITH_NULL(N) \
2521 ((!TREE_OPERAND (arg0, N) || !TREE_OPERAND (arg1, N)) \
2522 ? TREE_OPERAND (arg0, N) == TREE_OPERAND (arg1, N) : OP_SAME (N))
2525 {
2527 /* Two conversions are equal only if signedness and modes match. */
2529 {
2542 }
2552 /* For commutative ops, allow the other order. */
2560 /* If either of the pointer (or reference) expressions we are
2561 dereferencing contain a side effect, these cannot be equal. */
2567 {
2577 /* Operands 2 and 3 may be null. */
2584 /* Handle operand 2 the same as for ARRAY_REF. Operand 0
2585 may be NULL when we're called to compare MEM_EXPRs. */
2595 }
2599 {
2614 /* Otherwise take into account this is a commutative operation. */
2621 /* If the CALL_EXPRs call different functions, then they
2622 clearly can not be equal. */
2626 {
2630 else
2634 }
2636 /* Now see if all the arguments are the same. operand_equal_p
2637 does not handle TREE_LIST, so we walk the operands here
2638 feeding them to operand_equal_p. */
2642 {
2644 flags))
2649 }
2651 /* If we get here and both argument lists are exhausted
2652 then the CALL_EXPRs are equal. */
2657 }
2660 /* Consider __builtin_sqrt equal to sqrt. */
2668 }
2670 #undef OP_SAME
2671 #undef OP_SAME_WITH_NULL
2672 }
2673 \f
2674 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2675 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2677 When in doubt, return 0. */
2679 static int
2681 {
2693 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2694 and see if the inner values are the same. This removes any
2695 signedness comparison, which doesn't matter here. */
2702 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2703 actual comparison operand, ARG0.
2705 First throw away any conversions to wider types
2706 already present in the operands. */
2715 {
2718 /* Make sure shorter operand is extended the right way
2719 to match the longer operand. */
2725 }
2728 }
2729 \f
2730 /* See if ARG is an expression that is either a comparison or is performing
2731 arithmetic on comparisons. The comparisons must only be comparing
2732 two different values, which will be stored in *CVAL1 and *CVAL2; if
2733 they are nonzero it means that some operands have already been found.
2734 No variables may be used anywhere else in the expression except in the
2735 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2736 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2738 If this is true, return 1. Otherwise, return zero. */
2740 static int
2742 {
2746 /* We can handle some of the tcc_expression cases here. */
2756 {
2757 /* If we've already found a CVAL1 or CVAL2, this expression is
2758 two complex to handle. */
2764 }
2767 {
2790 /* First see if we can handle the first operand, then the second. For
2791 the second operand, we know *CVAL1 can't be zero. It must be that
2792 one side of the comparison is each of the values; test for the
2793 case where this isn't true by failing if the two operands
2794 are the same. */
2803 ;
2807 ;
2808 else
2812 ;
2816 ;
2817 else
2824 }
2825 }
2826 \f
2827 /* ARG is a tree that is known to contain just arithmetic operations and
2828 comparisons. Evaluate the operations in the tree substituting NEW0 for
2829 any occurrence of OLD0 as an operand of a comparison and likewise for
2830 NEW1 and OLD1. */
2832 static tree
2834 {
2839 /* We can handle some of the tcc_expression cases here. */
2847 {
2862 {
2879 }
2880 /* Fall through - ??? */
2883 {
2887 /* We need to check both for exact equality and tree equality. The
2888 former will be true if the operand has a side-effect. In that
2889 case, we know the operand occurred exactly once. */
2902 }
2906 }
2907 }
2908 \f
2909 /* Return a tree for the case when the result of an expression is RESULT
2910 converted to TYPE and OMITTED was previously an operand of the expression
2911 but is now not needed (e.g., we folded OMITTED * 0).
2913 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2914 the conversion of RESULT to TYPE. */
2916 tree
2918 {
2925 }
2927 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2929 static tree
2931 {
2938 }
2940 /* Return a tree for the case when the result of an expression is RESULT
2941 converted to TYPE and OMITTED1 and OMITTED2 were previously operands
2942 of the expression but are now not needed.
2944 If OMITTED1 or OMITTED2 has side effects, they must be evaluated.
2945 If both OMITTED1 and OMITTED2 have side effects, OMITTED1 is
2946 evaluated before OMITTED2. Otherwise, if neither has side effects,
2947 just do the conversion of RESULT to TYPE. */
2949 tree
2951 {
2960 }
2962 \f
2963 /* Return a simplified tree node for the truth-negation of ARG. This
2964 never alters ARG itself. We assume that ARG is an operation that
2965 returns a truth value (0 or 1).
2967 FIXME: one would think we would fold the result, but it causes
2968 problems with the dominator optimizer. */
2969 tree
2971 {
2978 /* If this is a comparison, we can simply invert it, except for
2979 floating-point non-equality comparisons, in which case we just
2980 enclose a TRUTH_NOT_EXPR around what we have. */
2983 {
2986 && flag_trapping_math
2990 else
2991 {
2996 else
2999 }
3000 }
3003 {
3018 /* Here we can invert either operand. We invert the first operand
3019 unless the second operand is a TRUTH_NOT_EXPR in which case our
3020 result is the XOR of the first operand with the inside of the
3021 negation of the second operand. */
3026 else
3045 {
3048 /* A COND_EXPR may have a throw as one operand, which
3049 then has void type. Just leave void operands
3050 as they are. */
3056 }
3089 }
3092 }
3094 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
3095 operands are another bit-wise operation with a common input. If so,
3096 distribute the bit operations to save an operation and possibly two if
3097 constants are involved. For example, convert
3098 (A | B) & (A | C) into A | (B & C)
3099 Further simplification will occur if B and C are constants.
3101 If this optimization cannot be done, 0 will be returned. */
3103 static tree
3105 {
3106 tree common;
3116 {
3120 }
3122 {
3126 }
3128 {
3132 }
3134 {
3138 }
3139 else
3144 }
3146 /* Knowing that ARG0 and ARG1 are both RDIV_EXPRs, simplify a binary operation
3147 with code CODE. This optimization is unsafe. */
3148 static tree
3150 {
3154 /* (A / C) +- (B / C) -> (A +- B) / C. */
3164 /* (A / C1) +- (A / C2) -> A * (1 / C1 +- 1 / C2). */
3169 {
3181 }
3184 }
3185 \f
3186 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
3187 starting at BITPOS. The field is unsigned if UNSIGNEDP is nonzero. */
3189 static tree
3192 {
3193 tree result;
3196 {
3203 }
3211 }
3213 /* Optimize a bit-field compare.
3215 There are two cases: First is a compare against a constant and the
3216 second is a comparison of two items where the fields are at the same
3217 bit position relative to the start of a chunk (byte, halfword, word)
3218 large enough to contain it. In these cases we can avoid the shift
3219 implicit in bitfield extractions.
3221 For constants, we emit a compare of the shifted constant with the
3222 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
3223 compared. For two fields at the same position, we do the ANDs with the
3224 similar mask and compare the result of the ANDs.
3226 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
3227 COMPARE_TYPE is the type of the comparison, and LHS and RHS
3228 are the left and right operands of the comparison, respectively.
3230 If the optimization described above can be done, we return the resulting
3231 tree. Otherwise we return zero. */
3233 static tree
3236 {
3245 tree mask;
3246 tree offset;
3248 /* Get all the information about the extractions being done. If the bit size
3249 if the same as the size of the underlying object, we aren't doing an
3250 extraction at all and so can do nothing. We also don't want to
3251 do anything if the inner expression is a PLACEHOLDER_EXPR since we
3252 then will no longer be able to replace it. */
3260 {
3261 /* If this is not a constant, we can only do something if bit positions,
3262 sizes, and signedness are the same. */
3270 }
3272 /* See if we can find a mode to refer to this field. We should be able to,
3273 but fail if we can't. */
3282 /* Set signed and unsigned types of the precision of this mode for the
3283 shifts below. */
3287 /* Compute the bit position and size for the new reference and our offset
3288 within it. If the new reference is the same size as the original, we
3289 won't optimize anything, so return zero. */
3299 /* Make the mask to be used against the extracted field. */
3308 /* If not comparing with constant, just rework the comparison
3309 and return. */
3314 mask),
3318 mask));
3320 /* Otherwise, we are handling the constant case. See if the constant is too
3321 big for the field. Warn and return a tree of for 0 (false) if so. We do
3322 this not only for its own sake, but to avoid having to test for this
3323 error case below. If we didn't, we might generate wrong code.
3325 For unsigned fields, the constant shifted right by the field length should
3326 be all zero. For signed fields, the high-order bits should agree with
3327 the sign bit. */
3330 {
3334 {
3338 }
3339 }
3340 else
3341 {
3345 {
3349 }
3350 }
3352 /* Single-bit compares should always be against zero. */
3354 {
3357 }
3359 /* Make a new bitfield reference, shift the constant over the
3360 appropriate number of bits and mask it with the computed mask
3361 (in case this was a signed field). If we changed it, make a new one. */
3364 {
3367 }
3377 rhs);
3378 }
3379 \f
3380 /* Subroutine for fold_truthop: decode a field reference.
3382 If EXP is a comparison reference, we return the innermost reference.
3384 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3385 set to the starting bit number.
3387 If the innermost field can be completely contained in a mode-sized
3388 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3390 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3391 otherwise it is not changed.
3393 *PUNSIGNEDP is set to the signedness of the field.
3395 *PMASK is set to the mask used. This is either contained in a
3396 BIT_AND_EXPR or derived from the width of the field.
3398 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3400 Return 0 if this is not a component reference or is one that we can't
3401 do anything with. */
3403 static tree
3408 {
3412 tree unsigned_type;
3415 /* All the optimizations using this function assume integer fields.
3416 There are problems with FP fields since the type_for_size call
3417 below can fail for, e.g., XFmode. */
3421 /* We are interested in the bare arrangement of bits, so strip everything
3422 that doesn't affect the machine mode. However, record the type of the
3423 outermost expression if it may matter below. */
3431 {
3437 }
3446 /* If the number of bits in the reference is the same as the bitsize of
3447 the outer type, then the outer type gives the signedness. Otherwise
3448 (in case of a small bitfield) the signedness is unchanged. */
3452 /* Compute the mask to access the bitfield. */
3462 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3470 }
3472 /* Return nonzero if MASK represents a mask of SIZE ones in the low-order
3473 bit positions. */
3475 static int
3477 {
3480 tree tmask;
3485 return
3492 }
3494 /* Subroutine for fold: determine if VAL is the INTEGER_CONST that
3495 represents the sign bit of EXP's type. If EXP represents a sign
3496 or zero extension, also test VAL against the unextended type.
3497 The return value is the (sub)expression whose sign bit is VAL,
3498 or NULL_TREE otherwise. */
3500 static tree
3502 {
3506 tree t;
3508 /* Tree EXP must have an integral type. */
3513 /* Tree VAL must be an integer constant. */
3520 {
3527 }
3528 else
3529 {
3536 }
3538 /* We mask off those bits beyond TREE_TYPE (exp) so that we can
3539 treat VAL as if it were unsigned. */
3544 /* Handle extension from a narrower type. */
3550 }
3552 /* Subroutine for fold_truthop: determine if an operand is simple enough
3553 to be evaluated unconditionally. */
3555 static int
3557 {
3558 /* Strip any conversions that don't change the machine mode. */
3567 /* Don't regard global variables as simple. They may be
3568 allocated in ways unknown to the compiler (shared memory,
3569 #pragma weak, etc). */
3572 /* Loading a static variable is unduly expensive, but global
3573 registers aren't expensive. */
3575 }
3576 \f
3577 /* The following functions are subroutines to fold_range_test and allow it to
3578 try to change a logical combination of comparisons into a range test.
3580 For example, both
3581 X == 2 || X == 3 || X == 4 || X == 5
3582 and
3583 X >= 2 && X <= 5
3584 are converted to
3585 (unsigned) (X - 2) <= 3
3587 We describe each set of comparisons as being either inside or outside
3588 a range, using a variable named like IN_P, and then describe the
3589 range with a lower and upper bound. If one of the bounds is omitted,
3590 it represents either the highest or lowest value of the type.
3592 In the comments below, we represent a range by two numbers in brackets
3593 preceded by a "+" to designate being inside that range, or a "-" to
3594 designate being outside that range, so the condition can be inverted by
3595 flipping the prefix. An omitted bound is represented by a "-". For
3596 example, "- [-, 10]" means being outside the range starting at the lowest
3597 possible value and ending at 10, in other words, being greater than 10.
3598 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3599 always false.
3601 We set up things so that the missing bounds are handled in a consistent
3602 manner so neither a missing bound nor "true" and "false" need to be
3603 handled using a special case. */
3605 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3606 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3607 and UPPER1_P are nonzero if the respective argument is an upper bound
3608 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3609 must be specified for a comparison. ARG1 will be converted to ARG0's
3610 type if both are specified. */
3612 static tree
3615 {
3616 tree tem;
3620 /* If neither arg represents infinity, do the normal operation.
3621 Else, if not a comparison, return infinity. Else handle the special
3622 comparison rules. Note that most of the cases below won't occur, but
3623 are handled for consistency. */
3626 {
3631 }
3636 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3637 for neither. In real maths, we cannot assume open ended ranges are
3638 the same. But, this is computer arithmetic, where numbers are finite.
3639 We can therefore make the transformation of any unbounded range with
3640 the value Z, Z being greater than any representable number. This permits
3641 us to treat unbounded ranges as equal. */
3645 {
3666 }
3669 }
3670 \f
3671 /* Given EXP, a logical expression, set the range it is testing into
3672 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3673 actually being tested. *PLOW and *PHIGH will be made of the same type
3674 as the returned expression. If EXP is not a comparison, we will most
3675 likely not be returning a useful value and range. */
3677 static tree
3679 {
3686 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3687 and see if we can refine the range. Some of the cases below may not
3688 happen, but it doesn't seem worth worrying about this. We "continue"
3689 the outer loop when we've changed something; otherwise we "break"
3690 the switch, which will "break" the while. */
3696 {
3701 {
3713 }
3716 {
3723 /* We can only do something if the range is testing for zero
3724 and if the second operand is an integer constant. Note that
3725 saying something is "in" the range we make is done by
3726 complementing IN_P since it will set in the initial case of
3727 being not equal to zero; "out" is leaving it alone. */
3734 {
3755 }
3757 /* If this is an unsigned comparison, we also know that EXP is
3758 greater than or equal to zero. We base the range tests we make
3759 on that fact, so we record it here so we can parse existing
3760 range tests. We test arg0_type since often the return type
3761 of, e.g. EQ_EXPR, is boolean. */
3763 {
3767 NULL_TREE))
3772 /* If the high bound is missing, but we have a nonzero low
3773 bound, reverse the range so it goes from zero to the low bound
3774 minus 1. */
3776 {
3781 }
3782 }
3788 /* (-x) IN [a,b] -> x in [-b, -a] */
3800 /* ~ X -> -X - 1 */
3809 /* If EXP is signed, any overflow in the computation is undefined,
3810 so we don't worry about it so long as our computations on
3811 the bounds don't overflow. For unsigned, overflow is defined
3812 and this is exactly the right thing. */
3821 /* Check for an unsigned range which has wrapped around the maximum
3822 value thus making n_high < n_low, and normalize it. */
3824 {
3830 /* If the range is of the form +/- [ x+1, x ], we won't
3831 be able to normalize it. But then, it represents the
3832 whole range or the empty set, so make it
3833 +/- [ -, - ]. */
3837 else
3839 }
3840 else
3864 /* If we're converting arg0 from an unsigned type, to exp,
3865 a signed type, we will be doing the comparison as unsigned.
3866 The tests above have already verified that LOW and HIGH
3867 are both positive.
3869 So we have to ensure that we will handle large unsigned
3870 values the same way that the current signed bounds treat
3871 negative values. */
3874 {
3875 tree high_positive;
3879 /* A range without an upper bound is, naturally, unbounded.
3880 Since convert would have cropped a very large value, use
3881 the max value for the destination type. */
3882 high_positive
3889 high_positive),
3891 integer_one_node));
3893 /* If the low bound is specified, "and" the range with the
3894 range for which the original unsigned value will be
3895 positive. */
3897 {
3901 integer_zero_node),
3902 high_positive))
3906 }
3907 else
3908 {
3909 /* Otherwise, "or" the range with the range of the input
3910 that will be interpreted as negative. */
3914 integer_zero_node),
3915 high_positive))
3919 }
3920 }
3928 }
3931 }
3933 /* If EXP is a constant, we can evaluate whether this is true or false. */
3935 {
3942 }
3946 }
3947 \f
3948 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3949 type, TYPE, return an expression to test if EXP is in (or out of, depending
3950 on IN_P) the range. Return 0 if the test couldn't be created. */
3952 static tree
3954 {
3956 tree value;
3958 #ifdef HAVE_canonicalize_funcptr_for_compare
3959 /* Disable this optimization for function pointer expressions
3960 on targets that require function pointer canonicalization. */
3965 #endif
3968 {
3974 }
3992 {
3994 {
3998 }
4000 }
4002 /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
4004 {
4006 HOST_WIDE_INT hi;
4011 {
4014 }
4015 else
4016 {
4019 }
4022 {
4024 {
4027 }
4030 }
4031 }
4036 {
4039 /* Check if (unsigned) INT_MAX + 1 == (unsigned) INT_MIN
4040 for the type in question, as we rely on this here. */
4042 {
4046 /* There is no requirement that LOW be within the range of ETYPE
4047 if the latter is a subtype. It must, however, be within the base
4048 type of ETYPE. So be sure we do the subtraction in that type. */
4058 {
4064 }
4068 }
4069 }
4072 {
4073 /* There is no requirement that LOW be within the range of ETYPE
4074 if the latter is a subtype. It must, however, be within the base
4075 type of ETYPE. So be sure we do the subtraction in that type. */
4077 {
4082 }
4087 }
4090 }
4091 \f
4092 /* Given two ranges, see if we can merge them into one. Return 1 if we
4093 can, 0 if we can't. Set the output range into the specified parameters. */
4095 static int
4098 {
4102 tree tem;
4112 /* Make range 0 be the range that starts first, or ends last if they
4113 start at the same value. Swap them if it isn't. */
4116 || (lowequal
4119 {
4123 }
4125 /* Now flag two cases, whether the ranges are disjoint or whether the
4126 second range is totally subsumed in the first. Note that the tests
4127 below are simplified by the ones above. */
4133 /* We now have four cases, depending on whether we are including or
4134 excluding the two ranges. */
4136 {
4137 /* If they don't overlap, the result is false. If the second range
4138 is a subset it is the result. Otherwise, the range is from the start
4139 of the second to the end of the first. */
4144 else
4146 }
4149 {
4150 /* If they don't overlap, the result is the first range. If they are
4151 equal, the result is false. If the second range is a subset of the
4152 first, and the ranges begin at the same place, we go from just after
4153 the end of the first range to the end of the second. If the second
4154 range is not a subset of the first, or if it is a subset and both
4155 ranges end at the same place, the range starts at the start of the
4156 first range and ends just before the second range.
4157 Otherwise, we can't describe this as a single range. */
4163 {
4167 }
4169 {
4173 }
4174 else
4176 }
4179 {
4180 /* If they don't overlap, the result is the second range. If the second
4181 is a subset of the first, the result is false. Otherwise,
4182 the range starts just after the first range and ends at the
4183 end of the second. */
4188 else
4189 {
4193 }
4194 }
4196 else
4197 {
4198 /* The case where we are excluding both ranges. Here the complex case
4199 is if they don't overlap. In that case, the only time we have a
4200 range is if they are adjacent. If the second is a subset of the
4201 first, the result is the first. Otherwise, the range to exclude
4202 starts at the beginning of the first range and ends at the end of the
4203 second. */
4205 {
4212 else
4213 {
4214 /* Canonicalize - [min, x] into - [-, x]. */
4217 {
4222 /* FALLTHROUGH */
4236 }
4238 /* Canonicalize - [x, max] into - [x, -]. */
4241 {
4246 /* FALLTHROUGH */
4262 }
4264 /* The ranges might be also adjacent between the maximum and
4265 minimum values of the given type. For
4266 - [{min,-}, x] and - [y, {max,-}] ranges where x + 1 < y
4267 return + [x + 1, y - 1]. */
4269 {
4278 }
4279 else
4281 }
4282 }
4285 else
4287 }
4291 }
4292 \f
4294 /* Subroutine of fold, looking inside expressions of the form
4295 A op B ? A : C, where ARG0, ARG1 and ARG2 are the three operands
4296 of the COND_EXPR. This function is being used also to optimize
4297 A op B ? C : A, by reversing the comparison first.
4299 Return a folded expression whose code is not a COND_EXPR
4300 anymore, or NULL_TREE if no folding opportunity is found. */
4302 static tree
4304 {
4309 tree tem;
4314 /* If we have A op 0 ? A : -A, consider applying the following
4315 transformations:
4317 A == 0? A : -A same as -A
4318 A != 0? A : -A same as A
4319 A >= 0? A : -A same as abs (A)
4320 A > 0? A : -A same as abs (A)
4321 A <= 0? A : -A same as -abs (A)
4322 A < 0? A : -A same as -abs (A)
4324 None of these transformations work for modes with signed
4325 zeros. If A is +/-0, the first two transformations will
4326 change the sign of the result (from +0 to -0, or vice
4327 versa). The last four will fix the sign of the result,
4328 even though the original expressions could be positive or
4329 negative, depending on the sign of A.
4331 Note that all these transformations are correct if A is
4332 NaN, since the two alternatives (A and -A) are also NaNs. */
4338 /* In the case that A is of the form X-Y, '-A' (arg2) may
4339 have already been folded to Y-X, check for that. */
4347 {
4359 /* Fall through. */
4381 }
4383 /* A != 0 ? A : 0 is simply A, unless A is -0. Likewise
4384 A == 0 ? A : 0 is always 0 unless A is -0. Note that
4385 both transformations are correct when A is NaN: A != 0
4386 is then true, and A == 0 is false. */
4389 {
4394 }
4396 /* Try some transformations of A op B ? A : B.
4398 A == B? A : B same as B
4399 A != B? A : B same as A
4400 A >= B? A : B same as max (A, B)
4401 A > B? A : B same as max (B, A)
4402 A <= B? A : B same as min (A, B)
4403 A < B? A : B same as min (B, A)
4405 As above, these transformations don't work in the presence
4406 of signed zeros. For example, if A and B are zeros of
4407 opposite sign, the first two transformations will change
4408 the sign of the result. In the last four, the original
4409 expressions give different results for (A=+0, B=-0) and
4410 (A=-0, B=+0), but the transformed expressions do not.
4412 The first two transformations are correct if either A or B
4413 is a NaN. In the first transformation, the condition will
4414 be false, and B will indeed be chosen. In the case of the
4415 second transformation, the condition A != B will be true,
4416 and A will be chosen.
4418 The conversions to max() and min() are not correct if B is
4419 a number and A is not. The conditions in the original
4420 expressions will be false, so all four give B. The min()
4421 and max() versions would give a NaN instead. */
4423 /* Avoid these transformations if the COND_EXPR may be used
4424 as an lvalue in the C++ front-end. PR c++/19199. */
4425 && (in_gimple_form
4429 {
4434 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
4436 {
4440 }
4443 {
4452 /* In C++ a ?: expression can be an lvalue, so put the
4453 operand which will be used if they are equal first
4454 so that we can convert this back to the
4455 corresponding COND_EXPR. */
4457 {
4464 }
4471 {
4478 }
4491 }
4492 }
4494 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
4495 we might still be able to simplify this. For example,
4496 if C1 is one less or one more than C2, this might have started
4497 out as a MIN or MAX and been transformed by this function.
4498 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
4504 {
4506 /* We can replace A with C1 in this case. */
4511 /* If C1 is C2 + 1, this is min(A, C2). */
4513 OEP_ONLY_CONST)
4517 OEP_ONLY_CONST))
4523 /* If C1 is C2 - 1, this is min(A, C2). */
4525 OEP_ONLY_CONST)
4529 OEP_ONLY_CONST))
4535 /* If C1 is C2 - 1, this is max(A, C2). */
4537 OEP_ONLY_CONST)
4541 OEP_ONLY_CONST))
4547 /* If C1 is C2 + 1, this is max(A, C2). */
4549 OEP_ONLY_CONST)
4553 OEP_ONLY_CONST))
4561 }
4564 }
4567 \f
4568 #ifndef LOGICAL_OP_NON_SHORT_CIRCUIT
4569 #define LOGICAL_OP_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
4570 #endif
4572 /* EXP is some logical combination of boolean tests. See if we can
4573 merge it into some range test. Return the new tree if so. */
4575 static tree
4577 {
4584 tree tem;
4586 /* If this is an OR operation, invert both sides; we will invert
4587 again at the end. */
4591 /* If both expressions are the same, if we can merge the ranges, and we
4592 can build the range test, return it or it inverted. If one of the
4593 ranges is always true or always false, consider it to be the same
4594 expression as the other. */
4604 /* On machines where the branch cost is expensive, if this is a
4605 short-circuited branch and the underlying object on both sides
4606 is the same, make a non-short-circuit operation. */
4612 {
4613 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
4614 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
4615 which cases we can't do this. */
4623 {
4635 }
4636 }
4639 }
4640 \f
4641 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
4642 bit value. Arrange things so the extra bits will be set to zero if and
4643 only if C is signed-extended to its full width. If MASK is nonzero,
4644 it is an INTEGER_CST that should be AND'ed with the extra bits. */
4646 static tree
4648 {
4651 tree temp;
4656 /* We work by getting just the sign bit into the low-order bit, then
4657 into the high-order bit, then sign-extend. We then XOR that value
4658 with C. */
4662 /* We must use a signed type in order to get an arithmetic right shift.
4663 However, we must also avoid introducing accidental overflows, so that
4664 a subsequent call to integer_zerop will work. Hence we must
4665 do the type conversion here. At this point, the constant is either
4666 zero or one, and the conversion to a signed type can never overflow.
4667 We could get an overflow if this conversion is done anywhere else. */
4676 /* If necessary, convert the type back to match the type of C. */
4681 }
4682 \f
4683 /* Find ways of folding logical expressions of LHS and RHS:
4684 Try to merge two comparisons to the same innermost item.
4685 Look for range tests like "ch >= '0' && ch <= '9'".
4686 Look for combinations of simple terms on machines with expensive branches
4687 and evaluate the RHS unconditionally.
4689 For example, if we have p->a == 2 && p->b == 4 and we can make an
4690 object large enough to span both A and B, we can do this with a comparison
4691 against the object ANDed with the a mask.
4693 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
4694 operations to do this with one comparison.
4696 We check for both normal comparisons and the BIT_AND_EXPRs made this by
4697 function and the one above.
4699 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
4700 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
4702 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
4703 two operands.
4705 We return the simplified tree or 0 if no optimization is possible. */
4707 static tree
4709 {
4710 /* If this is the "or" of two comparisons, we can do something if
4711 the comparisons are NE_EXPR. If this is the "and", we can do something
4712 if the comparisons are EQ_EXPR. I.e.,
4713 (a->b == 2 && a->c == 4) can become (a->new == NEW).
4715 WANTED_CODE is this operation code. For single bit fields, we can
4716 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
4717 comparison for one-bit fields. */
4737 /* Start by getting the comparison codes. Fail if anything is volatile.
4738 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
4739 it were surrounded with a NE_EXPR. */
4748 {
4752 }
4755 {
4759 }
4770 /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
4773 {
4774 tree result;
4777 {
4782 }
4785 {
4791 }
4792 }
4797 /* If the RHS can be evaluated unconditionally and its operands are
4798 simple, it wins to evaluate the RHS unconditionally on machines
4799 with expensive branches. In this case, this isn't a comparison
4800 that can be merged. Avoid doing this if the RHS is a floating-point
4801 comparison since those can trap. */
4807 {
4808 /* Convert (a != 0) || (b != 0) into (a | b) != 0. */
4818 /* Convert (a == 0) && (b == 0) into (a | b) == 0. */
4830 }
4832 /* See if the comparisons can be merged. Then get all the parameters for
4833 each side. */
4857 /* It must be true that the inner operation on the lhs of each
4858 comparison must be the same if we are to be able to do anything.
4859 Then see if we have constants. If not, the same must be true for
4860 the rhs's. */
4871 else
4874 /* If either comparison code is not correct for our logical operation,
4875 fail. However, we can convert a one-bit comparison against zero into
4876 the opposite comparison against that bit being set in the field. */
4880 {
4882 {
4883 /* Make the left operand unsigned, since we are only interested
4884 in the value of one bit. Otherwise we are doing the wrong
4885 thing below. */
4888 }
4889 else
4891 }
4893 /* This is analogous to the code for l_const above. */
4895 {
4897 {
4900 }
4901 else
4903 }
4905 /* After this point all optimizations will generate bit-field
4906 references, which we might not want. */
4910 /* See if we can find a mode that contains both fields being compared on
4911 the left. If we can't, fail. Otherwise, update all constants and masks
4912 to be relative to a field of that size. */
4917 volatilep);
4927 {
4930 }
4938 {
4946 {
4950 }
4951 }
4953 {
4961 {
4965 }
4966 }
4968 /* If the right sides are not constant, do the same for it. Also,
4969 disallow this optimization if a size or signedness mismatch occurs
4970 between the left and right sides. */
4972 {
4975 /* Make sure the two fields on the right
4976 correspond to the left without being swapped. */
4984 volatilep);
4994 {
4997 }
5004 /* Make a mask that corresponds to both fields being compared.
5005 Do this for both items being compared. If the operands are the
5006 same size and the bits being compared are in the same position
5007 then we can do this by masking both and comparing the masked
5008 results. */
5012 {
5024 }
5026 /* There is still another way we can do something: If both pairs of
5027 fields being compared are adjacent, we may be able to make a wider
5028 field containing them both.
5030 Note that we still must mask the lhs/rhs expressions. Furthermore,
5031 the mask must be shifted to account for the shift done by
5032 make_bit_field_ref. */
5037 {
5038 tree type;
5050 /* Convert to the smaller type before masking out unwanted bits. */
5053 {
5055 {
5059 }
5061 {
5065 }
5066 }
5075 }
5078 }
5080 /* Handle the case of comparisons with constants. If there is something in
5081 common between the masks, those bits of the constants must be the same.
5082 If not, the condition is always false. Test for this to avoid generating
5083 incorrect code below. */
5088 {
5090 {
5093 }
5094 else
5095 {
5098 }
5099 }
5101 /* Construct the expression we will return. First get the component
5102 reference we will make. Unless the mask is all ones the width of
5103 that field, perform the mask operation. Then compare with the
5104 merged constant. */
5114 }
5115 \f
5116 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
5117 constant. */
5119 static tree
5121 {
5125 tree minmax_const;
5127 tree inner;
5137 /* If something does not permit us to optimize, return the original tree. */
5145 /* Now handle all the various comparison codes. We only handle EQ_EXPR
5146 and GT_EXPR, doing the rest with recursive calls using logical
5147 simplifications. */
5149 {
5151 {
5152 /* FIXME: We should be able to invert code without building a
5153 scratch tree node, but doing so would require us to
5154 duplicate a part of invert_truthvalue here. */
5161 }
5164 return
5166 optimize_minmax_comparison
5168 optimize_minmax_comparison
5173 /* MAX (X, 0) == 0 -> X <= 0 */
5177 /* MAX (X, 0) == 5 -> X == 5 */
5181 /* MAX (X, 0) == -1 -> false */
5185 /* MIN (X, 0) == 0 -> X >= 0 */
5189 /* MIN (X, 0) == 5 -> false */
5192 else
5193 /* MIN (X, 0) == -1 -> X == -1 */
5198 /* MAX (X, 0) > 0 -> X > 0
5199 MAX (X, 0) > 5 -> X > 5 */
5203 /* MAX (X, 0) > -1 -> true */
5207 /* MIN (X, 0) > 0 -> false
5208 MIN (X, 0) > 5 -> false */
5211 else
5212 /* MIN (X, 0) > -1 -> X > -1 */
5217 }
5218 }
5219 \f
5220 /* T is an integer expression that is being multiplied, divided, or taken a
5221 modulus (CODE says which and what kind of divide or modulus) by a
5222 constant C. See if we can eliminate that operation by folding it with
5223 other operations already in T. WIDE_TYPE, if non-null, is a type that
5224 should be used for the computation if wider than our type.
5226 For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
5227 (X * 2) + (Y * 4). We must, however, be assured that either the original
5228 expression would not overflow or that overflow is undefined for the type
5229 in the language in question.
5231 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
5232 the machine has a multiply-accumulate insn or that this is part of an
5233 addressing calculation.
5235 If we return a non-null expression, it is an equivalent form of the
5236 original computation, but need not be in the original type. */
5238 static tree
5240 {
5241 /* To avoid exponential search depth, refuse to allow recursion past
5242 three levels. Beyond that (1) it's highly unlikely that we'll find
5243 something interesting and (2) we've probably processed it before
5244 when we built the inner expression. */
5247 tree ret;
5252 depth++;
5254 depth--;
5257 }
5259 static tree
5261 {
5271 /* Don't deal with constants of zero here; they confuse the code below. */
5281 /* Note that we need not handle conditional operations here since fold
5282 already handles those cases. So just do arithmetic here. */
5284 {
5286 /* For a constant, we can always simplify if we are a multiply
5287 or (for divide and modulus) if it is a multiple of our constant. */
5295 /* If op0 is an expression ... */
5300 /* ... and is unsigned, and its type is smaller than ctype,
5301 then we cannot pass through as widening. */
5307 /* ... or this is a truncation (t is narrower than op0),
5308 then we cannot pass through this narrowing. */
5311 /* ... or signedness changes for division or modulus,
5312 then we cannot pass through this conversion. */
5318 /* Pass the constant down and see if we can make a simplification. If
5319 we can, replace this expression with the inner simplification for
5320 possible later conversion to our or some other type. */
5325 code == MULT_EXPR
5331 /* If widening the type changes it from signed to unsigned, then we
5332 must avoid building ABS_EXPR itself as unsigned. */
5334 {
5337 {
5340 }
5342 }
5343 /* If the constant is negative, we cannot simplify this. */
5346 /* FALLTHROUGH */
5353 /* If widening the type changes the signedness, then we can't perform
5354 this optimization as that changes the result. */
5358 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
5361 {
5367 }
5371 /* If the second operand is constant, this is a multiplication
5372 or floor division, by a power of two, so we can treat it that
5373 way unless the multiplier or divisor overflows. Signed
5374 left-shift overflow is implementation-defined rather than
5375 undefined in C90, so do not convert signed left shift into
5376 multiplication. */
5379 /* const_binop may not detect overflow correctly,
5380 so check for it explicitly here. */
5385 size_one_node,
5395 /* See if we can eliminate the operation on both sides. If we can, we
5396 can return a new PLUS or MINUS. If we can't, the only remaining
5397 cases where we can do anything are if the second operand is a
5398 constant. */
5403 /* If not multiplication, we can only do this if both operands
5404 are divisible by c. */
5410 /* If this was a subtraction, negate OP1 and set it to be an addition.
5411 This simplifies the logic below. */
5418 /* If either OP1 or C are negative, this optimization is not safe for
5419 some of the division and remainder types while for others we need
5420 to change the code. */
5422 {
5430 }
5432 /* If it's a multiply or a division/modulus operation of a multiple
5433 of our constant, do the operation and verify it doesn't overflow. */
5436 {
5439 /* We allow the constant to overflow with wrapping semantics. */
5443 }
5444 else
5447 /* If we have an unsigned type is not a sizetype, we cannot widen
5448 the operation since it will change the result if the original
5449 computation overflowed. */
5455 /* If we were able to eliminate our operation from the first side,
5456 apply our operation to the second side and reform the PLUS. */
5460 /* The last case is if we are a multiply. In that case, we can
5461 apply the distributive law to commute the multiply and addition
5462 if the multiplication of the constants doesn't overflow. */
5468 op1);
5473 /* We have a special case here if we are doing something like
5474 (C * 8) % 4 since we know that's zero. */
5481 /* ... fall through ... */
5485 /* If we can extract our operation from the LHS, do so and return a
5486 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
5487 do something only if the second operand is a constant. */
5499 /* If these are the same operation types, we can associate them
5500 assuming no overflow. */
5507 /* If these operations "cancel" each other, we have the main
5508 optimizations of this pass, which occur when either constant is a
5509 multiple of the other, in which case we replace this with either an
5510 operation or CODE or TCODE.
5512 If we have an unsigned type that is not a sizetype, we cannot do
5513 this since it will change the result if the original computation
5514 overflowed. */
5517 && ! flag_wrapv
5522 {
5533 }
5538 }
5541 }
5542 \f
5543 /* Return a node which has the indicated constant VALUE (either 0 or
5544 1), and is of the indicated TYPE. */
5546 tree
5548 {
5553 else
5555 }
5558 /* Return true if expr looks like an ARRAY_REF and set base and
5559 offset to the appropriate trees. If there is no offset,
5560 offset is set to NULL_TREE. Base will be canonicalized to
5561 something you can get the element type from using
5562 TREE_TYPE (TREE_TYPE (base)). Offset will be the offset
5563 in bytes to the base. */
5565 static bool
5567 {
5568 /* One canonical form is a PLUS_EXPR with the first
5569 argument being an ADDR_EXPR with a possible NOP_EXPR
5570 attached. */
5572 {
5575 /* Strip NOP_EXPRs here because the C frontends and/or
5576 folders present us (int *)&x.a + 4B possibly. */
5579 {
5583 else
5587 }
5588 }
5589 /* Other canonical form is an ADDR_EXPR of an ARRAY_REF,
5590 which we transform into an ADDR_EXPR with appropriate
5591 offset. For other arguments to the ADDR_EXPR we assume
5592 zero offset and as such do not care about the ADDR_EXPR
5593 type and strip possible nops from it. */
5595 {
5598 {
5603 }
5604 else
5605 {
5606 /* Handle array-to-pointer decay as &a. */
5609 else
5612 }
5614 }
5615 /* The next canonical form is a VAR_DECL with POINTER_TYPE. */
5618 {
5622 }
5625 }
5628 /* Transform `a + (b ? x : y)' into `b ? (a + x) : (a + y)'.
5629 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
5630 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
5631 expression, and ARG to `a'. If COND_FIRST_P is nonzero, then the
5632 COND is the first argument to CODE; otherwise (as in the example
5633 given here), it is the second argument. TYPE is the type of the
5634 original expression. Return NULL_TREE if no simplification is
5635 possible. */
5637 static tree
5641 {
5648 /* This transformation is only worthwhile if we don't have to wrap
5649 arg in a SAVE_EXPR, and the operation can be simplified on at least
5650 one of the branches once its pushed inside the COND_EXPR. */
5655 {
5659 /* If this operand throws an expression, then it does not make
5660 sense to try to perform a logical or arithmetic operation
5661 involving it. */
5666 }
5667 else
5668 {
5673 }
5677 {
5681 else
5683 }
5685 {
5689 else
5691 }
5695 }
5697 \f
5698 /* Subroutine of fold() that checks for the addition of +/- 0.0.
5700 If !NEGATE, return true if ADDEND is +/-0.0 and, for all X of type
5701 TYPE, X + ADDEND is the same as X. If NEGATE, return true if X -
5702 ADDEND is the same as X.
5704 X + 0 and X - 0 both give X when X is NaN, infinite, or nonzero
5705 and finite. The problematic cases are when X is zero, and its mode
5706 has signed zeros. In the case of rounding towards -infinity,
5707 X - 0 is not the same as X because 0 - 0 is -0. In other rounding
5708 modes, X + 0 is not the same as X because -0 + 0 is 0. */
5710 static bool
5712 {
5716 /* Don't allow the fold with -fsignaling-nans. */
5720 /* Allow the fold if zeros aren't signed, or their sign isn't important. */
5724 /* Treat x + -0 as x - 0 and x - -0 as x + 0. */
5729 /* The mode has signed zeros, and we have to honor their sign.
5730 In this situation, there is only one case we can return true for.
5731 X - 0 is the same as X unless rounding towards -infinity is
5732 supported. */
5734 }
5736 /* Subroutine of fold() that checks comparisons of built-in math
5737 functions against real constants.
5739 FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
5740 operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR. TYPE
5741 is the type of the result and ARG0 and ARG1 are the operands of the
5742 comparison. ARG1 must be a TREE_REAL_CST.
5744 The function returns the constant folded tree if a simplification
5745 can be made, and NULL_TREE otherwise. */
5747 static tree
5750 {
5751 REAL_VALUE_TYPE c;
5754 {
5760 {
5761 /* sqrt(x) < y is always false, if y is negative. */
5765 /* sqrt(x) > y is always true, if y is negative and we
5766 don't care about NaNs, i.e. negative values of x. */
5770 /* sqrt(x) > y is the same as x >= 0, if y is negative. */
5773 }
5775 {
5776 REAL_VALUE_TYPE c2;
5782 {
5783 /* sqrt(x) > y is x == +Inf, when y is very large. */
5788 /* sqrt(x) > y is always false, when y is very large
5789 and we don't care about infinities. */
5791 }
5793 /* sqrt(x) > c is the same as x > c*c. */
5796 }
5798 {
5799 REAL_VALUE_TYPE c2;
5805 {
5806 /* sqrt(x) < y is always true, when y is a very large
5807 value and we don't care about NaNs or Infinities. */
5811 /* sqrt(x) < y is x != +Inf when y is very large and we
5812 don't care about NaNs. */
5817 /* sqrt(x) < y is x >= 0 when y is very large and we
5818 don't care about Infinities. */
5823 /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
5832 dconst0)),
5835 c2)));
5836 }
5838 /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
5843 /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
5846 {
5851 dconst0)),
5854 c2)));
5855 }
5856 }
5857 }
5860 }
5862 /* Subroutine of fold() that optimizes comparisons against Infinities,
5863 either +Inf or -Inf.
5865 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5866 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5867 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5869 The function returns the constant folded tree if a simplification
5870 can be made, and NULL_TREE otherwise. */
5872 static tree
5874 {
5876 REAL_VALUE_TYPE max;
5877 tree temp;
5882 /* For negative infinity swap the sense of the comparison. */
5888 {
5890 /* x > +Inf is always false, if with ignore sNANs. */
5896 /* x <= +Inf is always true, if we don't case about NaNs. */
5900 /* x <= +Inf is the same as x == x, i.e. isfinite(x). */
5903 {
5906 }
5911 /* x == +Inf and x >= +Inf are always equal to x > DBL_MAX. */
5917 /* x < +Inf is always equal to x <= DBL_MAX. */
5923 /* x != +Inf is always equal to !(x > DBL_MAX). */
5929 /* The transformation below creates non-gimple code and thus is
5930 not appropriate if we are in gimple form. */
5940 }
5943 }
5945 /* Subroutine of fold() that optimizes comparisons of a division by
5946 a nonzero integer constant against an integer constant, i.e.
5947 X/C1 op C2.
5949 CODE is the comparison operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR,
5950 GE_EXPR or LE_EXPR. TYPE is the type of the result and ARG0 and ARG1
5951 are the operands of the comparison. ARG1 must be a TREE_REAL_CST.
5953 The function returns the constant folded tree if a simplification
5954 can be made, and NULL_TREE otherwise. */
5956 static tree
5958 {
5963 HOST_WIDE_INT hpart;
5967 /* We have to do this the hard way to detect unsigned overflow.
5968 prod = int_const_binop (MULT_EXPR, arg01, arg1, 0); */
5978 {
5982 /* Likewise hi = int_const_binop (PLUS_EXPR, prod, tmp, 0). */
5991 }
5993 {
5996 {
6014 }
6015 }
6016 else
6017 {
6018 /* A negative divisor reverses the relational operators. */
6023 {
6041 }
6042 }
6045 {
6086 }
6089 }
6092 /* If CODE with arguments ARG0 and ARG1 represents a single bit
6093 equality/inequality test, then return a simplified form of the test
6094 using a sign testing. Otherwise return NULL. TYPE is the desired
6095 result type. */
6097 static tree
6099 tree result_type)
6100 {
6101 /* If this is testing a single bit, we can optimize the test. */
6105 {
6106 /* If we have (A & C) != 0 where C is the sign bit of A, convert
6107 this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
6111 /* This is only a win if casting to a signed type is cheap,
6112 i.e. when arg00's type is not a partial mode. */
6115 {
6120 }
6121 }
6124 }
6126 /* If CODE with arguments ARG0 and ARG1 represents a single bit
6127 equality/inequality test, then return a simplified form of
6128 the test using shifts and logical operations. Otherwise return
6129 NULL. TYPE is the desired result type. */
6131 tree
6133 tree result_type)
6134 {
6135 /* If this is testing a single bit, we can optimize the test. */
6139 {
6146 tree tem;
6148 /* First, see if we can fold the single bit test into a sign-bit
6149 test. */
6151 result_type);
6155 /* Otherwise we have (A & C) != 0 where C is a single bit,
6156 convert that into ((A >> C2) & 1). Where C2 = log2(C).
6157 Similarly for (A & C) == 0. */
6159 /* If INNER is a right shift of a constant and it plus BITNUM does
6160 not overflow, adjust BITNUM and INNER. */
6167 {
6170 }
6172 /* If we are going to be able to omit the AND below, we must do our
6173 operations as unsigned. If we must use the AND, we have a choice.
6174 Normally unsigned is faster, but for some machines signed is. */
6175 #ifdef LOAD_EXTEND_OP
6178 #else
6180 #endif
6195 /* Put the AND last so it can combine with more things. */
6199 /* Make sure to return the proper type. */
6203 }
6205 }
6207 /* Check whether we are allowed to reorder operands arg0 and arg1,
6208 such that the evaluation of arg1 occurs before arg0. */
6210 static bool
6212 {
6219 }
6221 /* Test whether it is preferable two swap two operands, ARG0 and
6222 ARG1, for example because ARG0 is an integer constant and ARG1
6223 isn't. If REORDER is true, only recommend swapping if we can
6224 evaluate the operands in reverse order. */
6226 bool
6228 {
6264 /* It is preferable to swap two SSA_NAME to ensure a canonical form
6265 for commutative and comparison operators. Ensuring a canonical
6266 form allows the optimizers to find additional redundancies without
6267 having to explicitly check for both orderings. */
6274 }
6276 /* Fold comparison ARG0 CODE ARG1 (with result in TYPE), where
6277 ARG0 is extended to a wider type. */
6279 static tree
6281 {
6283 tree arg1_unw;
6292 #ifdef HAVE_canonicalize_funcptr_for_compare
6293 /* Disable this optimization if we're casting a function pointer
6294 type on targets that require function pointer canonicalization. */
6299 #endif
6306 /* If possible, express the comparison in the shorter mode. */
6328 /* If we are comparing with the integer that does not fit into the range
6329 of the shorter type, the result is known. */
6340 {
6367 }
6370 }
6372 /* Fold comparison ARG0 CODE ARG1 (with result in TYPE), where for
6373 ARG0 just the signedness is changed. */
6375 static tree
6378 {
6390 #ifdef HAVE_canonicalize_funcptr_for_compare
6391 /* Disable this optimization if we're casting a function pointer
6392 type on targets that require function pointer canonicalization. */
6397 #endif
6414 {
6421 }
6422 else
6426 }
6428 /* Tries to replace &a[idx] CODE s * delta with &a[idx CODE delta], if s is
6429 step of the array. Reconstructs s and delta in the case of s * delta
6430 being an integer constant (and thus already folded).
6431 ADDR is the address. MULT is the multiplicative expression.
6432 If the function succeeds, the new address expression is returned. Otherwise
6433 NULL_TREE is returned. */
6435 static tree
6437 {
6441 tree itype;
6443 /* Canonicalize op1 into a possibly non-constant delta
6444 and an INTEGER_CST s. */
6446 {
6453 {
6456 }
6458 {
6461 }
6462 else
6464 }
6466 {
6469 }
6470 else
6471 {
6472 /* Simulate we are delta * 1. */
6475 }
6478 {
6480 {
6490 {
6493 }
6494 else
6495 {
6496 /* Try if delta is a multiple of step. */
6501 }
6504 }
6508 }
6510 /* We found the suitable array reference. So copy everything up to it,
6511 and replace the index. */
6518 {
6522 }
6530 }
6533 /* Fold A < X && A + 1 > Y to A < X && A >= Y. Normally A + 1 > Y
6534 means A >= Y && A != MAX, but in this case we know that
6535 A < X <= MAX. INEQ is A + 1 > Y, BOUND is A < X. */
6537 static tree
6539 {
6546 else
6555 {
6558 }
6560 {
6563 }
6564 else
6575 }
6577 /* Fold a unary expression of code CODE and type TYPE with operand
6578 OP0. Return the folded expression if folding is successful.
6579 Otherwise, return NULL_TREE. */
6581 tree
6583 {
6584 tree tem;
6585 tree arg0;
6593 {
6596 {
6597 /* Don't use STRIP_NOPS, because signedness of argument type
6598 matters. */
6600 }
6601 else
6602 {
6603 /* Strip any conversions that don't change the mode. This
6604 is safe for every expression, except for a comparison
6605 expression because its signedness is derived from its
6606 operands.
6608 Note that this is done as an internal manipulation within
6609 the constant folder, in order to find the simplest
6610 representation of the arguments so that their form can be
6611 studied. In any cases, the appropriate type conversions
6612 should be put back in the tree that will get out of the
6613 constant folder. */
6615 }
6616 }
6619 {
6624 {
6634 /* If this was a conversion, and all we did was to move into
6635 inside the COND_EXPR, bring it back out. But leave it if
6636 it is a conversion from integer to integer and the
6637 result precision is no wider than a word since such a
6638 conversion is cheap and may be optimized away by combine,
6639 while it couldn't if it were outside the COND_EXPR. Then return
6640 so we don't get into an infinite recursion loop taking the
6641 conversion out and then back in. */
6653 && (INTEGRAL_TYPE_P
6665 }
6667 {
6669 {
6673 }
6677 integer_one_node),
6679 integer_zero_node));
6680 }
6681 }
6684 {
6695 /* Handle cases of two conversions in a row. */
6698 {
6720 /* In addition to the cases of two conversions in a row
6721 handled below, if we are converting something to its own
6722 type via an object of identical or wider precision, neither
6723 conversion is needed. */
6729 /* Likewise, if the intermediate and final types are either both
6730 float or both integer, we don't need the middle conversion if
6731 it is wider than the final type and doesn't change the signedness
6732 (for integers). Avoid this if the final type is a pointer
6733 since then we sometimes need the inner conversion. Likewise if
6734 the outer has a precision not equal to the size of its mode. */
6743 && ! final_ptr
6747 /* If we have a sign-extension of a zero-extended value, we can
6748 replace that by a single zero-extension. */
6754 /* Two conversions in a row are not needed unless:
6755 - some conversion is floating-point (overstrict for now), or
6756 - some conversion is a vector (overstrict for now), or
6757 - the intermediate type is narrower than both initial and
6758 final, or
6759 - the intermediate type and innermost type differ in signedness,
6760 and the outermost type is wider than the intermediate, or
6761 - the initial type is a pointer type and the precisions of the
6762 intermediate and final types differ, or
6763 - the final type is a pointer type and the precisions of the
6764 initial and intermediate types differ. */
6779 }
6781 /* Handle (T *)&A.B.C for A being of type T and B and C
6782 living at offset zero. This occurs frequently in
6783 C++ upcasting and then accessing the base. */
6787 {
6789 tree offset;
6795 /* If the reference was to a (constant) zero offset, we can use
6796 the address of the base if it has the same base type
6797 as the result type. */
6802 }
6806 /* Detect assigning a bitfield. */
6809 {
6810 /* Don't leave an assignment inside a conversion
6811 unless assigning a bitfield. */
6813 /* First do the assignment, then return converted constant. */
6818 }
6820 /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
6821 constants (if x has signed type, the sign bit cannot be set
6822 in c). This folds extension into the BIT_AND_EXPR. */
6827 {
6837 <= HOST_BITS_PER_WIDE_INT
6839 {
6846 #ifdef LOAD_EXTEND_OP
6848 && !flag_syntax_only
6851 {
6855 }
6856 #endif
6857 }
6859 {
6866 }
6867 }
6869 /* Convert (T1)((T2)X op Y) into (T1)X op Y, for pointer types T1 and
6870 T2 being pointers to types of the same size. */
6875 {
6887 }
6900 /* Convert - (~A) to A + 1. */
6911 /* Convert fabs((double)float) into (double)fabsf(float). */
6914 {
6919 targ0));
6920 }
6921 /* ABS_EXPR<ABS_EXPR<x>> = ABS_EXPR<x> even if flag_wrapv is on. */
6925 /* Strip sign ops from argument. */
6927 {
6931 }
6959 /* Convert ~ (-A) to A - 1. */
6963 /* Convert ~ (A - 1) or ~ (A + -1) to -A. */
6970 /* Convert ~(X ^ Y) to ~X ^ Y or X ^ ~Y if ~X or ~Y simplify. */
6987 /* The argument to invert_truthvalue must have Boolean type. */
6991 /* Note that the operand of this must be an int
6992 and its values must be 0 or 1.
6993 ("true" is a fixed value perhaps depending on the language,
6994 but we don't handle values other than 1 correctly yet.) */
6996 /* Avoid infinite recursion. */
7036 }
7038 /* Fold a binary expression of code CODE and type TYPE with operands
7039 OP0 and OP1. Return the folded expression if folding is
7040 successful. Otherwise, return NULL_TREE. */
7042 tree
7044 {
7046 tree tem;
7050 /* WINS will be nonzero when the switch is done
7051 if all operands are constant. */
7061 {
7062 tree subop;
7064 /* Strip any conversions that don't change the mode. This is
7065 safe for every expression, except for a comparison expression
7066 because its signedness is derived from its operands. So, in
7067 the latter case, only strip conversions that don't change the
7068 signedness.
7070 Note that this is done as an internal manipulation within the
7071 constant folder, in order to find the simplest representation
7072 of the arguments so that their form can be studied. In any
7073 cases, the appropriate type conversions should be put back in
7074 the tree that will get out of the constant folder. */
7077 else
7082 else
7087 /* Note that TREE_CONSTANT isn't enough:
7088 static var addresses are constant but we can't
7089 do arithmetic on them. */
7091 }
7094 {
7095 tree subop;
7097 /* Strip any conversions that don't change the mode. This is
7098 safe for every expression, except for a comparison expression
7099 because its signedness is derived from its operands. So, in
7100 the latter case, only strip conversions that don't change the
7101 signedness.
7103 Note that this is done as an internal manipulation within the
7104 constant folder, in order to find the simplest representation
7105 of the arguments so that their form can be studied. In any
7106 cases, the appropriate type conversions should be put back in
7107 the tree that will get out of the constant folder. */
7110 else
7115 else
7120 /* Note that TREE_CONSTANT isn't enough:
7121 static var addresses are constant but we can't
7122 do arithmetic on them. */
7124 }
7126 /* If this is a commutative operation, and ARG0 is a constant, move it
7127 to ARG1 to reduce the number of tests below. */
7132 /* Now WINS is set as described above,
7133 ARG0 is the first operand of EXPR,
7134 and ARG1 is the second operand (if it has more than one operand).
7136 First check for cases where an arithmetic operation is applied to a
7137 compound, conditional, or comparison operation. Push the arithmetic
7138 operation inside the compound or conditional to see if any folding
7139 can then be done. Convert comparison to conditional for this purpose.
7140 The also optimizes non-constant cases that used to be done in
7141 expand_expr.
7143 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
7144 one of the operands is a comparison and the other is a comparison, a
7145 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
7146 code below would make the expression more complex. Change it to a
7147 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
7148 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
7160 {
7164 boolean_type_node,
7172 }
7176 {
7188 {
7194 }
7197 {
7203 }
7204 }
7207 {
7209 /* A + (-B) -> A - B */
7214 /* (-A) + B -> B - A */
7220 /* Convert ~A + 1 to -A. */
7227 {
7231 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
7232 with a constant, and the two constants have no bits in common,
7233 we should treat this as a BIT_IOR_EXPR since this may produce more
7234 simplifications. */
7242 {
7245 }
7247 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
7248 (plus (plus (mult) (mult)) (foo)) so that we can
7249 take advantage of the factoring cases below. */
7256 {
7262 else
7284 parg1)));
7285 }
7288 {
7292 /* (A * C) + (B * C) -> (A+B) * C.
7293 We are most concerned about the case where C is a constant,
7294 but other combinations show up during loop reduction. Since
7295 it is not difficult, try all four possibilities. */
7312 /* No identical multiplicands; see if we can find a common
7313 power-of-two factor in non-power-of-two multiplies. This
7314 can help in multi-dimensional array access. */
7319 {
7324 /* Move min of absolute values to int11. */
7327 {
7331 }
7334 {
7340 }
7341 }
7349 }
7351 /* Try replacing &a[i1] + c * i2 with &a[i1 + i2], if c is step
7352 of the array. Loop optimizer sometimes produce this type of
7353 expressions. */
7355 {
7359 }
7361 {
7365 }
7366 }
7367 else
7368 {
7369 /* See if ARG1 is zero and X + ARG1 reduces to X. */
7373 /* Likewise if the operands are reversed. */
7377 /* Convert X + -C into X - C. */
7380 {
7386 }
7394 /* Convert x+x into x*2.0. */
7400 /* Convert x*c+x into x*(c+1). */
7406 {
7407 REAL_VALUE_TYPE c;
7413 }
7415 /* Convert x+x*c into x*(c+1). */
7421 {
7422 REAL_VALUE_TYPE c;
7428 }
7430 /* Convert x*c1+x*c2 into x*(c1+c2). */
7440 {
7449 }
7450 /* Convert a + (b*c + d*e) into (a + b*c) + d*e. */
7454 {
7459 {
7460 tree tree0;
7463 }
7464 }
7465 /* Convert (b*c + d*e) + a into b*c + (d*e +a). */
7469 {
7474 {
7475 tree tree0;
7478 }
7479 }
7480 }
7482 bit_rotate:
7483 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
7484 is a rotate of A by C1 bits. */
7485 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
7486 is a rotate of A by B bits. */
7487 {
7496 {
7515 {
7523 TYPE_PRECISION
7528 ? LROTATE_EXPR
7531 }
7533 {
7541 TYPE_PRECISION
7546 ? LROTATE_EXPR
7549 }
7550 }
7551 }
7553 associate:
7554 /* In most languages, can't associate operations on floats through
7555 parentheses. Rather than remember where the parentheses were, we
7556 don't associate floats at all, unless the user has specified
7557 -funsafe-math-optimizations. */
7561 {
7566 /* Split both trees into variables, constants, and literals. Then
7567 associate each group together, the constants with literals,
7568 then the result with variables. This increases the chances of
7569 literals being recombined later and of generating relocatable
7570 expressions for the sum of a constant and literal. */
7575 /* With undefined overflow we can only associate constants
7576 with one variable. */
7581 {
7589 /* The only case we can still associate with two variables
7590 is if they are the same, modulo negation. */
7593 }
7595 /* Only do something if we found more than two objects. Otherwise,
7596 nothing has changed and we risk infinite recursion. */
7602 {
7603 /* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
7612 /* Preserve the MINUS_EXPR if the negative part of the literal is
7613 greater than the positive part. Otherwise, the multiplicative
7614 folding code (i.e extract_muldiv) may be fooled in case
7615 unsigned constants are subtracted, like in the following
7616 example: ((X*2 + 4) - 8U)/2. */
7618 {
7622 {
7626 }
7627 else
7628 {
7632 }
7633 }
7635 {
7640 else
7641 {
7647 }
7648 }
7653 }
7654 }
7656 binary:
7660 {
7661 /* The return value should always have
7662 the same type as the original expression. */
7667 }
7671 /* A - (-B) -> A + B */
7674 /* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
7682 /* Convert -A - 1 to ~A. */
7688 /* Convert -1 - A to ~A. */
7694 {
7700 /* Fold A - (A & B) into ~B & A. */
7703 {
7708 arg0);
7713 arg0);
7714 }
7716 /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
7717 any power of 2 minus 1. */
7722 {
7728 {
7732 }
7733 }
7734 }
7736 /* See if ARG1 is zero and X - ARG1 reduces to X. */
7740 /* (ARG0 - ARG1) is the same as (-ARG1 + ARG0). So check whether
7741 ARG0 is zero and X + ARG0 reduces to X, since that would mean
7742 (-ARG1 + ARG0) reduces to -ARG1. */
7746 /* Fold &x - &x. This can happen from &x.foo - &x.
7747 This is unsafe for certain floats even in non-IEEE formats.
7748 In IEEE, it is unsafe because it does wrong for NaNs.
7749 Also note that operand_equal_p is always false if an operand
7750 is volatile. */
7756 /* A - B -> A + (-B) if B is easily negatable. */
7759 /* Avoid this transformation if B is a positive REAL_CST. */
7767 /* Try folding difference of addresses. */
7768 {
7769 HOST_WIDE_INT diff;
7775 }
7777 /* Fold &a[i] - &a[j] to i-j. */
7782 {
7787 {
7795 }
7796 }
7798 /* Try replacing &a[i1] - c * i2 with &a[i1 - i2], if c is step
7799 of the array. Loop optimizer sometimes produce this type of
7800 expressions. */
7802 {
7806 }
7817 {
7818 /* (A * C) - (B * C) -> (A-B) * C. */
7826 /* (A * C1) - (A * C2) -> A * (C1-C2). */
7834 }
7839 /* (-A) * (-B) -> A * B */
7850 {
7855 /* Transform x * -1 into -x. */
7859 /* (a * (1 << b)) is (a << b) */
7875 }
7876 else
7877 {
7878 /* Maybe fold x * 0 to 0. The expressions aren't the same
7879 when x is NaN, since x * 0 is also NaN. Nor are they the
7880 same in modes with signed zeros, since multiplying a
7881 negative value by 0 gives -0, not +0. */
7886 /* In IEEE floating point, x*1 is not equivalent to x for snans. */
7891 /* Transform x * -1.0 into -x. */
7896 /* Convert (C1/X)*C2 into (C1*C2)/X. */
7901 {
7907 }
7909 /* Strip sign operations from X in X*X, i.e. -Y*-Y -> Y*Y. */
7911 {
7914 {
7917 }
7918 }
7921 {
7925 /* Optimizations of root(...)*root(...). */
7927 {
7932 /* Optimize sqrt(x)*sqrt(x) as x. */
7938 /* Optimize root(x)*root(y) as root(x*y). */
7943 }
7945 /* Optimize expN(x)*expN(y) as expN(x+y). */
7947 {
7954 }
7956 /* Optimizations of pow(...)*pow(...). */
7960 {
7968 /* Optimize pow(x,y)*pow(z,y) as pow(x*z,y). */
7970 {
7975 arg01));
7977 }
7979 /* Optimize pow(x,y)*pow(x,z) as pow(x,y+z). */
7981 {
7986 arg));
7988 }
7989 }
7991 /* Optimize tan(x)*cos(x) as sin(x). */
8000 {
8006 }
8008 /* Optimize x*pow(x,c) as pow(x,c+1). */
8012 {
8019 {
8021 REAL_VALUE_TYPE c;
8030 }
8031 }
8033 /* Optimize pow(x,c)*x as pow(x,c+1). */
8037 {
8044 {
8046 REAL_VALUE_TYPE c;
8055 }
8056 }
8058 /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
8061 {
8065 {
8070 }
8071 }
8072 }
8073 }
8077 bit_ior:
8085 /* ~X | X is -1. */
8089 {
8093 }
8095 /* X | ~X is -1. */
8099 {
8103 }
8105 /* Canonicalize (X & C1) | C2. */
8109 {
8117 /* If (C1&C2) == C1, then (X&C1)|C2 becomes (X,C2). */
8122 {
8126 }
8127 else
8128 {
8132 }
8134 /* If (C1|C2) == ~0 then (X&C1)|C2 becomes X|C2. */
8139 /* Minimize the number of bits set in C1, i.e. C1 := C1 & ~C2. */
8149 arg1);
8150 }
8156 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
8158 This results in more efficient code for machines without a NAND
8159 instruction. Combine will canonicalize to the first form
8160 which will allow use of NAND instructions provided by the
8161 backend if they exist. */
8164 {
8169 }
8171 /* See if this can be simplified into a rotate first. If that
8172 is unsuccessful continue in the association code. */
8183 /* ~X ^ X is -1. */
8187 {
8191 }
8193 /* X ^ ~X is -1. */
8197 {
8201 }
8203 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
8204 with a constant, and the two constants have no bits in common,
8205 we should treat this as a BIT_IOR_EXPR since this may produce more
8206 simplifications. */
8214 {
8217 }
8219 /* (X | Y) ^ X -> Y & ~ X*/
8222 {
8225 arg1);
8229 }
8231 /* (Y | X) ^ X -> Y & ~ X*/
8234 {
8237 arg1);
8241 }
8243 /* X ^ (X | Y) -> Y & ~ X*/
8246 {
8249 arg0);
8253 }
8255 /* X ^ (Y | X) -> Y & ~ X*/
8258 {
8261 arg0);
8265 }
8267 /* Convert ~X ^ ~Y to X ^ Y. */
8274 /* See if this can be simplified into a rotate first. If that
8275 is unsuccessful continue in the association code. */
8286 /* ~X & X is always zero. */
8291 /* X & ~X is always zero. */
8296 /* Canonicalize (X | C1) & C2 as (X & C2) | (C1 & C2). */
8309 /* Simplify ((int)c & 0377) into (int)c, if c is unsigned char. */
8312 {
8313 unsigned int prec
8320 }
8322 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
8324 This results in more efficient code for machines without a NOR
8325 instruction. Combine will canonicalize to the first form
8326 which will allow use of NOR instructions provided by the
8327 backend if they exist. */
8330 {
8335 }
8340 /* Don't touch a floating-point divide by zero unless the mode
8341 of the constant can represent infinity. */
8347 /* (-A) / (-B) -> A / B */
8357 /* In IEEE floating point, x/1 is not equivalent to x for snans. */
8362 /* In IEEE floating point, x/-1 is not equivalent to -x for snans. */
8367 /* If ARG1 is a constant, we can convert this to a multiply by the
8368 reciprocal. This does not have the same rounding properties,
8369 so only do this if -funsafe-math-optimizations. We can actually
8370 always safely do it if ARG1 is a power of two, but it's hard to
8371 tell if it is or not in a portable manner. */
8373 {
8378 /* Find the reciprocal if optimizing and the result is exact. */
8380 {
8381 REAL_VALUE_TYPE r;
8384 {
8388 }
8389 }
8390 }
8391 /* Convert A/B/C to A/(B*C). */
8398 /* Convert A/(B/C) to (A/B)*C. */
8406 /* Convert C1/(X*C2) into (C1/C2)/X. */
8411 {
8417 }
8420 {
8422 /* Optimize x/expN(y) into x*expN(-y). */
8424 {
8431 }
8433 /* Optimize x/pow(y,z) into x*pow(y,-z). */
8437 {
8446 }
8447 }
8450 {
8454 /* Optimize sin(x)/cos(x) as tan(x). */
8460 {
8466 }
8468 /* Optimize cos(x)/sin(x) as 1.0/tan(x). */
8474 {
8478 {
8483 }
8484 }
8486 /* Optimize pow(x,c)/x as pow(x,c-1). */
8490 {
8496 {
8498 REAL_VALUE_TYPE c;
8507 }
8508 }
8509 }
8521 /* X / -1 is -X. */
8528 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
8529 operation, EXACT_DIV_EXPR.
8531 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
8532 At one time others generated faster code, it's not clear if they do
8533 after the last round to changes to the DIV code in expmed.c. */
8548 /* X % 1 is always zero, but be sure to preserve any side
8549 effects in X. */
8553 /* X % 0, return X % 0 unchanged so that we can get the
8554 proper warnings and errors. */
8558 /* 0 % X is always zero, but be sure to preserve any side
8559 effects in X. Place this after checking for X == 0. */
8563 /* X % -1 is zero. */
8570 /* Optimize TRUNC_MOD_EXPR by a power of two into a BIT_AND_EXPR,
8571 i.e. "X % C" into "X & C2", if X and C are positive. */
8575 {
8577 tree mask;
8582 {
8586 }
8587 else
8588 {
8591 }
8596 }
8598 /* X % -C is the same as X % C. */
8604 && !flag_trapv
8605 /* Avoid this transformation if C is INT_MIN, i.e. C == -C. */
8610 /* X % -Y is the same as X % Y. */
8631 /* Optimize -1 >> x for arithmetic right shifts. */
8634 /* ... fall through ... */
8637 shift:
8643 /* Since negative shift count is not well-defined,
8644 don't try to compute it in the compiler. */
8648 /* Turn (a OP c1) OP c2 into a OP (c1+c2). */
8653 {
8657 /* Deal with a OP (c1 + c2) being undefined but (a OP c1) OP c2
8658 being well defined. */
8660 {
8665 else
8667 }
8671 }
8673 /* Transform (x >> c) << c into x & (-1<<c), or transform (x << c) >> c
8674 into x & ((unsigned)-1 >> c) for unsigned types. */
8682 {
8685 tree lshift;
8686 tree arg00;
8689 {
8696 }
8697 }
8699 /* Rewrite an LROTATE_EXPR by a constant into an
8700 RROTATE_EXPR by a new constant. */
8702 {
8708 }
8710 /* If we have a rotate of a bit operation with the rotate count and
8711 the second operand of the bit operation both constant,
8712 permute the two operations. */
8724 /* Two consecutive rotates adding up to the width of the mode can
8725 be ignored. */
8756 /* Note that the operands of this must be ints
8757 and their values must be 0 or 1.
8758 ("true" is a fixed value perhaps depending on the language.) */
8759 /* If first arg is constant zero, return it. */
8763 /* If either arg is constant true, drop it. */
8767 /* Preserve sequence points. */
8770 /* If second arg is constant zero, result is zero, but first arg
8771 must be evaluated. */
8774 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
8775 case will be handled here. */
8779 /* !X && X is always false. */
8783 /* X && !X is always false. */
8788 /* A < X && A + 1 > Y ==> A < X && A >= Y. Normally A + 1 > Y
8789 means A >= Y && A != MAX, but in this case we know that
8790 A < X <= MAX. */
8794 {
8802 }
8804 truth_andor:
8805 /* We only do these simplifications if we are optimizing. */
8809 /* Check for things like (A || B) && (A || C). We can convert this
8810 to A || (B && C). Note that either operator can be any of the four
8811 truth and/or operations and the transformation will still be
8812 valid. Also note that we only care about order for the
8813 ANDIF and ORIF operators. If B contains side effects, this
8814 might change the truth-value of A. */
8821 {
8841 /* This case if tricky because we must either have commutative
8842 operators or else A10 must not have side-effects. */
8848 a01);
8849 }
8851 /* See if we can build a range comparison. */
8855 /* Check for the possibility of merging component references. If our
8856 lhs is another similar operation, try to merge its rhs with our
8857 rhs. Then try to merge our lhs and rhs. */
8869 /* Note that the operands of this must be ints
8870 and their values must be 0 or true.
8871 ("true" is a fixed value perhaps depending on the language.) */
8872 /* If first arg is constant true, return it. */
8876 /* If either arg is constant zero, drop it. */
8880 /* Preserve sequence points. */
8883 /* If second arg is constant true, result is true, but we must
8884 evaluate first arg. */
8887 /* Likewise for first arg, but note this only occurs here for
8888 TRUTH_OR_EXPR. */
8892 /* !X || X is always true. */
8896 /* X || !X is always true. */
8904 /* If the second arg is constant zero, drop it. */
8907 /* If the second arg is constant true, this is a logical inversion. */
8909 {
8910 /* Only call invert_truthvalue if operand is a truth value. */
8913 else
8916 }
8917 /* Identical arguments cancel to zero. */
8921 /* !X ^ X is always true. */
8926 /* X ^ !X is always true. */
8939 /* If one arg is a real or integer constant, put it last. */
8943 /* bool_var != 0 becomes bool_var. */
8948 /* bool_var == 1 becomes bool_var. */
8953 /* If this is an equality comparison of the address of a non-weak
8954 object against zero, then we know the result. */
8962 /* If this is an equality comparison of the address of two non-weak,
8963 unaliased symbols neither of which are extern (since we do not
8964 have access to attributes for externs), then we know the result. */
8978 {
8979 /* We know that we're looking at the address of two
8980 non-weak, unaliased, static _DECL nodes.
8982 It is both wasteful and incorrect to call operand_equal_p
8983 to compare the two ADDR_EXPR nodes. It is wasteful in that
8984 all we need to do is test pointer equality for the arguments
8985 to the two ADDR_EXPR nodes. It is incorrect to use
8986 operand_equal_p as that function is NOT equivalent to a
8987 C equality test. It can in fact return false for two
8988 objects which would test as equal using the C equality
8989 operator. */
8993 type);
8994 }
8996 /* If this is a comparison of two exprs that look like an
8997 ARRAY_REF of the same object, then we can fold this to a
8998 comparison of the two offsets. This is only safe for
8999 EQ_EXPR and NE_EXPR because of overflow issues. */
9001 {
9007 {
9008 /* Handle no offsets on both sides specially. */
9012 integer_zero_node);
9016 {
9022 }
9023 }
9024 }
9026 /* Transform comparisons of the form X +- C CMP X. */
9035 {
9042 else
9045 /* (X - c) > X becomes false. */
9051 /* Likewise (X + c) < X becomes false. */
9057 /* Convert (X - c) <= X to true. */
9064 /* Convert (X + c) >= X to true. */
9072 {
9073 /* Convert X + c > X and X - c < X to true for integers. */
9084 /* Convert X + c <= X and X - c >= X to false for integers. */
9094 }
9095 }
9097 /* Transform comparisons of the form X +- C1 CMP C2 to X CMP C2 +- C1. */
9105 {
9109 tree lhs;
9119 }
9122 {
9130 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
9135 /* (-a) CMP (-b) -> b CMP a */
9142 {
9143 REAL_VALUE_TYPE cst;
9146 /* (-a) CMP CST -> a swap(CMP) (-CST) */
9148 return
9154 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
9155 /* a CMP (-0) -> a CMP 0 */
9160 /* x != NaN is always true, other ops are always false. */
9163 {
9166 }
9168 /* Fold comparisons against infinity. */
9170 {
9174 }
9175 }
9177 /* If this is a comparison of a real constant with a PLUS_EXPR
9178 or a MINUS_EXPR of a real constant, we can convert it into a
9179 comparison with a revised real constant as long as no overflow
9180 occurs when unsafe_math_optimizations are enabled. */
9192 /* Likewise, we can simplify a comparison of a real constant with
9193 a MINUS_EXPR whose first operand is also a real constant, i.e.
9194 (c1 - x) < c2 becomes x > c1-c2. */
9205 /* Fold comparisons against built-in math functions. */
9207 && flag_unsafe_math_optimizations
9209 {
9213 {
9217 }
9218 }
9219 }
9221 /* Convert foo++ == CONST into ++foo == CONST + INCR. */
9225 /* This optimization is invalid for ordered comparisons
9226 if CONST+INCR overflows or if foo+incr might overflow.
9227 This optimization is invalid for floating point due to rounding.
9228 For pointer types we assume overflow doesn't happen. */
9232 {
9236 {
9242 }
9243 else
9244 {
9250 }
9253 /* If VAROP is a reference to a bitfield, we must mask
9254 the constant by the width of the field. */
9259 {
9264 /* First check whether the comparison would come out
9265 always the same. If we don't do that we would
9266 change the meaning with the masking. */
9280 }
9283 }
9285 /* Change X >= C to X > (C - 1) and X < C to X <= (C - 1) if C > 0.
9286 This transformation affects the cases which are handled in later
9287 optimizations involving comparisons with non-negative constants. */
9291 {
9293 {
9308 }
9309 }
9311 /* Comparisons with the highest or lowest possible integer of
9312 the specified size will have known values. */
9313 {
9321 {
9322 HOST_WIDE_INT signed_max_hi;
9327 {
9334 {
9338 }
9339 else
9340 {
9344 }
9345 }
9346 else
9347 {
9356 {
9359 }
9360 else
9361 {
9364 }
9365 }
9370 {
9383 /* The GE_EXPR and LT_EXPR cases above are not normally
9384 reached because of previous transformations. */
9388 }
9390 == max_hi
9393 {
9398 arg1);
9403 arg1);
9406 }
9408 == min_hi
9411 {
9426 }
9428 == min_hi
9431 {
9436 arg1);
9441 arg1);
9444 }
9450 /* signed_type does not work on pointer types. */
9452 {
9453 /* The following case also applies to X < signed_max+1
9454 and X >= signed_max+1 because previous transformations. */
9456 {
9457 tree st;
9462 }
9463 }
9464 }
9465 }
9467 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
9468 a MINUS_EXPR of a constant, we can convert it into a comparison with
9469 a revised constant as long as no overflow occurs. */
9482 /* Similarly for a NEGATE_EXPR. */
9491 /* If we have X - Y == 0, we can convert that to X == Y and similarly
9492 for !=. Don't do this for ordered comparisons due to overflow. */
9501 {
9502 /* If we are widening one operand of an integer comparison,
9503 see if the other operand is similarly being widened. Perhaps we
9504 can do the comparison in the narrower type. */
9509 /* Or if we are changing signedness. */
9513 }
9515 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
9516 constant, we can simplify it. */
9521 {
9527 }
9529 /* If we are comparing an ABS_EXPR with a constant, we can
9530 convert all the cases into explicit comparisons, but they may
9531 well not be faster than doing the ABS and one comparison.
9532 But ABS (X) <= C is a range comparison, which becomes a subtraction
9533 and a comparison, and is probably faster. */
9546 /* Convert ABS_EXPR<x> >= 0 to true. */
9554 /* Convert ABS_EXPR<x> < 0 to false. */
9560 /* Convert ABS_EXPR<x> == 0 or ABS_EXPR<x> != 0 to x == 0 or x != 0. */
9566 /* If this is an EQ or NE comparison with zero and ARG0 is
9567 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
9568 two operations, but the latter can be done in one less insn
9569 on machines that have only two-operand insns or on which a
9570 constant cannot be the first operand. */
9573 {
9578 {
9585 }
9588 {
9595 }
9596 }
9598 /* If this is an NE or EQ comparison of zero against the result of a
9599 signed MOD operation whose second operand is a power of 2, make
9600 the MOD operation unsigned since it is simpler and equivalent. */
9609 {
9619 }
9621 /* If this is an NE comparison of zero with an AND of one, remove the
9622 comparison since the AND will give the correct value. */
9628 /* If we have (A & C) == C where C is a power of 2, convert this into
9629 (A & C) != 0. Similarly for NE_EXPR. */
9636 integer_zero_node));
9638 /* If we have (A & C) != 0 or (A & C) == 0 and C is the sign
9639 bit, then fold the expression into A < 0 or A >= 0. */
9644 /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
9645 Similarly for NE_EXPR. */
9650 {
9659 }
9661 /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
9662 Similarly for NE_EXPR. */
9667 {
9674 }
9676 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
9677 and similarly for >= into !=. */
9693 return
9701 /* Simplify comparison of something with itself. (For IEEE
9702 floating-point, we can only do some of these simplifications.) */
9704 {
9706 {
9721 /* For NE, we can only do this simplification if integer
9722 or we don't honor IEEE floating point NaNs. */
9726 /* ... fall through ... */
9732 }
9733 }
9735 /* If we are comparing an expression that just has comparisons
9736 of two integer values, arithmetic expressions of those comparisons,
9737 and constants, we can simplify it. There are only three cases
9738 to check: the two values can either be equal, the first can be
9739 greater, or the second can be greater. Fold the expression for
9740 those three values. Since each value must be 0 or 1, we have
9741 eight possibilities, each of which corresponds to the constant 0
9742 or 1 or one of the six possible comparisons.
9744 This handles common cases like (a > b) == 0 but also handles
9745 expressions like ((x > y) - (y > x)) > 0, which supposedly
9746 occur in macroized code. */
9749 {
9754 /* Don't handle degenerate cases here; they should already
9755 have been handled anyway. */
9764 {
9768 /* We can't just pass T to eval_subst in case cval1 or cval2
9769 was the same as ARG1. */
9771 tree high_result
9775 arg1);
9776 tree equal_result
9780 arg1);
9781 tree low_result
9785 arg1);
9787 /* All three of these results should be 0 or 1. Confirm they
9788 are. Then use those values to select the proper code
9789 to use. */
9797 {
9798 /* Make a 3-bit mask with the high-order bit being the
9799 value for `>', the next for '=', and the low for '<'. */
9803 {
9805 /* Always false. */
9826 /* Always true. */
9828 }
9832 else
9834 }
9835 }
9836 }
9838 /* If this is a comparison of a field, we may be able to simplify it. */
9843 /* Handle the constant case even without -O
9844 to make sure the warnings are given. */
9846 {
9850 }
9852 /* Fold a comparison of the address of COMPONENT_REFs with the same
9853 type and component to a comparison of the address of the base
9854 object. In short, &x->a OP &y->a to x OP y and
9855 &x->a OP &y.a to x OP &y */
9860 {
9864 {
9870 }
9871 }
9873 /* Optimize comparisons of strlen vs zero to a compare of the
9874 first character of the string vs zero. To wit,
9875 strlen(ptr) == 0 => *ptr == 0
9876 strlen(ptr) != 0 => *ptr != 0
9877 Other cases should reduce to one of these two (or a constant)
9878 due to the return value of strlen being unsigned. */
9882 {
9884 tree arglist;
9892 {
9896 }
9897 }
9899 /* We can fold X/C1 op C2 where C1 and C2 are integer constants
9900 into a single range test. */
9908 {
9912 }
9917 {
9920 }
9934 {
9938 }
9940 /* If the first operand is NaN, the result is constant. */
9944 {
9946 ? integer_zero_node
9949 }
9951 /* If the second operand is NaN, the result is constant. */
9955 {
9957 ? integer_zero_node
9960 }
9962 /* Simplify unordered comparison of something with itself. */
9968 && !flag_trapping_math
9972 /* Fold (double)float1 CMP (double)float2 into float1 CMP float2. */
9973 {
9984 }
9989 /* When pedantic, a compound expression can be neither an lvalue
9990 nor an integer constant expression. */
9993 /* Don't let (0, 0) be null pointer constant. */
10004 /* An ASSERT_EXPR should never be passed to fold_binary. */
10010 }
10012 /* Callback for walk_tree, looking for LABEL_EXPR.
10013 Returns tree TP if it is LABEL_EXPR. Otherwise it returns NULL_TREE.
10014 Do not check the sub-tree of GOTO_EXPR. */
10016 static tree
10020 {
10022 {
10027 /* no break */
10030 }
10031 }
10033 /* Checks whether the sub-tree ST contains a label LABEL_EXPR which is
10034 accessible from outside the sub-tree. Returns NULL_TREE if no
10035 addressable label is found. */
10037 static bool
10039 {
10041 }
10043 /* Fold a ternary expression of code CODE and type TYPE with operands
10044 OP0, OP1, and OP2. Return the folded expression if folding is
10045 successful. Otherwise, return NULL_TREE. */
10047 tree
10049 {
10050 tree tem;
10057 /* Strip any conversions that don't change the mode. This is safe
10058 for every expression, except for a comparison expression because
10059 its signedness is derived from its operands. So, in the latter
10060 case, only strip conversions that don't change the signedness.
10062 Note that this is done as an internal manipulation within the
10063 constant folder, in order to find the simplest representation of
10064 the arguments so that their form can be studied. In any cases,
10065 the appropriate type conversions should be put back in the tree
10066 that will get out of the constant folder. */
10068 {
10071 }
10074 {
10077 }
10080 {
10084 {
10090 }
10094 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
10095 so all simple results must be passed through pedantic_non_lvalue. */
10097 {
10100 /* Only optimize constant conditions when the selected branch
10101 has the same type as the COND_EXPR. This avoids optimizing
10102 away "c ? x : throw", where the throw has a void type.
10103 Avoid throwing away that operand which contains label. */
10110 }
10114 /* If we have A op B ? A : C, we may be able to convert this to a
10115 simpler expression, depending on the operation and the values
10116 of B and C. Signed zeros prevent all of these transformations,
10117 for reasons given above each one.
10119 Also try swapping the arguments and inverting the conditional. */
10124 {
10128 }
10132 op2,
10135 {
10138 {
10142 }
10143 }
10145 /* If the second operand is simpler than the third, swap them
10146 since that produces better jump optimization results. */
10149 {
10150 /* See if this can be inverted. If it can't, possibly because
10151 it was a floating-point inequality comparison, don't do
10152 anything. */
10157 }
10159 /* Convert A ? 1 : 0 to simply A. */
10162 /* If we try to convert OP0 to our type, the
10163 call to fold will try to move the conversion inside
10164 a COND, which will recurse. In that case, the COND_EXPR
10165 is probably the best choice, so leave it alone. */
10169 /* Convert A ? 0 : 1 to !A. This prefers the use of NOT_EXPR
10170 over COND_EXPR in cases such as floating point comparisons. */
10177 /* A < 0 ? <sign bit of A> : 0 is simply (A & <sign bit of A>). */
10182 {
10183 /* sign_bit_p only checks ARG1 bits within A's precision.
10184 If <sign bit of A> has wider type than A, bits outside
10185 of A's precision in <sign bit of A> need to be checked.
10186 If they are all 0, this optimization needs to be done
10187 in unsigned A's type, if they are all 1 in signed A's type,
10188 otherwise this can't be done. */
10193 {
10195 HOST_WIDE_INT mask_hi;
10197 tree tem_type;
10205 {
10209 }
10210 else
10211 {
10215 }
10217 {
10221 }
10222 else
10228 {
10231 }
10234 {
10237 }
10238 else
10240 }
10247 arg1)));
10248 }
10250 /* (A >> N) & 1 ? (1 << N) : 0 is simply A & (1 << N). A & 1 was
10251 already handled above. */
10256 {
10265 }
10267 /* A & N ? N : 0 is simply A & N if N is a power of two. This
10268 is probably obsolete because the first operand should be a
10269 truth value (that's why we have the two cases above), but let's
10270 leave it in until we can confirm this for all front-ends. */
10281 /* Convert A ? B : 0 into A && B if A and B are truth values. */
10287 arg1);
10289 /* Convert A ? B : 1 into !A || B if A and B are truth values. */
10293 {
10294 /* Only perform transformation if ARG0 is easily inverted. */
10299 arg1);
10300 }
10302 /* Convert A ? 0 : B into !A && B if A and B are truth values. */
10306 {
10307 /* Only perform transformation if ARG0 is easily inverted. */
10312 op2);
10313 }
10315 /* Convert A ? 1 : B into A || B if A and B are truth values. */
10321 op2);
10326 /* Check for a built-in function. */
10338 {
10347 {
10353 else
10355 }
10356 }
10362 }
10364 /* Perform constant folding and related simplification of EXPR.
10365 The related simplifications include x*1 => x, x*0 => 0, etc.,
10366 and application of the associative law.
10367 NOP_EXPR conversions may be removed freely (as long as we
10368 are careful not to change the type of the overall expression).
10369 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
10370 but we can constant-fold them if they have constant operands. */
10372 #ifdef ENABLE_FOLD_CHECKING
10373 # define fold(x) fold_1 (x)
10375 static
10376 #endif
10377 tree
10379 {
10383 tree tem;
10385 /* Return right away if a constant. */
10390 {
10395 {
10413 }
10414 }
10417 {
10424 }
10426 #ifdef ENABLE_FOLD_CHECKING
10427 #undef fold
10433 /* When --enable-checking=fold, compute a digest of expr before
10434 and after actual fold call to see if fold did not accidentally
10435 change original expr. */
10437 tree
10439 {
10440 tree ret;
10443 htab_t ht;
10462 }
10464 void
10466 {
10469 htab_t ht;
10479 }
10481 static void
10483 {
10485 }
10487 static void
10489 {
10495 recursive_label:
10509 {
10510 /* Allow DECL_ASSEMBLER_NAME to be modified. */
10514 }
10519 {
10520 /* Allow these fields to be modified. */
10527 {
10530 }
10531 }
10539 {
10542 {
10556 }
10560 {
10573 }
10597 {
10601 }
10612 {
10615 }
10625 }
10626 }
10628 #endif
10630 /* Fold a unary tree expression with code CODE of type TYPE with an
10631 operand OP0. Return a folded expression if successful. Otherwise,
10632 return a tree expression with code CODE of type TYPE with an
10633 operand OP0. */
10635 tree
10637 {
10638 tree tem;
10639 #ifdef ENABLE_FOLD_CHECKING
10642 htab_t ht;
10649 #endif
10655 #ifdef ENABLE_FOLD_CHECKING
10663 #endif
10665 }
10667 /* Fold a binary tree expression with code CODE of type TYPE with
10668 operands OP0 and OP1. Return a folded expression if successful.
10669 Otherwise, return a tree expression with code CODE of type TYPE
10670 with operands OP0 and OP1. */
10672 tree
10674 MEM_STAT_DECL)
10675 {
10676 tree tem;
10677 #ifdef ENABLE_FOLD_CHECKING
10683 htab_t ht;
10695 #endif
10701 #ifdef ENABLE_FOLD_CHECKING
10717 #endif
10719 }
10721 /* Fold a ternary tree expression with code CODE of type TYPE with
10722 operands OP0, OP1, and OP2. Return a folded expression if
10723 successful. Otherwise, return a tree expression with code CODE of
10724 type TYPE with operands OP0, OP1, and OP2. */
10726 tree
10728 MEM_STAT_DECL)
10729 {
10730 tree tem;
10731 #ifdef ENABLE_FOLD_CHECKING
10739 htab_t ht;
10756 #endif
10762 #ifdef ENABLE_FOLD_CHECKING
10786 #endif
10788 }
10790 /* Perform constant folding and related simplification of initializer
10791 expression EXPR. These behave identically to "fold_buildN" but ignore
10792 potential run-time traps and exceptions that fold must preserve. */
10794 #define START_FOLD_INIT \
10795 int saved_signaling_nans = flag_signaling_nans;\
10796 int saved_trapping_math = flag_trapping_math;\
10797 int saved_rounding_math = flag_rounding_math;\
10798 int saved_trapv = flag_trapv;\
10799 flag_signaling_nans = 0;\
10800 flag_trapping_math = 0;\
10801 flag_rounding_math = 0;\
10802 flag_trapv = 0
10804 #define END_FOLD_INIT \
10805 flag_signaling_nans = saved_signaling_nans;\
10806 flag_trapping_math = saved_trapping_math;\
10807 flag_rounding_math = saved_rounding_math;\
10808 flag_trapv = saved_trapv
10810 tree
10812 {
10813 tree result;
10814 START_FOLD_INIT;
10818 END_FOLD_INIT;
10820 }
10822 tree
10824 {
10825 tree result;
10826 START_FOLD_INIT;
10830 END_FOLD_INIT;
10832 }
10834 tree
10836 tree op2)
10837 {
10838 tree result;
10839 START_FOLD_INIT;
10843 END_FOLD_INIT;
10845 }
10847 #undef START_FOLD_INIT
10848 #undef END_FOLD_INIT
10850 /* Determine if first argument is a multiple of second argument. Return 0 if
10851 it is not, or we cannot easily determined it to be.
10853 An example of the sort of thing we care about (at this point; this routine
10854 could surely be made more general, and expanded to do what the *_DIV_EXPR's
10855 fold cases do now) is discovering that
10857 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
10859 is a multiple of
10861 SAVE_EXPR (J * 8)
10863 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
10865 This code also handles discovering that
10867 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
10869 is a multiple of 8 so we don't have to worry about dealing with a
10870 possible remainder.
10872 Note that we *look* inside a SAVE_EXPR only to determine how it was
10873 calculated; it is not safe for fold to do much of anything else with the
10874 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
10875 at run time. For example, the latter example above *cannot* be implemented
10876 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
10877 evaluation time of the original SAVE_EXPR is not necessarily the same at
10878 the time the new expression is evaluated. The only optimization of this
10879 sort that would be valid is changing
10881 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
10883 divided by 8 to
10885 SAVE_EXPR (I) * SAVE_EXPR (J)
10887 (where the same SAVE_EXPR (J) is used in the original and the
10888 transformed version). */
10890 static int
10892 {
10900 {
10902 /* Bitwise and provides a power of two multiple. If the mask is
10903 a multiple of BOTTOM then TOP is a multiple of BOTTOM. */
10906 /* FALLTHRU */
10919 {
10923 /* const_binop may not detect overflow correctly,
10924 so check for it explicitly here. */
10930 size_one_node,
10934 }
10938 /* Can't handle conversions from non-integral or wider integral type. */
10944 /* .. fall through ... */
10960 }
10961 }
10963 /* Return true if `t' is known to be non-negative. */
10965 int
10967 {
10975 {
10977 /* We can't return 1 if flag_wrapv is set because
10978 ABS_EXPR<INT_MIN> = INT_MIN. */
10994 /* zero_extend(x) + zero_extend(y) is non-negative if x and y are
10995 both unsigned and at least 2 bits shorter than the result. */
10999 {
11004 {
11008 }
11009 }
11014 {
11015 /* x * x for floating point x is always non-negative. */
11020 }
11022 /* zero_extend(x) * zero_extend(y) is non-negative if x and y are
11023 both unsigned and their total bits is shorter than the result. */
11027 {
11034 }
11074 {
11079 {
11083 {
11087 }
11088 }
11090 {
11096 }
11097 }
11101 {
11105 /* If the initializer is non-void, then it's a normal expression
11106 that will be assigned to the slot. */
11110 /* Otherwise, the initializer sets the slot in some way. One common
11111 way is an assignment statement at the end of the initializer. */
11113 {
11121 else
11123 }
11129 }
11132 {
11137 {
11138 #define CASE_BUILTIN_F(BUILT_IN_FN) \
11139 case BUILT_IN_FN: case BUILT_IN_FN##F: case BUILT_IN_FN##L:
11140 #define CASE_BUILTIN_I(BUILT_IN_FN) \
11141 case BUILT_IN_FN: case BUILT_IN_FN##L: case BUILT_IN_FN##LL:
11158 /* Always true. */
11162 /* sqrt(-0.0) is -0.0. */
11195 /* True if the 1st argument is nonnegative. */
11199 /* True if the 1st OR 2nd arguments are nonnegative. */
11204 /* True if the 1st AND 2nd arguments are nonnegative. */
11209 /* True if the 2nd argument is nonnegative. */
11214 #undef CASE_BUILTIN_F
11215 #undef CASE_BUILTIN_I
11216 }
11217 }
11219 /* ... fall through ... */
11223 /* Truth values evaluate to 0 or 1, which is nonnegative. */
11225 }
11227 /* We don't know sign of `t', so be conservative and return false. */
11229 }
11231 /* Return true when T is an address and is known to be nonzero.
11232 For floating point we further ensure that T is not denormal.
11233 Similar logic is present in nonzero_address in rtlanal.h. */
11235 bool
11237 {
11240 /* Doing something useful for floating point would need more work. */
11245 {
11250 /* We used to test for !integer_zerop here. This does not work correctly
11251 if TREE_CONSTANT_OVERFLOW (t). */
11257 {
11258 /* With the presence of negative values it is hard
11259 to say something. */
11263 /* One of operands must be positive and the other non-negative. */
11266 }
11271 {
11274 }
11278 {
11284 }
11288 {
11294 /* Weak declarations may link to NULL. */
11298 /* Constants are never weak. */
11303 }
11315 {
11316 /* When both operands are nonzero, then MAX must be too. */
11320 /* MAX where operand 0 is positive is positive. */
11322 }
11323 /* MAX where operand 1 is positive is positive. */
11347 }
11349 }
11351 /* Given the components of a binary expression CODE, TYPE, OP0 and OP1,
11352 attempt to fold the expression to a constant without modifying TYPE,
11353 OP0 or OP1.
11355 If the expression could be simplified to a constant, then return
11356 the constant. If the expression would not be simplified to a
11357 constant, then return NULL_TREE. */
11359 tree
11361 {
11364 }
11366 /* Given the components of a unary expression CODE, TYPE and OP0,
11367 attempt to fold the expression to a constant without modifying
11368 TYPE or OP0.
11370 If the expression could be simplified to a constant, then return
11371 the constant. If the expression would not be simplified to a
11372 constant, then return NULL_TREE. */
11374 tree
11376 {
11379 }
11381 /* If EXP represents referencing an element in a constant string
11382 (either via pointer arithmetic or array indexing), return the
11383 tree representing the value accessed, otherwise return NULL. */
11385 tree
11387 {
11389 {
11391 tree index;
11392 tree string;
11396 else
11397 {
11401 /* Optimize the special-case of a zero lower bound.
11403 We convert the low_bound to sizetype to avoid some problems
11404 with constant folding. (E.g. suppose the lower bound is 1,
11405 and its mode is QI. Without the conversion,l (ARRAY
11406 +(INDEX-(unsigned char)1)) becomes ((ARRAY+(-(unsigned char)1))
11407 +INDEX), which becomes (ARRAY+255+INDEX). Opps!) */
11412 }
11426 }
11428 }
11430 /* Return the tree for neg (ARG0) when ARG0 is known to be either
11431 an integer constant or real constant.
11433 TYPE is the type of the result. */
11435 static tree
11437 {
11441 {
11443 {
11445 HOST_WIDE_INT high;
11455 }
11463 }
11466 }
11468 /* Return the tree for abs (ARG0) when ARG0 is known to be either
11469 an integer constant or real constant.
11471 TYPE is the type of the result. */
11473 tree
11475 {
11479 {
11481 /* If the value is unsigned, then the absolute value is
11482 the same as the ordinary value. */
11485 /* Similarly, if the value is non-negative. */
11488 /* If the value is negative, then the absolute value is
11489 its negation. */
11490 else
11491 {
11493 HOST_WIDE_INT high;
11500 }
11506 else
11512 }
11515 }
11517 /* Return the tree for not (ARG0) when ARG0 is known to be an integer
11518 constant. TYPE is the type of the result. */
11520 static tree
11522 {
11534 }
11536 /* Given CODE, a relational operator, the target type, TYPE and two
11537 constant operands OP0 and OP1, return the result of the
11538 relational operation. If the result is not a compile time
11539 constant, then return NULL_TREE. */
11541 static tree
11543 {
11546 /* From here on, the only cases we handle are when the result is
11547 known to be a constant. */
11550 {
11554 /* Handle the cases where either operand is a NaN. */
11556 {
11558 {
11586 }
11589 }
11592 }
11594 /* Handle equality/inequality of complex constants. */
11596 {
11607 else
11609 }
11611 /* From here on we only handle LT, LE, GT, GE, EQ and NE.
11613 To compute GT, swap the arguments and do LT.
11614 To compute GE, do LT and invert the result.
11615 To compute LE, swap the arguments, do LT and invert the result.
11616 To compute NE, do EQ and invert the result.
11618 Therefore, the code below must handle only EQ and LT. */
11621 {
11626 }
11628 /* Note that it is safe to invert for real values here because we
11629 have already handled the one case that it matters. */
11633 {
11636 }
11638 /* Compute a result for LT or EQ if args permit;
11639 Otherwise return T. */
11641 {
11646 else
11648 }
11649 else
11655 }
11657 /* Build an expression for the a clean point containing EXPR with type TYPE.
11658 Don't build a cleanup point expression for EXPR which don't have side
11659 effects. */
11661 tree
11663 {
11664 /* If the expression does not have side effects then we don't have to wrap
11665 it with a cleanup point expression. */
11669 /* If the expression is a return, check to see if the expression inside the
11670 return has no side effects or the right hand side of the modify expression
11671 inside the return. If either don't have side effects set we don't need to
11672 wrap the expression in a cleanup point expression. Note we don't check the
11673 left hand side of the modify because it should always be a return decl. */
11675 {
11682 }
11685 }
11687 /* Build an expression for the address of T. Folds away INDIRECT_REF to
11688 avoid confusing the gimplify process. */
11690 tree
11692 {
11693 /* The size of the object is not relevant when talking about its address. */
11697 /* Note: doesn't apply to ALIGN_INDIRECT_REF */
11700 {
11704 }
11705 else
11706 {
11715 }
11718 }
11720 tree
11722 {
11724 }
11726 /* Given a pointer value OP0 and a type TYPE, return a simplified version
11727 of an indirection through OP0, or NULL_TREE if no simplification is
11728 possible. */
11730 tree
11732 {
11734 tree subtype;
11742 {
11745 /* *&CONST_DECL -> to the value of the const decl. */
11748 /* *&p => p */
11751 /* *(foo *)&fooarray => fooarray[0] */
11754 {
11760 }
11761 }
11763 /* *(foo *)fooarrptr => (*fooarrptr)[0] */
11766 {
11767 tree type_domain;
11774 }
11777 }
11779 /* Builds an expression for an indirection through T, simplifying some
11780 cases. */
11782 tree
11784 {
11790 else
11792 }
11794 /* Given an INDIRECT_REF T, return either T or a simplified version. */
11796 tree
11798 {
11803 else
11805 }
11807 /* Strip non-trapping, non-side-effecting tree nodes from an expression
11808 whose result is ignored. The type of the returned tree need not be
11809 the same as the original expression. */
11811 tree
11813 {
11819 {
11830 else
11836 {
11852 }
11857 }
11858 }
11860 /* Return the value of VALUE, rounded up to a multiple of DIVISOR.
11861 This can only be applied to objects of a sizetype. */
11863 tree
11865 {
11872 /* See if VALUE is already a multiple of DIVISOR. If so, we don't
11873 have to do anything. Only do this when we are not given a const,
11874 because in that case, this check is more expensive than just
11875 doing it. */
11877 {
11882 }
11884 /* If divisor is a power of two, simplify this to bit manipulation. */
11886 {
11887 tree t;
11893 }
11894 else
11895 {
11900 }
11903 }
11905 /* Likewise, but round down. */
11907 tree
11909 {
11916 /* See if VALUE is already a multiple of DIVISOR. If so, we don't
11917 have to do anything. Only do this when we are not given a const,
11918 because in that case, this check is more expensive than just
11919 doing it. */
11921 {
11926 }
11928 /* If divisor is a power of two, simplify this to bit manipulation. */
11930 {
11931 tree t;
11935 }
11936 else
11937 {
11942 }
11945 }
11947 /* Returns the pointer to the base of the object addressed by EXP and
11948 extracts the information about the offset of the access, storing it
11949 to PBITPOS and POFFSET. */
11951 static tree
11954 {
11955 tree core;
11958 HOST_WIDE_INT bitsize;
11961 {
11966 }
11967 else
11968 {
11972 }
11975 }
11977 /* Returns true if addresses of E1 and E2 differ by a constant, false
11978 otherwise. If they do, E1 - E2 is stored in *DIFF. */
11980 bool
11982 {
11996 {
12006 }
12008 {
12009 /* If only one of the offsets is non-constant, the difference cannot
12010 be a constant. */
12012 }
12013 else
12018 }
12020 /* Simplify the floating point expression EXP when the sign of the
12021 result is not significant. Return NULL_TREE if no simplification
12022 is possible. */
12024 tree
12026 {
12030 {
12050 }
12052 }