arch/x86/math-emu/reg_constant.c

   1 /*---------------------------------------------------------------------------+
   2  |  reg_constant.c                                                           |
   3  |                                                                           |
   4  | All of the constant FPU_REGs                                              |
   5  |                                                                           |
   6  | Copyright (C) 1992,1993,1994,1997                                         |
   7  |                     W. Metzenthen, 22 Parker St, Ormond, Vic 3163,        |
   8  |                     Australia.  E-mail   billm@suburbia.net               |
   9  |                                                                           |
  10  |                                                                           |
  11  +---------------------------------------------------------------------------*/
  12
  13 #include "fpu_system.h"
  14 #include "fpu_emu.h"
  15 #include "status_w.h"
  16 #include "reg_constant.h"
  17 #include "control_w.h"
  18
  19 #define MAKE_REG(s, e, l, h) { l, h, \
  20                 ((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }
  21
  22 FPU_REG const CONST_1 = MAKE_REG(POS, 0, 0x00000000, 0x80000000);
  23 #if 0
  24 FPU_REG const CONST_2 = MAKE_REG(POS, 1, 0x00000000, 0x80000000);
  25 FPU_REG const CONST_HALF = MAKE_REG(POS, -1, 0x00000000, 0x80000000);
  26 #endif /*  0  */
  27 static FPU_REG const CONST_L2T = MAKE_REG(POS, 1, 0xcd1b8afe, 0xd49a784b);
  28 static FPU_REG const CONST_L2E = MAKE_REG(POS, 0, 0x5c17f0bc, 0xb8aa3b29);
  29 FPU_REG const CONST_PI = MAKE_REG(POS, 1, 0x2168c235, 0xc90fdaa2);
  30 FPU_REG const CONST_PI2 = MAKE_REG(POS, 0, 0x2168c235, 0xc90fdaa2);
  31 FPU_REG const CONST_PI4 = MAKE_REG(POS, -1, 0x2168c235, 0xc90fdaa2);
  32 static FPU_REG const CONST_LG2 = MAKE_REG(POS, -2, 0xfbcff799, 0x9a209a84);
  33 static FPU_REG const CONST_LN2 = MAKE_REG(POS, -1, 0xd1cf79ac, 0xb17217f7);
  34
  35 /* Extra bits to take pi/2 to more than 128 bits precision. */
  36 FPU_REG const CONST_PI2extra = MAKE_REG(NEG, -66,
  37                                         0xfc8f8cbb, 0xece675d1);
  38
  39 /* Only the sign (and tag) is used in internal zeroes */
  40 FPU_REG const CONST_Z = MAKE_REG(POS, EXP_UNDER, 0x0, 0x0);
  41
  42 /* Only the sign and significand (and tag) are used in internal NaNs */
  43 /* The 80486 never generates one of these
  44 FPU_REG const CONST_SNAN = MAKE_REG(POS, EXP_OVER, 0x00000001, 0x80000000);
  45  */
  46 /* This is the real indefinite QNaN */
  47 FPU_REG const CONST_QNaN = MAKE_REG(NEG, EXP_OVER, 0x00000000, 0xC0000000);
  48
  49 /* Only the sign (and tag) is used in internal infinities */
  50 FPU_REG const CONST_INF = MAKE_REG(POS, EXP_OVER, 0x00000000, 0x80000000);
  51
  52 static void fld_const(FPU_REG const * c, int adj, u_char tag)
  53 {
  54         FPU_REG *st_new_ptr;
  55
  56         if (STACK_OVERFLOW) {
  57                 FPU_stack_overflow();
  58                 return;
  59         }
  60         push();
  61         reg_copy(c, st_new_ptr);
  62         st_new_ptr->sigl += adj;        /* For all our fldxxx constants, we don't need to
  63                                            borrow or carry. */
  64         FPU_settag0(tag);
  65         clear_C1();
  66 }
  67
  68 /* A fast way to find out whether x is one of RC_DOWN or RC_CHOP
  69    (and not one of RC_RND or RC_UP).
  70    */
  71 #define DOWN_OR_CHOP(x)  (x & RC_DOWN)
  72
  73 static void fld1(int rc)
  74 {
  75         fld_const(&CONST_1, 0, TAG_Valid);
  76 }
  77
  78 static void fldl2t(int rc)
  79 {
  80         fld_const(&CONST_L2T, (rc == RC_UP) ? 1 : 0, TAG_Valid);
  81 }
  82
  83 static void fldl2e(int rc)
  84 {
  85         fld_const(&CONST_L2E, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  86 }
  87
  88 static void fldpi(int rc)
  89 {
  90         fld_const(&CONST_PI, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  91 }
  92
  93 static void fldlg2(int rc)
  94 {
  95         fld_const(&CONST_LG2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  96 }
  97
  98 static void fldln2(int rc)
  99 {
 100         fld_const(&CONST_LN2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
 101 }
 102
 103 static void fldz(int rc)
 104 {
 105         fld_const(&CONST_Z, 0, TAG_Zero);
 106 }
 107
 108 typedef void (*FUNC_RC) (int);
 109
 110 static FUNC_RC constants_table[] = {
 111         fld1, fldl2t, fldl2e, fldpi, fldlg2, fldln2, fldz, (FUNC_RC) FPU_illegal
 112 };
 113
 114 void fconst(void)
 115 {
 116         (constants_table[FPU_rm]) (control_word & CW_RC);
 117 }