lib/Support/ConstantRange.cpp

   1 //===-- ConstantRange.cpp - ConstantRange implementation ------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file was developed by the LLVM research group and is distributed under
   6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // Represent a range of possible values that may occur when the program is run
  11 // for an integral value.  This keeps track of a lower and upper bound for the
  12 // constant, which MAY wrap around the end of the numeric range.  To do this, it
  13 // keeps track of a [lower, upper) bound, which specifies an interval just like
  14 // STL iterators.  When used with boolean values, the following are important
  15 // ranges (other integral ranges use min/max values for special range values):
  16 //
  17 //  [F, F) = {}     = Empty set
  18 //  [T, F) = {T}
  19 //  [F, T) = {F}
  20 //  [T, T) = {F, T} = Full set
  21 //
  22 //===----------------------------------------------------------------------===//
  23
  24 #include "llvm/Support/ConstantRange.h"
  25 #include "llvm/Constants.h"
  26 #include "llvm/Instruction.h"
  27 #include "llvm/Type.h"
  28 #include <iostream>
  29
  30 using namespace llvm;
  31
  32 static ConstantIntegral *Next(ConstantIntegral *CI) {
  33   if (CI->getType() == Type::BoolTy)
  34     return CI == ConstantBool::True ? ConstantBool::False : ConstantBool::True;
  35
  36   Constant *Result = ConstantExpr::getAdd(CI,
  37                                           ConstantInt::get(CI->getType(), 1));
  38   return cast<ConstantIntegral>(Result);
  39 }
  40
  41 static bool LT(ConstantIntegral *A, ConstantIntegral *B) {
  42   Constant *C = ConstantExpr::getSetLT(A, B);
  43   assert(isa<ConstantBool>(C) && "Constant folding of integrals not impl??");
  44   return cast<ConstantBool>(C)->getValue();
  45 }
  46
  47 static bool LTE(ConstantIntegral *A, ConstantIntegral *B) {
  48   Constant *C = ConstantExpr::getSetLE(A, B);
  49   assert(isa<ConstantBool>(C) && "Constant folding of integrals not impl??");
  50   return cast<ConstantBool>(C)->getValue();
  51 }
  52
  53 static bool GT(ConstantIntegral *A, ConstantIntegral *B) { return LT(B, A); }
  54
  55 static ConstantIntegral *Min(ConstantIntegral *A, ConstantIntegral *B) {
  56   return LT(A, B) ? A : B;
  57 }
  58 static ConstantIntegral *Max(ConstantIntegral *A, ConstantIntegral *B) {
  59   return GT(A, B) ? A : B;
  60 }
  61
  62 /// Initialize a full (the default) or empty set for the specified type.
  63 ///
  64 ConstantRange::ConstantRange(const Type *Ty, bool Full) {
  65   assert(Ty->isIntegral() &&
  66          "Cannot make constant range of non-integral type!");
  67   if (Full)
  68     Lower = Upper = ConstantIntegral::getMaxValue(Ty);
  69   else
  70     Lower = Upper = ConstantIntegral::getMinValue(Ty);
  71 }
  72
  73 /// Initialize a range to hold the single specified value.
  74 ///
  75 ConstantRange::ConstantRange(Constant *V)
  76   : Lower(cast<ConstantIntegral>(V)), Upper(Next(cast<ConstantIntegral>(V))) {
  77 }
  78
  79 /// Initialize a range of values explicitly... this will assert out if
  80 /// Lower==Upper and Lower != Min or Max for its type (or if the two constants
  81 /// have different types)
  82 ///
  83 ConstantRange::ConstantRange(Constant *L, Constant *U)
  84   : Lower(cast<ConstantIntegral>(L)), Upper(cast<ConstantIntegral>(U)) {
  85   assert(Lower->getType() == Upper->getType() &&
  86          "Incompatible types for ConstantRange!");
  87
  88   // Make sure that if L & U are equal that they are either Min or Max...
  89   assert((L != U || (L == ConstantIntegral::getMaxValue(L->getType()) ||
  90                      L == ConstantIntegral::getMinValue(L->getType()))) &&
  91          "Lower == Upper, but they aren't min or max for type!");
  92 }
  93
  94 /// Initialize a set of values that all satisfy the condition with C.
  95 ///
  96 ConstantRange::ConstantRange(unsigned SetCCOpcode, ConstantIntegral *C) {
  97   switch (SetCCOpcode) {
  98   default: assert(0 && "Invalid SetCC opcode to ConstantRange ctor!");
  99   case Instruction::SetEQ: Lower = C; Upper = Next(C); return;
 100   case Instruction::SetNE: Upper = C; Lower = Next(C); return;
 101   case Instruction::SetLT:
 102     Lower = ConstantIntegral::getMinValue(C->getType());
 103     Upper = C;
 104     return;
 105   case Instruction::SetGT:
 106     Lower = Next(C);
 107     Upper = ConstantIntegral::getMinValue(C->getType());  // Min = Next(Max)
 108     return;
 109   case Instruction::SetLE:
 110     Lower = ConstantIntegral::getMinValue(C->getType());
 111     Upper = Next(C);
 112     return;
 113   case Instruction::SetGE:
 114     Lower = C;
 115     Upper = ConstantIntegral::getMinValue(C->getType());  // Min = Next(Max)
 116     return;
 117   }
 118 }
 119
 120 /// getType - Return the LLVM data type of this range.
 121 ///
 122 const Type *ConstantRange::getType() const { return Lower->getType(); }
 123
 124 /// isFullSet - Return true if this set contains all of the elements possible
 125 /// for this data-type
 126 bool ConstantRange::isFullSet() const {
 127   return Lower == Upper && Lower == ConstantIntegral::getMaxValue(getType());
 128 }
 129
 130 /// isEmptySet - Return true if this set contains no members.
 131 ///
 132 bool ConstantRange::isEmptySet() const {
 133   return Lower == Upper && Lower == ConstantIntegral::getMinValue(getType());
 134 }
 135
 136 /// isWrappedSet - Return true if this set wraps around the top of the range,
 137 /// for example: [100, 8)
 138 ///
 139 bool ConstantRange::isWrappedSet() const {
 140   return GT(Lower, Upper);
 141 }
 142
 143
 144 /// getSingleElement - If this set contains a single element, return it,
 145 /// otherwise return null.
 146 ConstantIntegral *ConstantRange::getSingleElement() const {
 147   if (Upper == Next(Lower))  // Is it a single element range?
 148     return Lower;
 149   return 0;
 150 }
 151
 152 /// getSetSize - Return the number of elements in this set.
 153 ///
 154 uint64_t ConstantRange::getSetSize() const {
 155   if (isEmptySet()) return 0;
 156   if (getType() == Type::BoolTy) {
 157     if (Lower != Upper)  // One of T or F in the set...
 158       return 1;
 159     return 2;            // Must be full set...
 160   }
 161
 162   // Simply subtract the bounds...
 163   Constant *Result = ConstantExpr::getSub(Upper, Lower);
 164   return cast<ConstantInt>(Result)->getRawValue();
 165 }
 166
 167 /// contains - Return true if the specified value is in the set.
 168 ///
 169 bool ConstantRange::contains(ConstantInt *Val) const {
 170   if (Lower == Upper) {
 171     if (isFullSet()) return true;
 172     return false;
 173   }
 174
 175   if (!isWrappedSet())
 176     return LTE(Lower, Val) && LT(Val, Upper);
 177   return LTE(Lower, Val) || LT(Val, Upper);
 178 }
 179
 180
 181
 182 /// subtract - Subtract the specified constant from the endpoints of this
 183 /// constant range.
 184 ConstantRange ConstantRange::subtract(ConstantInt *CI) const {
 185   assert(CI->getType() == getType() && getType()->isInteger() &&
 186          "Cannot subtract from different type range or non-integer!");
 187   // If the set is empty or full, don't modify the endpoints.
 188   if (Lower == Upper) return *this;
 189   return ConstantRange(ConstantExpr::getSub(Lower, CI),
 190                        ConstantExpr::getSub(Upper, CI));
 191 }
 192
 193
 194 // intersect1Wrapped - This helper function is used to intersect two ranges when
 195 // it is known that LHS is wrapped and RHS isn't.
 196 //
 197 static ConstantRange intersect1Wrapped(const ConstantRange &LHS,
 198                                        const ConstantRange &RHS) {
 199   assert(LHS.isWrappedSet() && !RHS.isWrappedSet());
 200
 201   // Check to see if we overlap on the Left side of RHS...
 202   //
 203   if (LT(RHS.getLower(), LHS.getUpper())) {
 204     // We do overlap on the left side of RHS, see if we overlap on the right of
 205     // RHS...
 206     if (GT(RHS.getUpper(), LHS.getLower())) {
 207       // Ok, the result overlaps on both the left and right sides.  See if the
 208       // resultant interval will be smaller if we wrap or not...
 209       //
 210       if (LHS.getSetSize() < RHS.getSetSize())
 211         return LHS;
 212       else
 213         return RHS;
 214
 215     } else {
 216       // No overlap on the right, just on the left.
 217       return ConstantRange(RHS.getLower(), LHS.getUpper());
 218     }
 219
 220   } else {
 221     // We don't overlap on the left side of RHS, see if we overlap on the right
 222     // of RHS...
 223     if (GT(RHS.getUpper(), LHS.getLower())) {
 224       // Simple overlap...
 225       return ConstantRange(LHS.getLower(), RHS.getUpper());
 226     } else {
 227       // No overlap...
 228       return ConstantRange(LHS.getType(), false);
 229     }
 230   }
 231 }
 232
 233 /// intersect - Return the range that results from the intersection of this
 234 /// range with another range.
 235 ///
 236 ConstantRange ConstantRange::intersectWith(const ConstantRange &CR) const {
 237   assert(getType() == CR.getType() && "ConstantRange types don't agree!");
 238   // Handle common special cases
 239   if (isEmptySet() || CR.isFullSet())  return *this;
 240   if (isFullSet()  || CR.isEmptySet()) return CR;
 241
 242   if (!isWrappedSet()) {
 243     if (!CR.isWrappedSet()) {
 244       ConstantIntegral *L = Max(Lower, CR.Lower);
 245       ConstantIntegral *U = Min(Upper, CR.Upper);
 246
 247       if (LT(L, U))  // If range isn't empty...
 248         return ConstantRange(L, U);
 249       else
 250         return ConstantRange(getType(), false);  // Otherwise, return empty set
 251     } else
 252       return intersect1Wrapped(CR, *this);
 253   } else {   // We know "this" is wrapped...
 254     if (!CR.isWrappedSet())
 255       return intersect1Wrapped(*this, CR);
 256     else {
 257       // Both ranges are wrapped...
 258       ConstantIntegral *L = Max(Lower, CR.Lower);
 259       ConstantIntegral *U = Min(Upper, CR.Upper);
 260       return ConstantRange(L, U);
 261     }
 262   }
 263   return *this;
 264 }
 265
 266 /// union - Return the range that results from the union of this range with
 267 /// another range.  The resultant range is guaranteed to include the elements of
 268 /// both sets, but may contain more.  For example, [3, 9) union [12,15) is [3,
 269 /// 15), which includes 9, 10, and 11, which were not included in either set
 270 /// before.
 271 ///
 272 ConstantRange ConstantRange::unionWith(const ConstantRange &CR) const {
 273   assert(getType() == CR.getType() && "ConstantRange types don't agree!");
 274
 275   assert(0 && "Range union not implemented yet!");
 276
 277   return *this;
 278 }
 279
 280 /// zeroExtend - Return a new range in the specified integer type, which must
 281 /// be strictly larger than the current type.  The returned range will
 282 /// correspond to the possible range of values if the source range had been
 283 /// zero extended.
 284 ConstantRange ConstantRange::zeroExtend(const Type *Ty) const {
 285   assert(getLower()->getType()->getPrimitiveSize() < Ty->getPrimitiveSize() &&
 286          "Not a value extension");
 287   if (isFullSet()) {
 288     // Change a source full set into [0, 1 << 8*numbytes)
 289     unsigned SrcTySize = getLower()->getType()->getPrimitiveSize();
 290     return ConstantRange(Constant::getNullValue(Ty),
 291                          ConstantUInt::get(Ty, 1ULL << SrcTySize*8));
 292   }
 293
 294   Constant *Lower = getLower();
 295   Constant *Upper = getUpper();
 296   if (Lower->getType()->isInteger() && !Lower->getType()->isUnsigned()) {
 297     // Ensure we are doing a ZERO extension even if the input range is signed.
 298     Lower = ConstantExpr::getCast(Lower, Ty->getUnsignedVersion());
 299     Upper = ConstantExpr::getCast(Upper, Ty->getUnsignedVersion());
 300   }
 301
 302   return ConstantRange(ConstantExpr::getCast(Lower, Ty),
 303                        ConstantExpr::getCast(Upper, Ty));
 304 }
 305
 306 /// truncate - Return a new range in the specified integer type, which must be
 307 /// strictly smaller than the current type.  The returned range will
 308 /// correspond to the possible range of values if the source range had been
 309 /// truncated to the specified type.
 310 ConstantRange ConstantRange::truncate(const Type *Ty) const {
 311   assert(getLower()->getType()->getPrimitiveSize() > Ty->getPrimitiveSize() &&
 312          "Not a value truncation");
 313   uint64_t Size = 1ULL << Ty->getPrimitiveSize()*8;
 314   if (isFullSet() || getSetSize() >= Size)
 315     return ConstantRange(getType());
 316
 317   return ConstantRange(ConstantExpr::getCast(getLower(), Ty),
 318                        ConstantExpr::getCast(getUpper(), Ty));
 319 }
 320
 321
 322 /// print - Print out the bounds to a stream...
 323 ///
 324 void ConstantRange::print(std::ostream &OS) const {
 325   OS << "[" << *Lower << "," << *Upper << " )";
 326 }
 327
 328 /// dump - Allow printing from a debugger easily...
 329 ///
 330 void ConstantRange::dump() const {
 331   print(std::cerr);
 332 }