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For PR1205: 

Implement review feedback:
1. Use new APInt::RoundDoubleToAPInt interface to specify the bit width so
   that we don't have to truncate or extend in constant folding.
2. Fix a pasteo in SDiv that prevented a check for overflow.
3. Fix the shift operators: undef happens when the shift amount is equal
   to the bitwidth.

llvm-svn: 34677
This commit is contained in:
Reid Spencer 2007-02-27 19:29:54 +00:00
parent e4f65e1983
commit ac419b52ad
1 changed files with 5 additions and 14 deletions
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19
llvm/lib/VMCore/ConstantFold.cpp
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@ -176,23 +176,15 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
return 0; // Can't fold.
case Instruction::FPToUI:
if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue()));
uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
if (Val.getBitWidth() > DestBitWidth)
Val.trunc(DestBitWidth);
else if (Val.getBitWidth() < DestBitWidth)
Val.zext(DestBitWidth);
APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
return ConstantInt::get(DestTy, Val);
}
return 0; // Can't fold.
case Instruction::FPToSI:
if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue()));
uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
if (Val.getBitWidth() > DestBitWidth)
Val.trunc(DestBitWidth);
else if (Val.getBitWidth() < DestBitWidth)
Val.sext(DestBitWidth);
APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
return ConstantInt::get(DestTy, Val);
}
return 0; // Can't fold.
@ -604,7 +596,6 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
case Instruction::SDiv:
if (CI2->isNullValue())
return 0; // X / 0 -> can't fold
return ConstantInt::get(C1->getType(), C1V.sdiv(C2V));
if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
return 0; // MIN_INT / -1 -> overflow
return ConstantInt::get(C1->getType(), C1V.sdiv(C2V));
@ -626,21 +617,21 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
return ConstantInt::get(C1->getType(), C1V ^ C2V);
case Instruction::Shl:
if (uint32_t shiftAmt = C2V.getZExtValue())
if (shiftAmt <= C1V.getBitWidth())
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(C1->getType(), C1V.shl(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
return const_cast<ConstantInt*>(CI1); // Zero shift is identity
case Instruction::LShr:
if (uint32_t shiftAmt = C2V.getZExtValue())
if (shiftAmt <= C1V.getBitWidth())
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(C1->getType(), C1V.lshr(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
return const_cast<ConstantInt*>(CI1); // Zero shift is identity
case Instruction::AShr:
if (uint32_t shiftAmt = C2V.getZExtValue())
if (shiftAmt <= C1V.getBitWidth())
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(C1->getType(), C1V.ashr(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef