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Implement InstCombine/sub.ll:test12 & test13

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12353 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-03-12 23:53:13 +00:00
parent 99780ce874
commit 9c2906744a
1 changed files with 36 additions and 0 deletions
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36
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -212,6 +212,18 @@ static const Type *getSignedIntegralType(const Type *Ty) {
}
}
// getUnsignedIntegralType - Given an signed integral type, return the unsigned
// version of it that has the same size.
static const Type *getUnsignedIntegralType(const Type *Ty) {
switch (Ty->getPrimitiveID()) {
default: assert(0 && "Invalid signed integer type!"); abort();
case Type::SByteTyID: return Type::UByteTy;
case Type::ShortTyID: return Type::UShortTy;
case Type::IntTyID: return Type::UIntTy;
case Type::LongTyID: return Type::ULongTy;
}
}
// getPromotedType - Return the specified type promoted as it would be to pass
// though a va_arg area...
static const Type *getPromotedType(const Type *Ty) {
@ -558,6 +570,30 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
ConstantExpr::get(Instruction::Add, C,
ConstantInt::get(I.getType(), 1)));
// -((uint)X >> 31) -> ((int)X >> 31)
// -((int)X >> 31) -> ((uint)X >> 31)
if (C->isNullValue())
if (ShiftInst *SI = dyn_cast<ShiftInst>(Op1))
if (SI->getOpcode() == Instruction::Shr)
if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
const Type *NewTy;
if (C->getType()->isSigned())
NewTy = getUnsignedIntegralType(C->getType());
else
NewTy = getSignedIntegralType(C->getType());
// Check to see if we are shifting out everything but the sign bit.
if (CU->getValue() == C->getType()->getPrimitiveSize()*8-1) {
// Ok, the transformation is safe. Insert a cast of the incoming
// value, then the new shift, then the new cast.
Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
SI->getOperand(0)->getName());
Value *InV = InsertNewInstBefore(FirstCast, I);
Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
CU, SI->getName());
InV = InsertNewInstBefore(NewShift, I);
return new CastInst(NewShift, I.getType());
}
}
}
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))