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In APInt version ComputeMaskedBits():

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1. Ensure VTy, KnownOne and KnownZero have same bitwidth.
  2. Make code more efficient.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35078 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zhou Sheng 2007-03-13 02:23:10 +00:00
parent e8308df0b9
commit 771dbf7677
1 changed files with 28 additions and 15 deletions
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43
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -582,29 +582,30 @@ static ConstantInt *SubOne(ConstantInt *C) {
/// this won't lose us code quality.
static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
APInt& KnownOne, unsigned Depth = 0) {
assert(V && "No Value?");
assert(Depth <= 6 && "Limit Search Depth");
uint32_t BitWidth = Mask.getBitWidth();
assert(KnownZero.getBitWidth() == BitWidth &&
const IntegerType *VTy = cast<IntegerType>(V->getType());
assert(VTy->getBitWidth() == BitWidth &&
KnownZero.getBitWidth() == BitWidth &&
KnownOne.getBitWidth() == BitWidth &&
"Mask, KnownOne and KnownZero should have same BitWidth");
"VTy, Mask, KnownOne and KnownZero should have same BitWidth");
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
// We know all of the bits for a constant!
APInt Tmp(CI->getValue());
Tmp.zextOrTrunc(BitWidth);
KnownOne = Tmp & Mask;
KnownOne = CI->getValue() & Mask;
KnownZero = ~KnownOne & Mask;
return;
}
KnownZero.clear(); KnownOne.clear(); // Don't know anything.
if (Depth == 6 || Mask == 0)
return; // Limit search depth.
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return;
KnownZero.clear(); KnownOne.clear(); // Don't know anything.
APInt KnownZero2(KnownZero), KnownOne2(KnownOne);
Mask &= APInt::getAllOnesValue(
cast<IntegerType>(V->getType())->getBitWidth()).zextOrTrunc(BitWidth);
Mask &= APInt::getAllOnesValue(BitWidth);
switch (I->getOpcode()) {
case Instruction::And:
@ -664,10 +665,16 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
case Instruction::UIToFP:
case Instruction::IntToPtr:
return; // Can't work with floating point or pointers
case Instruction::Trunc:
case Instruction::Trunc: {
// All these have integer operands
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
uint32_t SrcBitWidth =
cast<IntegerType>(I->getOperand(0)->getType())->getBitWidth();
ComputeMaskedBits(I->getOperand(0), Mask.zext(SrcBitWidth),
KnownZero.zext(SrcBitWidth), KnownOne.zext(SrcBitWidth), Depth+1);
KnownZero.trunc(BitWidth);
KnownOne.trunc(BitWidth);
return;
}
case Instruction::BitCast: {
const Type *SrcTy = I->getOperand(0)->getType();
if (SrcTy->isInteger()) {
@ -681,10 +688,13 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
APInt NewBits(APInt::getAllOnesValue(BitWidth).shl(SrcTy->getBitWidth()));
Mask &= SrcTy->getMask().zextOrTrunc(BitWidth);
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
uint32_t SrcBitWidth = SrcTy->getBitWidth();
ComputeMaskedBits(I->getOperand(0), Mask.trunc(SrcBitWidth),
KnownZero.trunc(SrcBitWidth), KnownOne.trunc(SrcBitWidth), Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
// The top bits are known to be zero.
KnownZero.zext(BitWidth);
KnownOne.zext(BitWidth);
KnownZero |= NewBits;
return;
}
@ -693,14 +703,17 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
APInt NewBits(APInt::getAllOnesValue(BitWidth).shl(SrcTy->getBitWidth()));
Mask &= SrcTy->getMask().zextOrTrunc(BitWidth);
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
uint32_t SrcBitWidth = SrcTy->getBitWidth();
ComputeMaskedBits(I->getOperand(0), Mask.trunc(SrcBitWidth),
KnownZero.trunc(SrcBitWidth), KnownOne.trunc(SrcBitWidth), Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero.zext(BitWidth);
KnownOne.zext(BitWidth);
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
APInt InSignBit(APInt::getSignBit(SrcTy->getBitWidth()));
InSignBit.zextOrTrunc(BitWidth);
InSignBit.zext(BitWidth);
if ((KnownZero & InSignBit) != 0) { // Input sign bit known zero
KnownZero |= NewBits;
KnownOne &= ~NewBits;