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Clean up codes in InstCombiner::SimplifyDemandedBits():

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1. Line out nested call of APInt::zext/trunc.
2. Make more use of APInt::getHighBitsSet/getLowBitsSet.
3. Use APInt[] operator instead of expression like "APIntVal & SignBit".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35444 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zhou Sheng 2007-03-29 02:26:30 +00:00
parent 97b52c260f
commit 01542f3d80
1 changed files with 35 additions and 32 deletions
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67
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1106,8 +1106,11 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
case Instruction::Trunc: {
uint32_t truncBf =
cast<IntegerType>(I->getOperand(0)->getType())->getBitWidth();
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask.zext(truncBf),
RHSKnownZero.zext(truncBf), RHSKnownOne.zext(truncBf), Depth+1))
DemandedMask.zext(truncBf);
RHSKnownZero.zext(truncBf);
RHSKnownOne.zext(truncBf);
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
DemandedMask.trunc(BitWidth);
RHSKnownZero.trunc(BitWidth);
@ -1130,12 +1133,14 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// Compute the bits in the result that are not present in the input.
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
uint32_t SrcBitWidth = SrcTy->getBitWidth();
APInt NewBits(APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth));
DemandedMask &= SrcTy->getMask().zext(BitWidth);
uint32_t zextBf = SrcTy->getBitWidth();
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask.trunc(zextBf),
RHSKnownZero.trunc(zextBf), RHSKnownOne.trunc(zextBf), Depth+1))
DemandedMask.trunc(zextBf);
RHSKnownZero.trunc(zextBf);
RHSKnownOne.trunc(zextBf);
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
DemandedMask.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
@ -1143,29 +1148,32 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
// The top bits are known to be zero.
RHSKnownZero |= NewBits;
RHSKnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
break;
}
case Instruction::SExt: {
// Compute the bits in the result that are not present in the input.
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
uint32_t SrcBitWidth = SrcTy->getBitWidth();
APInt NewBits(APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth));
// Get the sign bit for the source type
APInt InSignBit(APInt::getSignBit(SrcTy->getPrimitiveSizeInBits()));
APInt InSignBit(APInt::getSignBit(SrcBitWidth));
InSignBit.zext(BitWidth);
APInt InputDemandedBits = DemandedMask &
SrcTy->getMask().zext(BitWidth);
APInt::getLowBitsSet(BitWidth, SrcBitWidth);
APInt NewBits(APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth));
// If any of the sign extended bits are demanded, we know that the sign
// bit is demanded.
if ((NewBits & DemandedMask) != 0)
InputDemandedBits |= InSignBit;
uint32_t sextBf = SrcTy->getBitWidth();
if (SimplifyDemandedBits(I->getOperand(0), InputDemandedBits.trunc(sextBf),
RHSKnownZero.trunc(sextBf), RHSKnownOne.trunc(sextBf), Depth+1))
InputDemandedBits.trunc(sextBf);
RHSKnownZero.trunc(sextBf);
RHSKnownOne.trunc(sextBf);
if (SimplifyDemandedBits(I->getOperand(0), InputDemandedBits,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
InputDemandedBits.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
@ -1178,12 +1186,12 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// If the input sign bit is known zero, or if the NewBits are not demanded
// convert this into a zero extension.
if ((RHSKnownZero & InSignBit) != 0 || (NewBits & ~DemandedMask) == NewBits)
if (RHSKnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits)
{
// Convert to ZExt cast
CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName(), I);
return UpdateValueUsesWith(I, NewCast);
} else if ((RHSKnownOne & InSignBit) != 0) { // Input sign bit known set
} else if (RHSKnownOne[SrcBitWidth-1]) { // Input sign bit known set
RHSKnownOne |= NewBits;
RHSKnownZero &= ~NewBits;
} else { // Input sign bit unknown
@ -1208,7 +1216,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// If the top bit of the output is demanded, demand everything from the
// input. Otherwise, we demand all the input bits except NLZ top bits.
APInt InDemandedBits(APInt::getAllOnesValue(BitWidth).lshr(NLZ));
APInt InDemandedBits(APInt::getLowBitsSet(BitWidth, BitWidth - NLZ));
// Find information about known zero/one bits in the input.
if (SimplifyDemandedBits(I->getOperand(0), InDemandedBits,
@ -1272,10 +1280,10 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
} else {
// If the high-bits of this ADD are not demanded, then it does not demand
// the high bits of its LHS or RHS.
if ((DemandedMask & APInt::getSignBit(BitWidth)) == 0) {
if (DemandedMask[BitWidth-1] == 0) {
// Right fill the mask of bits for this ADD to demand the most
// significant bit and all those below it.
APInt DemandedFromOps = APInt::getAllOnesValue(BitWidth).lshr(NLZ);
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
@ -1289,11 +1297,11 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
case Instruction::Sub:
// If the high-bits of this SUB are not demanded, then it does not demand
// the high bits of its LHS or RHS.
if ((DemandedMask & APInt::getSignBit(BitWidth)) == 0) {
if (DemandedMask[BitWidth-1] == 0) {
// Right fill the mask of bits for this SUB to demand the most
// significant bit and all those below it.
unsigned NLZ = DemandedMask.countLeadingZeros();
APInt DemandedFromOps(APInt::getAllOnesValue(BitWidth).lshr(NLZ));
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
@ -1305,7 +1313,8 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
case Instruction::Shl:
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getZExtValue();
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask.lshr(ShiftAmt),
APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
if (SimplifyDemandedBits(I->getOperand(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
@ -1322,22 +1331,18 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
unsigned ShiftAmt = SA->getZExtValue();
APInt TypeMask(APInt::getAllOnesValue(BitWidth));
// Unsigned shift right.
if (SimplifyDemandedBits(I->getOperand(0),
(DemandedMask.shl(ShiftAmt)) & TypeMask,
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
if (SimplifyDemandedBits(I->getOperand(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
RHSKnownZero &= TypeMask;
RHSKnownOne &= TypeMask;
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
if (ShiftAmt) {
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(
BitWidth - ShiftAmt));
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
RHSKnownZero |= HighBits; // high bits known zero.
}
}
@ -1358,18 +1363,16 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
unsigned ShiftAmt = SA->getZExtValue();
APInt TypeMask(APInt::getAllOnesValue(BitWidth));
// Signed shift right.
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
if (SimplifyDemandedBits(I->getOperand(0),
(DemandedMask.shl(ShiftAmt)) & TypeMask,
DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(BitWidth - ShiftAmt));
RHSKnownZero &= TypeMask;
RHSKnownOne &= TypeMask;
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
@ -1380,7 +1383,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// If the input sign bit is known to be zero, or if none of the top bits
// are demanded, turn this into an unsigned shift right.
if ((RHSKnownZero & SignBit) != 0 ||
if (RHSKnownZero[BitWidth-ShiftAmt-1] ||
(HighBits & ~DemandedMask) == HighBits) {
// Perform the logical shift right.
Value *NewVal = BinaryOperator::createLShr(