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Having RHSKnownZero and RHSKnownOne be alternative names for KnownZero and KnownOne

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(via APInt &RHSKnownZero = KnownZero, etc) seems dangerous and confusing to me: it
is easy not to notice this, and then wonder why KnownZero/RHSKnownZero changed
underneath you when you modified RHSKnownZero/KnownZero etc.  So get rid of this.
No intended functionality change (tested with "make check" + llvm-gcc bootstrap).

llvm-svn: 94802
This commit is contained in:
Duncan Sands 2010-01-29 06:18:46 +00:00
parent 6f0edf859c
commit d6baca9159
1 changed files with 69 additions and 75 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

144
lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
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@ -138,11 +138,11 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
return 0;
APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
APInt &RHSKnownZero = KnownZero, &RHSKnownOne = KnownOne;
APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
Instruction *I = dyn_cast<Instruction>(V);
if (!I) {
ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
return 0; // Only analyze instructions.
}
@ -219,7 +219,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
switch (I->getOpcode()) {
default:
ComputeMaskedBits(I, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
ComputeMaskedBits(I, DemandedMask, KnownZero, KnownOne, Depth);
break;
case Instruction::And:
// If either the LHS or the RHS are Zero, the result is zero.
@ -249,9 +249,9 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
return I;
// Output known-1 bits are only known if set in both the LHS & RHS.
RHSKnownOne &= LHSKnownOne;
KnownOne = RHSKnownOne & LHSKnownOne;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
RHSKnownZero |= LHSKnownZero;
KnownZero = RHSKnownZero | LHSKnownZero;
break;
case Instruction::Or:
// If either the LHS or the RHS are One, the result is One.
@ -286,9 +286,9 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
return I;
// Output known-0 bits are only known if clear in both the LHS & RHS.
RHSKnownZero &= LHSKnownZero;
KnownZero = RHSKnownZero & LHSKnownZero;
// Output known-1 are known to be set if set in either the LHS | RHS.
RHSKnownOne |= LHSKnownOne;
KnownOne = RHSKnownOne | LHSKnownOne;
break;
case Instruction::Xor: {
if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
@ -306,13 +306,6 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
if ((DemandedMask & LHSKnownZero) == DemandedMask)
return I->getOperand(1);
// Output known-0 bits are known if clear or set in both the LHS & RHS.
APInt KnownZeroOut = (RHSKnownZero & LHSKnownZero) |
(RHSKnownOne & LHSKnownOne);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
APInt KnownOneOut = (RHSKnownZero & LHSKnownOne) |
(RHSKnownOne & LHSKnownZero);
// If all of the demanded bits are known to be zero on one side or the
// other, turn this into an *inclusive* or.
// e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
@ -368,10 +361,11 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
BinaryOperator::CreateXor(NewAnd, XorC, "tmp");
return InsertNewInstBefore(NewXor, *I);
}
RHSKnownZero = KnownZeroOut;
RHSKnownOne = KnownOneOut;
// Output known-0 bits are known if clear or set in both the LHS & RHS.
KnownZero= (RHSKnownZero & LHSKnownZero) | (RHSKnownOne & LHSKnownOne);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
KnownOne = (RHSKnownZero & LHSKnownOne) | (RHSKnownOne & LHSKnownZero);
break;
}
case Instruction::Select:
@ -389,61 +383,61 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
return I;
// Only known if known in both the LHS and RHS.
RHSKnownOne &= LHSKnownOne;
RHSKnownZero &= LHSKnownZero;
KnownOne = RHSKnownOne & LHSKnownOne;
KnownZero = RHSKnownZero & LHSKnownZero;
break;
case Instruction::Trunc: {
unsigned truncBf = I->getOperand(0)->getType()->getScalarSizeInBits();
DemandedMask.zext(truncBf);
RHSKnownZero.zext(truncBf);
RHSKnownOne.zext(truncBf);
KnownZero.zext(truncBf);
KnownOne.zext(truncBf);
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
KnownZero, KnownOne, Depth+1))
return I;
DemandedMask.trunc(BitWidth);
RHSKnownZero.trunc(BitWidth);
RHSKnownOne.trunc(BitWidth);
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
KnownZero.trunc(BitWidth);
KnownOne.trunc(BitWidth);
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
break;
}
case Instruction::BitCast:
if (!I->getOperand(0)->getType()->isIntOrIntVector())
return false; // vector->int or fp->int?
return 0; // vector->int or fp->int?
if (const VectorType *DstVTy = dyn_cast<VectorType>(I->getType())) {
if (const VectorType *SrcVTy =
dyn_cast<VectorType>(I->getOperand(0)->getType())) {
if (DstVTy->getNumElements() != SrcVTy->getNumElements())
// Don't touch a bitcast between vectors of different element counts.
return false;
return 0;
} else
// Don't touch a scalar-to-vector bitcast.
return false;
return 0;
} else if (isa<VectorType>(I->getOperand(0)->getType()))
// Don't touch a vector-to-scalar bitcast.
return false;
return 0;
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
KnownZero, KnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
break;
case Instruction::ZExt: {
// Compute the bits in the result that are not present in the input.
unsigned SrcBitWidth =I->getOperand(0)->getType()->getScalarSizeInBits();
DemandedMask.trunc(SrcBitWidth);
RHSKnownZero.trunc(SrcBitWidth);
RHSKnownOne.trunc(SrcBitWidth);
KnownZero.trunc(SrcBitWidth);
KnownOne.trunc(SrcBitWidth);
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
KnownZero, KnownOne, Depth+1))
return I;
DemandedMask.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
RHSKnownOne.zext(BitWidth);
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
KnownZero.zext(BitWidth);
KnownOne.zext(BitWidth);
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
// The top bits are known to be zero.
RHSKnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
break;
}
case Instruction::SExt: {
@ -460,27 +454,27 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
InputDemandedBits.set(SrcBitWidth-1);
InputDemandedBits.trunc(SrcBitWidth);
RHSKnownZero.trunc(SrcBitWidth);
RHSKnownOne.trunc(SrcBitWidth);
KnownZero.trunc(SrcBitWidth);
KnownOne.trunc(SrcBitWidth);
if (SimplifyDemandedBits(I->getOperandUse(0), InputDemandedBits,
RHSKnownZero, RHSKnownOne, Depth+1))
KnownZero, KnownOne, Depth+1))
return I;
InputDemandedBits.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
RHSKnownOne.zext(BitWidth);
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
KnownZero.zext(BitWidth);
KnownOne.zext(BitWidth);
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
// If the input sign bit is known zero, or if the NewBits are not demanded
// convert this into a zero extension.
if (RHSKnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits) {
if (KnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits) {
// Convert to ZExt cast
CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName());
return InsertNewInstBefore(NewCast, *I);
} else if (RHSKnownOne[SrcBitWidth-1]) { // Input sign bit known set
RHSKnownOne |= NewBits;
} else if (KnownOne[SrcBitWidth-1]) { // Input sign bit known set
KnownOne |= NewBits;
}
break;
}
@ -540,12 +534,12 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
// Bits are known one if they are known zero in one operand and one in the
// other, and there is no input carry.
RHSKnownOne = ((LHSKnownZero & RHSVal) |
(LHSKnownOne & ~RHSVal)) & ~CarryBits;
KnownOne = ((LHSKnownZero & RHSVal) |
(LHSKnownOne & ~RHSVal)) & ~CarryBits;
// Bits are known zero if they are known zero in both operands and there
// is no input carry.
RHSKnownZero = LHSKnownZero & ~RHSVal & ~CarryBits;
KnownZero = LHSKnownZero & ~RHSVal & ~CarryBits;
} else {
// If the high-bits of this ADD are not demanded, then it does not demand
// the high bits of its LHS or RHS.
@ -578,21 +572,21 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
}
// Otherwise just hand the sub off to ComputeMaskedBits to fill in
// the known zeros and ones.
ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
break;
case Instruction::Shl:
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
KnownZero, KnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
RHSKnownZero <<= ShiftAmt;
RHSKnownOne <<= ShiftAmt;
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
KnownZero <<= ShiftAmt;
KnownOne <<= ShiftAmt;
// low bits known zero.
if (ShiftAmt)
RHSKnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
KnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
}
break;
case Instruction::LShr:
@ -603,15 +597,15 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
// Unsigned shift right.
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
KnownZero, KnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
if (ShiftAmt) {
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
RHSKnownZero |= HighBits; // high bits known zero.
KnownZero |= HighBits; // high bits known zero.
}
}
break;
@ -642,13 +636,13 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
if (DemandedMask.countLeadingZeros() <= ShiftAmt)
DemandedMaskIn.set(BitWidth-1);
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
KnownZero, KnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
// Handle the sign bits.
APInt SignBit(APInt::getSignBit(BitWidth));
@ -657,14 +651,14 @@ Value *InstCombiner::SimplifyDemandedUseBits(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 (BitWidth <= ShiftAmt || RHSKnownZero[BitWidth-ShiftAmt-1] ||
if (BitWidth <= ShiftAmt || KnownZero[BitWidth-ShiftAmt-1] ||
(HighBits & ~DemandedMask) == HighBits) {
// Perform the logical shift right.
Instruction *NewVal = BinaryOperator::CreateLShr(
I->getOperand(0), SA, I->getName());
return InsertNewInstBefore(NewVal, *I);
} else if ((RHSKnownOne & SignBit) != 0) { // New bits are known one.
RHSKnownOne |= HighBits;
} else if ((KnownOne & SignBit) != 0) { // New bits are known one.
KnownOne |= HighBits;
}
}
break;
@ -682,8 +676,8 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
return I;
// The low bits of LHS are unchanged by the srem.
KnownZero |= LHSKnownZero & LowBits;
KnownOne |= LHSKnownOne & LowBits;
KnownZero = LHSKnownZero & LowBits;
KnownOne = LHSKnownOne & LowBits;
// If LHS is non-negative or has all low bits zero, then the upper bits
// are all zero.
@ -752,15 +746,15 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
}
}
}
ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
break;
}
// If the client is only demanding bits that we know, return the known
// constant.
if ((DemandedMask & (RHSKnownZero|RHSKnownOne)) == DemandedMask)
return Constant::getIntegerValue(VTy, RHSKnownOne);
return false;
if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask)
return Constant::getIntegerValue(VTy, KnownOne);
return 0;
}