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Make MaskedValueIsZero take a uint64_t instead of a ConstantIntegral as a

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mask.  This allows the code to be simpler and more efficient.

Also, generalize some of the cases in MVIZ a bit, making it slightly more aggressive.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26035 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-02-07 07:27:52 +00:00
parent 1a074fce15
commit 3bedbd9d71
1 changed files with 58 additions and 69 deletions
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127
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -406,20 +406,19 @@ static ConstantInt *SubOne(ConstantInt *C) {
}
/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
/// this predicate to simplify operations downstream. V and Mask are known to
/// be the same type.
static bool MaskedValueIsZero(Value *V, ConstantIntegral *Mask,
unsigned Depth = 0) {
/// this predicate to simplify operations downstream. Mask is known to be zero
/// for bits that V cannot have.
static bool MaskedValueIsZero(Value *V, uint64_t Mask, unsigned Depth = 0) {
// Note, we cannot consider 'undef' to be "IsZero" here. The problem is that
// we cannot optimize based on the assumption that it is zero without changing
// to to an explicit zero. If we don't change it to zero, other code could
// it to be an explicit zero. If we don't change it to zero, other code could
// optimized based on the contradictory assumption that it is non-zero.
// Because instcombine aggressively folds operations with undef args anyway,
// this won't lose us code quality.
if (Mask->isNullValue())
if (Mask == 0)
return true;
if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V))
return ConstantExpr::getAnd(CI, Mask)->isNullValue();
return (CI->getRawValue() & Mask) == 0;
if (Depth == 6) return false; // Limit search depth.
@ -427,12 +426,9 @@ static bool MaskedValueIsZero(Value *V, ConstantIntegral *Mask,
switch (I->getOpcode()) {
case Instruction::And:
// (X & C1) & C2 == 0 iff C1 & C2 == 0.
if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(I->getOperand(1))) {
ConstantIntegral *C1C2 =
cast<ConstantIntegral>(ConstantExpr::getAnd(CI, Mask));
if (MaskedValueIsZero(I->getOperand(0), C1C2, Depth+1))
return true;
}
if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(I->getOperand(1)))
return MaskedValueIsZero(I->getOperand(0), CI->getRawValue() & Mask,
Depth+1);
// If either the LHS or the RHS are MaskedValueIsZero, the result is zero.
return MaskedValueIsZero(I->getOperand(1), Mask, Depth+1) ||
MaskedValueIsZero(I->getOperand(0), Mask, Depth+1);
@ -448,41 +444,34 @@ static bool MaskedValueIsZero(Value *V, ConstantIntegral *Mask,
case Instruction::Cast: {
const Type *SrcTy = I->getOperand(0)->getType();
if (SrcTy == Type::BoolTy)
return (Mask->getRawValue() & 1) == 0;
return (Mask & 1) == 0;
if (!SrcTy->isInteger()) return false;
if (SrcTy->isInteger()) {
// (cast <ty> X to int) & C2 == 0 iff <ty> could not have contained C2.
if (SrcTy->isUnsigned() && // Only handle zero ext.
ConstantExpr::getCast(Mask, SrcTy)->isNullValue())
return true;
// If this is a noop cast, recurse.
if ((SrcTy->isSigned() && SrcTy->getUnsignedVersion() == I->getType())||
SrcTy->getSignedVersion() == I->getType()) {
Constant *NewMask =
ConstantExpr::getCast(Mask, I->getOperand(0)->getType());
return MaskedValueIsZero(I->getOperand(0),
cast<ConstantIntegral>(NewMask), Depth+1);
}
}
// (cast <ty> X to int) & C2 == 0 iff <ty> could not have contained C2.
if (SrcTy->isUnsigned()) // Only handle zero ext.
return MaskedValueIsZero(I->getOperand(0),
Mask & SrcTy->getIntegralTypeMask(), Depth+1);
// If this is a noop or trunc cast, recurse.
if (SrcTy->getPrimitiveSizeInBits() >=
I->getType()->getPrimitiveSizeInBits())
return MaskedValueIsZero(I->getOperand(0),
Mask & SrcTy->getIntegralTypeMask(), Depth+1);
break;
}
case Instruction::Shl:
// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
return MaskedValueIsZero(I->getOperand(0),
cast<ConstantIntegral>(ConstantExpr::getUShr(Mask, SA)),
return MaskedValueIsZero(I->getOperand(0), Mask >> SA->getValue(),
Depth+1);
break;
case Instruction::Shr:
// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
if (I->getType()->isUnsigned()) {
Constant *C1 = ConstantIntegral::getAllOnesValue(I->getType());
C1 = ConstantExpr::getShr(C1, SA);
C1 = ConstantExpr::getAnd(C1, Mask);
if (C1->isNullValue())
return true;
Mask <<= SA->getValue();
Mask &= I->getType()->getIntegralTypeMask();
return MaskedValueIsZero(I->getOperand(0), Mask, Depth+1);
}
break;
}
@ -877,10 +866,9 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
}
if (Found) {
// This is a sign extend if the top bits are known zero.
Constant *Mask = ConstantInt::getAllOnesValue(XorLHS->getType());
Mask = ConstantExpr::getShl(Mask,
ConstantInt::get(Type::UByteTy, 64-(TySizeBits-Size)));
if (!MaskedValueIsZero(XorLHS, cast<ConstantInt>(Mask)))
uint64_t Mask = XorLHS->getType()->getIntegralTypeMask();
Mask <<= 64-(TySizeBits-Size);
if (!MaskedValueIsZero(XorLHS, Mask))
Size = 0; // Not a sign ext, but can't be any others either.
goto FoundSExt;
}
@ -1375,10 +1363,10 @@ Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (I.getType()->isSigned()) {
// If the top bits of both operands are zero (i.e. we can prove they are
// If the sign bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a udiv.
ConstantIntegral *MaskV = ConstantSInt::getMinValue(I.getType());
if (MaskedValueIsZero(Op1, MaskV) && MaskedValueIsZero(Op0, MaskV)) {
uint64_t Mask = 1ULL << (I.getType()->getPrimitiveSizeInBits()-1);
if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
const Type *NTy = Op0->getType()->getUnsignedVersion();
Instruction *LHS = new CastInst(Op0, NTy, Op0->getName());
InsertNewInstBefore(LHS, I);
@ -1430,8 +1418,8 @@ Instruction *InstCombiner::visitRem(BinaryOperator &I) {
// If the top bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a urem.
ConstantIntegral *MaskV = ConstantSInt::getMinValue(I.getType());
if (MaskedValueIsZero(Op1, MaskV) && MaskedValueIsZero(Op0, MaskV)) {
uint64_t Mask = 1ULL << (I.getType()->getPrimitiveSizeInBits()-1);
if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
const Type *NTy = Op0->getType()->getUnsignedVersion();
Instruction *LHS = new CastInst(Op0, NTy, Op0->getName());
InsertNewInstBefore(LHS, I);
@ -1888,11 +1876,9 @@ Value *InstCombiner::FoldLogicalPlusAnd(Value *LHS, Value *RHS,
// is all N is, ignore it.
unsigned MB, ME;
if (isRunOfOnes(Mask, MB, ME)) { // begin/end bit of run, inclusive
Constant *Mask = ConstantInt::getAllOnesValue(RHS->getType());
Mask = ConstantExpr::getUShr(Mask,
ConstantInt::get(Type::UByteTy,
(64-MB+1)));
if (MaskedValueIsZero(RHS, cast<ConstantIntegral>(Mask)))
uint64_t Mask = RHS->getType()->getIntegralTypeMask();
Mask >>= 64-MB+1;
if (MaskedValueIsZero(RHS, Mask))
break;
}
}
@ -1939,13 +1925,13 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
return BinaryOperator::createAnd(X, ConstantExpr::getAnd(C1, AndRHS));
}
if (MaskedValueIsZero(Op0, AndRHS)) // LHS & RHS == 0
if (MaskedValueIsZero(Op0, AndRHS->getZExtValue())) // LHS & RHS == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// If the mask is not masking out any bits, there is no reason to do the
// and in the first place.
ConstantIntegral *NotAndRHS =
cast<ConstantIntegral>(ConstantExpr::getNot(AndRHS));
uint64_t NotAndRHS = // ~ANDRHS
AndRHS->getZExtValue()^Op0->getType()->getIntegralTypeMask();
if (MaskedValueIsZero(Op0, NotAndRHS))
return ReplaceInstUsesWith(I, Op0);
@ -1964,9 +1950,9 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
case Instruction::Or:
// (X ^ V) & C2 --> (X & C2) iff (V & C2) == 0
// (X | V) & C2 --> (X & C2) iff (V & C2) == 0
if (MaskedValueIsZero(Op0LHS, AndRHS))
if (MaskedValueIsZero(Op0LHS, AndRHS->getZExtValue()))
return BinaryOperator::createAnd(Op0RHS, AndRHS);
if (MaskedValueIsZero(Op0RHS, AndRHS))
if (MaskedValueIsZero(Op0RHS, AndRHS->getZExtValue()))
return BinaryOperator::createAnd(Op0LHS, AndRHS);
// If the mask is only needed on one incoming arm, push it up.
@ -1979,7 +1965,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
return BinaryOperator::create(
cast<BinaryOperator>(Op0I)->getOpcode(), Op0LHS, NewRHS);
}
if (!isa<Constant>(NotAndRHS) &&
if (!isa<Constant>(Op0RHS) &&
MaskedValueIsZero(Op0RHS, NotAndRHS)) {
// Not masking anything out for the RHS, move to LHS.
Instruction *NewLHS = BinaryOperator::createAnd(Op0LHS, AndRHS,
@ -1993,8 +1979,8 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
break;
case Instruction::And:
// (X & V) & C2 --> 0 iff (V & C2) == 0
if (MaskedValueIsZero(Op0LHS, AndRHS) ||
MaskedValueIsZero(Op0RHS, AndRHS))
if (MaskedValueIsZero(Op0LHS, AndRHS->getZExtValue()) ||
MaskedValueIsZero(Op0RHS, AndRHS->getZExtValue()))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
break;
case Instruction::Add:
@ -2239,8 +2225,8 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
// If X is known to only contain bits that already exist in RHS, just
// replace this instruction with RHS directly.
if (MaskedValueIsZero(Op0,
cast<ConstantIntegral>(ConstantExpr::getNot(RHS))))
if (MaskedValueIsZero(Op0,
RHS->getZExtValue()^RHS->getType()->getIntegralTypeMask()))
return ReplaceInstUsesWith(I, RHS);
ConstantInt *C1 = 0; Value *X = 0;
@ -2282,7 +2268,7 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
// (X^C)|Y -> (X|Y)^C iff Y&C == 0
if (Op0->hasOneUse() && match(Op0, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
MaskedValueIsZero(Op1, C1)) {
MaskedValueIsZero(Op1, C1->getZExtValue())) {
Instruction *NOr = BinaryOperator::createOr(A, Op1, Op0->getName());
Op0->setName("");
return BinaryOperator::createXor(InsertNewInstBefore(NOr, I), C1);
@ -2290,7 +2276,7 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
// Y|(X^C) -> (X|Y)^C iff Y&C == 0
if (Op1->hasOneUse() && match(Op1, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
MaskedValueIsZero(Op0, C1)) {
MaskedValueIsZero(Op0, C1->getZExtValue())) {
Instruction *NOr = BinaryOperator::createOr(A, Op0, Op1->getName());
Op0->setName("");
return BinaryOperator::createXor(InsertNewInstBefore(NOr, I), C1);
@ -2312,18 +2298,18 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if ((C2->getRawValue() & (C2->getRawValue()+1)) == 0 && // C2 == 0+1+
match(A, m_Add(m_Value(V1), m_Value(V2)))) {
// Add commutes, try both ways.
if (V1 == B && MaskedValueIsZero(V2, C2))
if (V1 == B && MaskedValueIsZero(V2, C2->getZExtValue()))
return ReplaceInstUsesWith(I, A);
if (V2 == B && MaskedValueIsZero(V1, C2))
if (V2 == B && MaskedValueIsZero(V1, C2->getZExtValue()))
return ReplaceInstUsesWith(I, A);
}
// Or commutes, try both ways.
if ((C1->getRawValue() & (C1->getRawValue()+1)) == 0 &&
match(B, m_Add(m_Value(V1), m_Value(V2)))) {
// Add commutes, try both ways.
if (V1 == A && MaskedValueIsZero(V2, C1))
if (V1 == A && MaskedValueIsZero(V2, C1->getZExtValue()))
return ReplaceInstUsesWith(I, B);
if (V2 == A && MaskedValueIsZero(V1, C1))
if (V2 == A && MaskedValueIsZero(V1, C1->getZExtValue()))
return ReplaceInstUsesWith(I, B);
}
}
@ -3599,7 +3585,8 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
// See if we can turn a signed shr into an unsigned shr.
if (!isLeftShift && I.getType()->isSigned()) {
if (MaskedValueIsZero(Op0, ConstantInt::getMinValue(I.getType()))) {
if (MaskedValueIsZero(Op0,
1ULL << (I.getType()->getPrimitiveSizeInBits()-1))) {
Value *V = InsertCastBefore(Op0, I.getType()->getUnsignedVersion(), I);
V = InsertNewInstBefore(new ShiftInst(Instruction::Shr, V, Op1,
I.getName()), I);
@ -4373,7 +4360,8 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) {
Constant *Not1 =
ConstantExpr::getNot(ConstantInt::get(Op0->getType(), 1));
// cast (X != 0) to int --> X if X&~1 == 0
if (MaskedValueIsZero(Op0, cast<ConstantIntegral>(Not1))) {
if (MaskedValueIsZero(Op0,
cast<ConstantIntegral>(Not1)->getZExtValue())) {
if (CI.getType() == Op0->getType())
return ReplaceInstUsesWith(CI, Op0);
else
@ -4415,7 +4403,8 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) {
if (Op1C->getRawValue() == 1) {
Constant *Not1 =
ConstantExpr::getNot(ConstantInt::get(Op0->getType(), 1));
if (MaskedValueIsZero(Op0, cast<ConstantIntegral>(Not1))) {
if (MaskedValueIsZero(Op0,
cast<ConstantIntegral>(Not1)->getZExtValue())) {
if (CI.getType() == Op0->getType())
return ReplaceInstUsesWith(CI, Op0);
else