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[InstCombine] refactor eq/ne cases in foldICmpUsingKnownBits() ; NFCI 

The pattern matching and transforms are identical; the cmp predicate just changes.

llvm-svn: 281561
This commit is contained in:
Sanjay Patel 2016-09-14 23:38:56 +00:00
parent 9f664051ab
commit 9efb1bdcc4
1 changed files with 27 additions and 62 deletions
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89
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -3201,53 +3201,13 @@ Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
switch (Pred) {
default:
llvm_unreachable("Unknown icmp opcode!");
case ICmpInst::ICMP_EQ: {
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
// If all bits are known zero except for one, then we know at most one bit
// is set. If the comparison is against zero, then this is a check to see if
// *that* bit is set.
APInt Op0KnownZeroInverted = ~Op0KnownZero;
if (~Op1KnownZero == 0) {
// If the LHS is an AND with the same constant, look through it.
Value *LHS = nullptr;
ConstantInt *LHSC = nullptr;
if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) ||
LHSC->getValue() != Op0KnownZeroInverted)
LHS = Op0;
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) == 0" into "x != 3".
// or turn "((1 << x)&7) == 0" into "x > 2".
Value *X = nullptr;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
APInt ValToCheck = Op0KnownZeroInverted;
if (ValToCheck.isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_NE, X,
ConstantInt::get(X->getType(), CmpVal));
} else if ((++ValToCheck).isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros() - 1;
return new ICmpInst(ICmpInst::ICMP_UGT, X,
ConstantInt::get(X->getType(), CmpVal));
}
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
// then turn "((8 >>u x)&1) == 0" into "x != 3".
const APInt *CI;
if (Op0KnownZeroInverted == 1 &&
match(LHS, m_LShr(m_Power2(CI), m_Value(X))))
return new ICmpInst(
ICmpInst::ICMP_NE, X,
ConstantInt::get(X->getType(), CI->countTrailingZeros()));
}
break;
}
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_NE: {
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) {
return Pred == CmpInst::ICMP_EQ
? replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()))
: replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
}
// If all bits are known zero except for one, then we know at most one bit
// is set. If the comparison is against zero, then this is a check to see if
@ -3261,31 +3221,36 @@ Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
LHSC->getValue() != Op0KnownZeroInverted)
LHS = Op0;
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) != 0" into "x == 3".
// or turn "((1 << x)&7) != 0" into "x < 3".
Value *X = nullptr;
Value *X;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
APInt ValToCheck = Op0KnownZeroInverted;
Type *XTy = X->getType();
if (ValToCheck.isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_EQ, X,
ConstantInt::get(X->getType(), CmpVal));
// ((1 << X) & 8) == 0 -> X != 3
// ((1 << X) & 8) != 0 -> X == 3
auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
auto NewPred = ICmpInst::getInversePredicate(Pred);
return new ICmpInst(NewPred, X, CmpC);
} else if ((++ValToCheck).isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_ULT, X,
ConstantInt::get(X->getType(), CmpVal));
// ((1 << X) & 7) == 0 -> X >= 3
// ((1 << X) & 7) != 0 -> X < 3
auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
auto NewPred =
Pred == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGE : CmpInst::ICMP_ULT;
return new ICmpInst(NewPred, X, CmpC);
}
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
// then turn "((8 >>u x)&1) != 0" into "x == 3".
// Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
const APInt *CI;
if (Op0KnownZeroInverted == 1 &&
match(LHS, m_LShr(m_Power2(CI), m_Value(X))))
return new ICmpInst(
ICmpInst::ICMP_EQ, X,
ConstantInt::get(X->getType(), CI->countTrailingZeros()));
match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
// ((8 >>u X) & 1) == 0 -> X != 3
// ((8 >>u X) & 1) != 0 -> X == 3
unsigned CmpVal = CI->countTrailingZeros();
auto NewPred = ICmpInst::getInversePredicate(Pred);
return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
}
}
break;
}