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[InstCombine] Replace call to haveNoCommonBitsSet in visitXor with just the special case that doesn't use computeKnownBits. 

Summary: computeKnownBits is expensive. The cases that would be detected by the computeKnownBits portion of haveNoCommonBitsSet were already handled by the earlier call to SimplifyDemandedInstructionBits.

Reviewers: spatel, lebedev.ri

Reviewed By: lebedev.ri

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D50604

llvm-svn: 339531
This commit is contained in:
Craig Topper 2018-08-13 00:38:27 +00:00
parent 3b2a17bd1d
commit 8bb49218bc
1 changed files with 8 additions and 2 deletions
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10
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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@ -2507,9 +2507,15 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
if (Value *V = SimplifyBSwap(I, Builder)) if (Value *V = SimplifyBSwap(I, Builder))
return replaceInstUsesWith(I, V); return replaceInstUsesWith(I, V);
// A^B --> A|B iff A and B have no bits set in common.
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (haveNoCommonBitsSet(Op0, Op1, DL, &AC, &I, &DT))
// Fold (X & M) ^ (Y & ~M) -> (X & M) | (Y & ~M)
// This it a special case in haveNoCommonBitsSet, but the commputeKnownBits
// calls in there are unnecessary as SimplifyDemandedInstructionBits should
// have already taken care of those cases.
Value *M;
if (match(&I, m_c_Xor(m_c_And(m_Not(m_Value(M)), m_Value()),
m_c_And(m_Deferred(M), m_Value()))))
return BinaryOperator::CreateOr(Op0, Op1); return BinaryOperator::CreateOr(Op0, Op1);
// Apply DeMorgan's Law for 'nand' / 'nor' logic with an inverted operand. // Apply DeMorgan's Law for 'nand' / 'nor' logic with an inverted operand.