diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 5493b4a85b3..467c6d9453b 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3830,6 +3830,26 @@ Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) { match(Op1, m_BitReverse(m_Value(B))))) return new ICmpInst(Pred, A, B); + // Canonicalize checking for a power-of-2-or-zero value: + // (A & -A) == A --> (A & (A - 1)) == 0 + // (-A & A) == A --> (A & (A - 1)) == 0 + // A == (A & -A) --> (A & (A - 1)) == 0 + // A == (-A & A) --> (A & (A - 1)) == 0 + // TODO: This could be reduced by using the popct intrinsic. + A = nullptr; + if (match(Op0, m_OneUse(m_c_And(m_OneUse(m_Neg(m_Specific(Op1))), + m_Specific(Op1))))) + A = Op1; + else if (match(Op1, m_OneUse(m_c_And(m_OneUse(m_Neg(m_Specific(Op0))), + m_Specific(Op0))))) + A = Op0; + if (A) { + Type *Ty = A->getType(); + Value *Dec = Builder.CreateAdd(A, ConstantInt::getAllOnesValue(Ty)); + Value *And = Builder.CreateAnd(A, Dec); + return new ICmpInst(Pred, And, ConstantInt::getNullValue(Ty)); + } + return nullptr; } |
