diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 24 |
1 files changed, 10 insertions, 14 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index a95a775ead6..2b8e23b9569 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -4168,20 +4168,16 @@ static Value *SimplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags FMF, (FMF.noSignedZeros() || CannotBeNegativeZero(Op0, Q.TLI))) return Op0; - // fadd [nnan ninf] X, (fsub [nnan ninf] 0, X) ==> 0 - // where nnan and ninf have to occur at least once somewhere in this - // expression - Value *SubOp = nullptr; - if (match(Op1, m_FSub(m_AnyZero(), m_Specific(Op0)))) - SubOp = Op1; - else if (match(Op0, m_FSub(m_AnyZero(), m_Specific(Op1)))) - SubOp = Op0; - if (SubOp) { - Instruction *FSub = cast<Instruction>(SubOp); - if ((FMF.noNaNs() || FSub->hasNoNaNs()) && - (FMF.noInfs() || FSub->hasNoInfs())) - return Constant::getNullValue(Op0->getType()); - } + // With nnan: (+/-0.0 - X) + X --> 0.0 (and commuted variant) + // We don't have to explicitly exclude infinities (ninf): INF + -INF == NaN. + // Negative zeros are allowed because we always end up with positive zero: + // X = -0.0: (-0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0 + // X = -0.0: ( 0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0 + // X = 0.0: (-0.0 - ( 0.0)) + ( 0.0) == (-0.0) + ( 0.0) == 0.0 + // X = 0.0: ( 0.0 - ( 0.0)) + ( 0.0) == ( 0.0) + ( 0.0) == 0.0 + if (FMF.noNaNs() && (match(Op0, m_FSub(m_AnyZero(), m_Specific(Op1))) || + match(Op1, m_FSub(m_AnyZero(), m_Specific(Op0))))) + return ConstantFP::getNullValue(Op0->getType()); return nullptr; } |
