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[FPEnv] PatternMatcher support for checking FNEG ignoring signed zeros

Browse Source 
https://reviews.llvm.org/D52934

llvm-svn: 344084
This commit is contained in:
Cameron McInally 2018-10-09 21:48:00 +00:00
parent 00cde5538b
commit aaf0519690
3 changed files with 10 additions and 7 deletions
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7
include/llvm/IR/PatternMatch.h
View File

@ -666,6 +666,13 @@ m_FNeg(const RHS &X) {
return m_FSub(m_NegZeroFP(), X);
}
/// Match 'fneg X' as 'fsub +-0.0, X'.
template <typename RHS>
inline BinaryOp_match<cstfp_pred_ty<is_any_zero_fp>, RHS, Instruction::FSub>
m_FNegNSZ(const RHS &X) {
return m_FSub(m_AnyZeroFP(), X);
}
template <typename LHS, typename RHS>
inline BinaryOp_match<LHS, RHS, Instruction::Mul> m_Mul(const LHS &L,
const RHS &R) {

6
lib/Analysis/InstructionSimplify.cpp
View File

@ -4508,10 +4508,8 @@ static Value *SimplifyFDivInst(Value *Op0, Value *Op1, FastMathFlags FMF,
// -X / X -> -1.0 and
// X / -X -> -1.0 are legal when NaNs are ignored.
// We can ignore signed zeros because +-0.0/+-0.0 is NaN and ignored.
if ((BinaryOperator::isFNeg(Op0, /*IgnoreZeroSign=*/true) &&
BinaryOperator::getFNegArgument(Op0) == Op1) ||
(BinaryOperator::isFNeg(Op1, /*IgnoreZeroSign=*/true) &&
BinaryOperator::getFNegArgument(Op1) == Op0))
if (match(Op0, m_FNegNSZ(m_Specific(Op1))) ||
match(Op1, m_FNegNSZ(m_Specific(Op0))))
return ConstantFP::get(Op0->getType(), -1.0);
}

4
test/Transforms/InstSimplify/fast-math.ll
View File

@ -401,9 +401,7 @@ define float @fdiv_neg_swapped2(float %f) {
define <2 x float> @fdiv_neg_vec_undef_elt(<2 x float> %f) {
; CHECK-LABEL: @fdiv_neg_vec_undef_elt(
; CHECK-NEXT: [[NEG:%.*]] = fsub <2 x float> <float 0.000000e+00, float undef>, [[F:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = fdiv nnan <2 x float> [[F]], [[NEG]]
; CHECK-NEXT: ret <2 x float> [[DIV]]
; CHECK-NEXT: ret <2 x float> <float -1.000000e+00, float -1.000000e+00>
;
%neg = fsub <2 x float> <float 0.0, float undef>, %f
%div = fdiv nnan <2 x float> %f, %neg