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easing the constraint for isNegatibleForFree and GetNegatedExpression

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Summary:
Here we relax the old constraint which utilized unsafe with the TargetOption flag HonorSignDependentRoundingFPMathOption, with the assertion that unsafe is no longer needed or never was required for correctness on FDIV/FMUL.  



Reviewers: spatel, hfinkel, wristow, arsenm, javed.absar

Reviewed By: spatel

Subscribers: efriedma, wdng, tpr

Differential Revision: https://reviews.llvm.org/D48057

llvm-svn: 334769
This commit is contained in:
Michael Berg 2018-06-14 20:54:13 +00:00
parent 88222e23c3
commit 10e6427e7a
2 changed files with 5 additions and 11 deletions
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4
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -729,8 +729,6 @@ static char isNegatibleForFree(SDValue Op, bool LegalOperations,
case ISD::FMUL:
case ISD::FDIV:
if (Options->HonorSignDependentRoundingFPMath()) return 0;
// fold (fneg (fmul X, Y)) -> (fmul (fneg X), Y) or (fmul X, (fneg Y))
if (char V = isNegatibleForFree(Op.getOperand(0), LegalOperations, TLI,
Options, Depth + 1))
@ -792,8 +790,6 @@ static SDValue GetNegatedExpression(SDValue Op, SelectionDAG &DAG,
case ISD::FMUL:
case ISD::FDIV:
assert(!Options.HonorSignDependentRoundingFPMath());
// fold (fneg (fmul X, Y)) -> (fmul (fneg X), Y)
if (isNegatibleForFree(Op.getOperand(0), LegalOperations,
DAG.getTargetLoweringInfo(), &Options, Depth+1))

12
test/CodeGen/ARM/fnmul.ll
View File

@ -1,17 +1,15 @@
; RUN: llc -mtriple=arm-eabi -mattr=+v6,+vfp2 %s -o - | FileCheck %s
; RUN: llc -mtriple=arm-eabi -mattr=+v6,+vfp2 -enable-sign-dependent-rounding-fp-math %s -o - \
; RUN: | FileCheck %s -check-prefix CHECK-ROUNDING
; RUN: llc -mtriple=arm-eabi -mattr=+v6,+vfp2 %s -o - | FileCheck %s -check-prefix STRICT
; RUN: llc -mtriple=arm-eabi -mattr=+v6,+vfp2 -enable-unsafe-fp-math %s -o - | FileCheck %s -check-prefix UNSAFE
define double @t1(double %a, double %b) {
; STRICT: vnmul.f64
;
; UNSAFE: vnmul.f64
entry:
%tmp2 = fsub double -0.000000e+00, %a ; <double> [#uses=1]
%tmp4 = fmul double %tmp2, %b ; <double> [#uses=1]
ret double %tmp4
}
; CHECK: vnmul.f64
; CHECK-ROUNDING: vmul.f64