easing the constraint for isNegatibleForFree and GetNegatedExpression

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

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -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))

llvm/test/CodeGen/ARM/fnmul.ll

@@ -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