Remove NoNaNsFPMath in visitFSUB

Author: paperchalice

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -17973,7 +17973,6 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
   ConstantFPSDNode *N1CFP = isConstOrConstSplatFP(N1, true);
   EVT VT = N->getValueType(0);
   SDLoc DL(N);
-  const TargetOptions &Options = DAG.getTarget().Options;
   const SDNodeFlags Flags = N->getFlags();
   SelectionDAG::FlagInserter FlagsInserter(DAG, N);
 
@@ -18001,7 +18000,7 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
 
   if (N0 == N1) {
     // (fsub x, x) -> 0.0
-    if (Options.NoNaNsFPMath || Flags.hasNoNaNs())
+    if (Flags.hasNoNaNs())
       return DAG.getConstantFP(0.0f, DL, VT);
   }
 

llvm/test/CodeGen/ARM/nnan-fsub.ll

@@ -1,18 +1,22 @@
-; RUN: llc -mcpu=cortex-a9 < %s | FileCheck -check-prefix=SAFE %s
-; RUN: llc -mcpu=cortex-a9 --enable-no-nans-fp-math < %s | FileCheck -check-prefix=FAST %s
+; RUN: llc -mcpu=cortex-a9 < %s | FileCheck %s
 
 target triple = "armv7-apple-ios"
 
-; SAFE: test
-; FAST: test
+; CHECK-LABEL: test
 define float @test(float %x, float %y) {
 entry:
-; SAFE: vmul.f32
-; SAFE: vsub.f32
-; FAST: mov r0, #0
+; CHECK: vmul.f32
+; CHECK-NEXT: vsub.f32
   %0 = fmul float %x, %y
   %1 = fsub float %0, %0
   ret float %1
 }
 
-
+; CHECK-LABEL: test_nnan
+define float @test_nnan(float %x, float %y) {
+entry:
+; CHECK: mov r0, #0
+  %0 = fmul float %x, %y
+  %1 = fsub nnan float %0, %0
+  ret float %1
+}