Teach DAG combine that multiplication by 1.0 can always be constant f…

…olded. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156023 91177308-0d34-0410-b5e6-96231b3b80d8
darkbasic · May 2, 2012 · 363e4b9 · 363e4b9
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diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5715,6 +5715,9 @@ SDValue DAGCombiner::visitFMUL(SDNode *N) {
   if (DAG.getTarget().Options.UnsafeFPMath &&
       ISD::isBuildVectorAllZeros(N1.getNode()))
     return N1;
+  // fold (fmul A, 1.0) -> A
+  if (N1CFP && N1CFP->isExactlyValue(1.0))
+    return N0;
   // fold (fmul X, 2.0) -> (fadd X, X)
   if (N1CFP && N1CFP->isExactlyValue(+2.0))
     return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0, N0);

diff --git a/test/CodeGen/ARM/fmuls.ll b/test/CodeGen/ARM/fmuls.ll
@@ -21,3 +21,12 @@ entry:
 ; CORTEXA8: 	vmul.f32	d0, d1, d0
 ; CORTEXA9: test:
 ; CORTEXA9: 	vmul.f32	s{{.}}, s{{.}}, s{{.}}
+
+; VFP2: test2
+define float @test2(float %a) nounwind {
+; CHECK-NOT: mul
+; CHECK: mov pc, lr
+  %ret = fmul float %a, 1.0
+  ret float %ret
+}
+