[InstCombine] simplify code for X * -1.0 --> -X; NFC

I've added random FMF to one of the tests to show those are propagated.

llvm-svn: 326377

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index f79e33f..b445c33 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -563,13 +563,9 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
     if (match(Op0, m_FNeg(m_Value(X))))
       return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I);
 
-    // (fmul X, -1.0) --> (fsub -0.0, X)
-    if (match(C, m_SpecificFP(-1.0))) {
-      Constant *NegZero = ConstantFP::getNegativeZero(Op1->getType());
-      Instruction *RI = BinaryOperator::CreateFSub(NegZero, Op0);
-      RI->copyFastMathFlags(&I);
-      return RI;
-    }
+    // X * -1.0 --> -X
+    if (match(C, m_SpecificFP(-1.0)))
+      return BinaryOperator::CreateFNegFMF(Op0, &I);
 
     if (AllowReassociate && C->isFiniteNonZeroFP()) {
       // Let MDC denote an expression in one of these forms:

diff --git a/llvm/test/Transforms/InstCombine/fmul.ll b/llvm/test/Transforms/InstCombine/fmul.ll
index 2eaa7c3..34e0047 100644 (file)
--- a/llvm/test/Transforms/InstCombine/fmul.ll
+++ b/llvm/test/Transforms/InstCombine/fmul.ll
@@ -153,10 +153,10 @@ define float @test9(float %x) {
 ; PR18532
 define <4 x float> @test10(<4 x float> %x) {
 ; CHECK-LABEL: @test10(
-; CHECK-NEXT:    [[MUL:%.*]] = fsub <4 x float> <float -0.000000e+00, float -0.000000e+00, float -0.000000e+00, float -0.000000e+00>, [[X:%.*]]
+; CHECK-NEXT:    [[MUL:%.*]] = fsub arcp afn <4 x float> <float -0.000000e+00, float -0.000000e+00, float -0.000000e+00, float -0.000000e+00>, [[X:%.*]]
 ; CHECK-NEXT:    ret <4 x float> [[MUL]]
 ;
-  %mul = fmul <4 x float> %x, <float -1.0, float -1.0, float -1.0, float -1.0>
+  %mul = fmul arcp afn <4 x float> %x, <float -1.0, float -1.0, float -1.0, float -1.0>
   ret <4 x float> %mul
 }