[clang] 8b23b2b - [CodeGen] Use CreateFNeg in buildFMulAdd

[Craig Topper via cfe-commits]

Author: Craig Topper
Date: 2019-12-30T13:24:11-08:00
New Revision: 8b23b2bbd9622c5f079a71c7078d167052f6a70c

URL: https://github.com/llvm/llvm-project/commit/8b23b2bbd9622c5f079a71c7078d167052f6a70c
DIFF: https://github.com/llvm/llvm-project/commit/8b23b2bbd9622c5f079a71c7078d167052f6a70c.diff

LOG: [CodeGen] Use CreateFNeg in buildFMulAdd

We have an fneg instruction now and should use it instead of the fsub -0.0 idiom. Looks like we had no test that showed that we handled the negation cases here so I've added new tests.

Differential Revision: https://reviews.llvm.org/D72010

Added: 
    

Modified: 
    clang/lib/CodeGen/CGExprScalar.cpp
    clang/test/CodeGen/fp-contract-pragma.cpp

Removed: 
    


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diff  --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index b8846162508e..12bf37e5343c 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -3345,17 +3345,10 @@ static Value* buildFMulAdd(llvm::BinaryOperator *MulOp, Value *Addend,
 
   Value *MulOp0 = MulOp->getOperand(0);
   Value *MulOp1 = MulOp->getOperand(1);
-  if (negMul) {
-    MulOp0 =
-      Builder.CreateFSub(
-        llvm::ConstantFP::getZeroValueForNegation(MulOp0->getType()), MulOp0,
-        "neg");
-  } else if (negAdd) {
-    Addend =
-      Builder.CreateFSub(
-        llvm::ConstantFP::getZeroValueForNegation(Addend->getType()), Addend,
-        "neg");
-  }
+  if (negMul)
+    MulOp0 = Builder.CreateFNeg(MulOp0, "neg");
+  if (negAdd)
+    Addend = Builder.CreateFNeg(Addend, "neg");
 
   Value *FMulAdd = Builder.CreateCall(
       CGF.CGM.getIntrinsic(llvm::Intrinsic::fmuladd, Addend->getType()),

diff  --git a/clang/test/CodeGen/fp-contract-pragma.cpp b/clang/test/CodeGen/fp-contract-pragma.cpp
index 1c5921a53f97..805cc5d9c299 100644
--- a/clang/test/CodeGen/fp-contract-pragma.cpp
+++ b/clang/test/CodeGen/fp-contract-pragma.cpp
@@ -74,3 +74,18 @@ float fp_contract_7(float a, float b, float c) {
   return (a = 2 * b) - c;
 }
 
+float fp_contract_8(float a, float b, float c) {
+// CHECK: _Z13fp_contract_8fff
+// CHECK: fneg float %c
+// CHECK: tail call float @llvm.fmuladd
+  #pragma STDC FP_CONTRACT ON
+  return a * b - c;
+}
+
+float fp_contract_9(float a, float b, float c) {
+// CHECK: _Z13fp_contract_9fff
+// CHECK: fneg float %a
+// CHECK: tail call float @llvm.fmuladd
+  #pragma STDC FP_CONTRACT ON
+  return c - a * b;
+}