[llvm] r199427 - Fix two cases where we could lose fast math flags when optimizing FADD expressions.

[Owen Anderson]

Author: resistor
Date: Thu Jan 16 15:26:02 2014
New Revision: 199427

URL: http://llvm.org/viewvc/llvm-project?rev=199427&view=rev
Log:
Fix two cases where we could lose fast math flags when optimizing FADD expressions.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    llvm/trunk/test/Transforms/InstCombine/fast-math.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=199427&r1=199426&r2=199427&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Thu Jan 16 15:26:02 2014
@@ -1198,13 +1198,19 @@ Instruction *InstCombiner::visitFAdd(Bin
 
   // -A + B  -->  B - A
   // -A + -B  -->  -(A + B)
-  if (Value *LHSV = dyn_castFNegVal(LHS))
-    return BinaryOperator::CreateFSub(RHS, LHSV);
+  if (Value *LHSV = dyn_castFNegVal(LHS)) {
+    Instruction *RI = BinaryOperator::CreateFSub(RHS, LHSV);
+    RI->copyFastMathFlags(&I);
+    return RI;
+  }
 
   // A + -B  -->  A - B
   if (!isa<Constant>(RHS))
-    if (Value *V = dyn_castFNegVal(RHS))
-      return BinaryOperator::CreateFSub(LHS, V);
+    if (Value *V = dyn_castFNegVal(RHS)) {
+      Instruction *RI = BinaryOperator::CreateFSub(LHS, V);
+      RI->copyFastMathFlags(&I);
+      return RI;
+    }
 
   // Check for (fadd double (sitofp x), y), see if we can merge this into an
   // integer add followed by a promotion.

Modified: llvm/trunk/test/Transforms/InstCombine/fast-math.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fast-math.ll?rev=199427&r1=199426&r2=199427&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fast-math.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/fast-math.ll Thu Jan 16 15:26:02 2014
@@ -140,6 +140,26 @@ define float @fold13(float %x) {
 ; CHECK: ret
 }
 
+; -x + y => y - x
+define float @fold14(float %x, float %y) {
+  %neg = fsub fast float -0.0, %x
+  %add = fadd fast float %neg, %y
+  ret float %add
+; CHECK: fold14
+; CHECK: fsub fast float %y, %x
+; CHECK: ret
+}
+
+; x + -y => x - y
+define float @fold15(float %x, float %y) {
+  %neg = fsub fast float -0.0, %y
+  %add = fadd fast float %x, %neg
+  ret float %add
+; CHECK: fold15
+; CHECK: fsub fast float %x, %y
+; CHECK: ret
+}
+
 ; =========================================================================
 ;
 ;   Testing-cases about fmul begin