Preserve fast-math flags after reassociation and commutation. Update test cases

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174571 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 9 deletions

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index dc7fe5cf6b..c6115e3e91 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -162,6 +162,21 @@ static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) {
   return !Overflow;
 }
 
+/// Conservatively clears subclassOptionalData after a reassociation or
+/// commutation. We preserve fast-math flags when applicable as they can be
+/// preserved.
+static void ClearSubclassDataAfterReassociation(BinaryOperator &I) {
+  FPMathOperator *FPMO = dyn_cast<FPMathOperator>(&I);
+  if (!FPMO) {
+    I.clearSubclassOptionalData();
+    return;
+  }
+
+  FastMathFlags FMF = I.getFastMathFlags();
+  I.clearSubclassOptionalData();
+  I.setFastMathFlags(FMF);
+}
+
 /// SimplifyAssociativeOrCommutative - This performs a few simplifications for
 /// operators which are associative or commutative:
 //
@@ -219,7 +234,7 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
             I.clearSubclassOptionalData();
             I.setHasNoSignedWrap(true);
           } else {
-            I.clearSubclassOptionalData();
+            ClearSubclassDataAfterReassociation(I);
           }
 
           Changed = true;
@@ -241,7 +256,7 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
           I.setOperand(1, C);
           // Conservatively clear the optional flags, since they may not be
           // preserved by the reassociation.
-          I.clearSubclassOptionalData();
+          ClearSubclassDataAfterReassociation(I);
           Changed = true;
           ++NumReassoc;
           continue;
@@ -263,7 +278,7 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
           I.setOperand(1, B);
           // Conservatively clear the optional flags, since they may not be
           // preserved by the reassociation.
-          I.clearSubclassOptionalData();
+          ClearSubclassDataAfterReassociation(I);
           Changed = true;
           ++NumReassoc;
           continue;
@@ -283,7 +298,7 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
           I.setOperand(1, V);
           // Conservatively clear the optional flags, since they may not be
           // preserved by the reassociation.
-          I.clearSubclassOptionalData();
+          ClearSubclassDataAfterReassociation(I);
           Changed = true;
           ++NumReassoc;
           continue;
@@ -310,7 +325,7 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
         I.setOperand(1, Folded);
         // Conservatively clear the optional flags, since they may not be
         // preserved by the reassociation.
-        I.clearSubclassOptionalData();
+        ClearSubclassDataAfterReassociation(I);
 
         Changed = true;
         continue;
diff --git a/test/Transforms/InstCombine/fast-math.ll b/test/Transforms/InstCombine/fast-math.ll
index 4de0c8234f..c97bd28222 100644
--- a/test/Transforms/InstCombine/fast-math.ll
+++ b/test/Transforms/InstCombine/fast-math.ll
@@ -7,7 +7,7 @@ define float @fold(float %a) {
   %mul1 = fmul fast float %mul, 0x4002666660000000
   ret float %mul1
 ; CHECK: @fold
-; CHECK: fmul float %a, 0x4006147AE0000000
+; CHECK: fmul fast float %a, 0x4006147AE0000000
 }
 
 ; Same testing-case as the one used in fold() except that the operators have
@@ -22,7 +22,7 @@ define float @notfold(float %a) {
 
 define float @fold2(float %a) {
 ; CHECK: @fold2
-; CHECK: fmul float %a, 0x4006147AE0000000
+; CHECK: fmul fast float %a, 0x4006147AE0000000
   %mul = fmul float %a, 0x3FF3333340000000
   %mul1 = fmul fast float %mul, 0x4002666660000000
   ret float %mul1
@@ -54,7 +54,7 @@ define float @fold5(float %f1, float %f2) {
   %add1 = fadd fast float %add, 5.000000e+00
   ret float %add1
 ; CHECK: @fold5
-; CHECK: fadd float %f1, 9.000000e+00
+; CHECK: fadd fast float %f1, 9.000000e+00
 }
 
 ; (X + X) + X => 3.0 * X
@@ -107,7 +107,7 @@ define float @fold10(float %f1, float %f2) {
   %t3 = fadd fast float %t1, %t2
   ret float %t3
 ; CHECK: @fold10
-; CHECK: %t3 = fadd float %t2, -1.000000e+00
+; CHECK: %t3 = fadd fast float %t2, -1.000000e+00
 ; CHECK: ret float %t3
 }