InstCombine: Replace manual fast math flag copying with the new IRBuilder RAII helper.

Defines away the issue where cast<Instruction> would fail because constant
folding happened. Also slightly cleaner.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191674 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 22 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 5c5ee1256f3..a7595482eed 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -463,10 +463,9 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
             if (Swap && FAddSub->getOpcode() == Instruction::FSub)
               std::swap(M0, M1);
 
-            Value *R = (FAddSub->getOpcode() == Instruction::FAdd) ?
-                        BinaryOperator::CreateFAdd(M0, M1) :
-                        BinaryOperator::CreateFSub(M0, M1);
-            Instruction *RI = cast<Instruction>(R);
+            Instruction *RI = (FAddSub->getOpcode() == Instruction::FAdd)
+                                  ? BinaryOperator::CreateFAdd(M0, M1)
+                                  : BinaryOperator::CreateFSub(M0, M1);
             RI->copyFastMathFlags(&I);
             return RI;
           }
@@ -493,13 +492,13 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
     }
     // if pattern detected emit alternate sequence
     if (OpX && OpY) {
+      BuilderTy::FastMathFlagGuard Guard(*Builder);
+      Builder->SetFastMathFlags(Log2->getFastMathFlags());
       Log2->setArgOperand(0, OpY);
       Value *FMulVal = Builder->CreateFMul(OpX, Log2);
-      Instruction *FMul = cast<Instruction>(FMulVal);
-      FMul->copyFastMathFlags(Log2);
-      Instruction *FSub = BinaryOperator::CreateFSub(FMulVal, OpX);
-      FSub->copyFastMathFlags(Log2);
-      return FSub;
+      Value *FSub = Builder->CreateFSub(FMulVal, OpX);
+      FSub->takeName(&I);
+      return ReplaceInstUsesWith(I, FSub);
     }
   }
 
@@ -509,6 +508,9 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
   for (int i = 0; i < 2; i++) {
     bool IgnoreZeroSign = I.hasNoSignedZeros();
     if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) {
+      BuilderTy::FastMathFlagGuard Guard(*Builder);
+      Builder->SetFastMathFlags(I.getFastMathFlags());
+
       Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign);
       Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign);
 
@@ -519,13 +521,9 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
       if (Opnd0->hasOneUse()) {
         // -X * Y => -(X*Y) (Promote negation as high as possible)
         Value *T = Builder->CreateFMul(N0, Opnd1);
-        Instruction *Neg = BinaryOperator::CreateFNeg(T);
-        if (I.getFastMathFlags().any()) {
-          if (Instruction *TI = dyn_cast<Instruction>(T))
-            TI->copyFastMathFlags(&I);
-          Neg->copyFastMathFlags(&I);
-        }
-        return Neg;
+        Value *Neg = Builder->CreateFNeg(T);
+        Neg->takeName(&I);
+        return ReplaceInstUsesWith(I, Neg);
       }
     }
 
@@ -548,13 +546,13 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
           Y = Opnd0_0;
 
         if (Y) {
-          Instruction *T = cast<Instruction>(Builder->CreateFMul(Opnd1, Opnd1));
-          T->copyFastMathFlags(&I);
-          T->setDebugLoc(I.getDebugLoc());
+          BuilderTy::FastMathFlagGuard Guard(*Builder);
+          Builder->SetFastMathFlags(I.getFastMathFlags());
+          Value *T = Builder->CreateFMul(Opnd1, Opnd1);
 
-          Instruction *R = BinaryOperator::CreateFMul(T, Y);
-          R->copyFastMathFlags(&I);
-          return R;
+          Value *R = Builder->CreateFMul(T, Y);
+          R->takeName(&I);
+          return ReplaceInstUsesWith(I, R);
         }
       }
     }