Revert "Revert r222040 because of bot failure."

This reverts commit r222203, reverting r222040 didn't end up turning the
bot green.

llvm-svn: 222261

1 files changed, 9 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index b41cdc65202..a0570f7ebd4 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1269,14 +1269,17 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
         // type of OpI doesn't enter into things at all.  We simply evaluate
         // in whichever source type is larger, then convert to the
         // destination type.
+        Value *NewLHS = LHSOrig, *NewRHS = RHSOrig;
         if (LHSWidth < SrcWidth)
-          LHSOrig = Builder->CreateFPExt(LHSOrig, RHSOrig->getType());
+          NewLHS = Builder->CreateFPExt(NewLHS, RHSOrig->getType());
         else if (RHSWidth <= SrcWidth)
-          RHSOrig = Builder->CreateFPExt(RHSOrig, LHSOrig->getType());
-        Value *ExactResult = Builder->CreateFRem(LHSOrig, RHSOrig);
-        if (Instruction *RI = dyn_cast<Instruction>(ExactResult))
-          RI->copyFastMathFlags(OpI);
-        return CastInst::CreateFPCast(ExactResult, CI.getType());
+          NewRHS = Builder->CreateFPExt(NewRHS, LHSOrig->getType());
+        if (NewLHS != LHSOrig || NewRHS != RHSOrig) {
+          Value *ExactResult = Builder->CreateFRem(NewLHS, NewRHS);
+          if (Instruction *RI = dyn_cast<Instruction>(ExactResult))
+            RI->copyFastMathFlags(OpI);
+          return CastInst::CreateFPCast(ExactResult, CI.getType());
+        }
     }
 
     // (fptrunc (fneg x)) -> (fneg (fptrunc x))