SimplifyCFG: Don't generate invalid code for switch used to initialize

two variables where the first variable is returned and the second
ignored.

I don't think this occurs in practice (other passes should have cleaned
up the unused phi node), but it should still be handled correctly.

Also make the logic for determining if we should return early less
sketchy.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164225 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 9 deletions

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 3365c2feed..7c6a152329 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -3258,17 +3258,16 @@ static bool SwitchToLookupTable(SwitchInst *SI,
                                            "switch.gep");
     Value *Result = Builder.CreateLoad(GEP, "switch.load");
 
-    // If the result is only going to be used to return from the function,
-    // we want to do that right here.
-    if (PHI->hasOneUse() && isa<ReturnInst>(*PHI->use_begin())) {
-      if (CommonDest->getFirstNonPHIOrDbg() == CommonDest->getTerminator()) {
-        Builder.CreateRet(Result);
-        ReturnedEarly = true;
-      }
+    // If the result is used to return immediately from the function, we want to
+    // do that right here.
+    if (PHI->hasOneUse() && isa<ReturnInst>(*PHI->use_begin()) &&
+        *PHI->use_begin() == CommonDest->getFirstNonPHIOrDbg()) {
+      Builder.CreateRet(Result);
+      ReturnedEarly = true;
+      break;
     }
 
-    if (!ReturnedEarly)
-      PHI->addIncoming(Result, LookupBB);
+    PHI->addIncoming(Result, LookupBB);
   }
 
   if (!ReturnedEarly)