Make sure we use the right insertion point when instcombine replaces a PHI with another instruction. (Specifically, don't insert an arbitrary instruction before a PHI.) Fixes PR11275.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143437 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 3 deletions

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 288fe68097..0cc969b01d 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2028,9 +2028,10 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
         BasicBlock *InstParent = I->getParent();
         BasicBlock::iterator InsertPos = I;
 
-        if (!isa<PHINode>(Result))        // If combining a PHI, don't insert
-          while (isa<PHINode>(InsertPos)) // middle of a block of PHIs.
-            ++InsertPos;
+        // If we replace a PHI with something that isn't a PHI, fix up the
+        // insertion point.
+        if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos))
+          InsertPos = InstParent->getFirstInsertionPt();
 
         InstParent->getInstList().insert(InsertPos, Result);