Fix PR3298, a crash in Jump Threading. Apparently even

jump threading can have bugs, who knew? ;-)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61983 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 59af14b865..94d33aa787 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -504,6 +504,10 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
     // If the value if the load is locally available within the block, just use
     // it.  This frequently occurs for reg2mem'd allocas.
     //cerr << "LOAD ELIMINATED:\n" << *BBIt << *LI << "\n";
+    
+    // If the returned value is the load itself, replace with an undef. This can
+    // only happen in dead loops.
+    if (AvailableVal == LI) AvailableVal = UndefValue::get(LI->getType());
     LI->replaceAllUsesWith(AvailableVal);
     LI->eraseFromParent();
     return true;