fix PR6743, a case where we'd delete an instruction before using it

in some cases.

llvm-svn: 100937

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index a6489ecc2dc..df05b712dcb 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -670,8 +670,10 @@ bool JumpThreading::ProcessBranchOnDuplicateCond(BasicBlock *PredBB,
     Value *OldCond = DestBI->getCondition();
     DestBI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()),
                                           BranchDir));
-    ConstantFoldTerminator(BB);
+    // Delete dead instructions before we fold the branch.  Folding the branch
+    // can eliminate edges from the CFG which can end up deleting OldCond.
     RecursivelyDeleteTriviallyDeadInstructions(OldCond);
+    ConstantFoldTerminator(BB);
     return true;
   }