If the block that we're threading through is jumped to by an indirect branch,

then we don't want to set the destination in the indirect branch to the
destination. This is because the indirect branch needs its destinations to have
had their block addresses taken. This isn't so of the new critical edge that's
split during this process. If it turns out that the destination block has only
one predecessor, and that being a BB with an indirect branch, then it won't be
marked as 'used' and may be removed.
PR10072

llvm-svn: 132638

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 5ab9a2877cd..6df846cbd18 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1171,6 +1171,8 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) {
     BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
     
     if (RealDest == BB) continue;  // Skip self loops.
+    // Skip if the predecessor's terminator is an indirect branch.
+    if (isa<IndirectBrInst>(PredBB->getTerminator())) continue;
     
     // The dest block might have PHI nodes, other predecessors and other
     // difficult cases.  Instead of being smart about this, just insert a new
@@ -1226,7 +1228,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) {
         BB->removePredecessor(PredBB);
         PredBBTI->setSuccessor(i, EdgeBB);
       }
-    
+
     // Recurse, simplifying any other constants.
     return FoldCondBranchOnPHI(BI, TD) | true;
   }