An MBB which branches to an EH landing pad shouldn't be considered for tail merging.

In SjLj EH, the jump to the landing pad is not done explicitly through a branch
statement. The EH landing pad is added as a successor to the throwing
BB. Because of that however, the branch folding pass could mistakenly think that
it could merge the throwing BB with another BB. This isn't safe to do.
<rdar://problem/10334833>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142891 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 75288b0934cbe55b7b34c1c4053ecf0c1892114b..2c39f64998c6645d674288713c2ebc19676438b0 100644 (file)
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -913,7 +913,8 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
               // reinsert conditional branch only, for now
               TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond, dl);
           }
-          MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P));
+          if (!PBB->getLandingPadSuccessor())
+            MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB),*P));
         }
       }
       // If this is a large problem, avoid visiting the same basic blocks