From: Bill Wendling <isanbard@gmail.com>
Date: Tue, 25 Oct 2011 00:54:05 +0000 (+0000)
Subject: An MBB which branches to an EH landing pad shouldn't be considered for tail merging.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=86ed4089e367956ea7134dd7e99334a084fec6df;p=oota-llvm.git

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 75288b0934c..2c39f64998c 100644
--- 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