[llvm-commits] [llvm] r143001 - /llvm/trunk/lib/CodeGen/BranchFolding.cpp

[Bill Wendling]

Author: void
Date: Tue Oct 25 20:10:25 2011
New Revision: 143001

URL: http://llvm.org/viewvc/llvm-project?rev=143001&view=rev
Log:
Reapply r142920 with fix:

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>

Modified:
    llvm/trunk/lib/CodeGen/BranchFolding.cpp

Modified: llvm/trunk/lib/CodeGen/BranchFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/BranchFolding.cpp?rev=143001&r1=143000&r2=143001&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp (original)
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp Tue Oct 25 20:10:25 2011
@@ -870,6 +870,9 @@
         // Visit each predecessor only once.
         if (!UniquePreds.insert(PBB))
           continue;
+        // Skip blocks which may jump to a landing pad. Can't tail merge these.
+        if (PBB->getLandingPadSuccessor())
+          continue;
         MachineBasicBlock *TBB = 0, *FBB = 0;
         SmallVector<MachineOperand, 4> Cond;
         if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) {