Teach SplitBlockPredecessors how to handle landingpad blocks.

Patch by: Igor Laevsky <igor@azulsystems.com>

"Currently SplitBlockPredecessors generates incorrect code in case if basic block we are going to split has a landingpad. Also seems like it is fairly common case among it's users to conditionally call either SplitBlockPredecessors or SplitLandingPadPredecessors. Because of this I think it is reasonable to add this condition directly into SplitBlockPredecessors."

Differential Revision: http://reviews.llvm.org/D7157

llvm-svn: 227390

1 files changed, 20 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index efd5effa9a4..b4552576e46 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -454,11 +454,15 @@ static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB,
   }
 }
 
-/// SplitBlockPredecessors - This method transforms BB by introducing a new
-/// basic block into the function, and moving some of the predecessors of BB to
-/// be predecessors of the new block.  The new predecessors are indicated by the
-/// Preds array, which has NumPreds elements in it.  The new block is given a
-/// suffix of 'Suffix'.
+/// SplitBlockPredecessors - This method introduces at least one new basic block
+/// into the function and moves some of the predecessors of BB to be
+/// predecessors of the new block. The new predecessors are indicated by the
+/// Preds array. The new block is given a suffix of 'Suffix'. Returns new basic
+/// block to which predecessors from Preds are now pointing.
+///
+/// If BB is a landingpad block then additional basicblock might be introduced.
+/// It will have suffix of 'Suffix'+".split_lp".
+/// See SplitLandingPadPredecessors for more details on this case.
 ///
 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
 /// LoopInfo, and LCCSA but no other analyses. In particular, it does not
@@ -470,6 +474,17 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
                                          const char *Suffix, AliasAnalysis *AA,
                                          DominatorTree *DT, LoopInfo *LI,
                                          bool PreserveLCSSA) {
+  // For the landingpads we need to act a bit differently.
+  // Delegate this work to the SplitLandingPadPredecessors.
+  if (BB->isLandingPad()) {
+    SmallVector<BasicBlock*, 2> NewBBs;
+    std::string NewName = std::string(Suffix) + ".split-lp";
+
+    SplitLandingPadPredecessors(BB, Preds, Suffix, NewName.c_str(),
+                                NewBBs, AA, DT, LI, PreserveLCSSA);
+    return NewBBs[0];
+  }
+
   // Create new basic block, insert right before the original block.
   BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix,
                                          BB->getParent(), BB);