[SimplifyCFG] Extend TryToSimplifyUncondBranchFromEmptyBlock for empty block including lifetime intrinsics

Make it possible that TryToSimplifyUncondBranchFromEmptyBlock merges empty
basic block including lifetime intrinsics as well as phi nodes and
unconditional branch into its successor or predecessor(s).

If successor of empty block has single predecessor, all contents including
lifetime intrinsics are sinked into the successor. Otherwise, they are
hoisted into its predecessor(s) and then merged into the predecessor(s).

Patch by Josh Yoon <josh.yoon@samsung.com>!

Differential Revision: http://reviews.llvm.org/D19257

llvm-svn: 268254

1 files changed, 5 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 6ac039d8a1a..7454a9607fe 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -5056,14 +5056,15 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){
 
   if (SinkCommon && SinkThenElseCodeToEnd(BI))
     return true;
-
-  // If the Terminator is the only non-phi instruction, simplify the block.
-  // if LoopHeader is provided, check if the block is a loop header
+  // If the Terminator is the only non-phi instruction except for bitcast
+  // instruction coupled with the following lifetime intrinsic, simplify the
+  // block. If LoopHeader is provided, check if the block is a loop header
   // (This is for early invocations before loop simplify and vectorization
   // to keep canonical loop forms for nested loops.
   // These blocks can be eliminated when the pass is invoked later
   // in the back-end.)
-  BasicBlock::iterator I = BB->getFirstNonPHIOrDbg()->getIterator();
+  BasicBlock::iterator I =
+      BB->getFirstNonPHIOrDbgOrLifetimeOrBitCast()->getIterator();
   if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
       (!LoopHeaders || !LoopHeaders->count(BB)) &&
       TryToSimplifyUncondBranchFromEmptyBlock(BB))