Add a utility function to LoopInfo to return the exit block

when the loop has exactly one exit, and make use of it in
LoopIndexSplit.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64388 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 14 insertions, 5 deletions

diff --git a/include/llvm/Analysis/LoopInfo.h b/include/llvm/Analysis/LoopInfo.h
index 0fa4abe056..b2268a2d74 100644
--- a/include/llvm/Analysis/LoopInfo.h
+++ b/include/llvm/Analysis/LoopInfo.h
@@ -184,6 +184,16 @@ public:
         }
   }
 
+  /// getExitingBlock - If getExitingBlocks would return exactly one block,
+  /// return that block. Otherwise return null.
+  BlockT *getExitingBlock() const {
+    SmallVector<BlockT*, 8> ExitingBlocks;
+    getExitingBlocks(ExitingBlocks);
+    if (ExitingBlocks.size() == 1)
+      return ExitingBlocks[0];
+    return 0;
+  }
+
   /// getExitBlocks - Return all of the successor blocks of this loop.  These
   /// are the blocks _outside of the current loop_ which are branched to.
   ///
diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
index f625c13d45..2bcb10849e 100644
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -236,15 +236,14 @@ bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) {
     }
 
   // Reject loop if loop exit condition is not suitable.
-  SmallVector<BasicBlock *, 2> EBs;
-  L->getExitingBlocks(EBs);
-  if (EBs.size() != 1)
+  BasicBlock *ExitingBlock = L->getExitingBlock();
+  if (!ExitingBlock)
     return false;
-  BranchInst *EBR = dyn_cast<BranchInst>(EBs[0]->getTerminator());
+  BranchInst *EBR = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
   if (!EBR) return false;
   ExitCondition = dyn_cast<ICmpInst>(EBR->getCondition());
   if (!ExitCondition) return false;
-  if (EBs[0] != L->getLoopLatch()) return false;
+  if (ExitingBlock != L->getLoopLatch()) return false;
   IVExitValue = ExitCondition->getOperand(1);
   if (!L->isLoopInvariant(IVExitValue))
     IVExitValue = ExitCondition->getOperand(0);