Merge the enhancements from LoopUnroll's FoldBlockIntoPredecessor into

MergeBlockIntoPredecessor. This makes SimplifyCFG slightly more aggressive,
and makes it unnecessary for LoopUnroll to have its own copy of this code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85667 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 3 deletions

diff --git a/include/llvm/Transforms/Utils/BasicBlockUtils.h b/include/llvm/Transforms/Utils/BasicBlockUtils.h
index e766d72..47d6895 100644
--- a/include/llvm/Transforms/Utils/BasicBlockUtils.h
+++ b/include/llvm/Transforms/Utils/BasicBlockUtils.h
@@ -43,9 +43,11 @@ void FoldSingleEntryPHINodes(BasicBlock *BB);
 /// it is ultimately unused or if it reaches an unused cycle.
 void DeleteDeadPHIs(BasicBlock *BB);
 
-/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
-/// if possible.  The return value indicates success or failure.
-bool MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P = 0);
+/// MergeBlockIntoPredecessor - Folds a basic block into its predecessor if it
+/// only has one predecessor, and that predecessor only has one successor.
+/// If a Pass is given, the LoopInfo and DominatorTree analyses will be kept
+/// current. Returns the combined block, or null if no merging was performed.
+BasicBlock *MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P = 0);
 
 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
 // with a value, then remove and delete the original instruction.