Create utility function to Merge Adjacent Basic Blocks

Summary: The following code from
/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp can be used by other
transformations:

while (!MergeBlocks.empty()) {
    BasicBlock *BB = *MergeBlocks.begin();
    BranchInst *Term = dyn_cast<BranchInst>(BB->getTerminator());
    if (Term && Term->isUnconditional() &&
L->contains(Term->getSuccessor(0))) {
      BasicBlock *Dest = Term->getSuccessor(0);
      BasicBlock *Fold = Dest->getUniquePredecessor();
      if (MergeBlockIntoPredecessor(Dest, &DTU, LI)) {
        // Don't remove BB and add Fold as they are the same BB
        assert(Fold == BB);
        (void)Fold;
        MergeBlocks.erase(Dest);
      } else
        MergeBlocks.erase(BB);
    } else
      MergeBlocks.erase(BB);
  }
Hence it should be separated into its own utility function.

Authored By: sidbav
Reviewer: Whitney, Meinersbur, asbirlea, dmgreen, etiotto
Reviewed By: asbirlea
Subscribers: hiraditya, zzheng, llvm-commits
Tag: LLVM
Differential Revision: https://reviews.llvm.org/D80583

1 files changed, 3 insertions, 16 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
index 8ac6b08..dd628f3 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
@@ -593,22 +593,9 @@ llvm::UnrollAndJamLoop(Loop *L, unsigned Count, unsigned TripCount,
   MergeBlocks.insert(ForeBlocksLast.begin(), ForeBlocksLast.end());
   MergeBlocks.insert(SubLoopBlocksLast.begin(), SubLoopBlocksLast.end());
   MergeBlocks.insert(AftBlocksLast.begin(), AftBlocksLast.end());
-  while (!MergeBlocks.empty()) {
-    BasicBlock *BB = *MergeBlocks.begin();
-    BranchInst *Term = dyn_cast<BranchInst>(BB->getTerminator());
-    if (Term && Term->isUnconditional() && L->contains(Term->getSuccessor(0))) {
-      BasicBlock *Dest = Term->getSuccessor(0);
-      BasicBlock *Fold = Dest->getUniquePredecessor();
-      if (MergeBlockIntoPredecessor(Dest, &DTU, LI)) {
-        // Don't remove BB and add Fold as they are the same BB
-        assert(Fold == BB);
-        (void)Fold;
-        MergeBlocks.erase(Dest);
-      } else
-        MergeBlocks.erase(BB);
-    } else
-      MergeBlocks.erase(BB);
-  }
+
+  MergeBlockSuccessorsIntoGivenBlocks(MergeBlocks, L, &DTU, LI);
+
   // Apply updates to the DomTree.
   DT = &DTU.getDomTree();