Revert r85667. LoopUnroll currently can't call utility functions which
auto-update the DominatorTree because it doesn't keep the DominatorTree
current while it works.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85670 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/LoopUnroll.cpp b/lib/Transforms/Utils/LoopUnroll.cpp
index 9b68df0..d68427a 100644
--- a/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/lib/Transforms/Utils/LoopUnroll.cpp
@@ -49,6 +49,52 @@
}
}
+/// FoldBlockIntoPredecessor - Folds a basic block into its predecessor if it
+/// only has one predecessor, and that predecessor only has one successor.
+/// The LoopInfo Analysis that is passed will be kept consistent.
+/// Returns the new combined block.
+static BasicBlock *FoldBlockIntoPredecessor(BasicBlock *BB, LoopInfo* LI) {
+ // Merge basic blocks into their predecessor if there is only one distinct
+ // pred, and if there is only one distinct successor of the predecessor, and
+ // if there are no PHI nodes.
+ BasicBlock *OnlyPred = BB->getSinglePredecessor();
+ if (!OnlyPred) return 0;
+
+ if (OnlyPred->getTerminator()->getNumSuccessors() != 1)
+ return 0;
+
+ DEBUG(errs() << "Merging: " << *BB << "into: " << *OnlyPred);
+
+ // Resolve any PHI nodes at the start of the block. They are all
+ // guaranteed to have exactly one entry if they exist, unless there are
+ // multiple duplicate (but guaranteed to be equal) entries for the
+ // incoming edges. This occurs when there are multiple edges from
+ // OnlyPred to OnlySucc.
+ FoldSingleEntryPHINodes(BB);
+
+ // Delete the unconditional branch from the predecessor...
+ OnlyPred->getInstList().pop_back();
+
+ // Move all definitions in the successor to the predecessor...
+ OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());
+
+ // Make all PHI nodes that referred to BB now refer to Pred as their
+ // source...
+ BB->replaceAllUsesWith(OnlyPred);
+
+ std::string OldName = BB->getName();
+
+ // Erase basic block from the function...
+ LI->removeBlock(BB);
+ BB->eraseFromParent();
+
+ // Inherit predecessor's name if it exists...
+ if (!OldName.empty() && !OnlyPred->hasName())
+ OnlyPred->setName(OldName);
+
+ return OnlyPred;
+}
+
/// Unroll the given loop by Count. The loop must be in LCSSA form. Returns true
/// if unrolling was succesful, or false if the loop was unmodified. Unrolling
/// can only fail when the loop's latch block is not terminated by a conditional
@@ -287,7 +333,7 @@
} else {
Term->setUnconditionalDest(Dest);
// Merge adjacent basic blocks, if possible.
- if (BasicBlock *Fold = MergeBlockIntoPredecessor(Dest, LI)) {
+ if (BasicBlock *Fold = FoldBlockIntoPredecessor(Dest, LI)) {
std::replace(Latches.begin(), Latches.end(), Dest, Fold);
std::replace(Headers.begin(), Headers.end(), Dest, Fold);
}