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/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index e7f33d3..f3c1754 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -92,28 +92,54 @@
RecursivelyDeleteDeadPHINode(PN);
}
-/// 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 *llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
- // Don't merge if the block has multiple predecessors.
- BasicBlock *PredBB = BB->getSinglePredecessor();
- if (!PredBB) return 0;
- // Don't merge if the predecessor has multiple successors.
- if (PredBB->getTerminator()->getNumSuccessors() != 1) return 0;
- // Don't break self-loops.
- if (PredBB == BB) return 0;
- // Don't break invokes.
- if (isa<InvokeInst>(PredBB->getTerminator())) return 0;
+/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
+/// if possible. The return value indicates success or failure.
+bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
+ pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
+ // Can't merge the entry block.
+ if (pred_begin(BB) == pred_end(BB)) return false;
- // 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
- // PredBB to BB.
- FoldSingleEntryPHINodes(BB);
+ BasicBlock *PredBB = *PI++;
+ for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
+ if (*PI != PredBB) {
+ PredBB = 0; // There are multiple different predecessors...
+ break;
+ }
+
+ // Can't merge if there are multiple predecessors.
+ if (!PredBB) return false;
+ // Don't break self-loops.
+ if (PredBB == BB) return false;
+ // Don't break invokes.
+ if (isa<InvokeInst>(PredBB->getTerminator())) return false;
+
+ succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
+ BasicBlock* OnlySucc = BB;
+ for (; SI != SE; ++SI)
+ if (*SI != OnlySucc) {
+ OnlySucc = 0; // There are multiple distinct successors!
+ break;
+ }
+
+ // Can't merge if there are multiple successors.
+ if (!OnlySucc) return false;
+ // Can't merge if there is PHI loop.
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
+ if (PHINode *PN = dyn_cast<PHINode>(BI)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == PN)
+ return false;
+ } else
+ break;
+ }
+
+ // Begin by getting rid of unneeded PHIs.
+ while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
+ PN->replaceAllUsesWith(PN->getIncomingValue(0));
+ BB->getInstList().pop_front(); // Delete the phi node...
+ }
+
// Delete the unconditional branch from the predecessor...
PredBB->getInstList().pop_back();
@@ -124,7 +150,7 @@
// source...
BB->replaceAllUsesWith(PredBB);
- // If the predecessor doesn't have a name, take the successor's name.
+ // Inherit predecessors name if it exists.
if (!PredBB->hasName())
PredBB->takeName(BB);
@@ -143,14 +169,12 @@
DT->eraseNode(BB);
}
}
- // Notify LoopInfo that the block is removed.
- if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
- LI->removeBlock(BB);
}
BB->eraseFromParent();
- return PredBB;
+
+ return true;
}
/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)