[llvm-commits] [llvm] r53731 - in /llvm/trunk: include/llvm/Transforms/Utils/BasicBlockUtils.h lib/Transforms/Utils/BasicBlockUtils.cpp
Owen Anderson
resistor at mac.com
Thu Jul 17 12:42:29 PDT 2008
Author: resistor
Date: Thu Jul 17 14:42:29 2008
New Revision: 53731
URL: http://llvm.org/viewvc/llvm-project?rev=53731&view=rev
Log:
Make MergeBlockIntoPredecessor more aggressive when the same successor appears
more than once.
Modified:
llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h
llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h?rev=53731&r1=53730&r2=53731&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h Thu Jul 17 14:42:29 2008
@@ -27,7 +27,7 @@
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
-bool MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P);
+bool 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.
Modified: llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp?rev=53731&r1=53730&r2=53731&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp Thu Jul 17 14:42:29 2008
@@ -26,15 +26,30 @@
/// 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;
- // Can't merge if there are multiple preds.
- if (++pred_begin(BB) != pred_end(BB)) return false;
- BasicBlock* PredBB = *pred_begin(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 the edge is critical.
- if (PredBB->getTerminator()->getNumSuccessors() != 1) return false;
+ // Can't merge if there are multiple predecessors.
+ if (!PredBB) 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;
// Begin by getting rid of unneeded PHIs.
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
@@ -52,6 +67,10 @@
// source...
BB->replaceAllUsesWith(PredBB);
+ // Inherit predecessors name if it exists.
+ if (!PredBB->hasName())
+ PredBB->takeName(BB);
+
// Finally, erase the old block and update dominator info.
if (P) {
if (DominatorTree* DT = P->getAnalysisToUpdate<DominatorTree>()) {
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