Revert r133435 and r133449 to appease buildbots.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133499 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/BreakCriticalEdges.cpp b/lib/Transforms/Utils/BreakCriticalEdges.cpp
index 92ce500..d6206a3 100644
--- a/lib/Transforms/Utils/BreakCriticalEdges.cpp
+++ b/lib/Transforms/Utils/BreakCriticalEdges.cpp
@@ -193,22 +193,44 @@
// If there are any PHI nodes in DestBB, we need to update them so that they
// merge incoming values from NewBB instead of from TIBB.
- {
- unsigned BBIdx = 0;
- for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
- // We no longer enter through TIBB, now we come in through NewBB.
- // Revector exactly one entry in the PHI node that used to come from
- // TIBB to come from NewBB.
- PHINode *PN = cast<PHINode>(I);
-
- // Reuse the previous value of BBIdx if it lines up. In cases where we
- // have multiple phi nodes with *lots* of predecessors, this is a speed
- // win because we don't have to scan the PHI looking for TIBB. This
- // happens because the BB list of PHI nodes are usually in the same
- // order.
- if (PN->getIncomingBlock(BBIdx) != TIBB)
- BBIdx = PN->getBasicBlockIndex(TIBB);
- PN->setIncomingBlock(BBIdx, NewBB);
+ if (PHINode *APHI = dyn_cast<PHINode>(DestBB->begin())) {
+ // This conceptually does:
+ // foreach (PHINode *PN in DestBB)
+ // PN->setIncomingBlock(PN->getIncomingBlock(TIBB), NewBB);
+ // but is optimized for two cases.
+
+ if (APHI->getNumIncomingValues() <= 8) { // Small # preds case.
+ unsigned BBIdx = 0;
+ for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
+ // We no longer enter through TIBB, now we come in through NewBB.
+ // Revector exactly one entry in the PHI node that used to come from
+ // TIBB to come from NewBB.
+ PHINode *PN = cast<PHINode>(I);
+
+ // Reuse the previous value of BBIdx if it lines up. In cases where we
+ // have multiple phi nodes with *lots* of predecessors, this is a speed
+ // win because we don't have to scan the PHI looking for TIBB. This
+ // happens because the BB list of PHI nodes are usually in the same
+ // order.
+ if (PN->getIncomingBlock(BBIdx) != TIBB)
+ BBIdx = PN->getBasicBlockIndex(TIBB);
+ PN->setIncomingBlock(BBIdx, NewBB);
+ }
+ } else {
+ // However, the foreach loop is slow for blocks with lots of predecessors
+ // because PHINode::getIncomingBlock is O(n) in # preds. Instead, walk
+ // the user list of TIBB to find the PHI nodes.
+ SmallPtrSet<PHINode*, 16> UpdatedPHIs;
+
+ for (Value::use_iterator UI = TIBB->use_begin(), E = TIBB->use_end();
+ UI != E; ) {
+ Value::use_iterator Use = UI++;
+ if (PHINode *PN = dyn_cast<PHINode>(*Use)) {
+ // Remove one entry from each PHI.
+ if (PN->getParent() == DestBB && UpdatedPHIs.insert(PN))
+ PN->setOperand(Use.getOperandNo(), NewBB);
+ }
+ }
}
}