Changes in directory llvm/lib/Transforms/Utils:
BreakCriticalEdges.cpp updated: 1.34 -> 1.35
---
Log message:
Expose a smarter way to break critical edges.
---
Diffs of the changes: (+24 -5)
BreakCriticalEdges.cpp | 29 ++++++++++++++++++++++++-----
1 files changed, 24 insertions(+), 5 deletions(-)
Index: llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
diff -u llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp:1.34
llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp:1.35
--- llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp:1.34 Tue Oct 3
23:58:58 2006
+++ llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp Sat Oct 28 01:44:56 2006
@@ -100,10 +100,12 @@
// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
// split the critical edge. This will update DominatorSet, ImmediateDominator,
// DominatorTree, and DominatorFrontier information if it is available, thus
-// calling this pass will not invalidate either of them. This returns true if
-// the edge was split, false otherwise.
+// calling this pass will not invalidate any of them. This returns true if
+// the edge was split, false otherwise. This ensures that all edges to that
+// dest go to one block instead of each going to a different block.
//
-bool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
+bool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P,
+ bool MergeIdenticalEdges) {
if (!isCriticalEdge(TI, SuccNum)) return false;
BasicBlock *TIBB = TI->getParent();
BasicBlock *DestBB = TI->getSuccessor(SuccNum);
@@ -114,13 +116,13 @@
// Create our unconditional branch...
new BranchInst(DestBB, NewBB);
- // Branch to the new block, breaking the edge...
+ // Branch to the new block, breaking the edge.
TI->setSuccessor(SuccNum, NewBB);
// Insert the block into the function... right after the block TI lives in.
Function &F = *TIBB->getParent();
F.getBasicBlockList().insert(TIBB->getNext(), NewBB);
-
+
// 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.
//
@@ -132,6 +134,23 @@
int BBIdx = PN->getBasicBlockIndex(TIBB);
PN->setIncomingBlock(BBIdx, NewBB);
}
+
+ // If there are any other edges from TIBB to DestBB, update those to go
+ // through the split block, making those edges non-critical as well (and
+ // reducing the number of phi entries in the DestBB if relevant).
+ if (MergeIdenticalEdges) {
+ for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) {
+ if (TI->getSuccessor(i) != DestBB) continue;
+
+ // Remove an entry for TIBB from DestBB phi nodes.
+ DestBB->removePredecessor(TIBB);
+
+ // We found another edge to DestBB, go to NewBB instead.
+ TI->setSuccessor(i, NewBB);
+ }
+ }
+
+
// If we don't have a pass object, we can't update anything...
if (P == 0) return true;
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