[llvm-commits] CVS: llvm/lib/Transforms/Scalar/LoopSimplify.cpp
Chris Lattner
lattner at cs.uiuc.edu
Sun Oct 17 14:22:43 PDT 2004
Changes in directory llvm/lib/Transforms/Scalar:
LoopSimplify.cpp updated: 1.51 -> 1.52
---
Log message:
hasConstantValue will soon return instructions that don't dominate the PHI node,
so prepare for this.
---
Diffs of the changes: (+21 -16)
Index: llvm/lib/Transforms/Scalar/LoopSimplify.cpp
diff -u llvm/lib/Transforms/Scalar/LoopSimplify.cpp:1.51 llvm/lib/Transforms/Scalar/LoopSimplify.cpp:1.52
--- llvm/lib/Transforms/Scalar/LoopSimplify.cpp:1.51 Mon Sep 27 21:40:37 2004
+++ llvm/lib/Transforms/Scalar/LoopSimplify.cpp Sun Oct 17 16:22:29 2004
@@ -250,8 +250,11 @@
// Can we eliminate this phi node now?
if (Value *V = hasConstantValue(PN)) {
- PN->replaceAllUsesWith(V);
- BB->getInstList().erase(PN);
+ if (!isa<Instruction>(V) ||
+ getAnalysis<DominatorSet>().dominates(cast<Instruction>(V), PN)) {
+ PN->replaceAllUsesWith(V);
+ BB->getInstList().erase(PN);
+ }
}
}
@@ -426,22 +429,24 @@
/// FindPHIToPartitionLoops - The first part of loop-nestification is to find a
/// PHI node that tells us how to partition the loops.
-static PHINode *FindPHIToPartitionLoops(Loop *L) {
+static PHINode *FindPHIToPartitionLoops(Loop *L, DominatorSet &DS) {
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I);
++I;
- if (Value *V = hasConstantValue(PN)) {
- // This is a degenerate PHI already, don't modify it!
- PN->replaceAllUsesWith(V);
- PN->getParent()->getInstList().erase(PN);
- } else {
- // Scan this PHI node looking for a use of the PHI node by itself.
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (PN->getIncomingValue(i) == PN &&
- L->contains(PN->getIncomingBlock(i)))
- // We found something tasty to remove.
- return PN;
- }
+ if (Value *V = hasConstantValue(PN))
+ if (!isa<Instruction>(V) || DS.dominates(cast<Instruction>(V), PN)) {
+ // This is a degenerate PHI already, don't modify it!
+ PN->replaceAllUsesWith(V);
+ PN->getParent()->getInstList().erase(PN);
+ continue;
+ }
+
+ // Scan this PHI node looking for a use of the PHI node by itself.
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == PN &&
+ L->contains(PN->getIncomingBlock(i)))
+ // We found something tasty to remove.
+ return PN;
}
return 0;
}
@@ -464,7 +469,7 @@
/// created.
///
Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
- PHINode *PN = FindPHIToPartitionLoops(L);
+ PHINode *PN = FindPHIToPartitionLoops(L, getAnalysis<DominatorSet>());
if (PN == 0) return 0; // No known way to partition.
// Pull out all predecessors that have varying values in the loop. This
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