Fix performance regression.
Rationale:
One "improvement" overlooked in the previous CL hoists
a try-test out of the optimization to make sure we don't
change HIR when not needed. However, the try-test may
affect the outcome of the test, so that was bad, bad!
Bug: 64091002
Test: test-art-host
Change-Id: Icf5f73e7cbeb209ee5fa5f6c1bef64fe127bb2fd
diff --git a/compiler/optimizing/loop_optimization.cc b/compiler/optimizing/loop_optimization.cc
index 4143462..027ba77 100644
--- a/compiler/optimizing/loop_optimization.cc
+++ b/compiler/optimizing/loop_optimization.cc
@@ -490,13 +490,18 @@
for (HInstructionIterator it(header->GetPhis()); !it.Done(); it.Advance()) {
HPhi* phi = it.Current()->AsPhi();
if (TrySetPhiInduction(phi, /*restrict_uses*/ true) &&
- CanRemoveCycle() &&
TryAssignLastValue(node->loop_info, phi, preheader, /*collect_loop_uses*/ false)) {
- simplified_ = true;
- for (HInstruction* i : *iset_) {
- RemoveFromCycle(i);
+ // Note that it's ok to have replaced uses after the loop with the last value, without
+ // being able to remove the cycle. Environment uses (which are the reason we may not be
+ // able to remove the cycle) within the loop will still hold the right value. We must
+ // have tried first, however, to replace outside uses.
+ if (CanRemoveCycle()) {
+ simplified_ = true;
+ for (HInstruction* i : *iset_) {
+ RemoveFromCycle(i);
+ }
+ DCHECK(CheckInductionSetFullyRemoved(iset_));
}
- DCHECK(CheckInductionSetFullyRemoved(iset_));
}
}
}