optimizing: Build HConstructorFence for HNewArray/HNewInstance nodes
Also fixes:
* LSE, code_sinking to keep optimizing new-instance if it did so before
* Various tests to expect constructor fences after new-instance
Sidenote: new-instance String does not get a ConstructorFence; the
special StringFactory calls are assumed to be self-fencing.
Metric changes on go/lem:
* CodeSize -0.262% in ART-Compile (ARMv8)
* RunTime -0.747% for all (linux-armv8)
(No changes expected to x86, constructor fences are no-op).
The RunTime regression is temporary until art_quick_alloc_* entrypoints have their
DMBs removed in a follow up CL.
Test: art/test.py
Bug: 36656456
Change-Id: I6a936a6e51c623e1c6b5b22eee5c3c72bebbed35
diff --git a/compiler/optimizing/code_sinking.cc b/compiler/optimizing/code_sinking.cc
index 0b4dcd3..e598e19 100644
--- a/compiler/optimizing/code_sinking.cc
+++ b/compiler/optimizing/code_sinking.cc
@@ -56,6 +56,17 @@
return true;
}
+ // Check it is safe to move ConstructorFence.
+ // (Safe to move ConstructorFence for only protecting the new-instance but not for finals.)
+ if (instruction->IsConstructorFence()) {
+ HConstructorFence* ctor_fence = instruction->AsConstructorFence();
+
+ // A fence with "0" inputs is dead and should've been removed in a prior pass.
+ DCHECK_NE(0u, ctor_fence->InputCount());
+
+ return ctor_fence->GetAssociatedAllocation() != nullptr;
+ }
+
// All other instructions that can throw cannot be moved.
if (instruction->CanThrow()) {
return false;
@@ -134,11 +145,11 @@
HInstruction* user,
const ArenaBitVector& post_dominated) {
if (instruction->IsNewInstance()) {
- return user->IsInstanceFieldSet() &&
+ return (user->IsInstanceFieldSet() || user->IsConstructorFence()) &&
(user->InputAt(0) == instruction) &&
!post_dominated.IsBitSet(user->GetBlock()->GetBlockId());
} else if (instruction->IsNewArray()) {
- return user->IsArraySet() &&
+ return (user->IsArraySet() || user->IsConstructorFence()) &&
(user->InputAt(0) == instruction) &&
!post_dominated.IsBitSet(user->GetBlock()->GetBlockId());
}
@@ -372,7 +383,9 @@
// Step (3): Try to move sinking candidates.
for (HInstruction* instruction : move_in_order) {
HInstruction* position = nullptr;
- if (instruction->IsArraySet() || instruction->IsInstanceFieldSet()) {
+ if (instruction->IsArraySet()
+ || instruction->IsInstanceFieldSet()
+ || instruction->IsConstructorFence()) {
if (!instructions_that_can_move.IsBitSet(instruction->InputAt(0)->GetId())) {
// A store can trivially move, but it can safely do so only if the heap
// location it stores to can also move.