Optimizations around escape analysis. With tests.
Details:
(1) added new intrinsics
(2) implemented optimizations
more !can be null information
more null check removals
replace return-this uses with incoming parameter
remove dead StringBuffer/Builder calls (with escape analysis)
(3) Fixed exposed bug in CanBeMoved()
Performance gain:
This improves CafeineString by about 360%
(removes null check from first loop, eliminates second loop completely)
Test: test-art-host
Change-Id: Iaf16a1b9cab6a7386f43d71c6b51dd59600e81c1
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 85b461d..658b804 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -16,6 +16,7 @@
#include "instruction_simplifier.h"
+#include "escape.h"
#include "intrinsics.h"
#include "mirror/class-inl.h"
#include "scoped_thread_state_change-inl.h"
@@ -107,6 +108,8 @@
void SimplifyStringCharAt(HInvoke* invoke);
void SimplifyStringIsEmptyOrLength(HInvoke* invoke);
void SimplifyNPEOnArgN(HInvoke* invoke, size_t);
+ void SimplifyReturnThis(HInvoke* invoke);
+ void SimplifyAllocationIntrinsic(HInvoke* invoke);
void SimplifyMemBarrier(HInvoke* invoke, MemBarrierKind barrier_kind);
OptimizingCompilerStats* stats_;
@@ -1864,11 +1867,61 @@
// is provably non-null, we can clear the flag.
void InstructionSimplifierVisitor::SimplifyNPEOnArgN(HInvoke* invoke, size_t n) {
HInstruction* arg = invoke->InputAt(n);
- if (!arg->CanBeNull()) {
+ if (invoke->CanThrow() && !arg->CanBeNull()) {
invoke->SetCanThrow(false);
}
}
+// Methods that return "this" can replace the returned value with the receiver.
+void InstructionSimplifierVisitor::SimplifyReturnThis(HInvoke* invoke) {
+ if (invoke->HasUses()) {
+ HInstruction* receiver = invoke->InputAt(0);
+ invoke->ReplaceWith(receiver);
+ RecordSimplification();
+ }
+}
+
+// Helper method for StringBuffer escape analysis.
+static bool NoEscapeForStringBufferReference(HInstruction* reference, HInstruction* user) {
+ if (user->IsInvokeStaticOrDirect()) {
+ // Any constructor on StringBuffer is okay.
+ return user->AsInvokeStaticOrDirect()->GetResolvedMethod()->IsConstructor() &&
+ user->InputAt(0) == reference;
+ } else if (user->IsInvokeVirtual()) {
+ switch (user->AsInvokeVirtual()->GetIntrinsic()) {
+ case Intrinsics::kStringBufferLength:
+ case Intrinsics::kStringBufferToString:
+ DCHECK_EQ(user->InputAt(0), reference);
+ return true;
+ case Intrinsics::kStringBufferAppend:
+ // Returns "this", so only okay if no further uses.
+ DCHECK_EQ(user->InputAt(0), reference);
+ DCHECK_NE(user->InputAt(1), reference);
+ return !user->HasUses();
+ default:
+ break;
+ }
+ }
+ return false;
+}
+
+// Certain allocation intrinsics are not removed by dead code elimination
+// because of potentially throwing an OOM exception or other side effects.
+// This method removes such intrinsics when special circumstances allow.
+void InstructionSimplifierVisitor::SimplifyAllocationIntrinsic(HInvoke* invoke) {
+ if (!invoke->HasUses()) {
+ // Instruction has no uses. If unsynchronized, we can remove right away, safely ignoring
+ // the potential OOM of course. Otherwise, we must ensure the receiver object of this
+ // call does not escape since only thread-local synchronization may be removed.
+ bool is_synchronized = invoke->GetIntrinsic() == Intrinsics::kStringBufferToString;
+ HInstruction* receiver = invoke->InputAt(0);
+ if (!is_synchronized || DoesNotEscape(receiver, NoEscapeForStringBufferReference)) {
+ invoke->GetBlock()->RemoveInstruction(invoke);
+ RecordSimplification();
+ }
+ }
+}
+
void InstructionSimplifierVisitor::SimplifyMemBarrier(HInvoke* invoke, MemBarrierKind barrier_kind) {
uint32_t dex_pc = invoke->GetDexPc();
HMemoryBarrier* mem_barrier = new (GetGraph()->GetArena()) HMemoryBarrier(barrier_kind, dex_pc);
@@ -1926,6 +1979,14 @@
case Intrinsics::kStringStringIndexOfAfter:
SimplifyNPEOnArgN(instruction, 1); // 0th has own NullCheck
break;
+ case Intrinsics::kStringBufferAppend:
+ case Intrinsics::kStringBuilderAppend:
+ SimplifyReturnThis(instruction);
+ break;
+ case Intrinsics::kStringBufferToString:
+ case Intrinsics::kStringBuilderToString:
+ SimplifyAllocationIntrinsic(instruction);
+ break;
case Intrinsics::kUnsafeLoadFence:
SimplifyMemBarrier(instruction, MemBarrierKind::kLoadAny);
break;