Introduce more compact ReadBarrierMark slow-paths.
Replace entry point ReadBarrierMark with 32
ReadBarrierMarkRegX entry points, using register
number X as input and output (instead of the standard
runtime calling convention) to save two moves in Baker's
read barrier mark slow-path code.
Test: ART host and target (ARM, ARM64) tests.
Bug: 29506760
Bug: 12687968
Change-Id: I73cfb82831cf040b8b018e984163c865cc44ed87
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index fc2c2c3..e480f12 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -580,8 +580,8 @@
// Slow path marking an object during a read barrier.
class ReadBarrierMarkSlowPathARM64 : public SlowPathCodeARM64 {
public:
- ReadBarrierMarkSlowPathARM64(HInstruction* instruction, Location out, Location obj)
- : SlowPathCodeARM64(instruction), out_(out), obj_(obj) {
+ ReadBarrierMarkSlowPathARM64(HInstruction* instruction, Location obj)
+ : SlowPathCodeARM64(instruction), obj_(obj) {
DCHECK(kEmitCompilerReadBarrier);
}
@@ -589,9 +589,8 @@
void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
LocationSummary* locations = instruction_->GetLocations();
- Primitive::Type type = Primitive::kPrimNot;
DCHECK(locations->CanCall());
- DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(out_.reg()));
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(obj_.reg()));
DCHECK(instruction_->IsInstanceFieldGet() ||
instruction_->IsStaticFieldGet() ||
instruction_->IsArrayGet() ||
@@ -605,24 +604,44 @@
<< instruction_->DebugName();
__ Bind(GetEntryLabel());
+ // Save live registers before the runtime call, and in particular
+ // W0 (if it is live), as it is clobbered by functions
+ // art_quick_read_barrier_mark_regX.
SaveLiveRegisters(codegen, locations);
InvokeRuntimeCallingConvention calling_convention;
CodeGeneratorARM64* arm64_codegen = down_cast<CodeGeneratorARM64*>(codegen);
- arm64_codegen->MoveLocation(LocationFrom(calling_convention.GetRegisterAt(0)), obj_, type);
- arm64_codegen->InvokeRuntime(QUICK_ENTRY_POINT(pReadBarrierMark),
+ DCHECK_NE(obj_.reg(), LR);
+ DCHECK_NE(obj_.reg(), WSP);
+ DCHECK_NE(obj_.reg(), WZR);
+ DCHECK(0 <= obj_.reg() && obj_.reg() < kNumberOfWRegisters) << obj_.reg();
+ // "Compact" slow path, saving two moves.
+ //
+ // Instead of using the standard runtime calling convention (input
+ // and output in W0):
+ //
+ // W0 <- obj
+ // W0 <- ReadBarrierMark(W0)
+ // obj <- W0
+ //
+ // we just use rX (the register holding `obj`) as input and output
+ // of a dedicated entrypoint:
+ //
+ // rX <- ReadBarrierMarkRegX(rX)
+ //
+ int32_t entry_point_offset =
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kArm64WordSize>(obj_.reg());
+ // TODO: Do not emit a stack map for this runtime call.
+ arm64_codegen->InvokeRuntime(entry_point_offset,
instruction_,
instruction_->GetDexPc(),
this);
- CheckEntrypointTypes<kQuickReadBarrierMark, mirror::Object*, mirror::Object*>();
- arm64_codegen->MoveLocation(out_, calling_convention.GetReturnLocation(type), type);
RestoreLiveRegisters(codegen, locations);
__ B(GetExitLabel());
}
private:
- const Location out_;
const Location obj_;
DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkSlowPathARM64);
@@ -5059,7 +5078,7 @@
// Slow path used to mark the GC root `root`.
SlowPathCodeARM64* slow_path =
- new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, root, root);
+ new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, root);
codegen_->AddSlowPath(slow_path);
MacroAssembler* masm = GetVIXLAssembler();
@@ -5267,7 +5286,7 @@
// Slow path used to mark the object `ref` when it is gray.
SlowPathCodeARM64* slow_path =
- new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, ref, ref);
+ new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, ref);
AddSlowPath(slow_path);
// if (rb_state == ReadBarrier::gray_ptr_)