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[maglev] Defer slow path of write barrier

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Move everything past the Smi check and "pointers-from-here" check in the
write barrier into deferred code. This matches what TF does for
kArchStoreWithWriteBarrier.

Bug: v8:7700
Change-Id: I869e6d5c85c01a3e265abca6cfa6f86066c1ab96
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3764443
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81752}
This commit is contained in:
Leszek Swirski 2022-07-15 13:37:06 +02:00 committed by V8 LUCI CQ
parent c74f34b169
commit ffd3a9d4e5
2 changed files with 56 additions and 22 deletions
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75
src/maglev/maglev-ir.cc
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@ -272,8 +272,9 @@ class DeferredCodeInfoImpl final : public DeferredCodeInfo {
};
template <typename Function, typename... Args>
void JumpToDeferredIf(Condition cond, MaglevCodeGenState* code_gen_state,
Function&& deferred_code_gen, Args&&... args) {
DeferredCodeInfo* PushDeferredCode(MaglevCodeGenState* code_gen_state,
Function&& deferred_code_gen,
Args&&... args) {
using DeferredCodeInfoT = DeferredCodeInfoImpl<Function>;
DeferredCodeInfoT* deferred_code =
code_gen_state->compilation_info()->zone()->New<DeferredCodeInfoT>(
@ -281,6 +282,15 @@ void JumpToDeferredIf(Condition cond, MaglevCodeGenState* code_gen_state,
std::forward<Args>(args)...);
code_gen_state->PushDeferredCode(deferred_code);
return deferred_code;
}
template <typename Function, typename... Args>
void JumpToDeferredIf(Condition cond, MaglevCodeGenState* code_gen_state,
Function&& deferred_code_gen, Args&&... args) {
DeferredCodeInfo* deferred_code = PushDeferredCode<Function, Args...>(
code_gen_state, std::forward<Function>(deferred_code_gen),
std::forward<Args>(args)...);
if (FLAG_code_comments) {
__ RecordComment("-- Jump to deferred code");
}
@ -971,32 +981,55 @@ void StoreTaggedFieldWithWriteBarrier::AllocateVreg(
MaglevVregAllocationState* vreg_state) {
UseFixed(object_input(), WriteBarrierDescriptor::ObjectRegister());
UseRegister(value_input());
// We need the slot address to be free, and an additional scratch register
// for the value.
// TODO(leszeks): Add input clobbering to remove the need for this
// unconditional value scratch register.
RequireSpecificTemporary(WriteBarrierDescriptor::SlotAddressRegister());
set_temporaries_needed(1);
}
void StoreTaggedFieldWithWriteBarrier::GenerateCode(
MaglevCodeGenState* code_gen_state, const ProcessingState& state) {
Register object = ToRegister(object_input());
// TODO(leszeks): Consider making this an arbitrary register and push/popping
// in the deferred path.
Register object = WriteBarrierDescriptor::ObjectRegister();
DCHECK_EQ(object, ToRegister(object_input()));
Register value = ToRegister(value_input());
__ AssertNotSmi(object);
RegList temps = temporaries();
DCHECK(temporaries().has(WriteBarrierDescriptor::SlotAddressRegister()));
temps.clear(WriteBarrierDescriptor::SlotAddressRegister());
__ StoreTaggedField(FieldOperand(object, offset()), value);
// TODO(leszeks): Add input clobbering to remove the need for this
// unconditional value scratch register.
Register value_scratch = temps.PopFirst();
__ movq(value_scratch, value);
// TODO(leszeks): Avoid saving fp registers if there aren't any live.
__ RecordWriteField(object, offset(), value_scratch,
WriteBarrierDescriptor::SlotAddressRegister(),
SaveFPRegsMode::kSave);
DeferredCodeInfo* deferred_write_barrier = PushDeferredCode(
code_gen_state,
[](MaglevCodeGenState* code_gen_state, Label* return_label,
Register value, Register object,
StoreTaggedFieldWithWriteBarrier* node) {
ASM_CODE_COMMENT_STRING(code_gen_state->masm(),
"Write barrier slow path");
Register slot_reg = WriteBarrierDescriptor::SlotAddressRegister();
RegList saved;
if (node->register_snapshot().live_registers.has(slot_reg)) {
saved.set(slot_reg);
}
__ PushAll(saved);
__ CheckPageFlag(value, kScratchRegister,
MemoryChunk::kPointersToHereAreInterestingMask, zero,
return_label);
__ leaq(slot_reg, FieldOperand(object, node->offset()));
SaveFPRegsMode const save_fp_mode =
!node->register_snapshot().live_double_registers.is_empty()
? SaveFPRegsMode::kSave
: SaveFPRegsMode::kIgnore;
__ CallRecordWriteStub(object, slot_reg, save_fp_mode);
__ PopAll(saved);
__ jmp(return_label);
},
value, object, this);
__ JumpIfSmi(value, &deferred_write_barrier->return_label);
__ CheckPageFlag(object, kScratchRegister,
MemoryChunk::kPointersFromHereAreInterestingMask, not_zero,
&deferred_write_barrier->deferred_code_label);
__ bind(&deferred_write_barrier->return_label);
}
void StoreTaggedFieldWithWriteBarrier::PrintParams(
std::ostream& os, MaglevGraphLabeller* graph_labeller) const {

3
src/maglev/maglev-ir.h
View File

@ -2140,7 +2140,8 @@ class StoreTaggedFieldWithWriteBarrier
explicit StoreTaggedFieldWithWriteBarrier(uint64_t bitfield, int offset)
: Base(bitfield), offset_(offset) {}
static constexpr OpProperties kProperties = OpProperties::Writing();
static constexpr OpProperties kProperties =
OpProperties::Writing() | OpProperties::DeferredCall();
int offset() const { return offset_; }