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deps: V8: cherry-pick 53784bdb8f01
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Original commit message:

    [liftoff] Handle constant memory indexes specially

    This adds detection for constant memory indexes which can statically be
    proven to be in-bounds (because the effective offset is within the
    minimum memory size). In these cases, we can skip the bounds check and
    the out-of-line code for the trap-handler.
    This often saves 1-2% of code size.

    R=ahaas@chromium.org

    Bug: v8:11802
    Change-Id: I0ee094e6f1f5d132af1d6a8a7c539a4af6c3cb5e
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2919827
    Commit-Queue: Clemens Backes <clemensb@chromium.org>
    Reviewed-by: Andreas Haas <ahaas@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#74825}

Refs: v8/v8@53784bd

PR-URL: #39337
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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@targos
targos committed Jul 13, 2021
1 parent 3d351b2 commit cf49ebb
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Showing 2 changed files with 99 additions and 43 deletions.
2 changes: 1 addition & 1 deletion common.gypi
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@

# Reset this number to 0 on major V8 upgrades.
# Increment by one for each non-official patch applied to deps/v8.
'v8_embedder_string': '-node.14',
'v8_embedder_string': '-node.15',

##### V8 defaults for Node.js #####

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140 changes: 98 additions & 42 deletions deps/v8/src/wasm/baseline/liftoff-compiler.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -2767,33 +2767,73 @@ class LiftoffCompiler {
return index;
}

bool IndexStaticallyInBounds(const LiftoffAssembler::VarState& index_slot,
int access_size, uintptr_t* offset) {
if (!index_slot.is_const()) return false;

// Potentially zero extend index (which is a 32-bit constant).
const uintptr_t index = static_cast<uint32_t>(index_slot.i32_const());
const uintptr_t effective_offset = index + *offset;

if (effective_offset < index // overflow
|| !base::IsInBounds<uintptr_t>(effective_offset, access_size,
env_->min_memory_size)) {
return false;
}

*offset = effective_offset;
return true;
}

void LoadMem(FullDecoder* decoder, LoadType type,
const MemoryAccessImmediate<validate>& imm,
const Value& index_val, Value* result) {
ValueKind kind = type.value_type().kind();
RegClass rc = reg_class_for(kind);
if (!CheckSupportedType(decoder, kind, "load")) return;
LiftoffRegister full_index = __ PopToRegister();
Register index = BoundsCheckMem(decoder, type.size(), imm.offset,
full_index, {}, kDontForceCheck);
if (index == no_reg) return;

uintptr_t offset = imm.offset;
LiftoffRegList pinned = LiftoffRegList::ForRegs(index);
index = AddMemoryMasking(index, &offset, &pinned);
DEBUG_CODE_COMMENT("load from memory");
Register addr = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
LOAD_INSTANCE_FIELD(addr, MemoryStart, kSystemPointerSize, pinned);
RegClass rc = reg_class_for(kind);
LiftoffRegister value = pinned.set(__ GetUnusedRegister(rc, pinned));
uint32_t protected_load_pc = 0;
__ Load(value, addr, index, offset, type, pinned, &protected_load_pc, true);
if (env_->use_trap_handler) {
AddOutOfLineTrap(decoder, WasmCode::kThrowWasmTrapMemOutOfBounds,
protected_load_pc);
Register index = no_reg;

// Only look at the slot, do not pop it yet (will happen in PopToRegister
// below, if this is not a statically-in-bounds index).
auto& index_slot = __ cache_state()->stack_state.back();
if (IndexStaticallyInBounds(index_slot, type.size(), &offset)) {
__ cache_state()->stack_state.pop_back();
DEBUG_CODE_COMMENT("load from memory (constant offset)");
LiftoffRegList pinned;
Register mem = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
LOAD_INSTANCE_FIELD(mem, MemoryStart, kSystemPointerSize, pinned);
LiftoffRegister value = pinned.set(__ GetUnusedRegister(rc, pinned));
__ Load(value, mem, no_reg, offset, type, pinned, nullptr, true);
__ PushRegister(kind, value);
} else {
LiftoffRegister full_index = __ PopToRegister();
index = BoundsCheckMem(decoder, type.size(), offset, full_index, {},
kDontForceCheck);
if (index == no_reg) return;

DEBUG_CODE_COMMENT("load from memory");
LiftoffRegList pinned = LiftoffRegList::ForRegs(index);
index = AddMemoryMasking(index, &offset, &pinned);

// Load the memory start address only now to reduce register pressure
// (important on ia32).
Register mem = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
LOAD_INSTANCE_FIELD(mem, MemoryStart, kSystemPointerSize, pinned);
LiftoffRegister value = pinned.set(__ GetUnusedRegister(rc, pinned));

uint32_t protected_load_pc = 0;
__ Load(value, mem, index, offset, type, pinned, &protected_load_pc,
true);
if (env_->use_trap_handler) {
AddOutOfLineTrap(decoder, WasmCode::kThrowWasmTrapMemOutOfBounds,
protected_load_pc);
}
__ PushRegister(kind, value);
}
__ PushRegister(kind, value);

if (FLAG_trace_wasm_memory) {
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) {
TraceMemoryOperation(false, type.mem_type().representation(), index,
offset, decoder->position());
}
Expand Down Expand Up @@ -2836,7 +2876,7 @@ class LiftoffCompiler {
}
__ PushRegister(kS128, value);

if (FLAG_trace_wasm_memory) {
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) {
// Again load extend is different.
MachineRepresentation mem_rep =
transform == LoadTransformationKind::kExtend
Expand Down Expand Up @@ -2878,7 +2918,7 @@ class LiftoffCompiler {

__ PushRegister(kS128, result);

if (FLAG_trace_wasm_memory) {
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) {
TraceMemoryOperation(false, type.mem_type().representation(), index,
offset, decoder->position());
}
Expand All @@ -2889,29 +2929,45 @@ class LiftoffCompiler {
const Value& index_val, const Value& value_val) {
ValueKind kind = type.value_type().kind();
if (!CheckSupportedType(decoder, kind, "store")) return;

LiftoffRegList pinned;
LiftoffRegister value = pinned.set(__ PopToRegister());
LiftoffRegister full_index = __ PopToRegister(pinned);
Register index = BoundsCheckMem(decoder, type.size(), imm.offset,
full_index, pinned, kDontForceCheck);
if (index == no_reg) return;

uintptr_t offset = imm.offset;
pinned.set(index);
index = AddMemoryMasking(index, &offset, &pinned);
DEBUG_CODE_COMMENT("store to memory");
Register addr = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
LOAD_INSTANCE_FIELD(addr, MemoryStart, kSystemPointerSize, pinned);
uint32_t protected_store_pc = 0;
LiftoffRegList outer_pinned;
if (FLAG_trace_wasm_memory) outer_pinned.set(index);
__ Store(addr, index, offset, value, type, outer_pinned,
&protected_store_pc, true);
if (env_->use_trap_handler) {
AddOutOfLineTrap(decoder, WasmCode::kThrowWasmTrapMemOutOfBounds,
protected_store_pc);
Register index = no_reg;

auto& index_slot = __ cache_state()->stack_state.back();
if (IndexStaticallyInBounds(index_slot, type.size(), &offset)) {
__ cache_state()->stack_state.pop_back();
DEBUG_CODE_COMMENT("store to memory (constant offset)");
Register mem = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
LOAD_INSTANCE_FIELD(mem, MemoryStart, kSystemPointerSize, pinned);
__ Store(mem, no_reg, offset, value, type, pinned, nullptr, true);
} else {
LiftoffRegister full_index = __ PopToRegister(pinned);
index = BoundsCheckMem(decoder, type.size(), imm.offset, full_index,
pinned, kDontForceCheck);
if (index == no_reg) return;

pinned.set(index);
index = AddMemoryMasking(index, &offset, &pinned);
DEBUG_CODE_COMMENT("store to memory");
uint32_t protected_store_pc = 0;
// Load the memory start address only now to reduce register pressure
// (important on ia32).
Register mem = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
LOAD_INSTANCE_FIELD(mem, MemoryStart, kSystemPointerSize, pinned);
LiftoffRegList outer_pinned;
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) outer_pinned.set(index);
__ Store(mem, index, offset, value, type, outer_pinned,
&protected_store_pc, true);
if (env_->use_trap_handler) {
AddOutOfLineTrap(decoder, WasmCode::kThrowWasmTrapMemOutOfBounds,
protected_store_pc);
}
}
if (FLAG_trace_wasm_memory) {

if (V8_UNLIKELY(FLAG_trace_wasm_memory)) {
TraceMemoryOperation(true, type.mem_rep(), index, offset,
decoder->position());
}
Expand Down Expand Up @@ -2940,7 +2996,7 @@ class LiftoffCompiler {
AddOutOfLineTrap(decoder, WasmCode::kThrowWasmTrapMemOutOfBounds,
protected_store_pc);
}
if (FLAG_trace_wasm_memory) {
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) {
TraceMemoryOperation(true, type.mem_rep(), index, offset,
decoder->position());
}
Expand Down Expand Up @@ -4156,9 +4212,9 @@ class LiftoffCompiler {
Register addr = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
LOAD_INSTANCE_FIELD(addr, MemoryStart, kSystemPointerSize, pinned);
LiftoffRegList outer_pinned;
if (FLAG_trace_wasm_memory) outer_pinned.set(index);
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) outer_pinned.set(index);
__ AtomicStore(addr, index, offset, value, type, outer_pinned);
if (FLAG_trace_wasm_memory) {
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) {
TraceMemoryOperation(true, type.mem_rep(), index, offset,
decoder->position());
}
Expand All @@ -4184,7 +4240,7 @@ class LiftoffCompiler {
__ AtomicLoad(value, addr, index, offset, type, pinned);
__ PushRegister(kind, value);

if (FLAG_trace_wasm_memory) {
if (V8_UNLIKELY(FLAG_trace_wasm_memory)) {
TraceMemoryOperation(false, type.mem_type().representation(), index,
offset, decoder->position());
}
Expand Down

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