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// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/wasm/wasm-code-specialization.h"
#include "src/assembler-inl.h"
#include "src/base/optional.h"
#include "src/objects-inl.h"
#include "src/source-position-table.h"
#include "src/wasm/decoder.h"
#include "src/wasm/wasm-code-manager.h"
#include "src/wasm/wasm-module.h"
#include "src/wasm/wasm-objects-inl.h"
namespace v8 {
namespace internal {
namespace wasm {
uint32_t ExtractDirectCallIndex(wasm::Decoder& decoder, const byte* pc) {
DCHECK_EQ(static_cast<int>(kExprCallFunction), static_cast<int>(*pc));
decoder.Reset(pc + 1, pc + 6);
uint32_t call_idx = decoder.consume_u32v("call index");
DCHECK(decoder.ok());
DCHECK_GE(kMaxInt, call_idx);
return call_idx;
}
namespace {
int AdvanceSourcePositionTableIterator(SourcePositionTableIterator& iterator,
size_t offset_l) {
DCHECK_GE(kMaxInt, offset_l);
int offset = static_cast<int>(offset_l);
DCHECK(!iterator.done());
int byte_pos;
do {
byte_pos = iterator.source_position().ScriptOffset();
iterator.Advance();
} while (!iterator.done() && iterator.code_offset() <= offset);
return byte_pos;
}
class PatchDirectCallsHelper {
public:
PatchDirectCallsHelper(NativeModule* native_module, const WasmCode* code)
: source_pos_it(code->source_positions()), decoder(nullptr, nullptr) {
uint32_t func_index = code->index();
WasmCompiledModule* comp_mod = native_module->compiled_module();
func_bytes =
comp_mod->shared()->module_bytes()->GetChars() +
comp_mod->shared()->module()->functions[func_index].code.offset();
}
SourcePositionTableIterator source_pos_it;
Decoder decoder;
const byte* func_bytes;
};
} // namespace
CodeSpecialization::CodeSpecialization() {}
CodeSpecialization::~CodeSpecialization() {}
void CodeSpecialization::UpdateInstanceReferences(
Handle<WeakCell> old_weak_instance, Handle<WeakCell> new_weak_instance) {
DCHECK(!old_weak_instance.is_null());
DCHECK(!new_weak_instance.is_null());
old_weak_instance_ = old_weak_instance;
new_weak_instance_ = new_weak_instance;
}
void CodeSpecialization::RelocateDirectCalls(NativeModule* native_module) {
DCHECK_NULL(relocate_direct_calls_module_);
DCHECK_NOT_NULL(native_module);
relocate_direct_calls_module_ = native_module;
}
bool CodeSpecialization::ApplyToWholeModule(NativeModule* native_module,
ICacheFlushMode icache_flush_mode) {
DisallowHeapAllocation no_gc;
WasmCompiledModule* compiled_module = native_module->compiled_module();
WasmSharedModuleData* shared = compiled_module->shared();
WasmModule* module = shared->module();
std::vector<WasmFunction>* wasm_functions = &shared->module()->functions;
DCHECK_EQ(compiled_module->export_wrappers()->length(),
shared->module()->num_exported_functions);
bool changed = false;
int func_index = module->num_imported_functions;
// Patch all wasm functions.
for (int num_wasm_functions = static_cast<int>(wasm_functions->size());
func_index < num_wasm_functions; ++func_index) {
WasmCode* wasm_function = native_module->GetCode(func_index);
// TODO(clemensh): Get rid of this nullptr check
if (wasm_function == nullptr ||
wasm_function->kind() != WasmCode::kFunction) {
continue;
}
changed |= ApplyToWasmCode(wasm_function, icache_flush_mode);
}
bool patch_wasm_weak_instances =
!old_weak_instance_.is_identical_to(new_weak_instance_);
// Patch all exported functions (JS_TO_WASM_FUNCTION).
int reloc_mode = 0;
// Patch CODE_TARGET if we shall relocate direct calls. If we patch direct
// calls, the instance registered for that (relocate_direct_calls_module_)
// should match the instance we currently patch (instance).
if (relocate_direct_calls_module_ != nullptr) {
DCHECK_EQ(native_module, relocate_direct_calls_module_);
reloc_mode |= RelocInfo::ModeMask(RelocInfo::JS_TO_WASM_CALL);
}
// Instance references are simply embedded objects.
if (patch_wasm_weak_instances) {
reloc_mode |= RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
}
if (!reloc_mode) return changed;
int wrapper_index = 0;
for (auto exp : module->export_table) {
if (exp.kind != kExternalFunction) continue;
Code* export_wrapper =
Code::cast(compiled_module->export_wrappers()->get(wrapper_index++));
if (export_wrapper->kind() != Code::JS_TO_WASM_FUNCTION) continue;
for (RelocIterator it(export_wrapper, reloc_mode); !it.done(); it.next()) {
RelocInfo::Mode mode = it.rinfo()->rmode();
switch (mode) {
case RelocInfo::JS_TO_WASM_CALL: {
changed = true;
const WasmCode* new_code =
native_module->GetIndirectlyCallableCode(exp.index);
it.rinfo()->set_js_to_wasm_address(new_code->instructions().start(),
icache_flush_mode);
} break;
case RelocInfo::EMBEDDED_OBJECT: {
changed = true;
const HeapObject* old = it.rinfo()->target_object();
if (*old_weak_instance_ == old) {
it.rinfo()->set_target_object(
*new_weak_instance_, WriteBarrierMode::UPDATE_WRITE_BARRIER,
icache_flush_mode);
}
} break;
default:
UNREACHABLE();
}
}
}
DCHECK_EQ(module->functions.size(), func_index);
DCHECK_EQ(compiled_module->export_wrappers()->length(), wrapper_index);
return changed;
}
bool CodeSpecialization::ApplyToWasmCode(wasm::WasmCode* code,
ICacheFlushMode icache_flush_mode) {
DisallowHeapAllocation no_gc;
DCHECK_EQ(wasm::WasmCode::kFunction, code->kind());
bool reloc_direct_calls = relocate_direct_calls_module_ != nullptr;
int reloc_mode = 0;
auto add_mode = [&reloc_mode](bool cond, RelocInfo::Mode mode) {
if (cond) reloc_mode |= RelocInfo::ModeMask(mode);
};
add_mode(reloc_direct_calls, RelocInfo::WASM_CALL);
// Always patch the code table entry address which is used in Liftoff
// prologue to jump to optimized code if existent.
reloc_mode |= RelocInfo::ModeMask(RelocInfo::WASM_CODE_TABLE_ENTRY);
base::Optional<PatchDirectCallsHelper> patch_direct_calls_helper;
bool changed = false;
NativeModule* native_module = code->native_module();
RelocIterator it(code->instructions(), code->reloc_info(),
code->constant_pool(), reloc_mode);
for (; !it.done(); it.next()) {
RelocInfo::Mode mode = it.rinfo()->rmode();
switch (mode) {
case RelocInfo::WASM_CALL: {
DCHECK(reloc_direct_calls);
// Iterate simultaneously over the relocation information and the source
// position table. For each call in the reloc info, move the source
// position iterator forward to that position to find the byte offset of
// the respective call. Then extract the call index from the module wire
// bytes to find the new compiled function.
size_t offset = it.rinfo()->pc() - code->instructions().start();
if (!patch_direct_calls_helper) {
patch_direct_calls_helper.emplace(relocate_direct_calls_module_,
code);
}
int byte_pos = AdvanceSourcePositionTableIterator(
patch_direct_calls_helper->source_pos_it, offset);
uint32_t called_func_index = ExtractDirectCallIndex(
patch_direct_calls_helper->decoder,
patch_direct_calls_helper->func_bytes + byte_pos);
const WasmCode* new_code = native_module->GetCode(called_func_index);
it.rinfo()->set_wasm_call_address(new_code->instructions().start(),
icache_flush_mode);
changed = true;
} break;
case RelocInfo::WASM_CODE_TABLE_ENTRY: {
DCHECK(FLAG_wasm_tier_up);
WasmCode* const* code_table_entry =
native_module->code_table().data() + code->index();
it.rinfo()->set_wasm_code_table_entry(
const_cast<Address>(
reinterpret_cast<byte const*>(code_table_entry)),
icache_flush_mode);
} break;
default:
UNREACHABLE();
}
}
return changed;
}
} // namespace wasm
} // namespace internal
} // namespace v8
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