[wasm] Shrink code table to only include wasm functions

The slots for imported functions are unused by now. Shrink the table to
only store pointers for non-imported functions (i.e. wasm functions
defined in this module).

R=mstarzinger@chromium.org

Change-Id: I6d13f889528b42beca73c860a800bde7a8e921ab
Reviewed-on: https://chromium-review.googlesource.com/1084845Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53493}

src/assembler.h

@@ -398,6 +398,7 @@ class RelocInfo {
     PC_JUMP,
 
     // Points to a wasm code table entry.
+    // TODO(clemensh): Remove this once we have the jump table (issue 7758).
     WASM_CODE_TABLE_ENTRY,
 
     // Pseudo-types

src/wasm/baseline/liftoff-compiler.cc

@@ -1949,8 +1949,11 @@ bool LiftoffCompilationUnit::ExecuteCompilation() {
       compiler::GetWasmCallDescriptor(&zone, wasm_unit_->func_body_.sig);
   base::Optional<TimedHistogramScope> liftoff_compile_time_scope(
       base::in_place, wasm_unit_->counters_->liftoff_compile_time());
+  // TODO(clemensh): Remove this once we have the jump table (issue 7758).
   wasm::WasmCode** code_table_entry =
-      &wasm_unit_->native_module_->code_table()[wasm_unit_->func_index_];
+      &wasm_unit_->native_module_
+           ->code_table()[wasm_unit_->func_index_ -
+                          wasm_unit_->native_module_->num_imported_functions()];
   DCHECK(!protected_instructions_);
   protected_instructions_.reset(
       new std::vector<trap_handler::ProtectedInstructionData>());

src/wasm/wasm-code-manager.cc

@@ -383,8 +383,9 @@ NativeModule::NativeModule(uint32_t num_functions, uint32_t num_imports,
       can_request_more_memory_(can_request_more),
       use_trap_handler_(env.use_trap_handler) {
   if (num_functions > 0) {
-    code_table_.reset(new WasmCode*[num_functions]);
-    memset(code_table_.get(), 0, num_functions * sizeof(WasmCode*));
+    uint32_t num_wasm_functions = num_functions - num_imports;
+    code_table_.reset(new WasmCode*[num_wasm_functions]);
+    memset(code_table_.get(), 0, num_wasm_functions * sizeof(WasmCode*));
   }
   VirtualMemory my_mem;
   owned_code_space_.push_back(my_mem);
@@ -394,9 +395,11 @@ NativeModule::NativeModule(uint32_t num_functions, uint32_t num_imports,
 
 void NativeModule::ReserveCodeTableForTesting(uint32_t max_functions) {
   DCHECK_LE(num_functions_, max_functions);
-  WasmCode** new_table = new WasmCode*[max_functions];
-  memset(new_table, 0, max_functions * sizeof(*new_table));
-  memcpy(new_table, code_table_.get(), num_functions_ * sizeof(*new_table));
+  uint32_t num_wasm = num_functions_ - num_imported_functions_;
+  uint32_t max_wasm = max_functions - num_imported_functions_;
+  WasmCode** new_table = new WasmCode*[max_wasm];
+  memset(new_table, 0, max_wasm * sizeof(*new_table));
+  memcpy(new_table, code_table_.get(), num_wasm * sizeof(*new_table));
   code_table_.reset(new_table);
 }
 
@@ -406,8 +409,8 @@ void NativeModule::SetNumFunctionsForTesting(uint32_t num_functions) {
 
 void NativeModule::SetCodeForTesting(uint32_t index, WasmCode* code) {
   DCHECK_LT(index, num_functions_);
-  DCHECK_LT(num_imported_functions_, index);
-  code_table_[index] = code;
+  DCHECK_LE(num_imported_functions_, index);
+  code_table_[index - num_imported_functions_] = code;
 }
 
 WasmCode* NativeModule::AddOwnedCode(
@@ -454,9 +457,11 @@ WasmCode* NativeModule::AddOwnedCode(
 
 WasmCode* NativeModule::AddCodeCopy(Handle<Code> code, WasmCode::Kind kind,
                                     uint32_t index) {
+  // TODO(wasm): Adding instance-specific wasm-to-js wrappers as owned code to
+  // this NativeModule is a memory leak until the whole NativeModule dies.
   WasmCode* ret = AddAnonymousCode(code, kind);
-  code_table_[index] = ret;
   ret->index_ = Just(index);
+  if (index >= num_imported_functions_) set_code(index, ret);
   return ret;
 }
 
@@ -468,8 +473,8 @@ WasmCode* NativeModule::AddInterpreterEntry(Handle<Code> code, uint32_t index) {
 
 void NativeModule::SetLazyBuiltin(Handle<Code> code) {
   WasmCode* lazy_builtin = AddAnonymousCode(code, WasmCode::kLazyStub);
-  for (uint32_t i = num_imported_functions_, e = num_functions_; i < e; ++i) {
-    code_table_[i] = lazy_builtin;
+  for (WasmCode*& code_table_entry : code_table()) {
+    code_table_entry = lazy_builtin;
   }
 }
 
@@ -586,7 +591,7 @@ WasmCode* NativeModule::AddCode(
       safepoint_table_offset, handler_table_offset,
       std::move(protected_instructions), tier, WasmCode::kNoFlushICache);
 
-  code_table_[index] = ret;
+  set_code(index, ret);
 
   // Apply the relocation delta by iterating over the RelocInfo.
   AllowDeferredHandleDereference embedding_raw_address;
@@ -812,7 +817,7 @@ WasmCode* NativeModule::CloneCode(const WasmCode* original_code,
       original_code->handler_table_offset_, std::move(protected_instructions),
       original_code->tier(), flush_icache);
   if (!ret->IsAnonymous()) {
-    code_table_[ret->index()] = ret;
+    set_code(ret->index(), ret);
   }
   return ret;
 }

src/wasm/wasm-code-manager.h

@@ -266,13 +266,13 @@ class V8_EXPORT_PRIVATE NativeModule final {
   WasmCode* code(uint32_t index) const {
     DCHECK_LT(index, num_functions_);
     DCHECK_LE(num_imported_functions_, index);
-    return code_table_[index];
+    return code_table_[index - num_imported_functions_];
   }
 
   bool has_code(uint32_t index) const {
     DCHECK_LT(index, num_functions_);
     DCHECK_LE(num_imported_functions_, index);
-    return code_table_[index] != nullptr;
+    return code_table_[index - num_imported_functions_] != nullptr;
   }
 
   WasmCode* runtime_stub(WasmCode::RuntimeStubId index) const {
@@ -309,7 +309,7 @@ class V8_EXPORT_PRIVATE NativeModule final {
   uint32_t num_functions() const { return num_functions_; }
   uint32_t num_imported_functions() const { return num_imported_functions_; }
   Vector<WasmCode*> code_table() const {
-    return {code_table_.get(), num_functions_};
+    return {code_table_.get(), num_functions_ - num_imported_functions_};
   }
   bool use_trap_handler() const { return use_trap_handler_; }
   void set_lazy_compile_frozen(bool frozen) { lazy_compile_frozen_ = frozen; }
@@ -351,6 +351,13 @@ class V8_EXPORT_PRIVATE NativeModule final {
   Address GetLocalAddressFor(Handle<Code>);
   Address CreateTrampolineTo(Handle<Code>);
 
+  void set_code(uint32_t index, WasmCode* code) {
+    DCHECK_LT(index, num_functions_);
+    DCHECK_LE(num_imported_functions_, index);
+    DCHECK_EQ(code->index(), index);
+    code_table_[index - num_imported_functions_] = code;
+  }
+
   // Holds all allocated code objects, is maintained to be in ascending order
   // according to the codes instruction start address to allow lookups.
   std::vector<std::unique_ptr<WasmCode>> owned_code_;

src/wasm/wasm-serialization.cc

@@ -499,7 +499,7 @@ bool NativeModuleDeserializer::ReadCode(uint32_t fn_index, Reader* reader) {
       constant_pool_offset, stack_slot_count, safepoint_table_offset,
       handler_table_offset, std::move(protected_instructions), tier,
       WasmCode::kNoFlushICache);
-  native_module_->code_table_[fn_index] = ret;
+  native_module_->set_code(fn_index, ret);
 
   // Relocate the code.
   int mask = RelocInfo::ModeMask(RelocInfo::CODE_TARGET) |
@@ -538,8 +538,10 @@ bool NativeModuleDeserializer::ReadCode(uint32_t fn_index, Reader* reader) {
       case RelocInfo::WASM_CODE_TABLE_ENTRY: {
         DCHECK(FLAG_wasm_tier_up);
         DCHECK(ret->is_liftoff());
+        uint32_t code_table_index =
+            ret->index() - native_module_->num_imported_functions_;
         WasmCode** code_table_entry =
-            &native_module_->code_table()[ret->index()];
+            &native_module_->code_table()[code_table_index];
         iter.rinfo()->set_wasm_code_table_entry(
             reinterpret_cast<Address>(code_table_entry), SKIP_ICACHE_FLUSH);
         break;