Implement Wasm GrowMemory opcode as a wasm runtime call

src/runtime/runtime-wasm.cc

+// Copyright 2016 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/runtime/runtime-utils.h"
+
+#include "src/arguments.h"
+#include "src/assembler.h"
+#include "src/conversions.h"
+#include "src/debug/debug.h"
+#include "src/factory.h"
+#include "src/frames-inl.h"
+#include "src/objects-inl.h"
+#include "src/v8memory.h"
+#include "src/wasm/wasm-module.h"
+
+namespace v8 {
+namespace internal {
+
+RUNTIME_FUNCTION(Runtime_WasmGrowMemory) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  uint32_t delta_pages = 0;
+  RUNTIME_ASSERT(args[0]->ToUint32(&delta_pages));
+
+  // Get the module JSObject
+  const Address entry = Isolate::c_entry_fp(isolate->thread_local_top());
+  Address pc =
+      Memory::Address_at(entry + StandardFrameConstants::kCallerPCOffset);
+  Code* code = isolate->inner_pointer_to_code_cache()->GetCacheEntry(pc)->code;
+  FixedArray* deopt_data = code->deoptimization_data();
+  DCHECK(deopt_data->length() == 2);
+  JSObject* module_object = JSObject::cast(deopt_data->get(0));
+  RUNTIME_ASSERT(!module_object->IsNull(isolate));
+
+  byte* old_mem_start;

[ahaas, 2016/06/24 11:10:15]

I think you could use {Address} as the type for old_mem_start, then you would
not have to reinterpret_cast everywhere.

[gdeepti, 2016/06/25 00:28:41]

Done.

+  byte* new_mem_start;
+  uint32_t old_size, new_size;
+  const int kWasmMemArrayBuffer = 2;
+
+  // Get mem buffer associated with module object
+  Object* obj = module_object->GetInternalField(kWasmMemArrayBuffer);
+  Handle<JSArrayBuffer> old_buffer = Handle<JSArrayBuffer>::null();

[ahaas, 2016/06/24 11:10:15]

Could you not just write?
Handle<JSArrayBuffer> old_buffer =
Handle<JSArrayBuffer>(JSArrayBuffer::cast(obj));

[gdeepti, 2016/06/25 00:28:41]

Done.

+  old_buffer = Handle<JSArrayBuffer>(JSArrayBuffer::cast(obj));
+
+  if (old_buffer->byte_length()->Number() == 0) {
+    // If module object does not have linear memory associated with it,
+    // Allocate new array buffer of given size.
+    old_mem_start = reinterpret_cast<byte*>(old_buffer->backing_store());
+    old_size = 0;
+    // TODO(gdeepti): Fix bounds check to take into account size of memtype.
+    new_size = delta_pages * wasm::WasmModule::kPageSize;
+    if (delta_pages > wasm::WasmModule::kMaxMemPages) {
+      THROW_NEW_ERROR_RETURN_FAILURE(
+          isolate, NewRangeError(MessageTemplate::kWasmTrapMemOutOfBounds));
+    }
+    new_mem_start =
+        reinterpret_cast<byte*>(isolate->array_buffer_allocator()->Allocate(
+            static_cast<uint32_t>(new_size)));
+    if (new_mem_start == NULL) {
+      THROW_NEW_ERROR_RETURN_FAILURE(
+          isolate, NewRangeError(MessageTemplate::kWasmTrapMemAllocationFail));
+    }
+#if DEBUG
+    // Double check the API allocator actually zero-initialized the memory.
+    for (size_t i = old_size; i < new_size; i++) {
+      DCHECK_EQ(0, new_mem_start[i]);
+    }
+#endif
+  } else {
+    old_mem_start = reinterpret_cast<byte*>(old_buffer->backing_store());
+    old_size = old_buffer->byte_length()->Number();
+    new_size = old_size + delta_pages * wasm::WasmModule::kPageSize;
+    if (new_size >
+        wasm::WasmModule::kMaxMemPages * wasm::WasmModule::kPageSize) {
+      THROW_NEW_ERROR_RETURN_FAILURE(
+          isolate, NewRangeError(MessageTemplate::kWasmTrapMemOutOfBounds));
+    }
+    new_mem_start = reinterpret_cast<byte*>(realloc(old_mem_start, new_size));
+    if (new_mem_start == NULL) {
+      THROW_NEW_ERROR_RETURN_FAILURE(
+          isolate, NewRangeError(MessageTemplate::kWasmTrapMemAllocationFail));
+    }
+    old_buffer->set_is_external(true);
+    isolate->heap()->UnregisterArrayBuffer(*old_buffer);
+    // Zero initializing uninitialized memory from realloc
+    for (size_t i = old_size; i < new_size; i++) {

[ahaas, 2016/06/24 11:10:15]

use memset to zero initialize memory?

[gdeepti, 2016/06/25 00:28:41]

Done.

+      new_mem_start[i] = 0;
+    }
+  }
+
+  Handle<JSArrayBuffer> buffer = isolate->factory()->NewJSArrayBuffer();
+  JSArrayBuffer::Setup(buffer, isolate, false, new_mem_start, new_size);
+  buffer->set_is_neuterable(false);
+
+  // Set new buffer to be wasm memory
+  module_object->SetInternalField(kWasmMemArrayBuffer, *buffer);
+
+  RUNTIME_ASSERT(wasm::UpdateWasmModuleMemory(
+      module_object, old_mem_start, new_mem_start, old_size, new_size));
+
+  return *isolate->factory()->NewNumberFromUint(old_size /
+                                                wasm::WasmModule::kPageSize);
+}
+
+}  // namespace internal
+}  // namespace v8