[wasm] Split off debug info from wasm object

src/wasm/wasm-debug.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/wasm/wasm-debug.h"
+
+#include "src/assert-scope.h"
+#include "src/debug/debug.h"
+#include "src/factory.h"
+#include "src/isolate.h"
+#include "src/wasm/module-decoder.h"
+#include "src/wasm/wasm-module.h"
+
+using namespace v8::internal;
+using namespace v8::internal::wasm;
+
+namespace {
+
+enum {
+  kWasmDebugInfoWasmObj,
+  kWasmDebugInfoWasmBytesHash,
+  kWasmDebugInfoFunctionByteOffsets,
+  kWasmDebugInfoNumEntries
+};
+
+ByteArray *GetOrCreateFunctionOffsetTable(WasmDebugInfo *debug_info) {
+  Object *offset_table = debug_info->get(kWasmDebugInfoFunctionByteOffsets);
+  Isolate *isolate = debug_info->GetIsolate();
+  if (!offset_table->IsUndefined(isolate)) return ByteArray::cast(offset_table);
+
+  FunctionOffsetsResult function_offsets;
+  {
+    DisallowHeapAllocation no_gc;
+    SeqOneByteString *wasm_bytes =
+        wasm::GetWasmBytes(debug_info->wasm_object());
+    const byte *bytes_start = wasm_bytes->GetChars();
+    const byte *bytes_end = bytes_start + wasm_bytes->length();
+    function_offsets = wasm::DecodeWasmFunctionOffsets(bytes_start, bytes_end);
+  }
+  DCHECK(function_offsets.ok());
+  size_t array_size = 2 * kIntSize * function_offsets.val.size();
+  CHECK_LE(array_size, static_cast<size_t>(kMaxInt));
+  ByteArray *arr =
+      *isolate->factory()->NewByteArray(static_cast<int>(array_size));
+  int idx = 0;
+  for (std::pair<int, int> p : function_offsets.val) {
+    arr->set_int(idx++, p.first);
+    arr->set_int(idx++, p.second);
+  }
+  DCHECK_EQ(arr->length(), idx * kIntSize);
+  debug_info->set(kWasmDebugInfoFunctionByteOffsets, arr);
+
+  return arr;
+}
+
+std::pair<int, int> GetFunctionOffsetAndLength(WasmDebugInfo *debug_info,
+                                               int func_index) {
+  ByteArray *arr = GetOrCreateFunctionOffsetTable(debug_info);
+  DCHECK(func_index >= 0 && func_index < arr->length() / kIntSize / 2);
+
+  int offset = arr->get_int(2 * func_index);
+  int length = arr->get_int(2 * func_index + 1);
+  // Assert that it's distinguishable from the "illegal function index" return.
+  DCHECK(offset > 0 && length > 0);
+  return {offset, length};
+}
+
+Vector<const uint8_t> GetFunctionBytes(WasmDebugInfo *debug_info,
+                                       int func_index) {
+  DCHECK(!AllowHeapAllocation::IsAllowed());
+  SeqOneByteString *module_bytes =
+      wasm::GetWasmBytes(debug_info->wasm_object());
+  std::pair<int, int> offset_and_length =
+      GetFunctionOffsetAndLength(debug_info, func_index);
+  return Vector<const uint8_t>(
+      module_bytes->GetChars() + offset_and_length.first,
+      offset_and_length.second);
+}
+
+}  // namespace
+
+Handle<WasmDebugInfo> WasmDebugInfo::New(Handle<JSObject> wasm) {
+  Isolate *isolate = wasm->GetIsolate();
+  Factory *factory = isolate->factory();
+  Handle<FixedArray> arr =
+      factory->NewFixedArray(kWasmDebugInfoNumEntries, TENURED);
+  arr->set(kWasmDebugInfoWasmObj, *wasm);
+  int hash = 0;
+  Handle<SeqOneByteString> wasm_bytes(GetWasmBytes(*wasm), isolate);
+  {
+    DisallowHeapAllocation no_gc;
+    hash = StringHasher::HashSequentialString(
+        wasm_bytes->GetChars(), wasm_bytes->length(), kZeroHashSeed);
+  }
+  Handle<Object> hash_obj = factory->NewNumberFromInt(hash, TENURED);
+  arr->set(kWasmDebugInfoWasmBytesHash, *hash_obj);
+
+  return Handle<WasmDebugInfo>::cast(arr);
+}
+
+bool WasmDebugInfo::IsDebugInfo(Object *object) {
+  if (!object->IsFixedArray()) return false;
+  FixedArray *arr = FixedArray::cast(object);
+  Isolate *isolate = arr->GetIsolate();
+  return arr->length() == kWasmDebugInfoNumEntries &&
+         IsWasmObject(arr->get(kWasmDebugInfoWasmObj)) &&
+         arr->get(kWasmDebugInfoWasmBytesHash)->IsNumber() &&
+         (arr->get(kWasmDebugInfoFunctionByteOffsets)->IsUndefined(isolate) ||
+          arr->get(kWasmDebugInfoFunctionByteOffsets)->IsByteArray());
+}
+
+WasmDebugInfo *WasmDebugInfo::cast(Object *object) {
+  DCHECK(IsDebugInfo(object));
+  return reinterpret_cast<WasmDebugInfo *>(object);
+}
+
+JSObject *WasmDebugInfo::wasm_object() {
+  return JSObject::cast(get(kWasmDebugInfoWasmObj));
+}
+
+bool WasmDebugInfo::SetBreakPoint(int byte_offset) {
+  // TODO(clemensh): Implement this.
+  return false;
+}
+
+Handle<String> WasmDebugInfo::DisassembleFunction(int func_index) {
+  std::ostringstream disassembly_os;
+
+  {
+    DisallowHeapAllocation no_gc;
+    Vector<const uint8_t> bytes_vec = GetFunctionBytes(this, func_index);
+
+    base::AccountingAllocator allocator;
+    bool ok = PrintAst(
+        &allocator, FunctionBodyForTesting(bytes_vec.start(), bytes_vec.end()),
+        disassembly_os, nullptr);
+    DCHECK(ok);
+    USE(ok);
+  }
+
+  // Unfortunately, we have to copy the string here.
+  std::string code_str = disassembly_os.str();
+  CHECK_LE(code_str.length(), static_cast<size_t>(kMaxInt));
+  return GetIsolate()
+      ->factory()
+      ->NewStringFromAscii(Vector<const char>(
+          code_str.data(), static_cast<int>(code_str.length())))
+      .ToHandleChecked();
+}
+
+Handle<FixedArray> WasmDebugInfo::GetFunctionOffsetTable(int func_index) {
+  class NullBuf : public std::streambuf {};
+  NullBuf null_buf;
+  std::ostream null_stream(&null_buf);
+
+  std::vector<std::tuple<uint32_t, int, int>> offset_table_vec;
+
+  {
+    DisallowHeapAllocation no_gc;
+    Vector<const uint8_t> bytes_vec = GetFunctionBytes(this, func_index);
+
+    v8::base::AccountingAllocator allocator;
+    bool ok = PrintAst(
+        &allocator, FunctionBodyForTesting(bytes_vec.start(), bytes_vec.end()),
+        null_stream, &offset_table_vec);
+    DCHECK(ok);
+    USE(ok);
+  }
+
+  size_t arr_size = 3 * offset_table_vec.size();
+  CHECK_LE(arr_size, static_cast<size_t>(kMaxInt));
+  Handle<FixedArray> offset_table = GetIsolate()->factory()->NewFixedArray(
+      static_cast<int>(arr_size), TENURED);
+
+  int idx = 0;
+  for (std::tuple<uint32_t, int, int> elem : offset_table_vec) {
+    offset_table->set(idx++, Smi::FromInt(std::get<0>(elem)));
+    offset_table->set(idx++, Smi::FromInt(std::get<1>(elem)));
+    offset_table->set(idx++, Smi::FromInt(std::get<2>(elem)));
+  }
+  DCHECK_EQ(idx, offset_table->length());
+
+  return offset_table;
+}