[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,
+  kWasmDebugInfoFunctionOffsets,
+  kWasmDebugInfoNumInternalFields
+};
+
+ByteArray *GetOrCreateFunctionOffsetTable(WasmDebugInfo *debug_info) {
+  Object *offset_table =
+      debug_info->GetInternalField(kWasmDebugInfoFunctionOffsets);
+  if (!offset_table->IsUndefined()) 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());
+  Isolate *isolate = debug_info->GetIsolate();
+  size_t array_size =
+      2 * sizeof(int) * static_cast<int>(function_offsets.val.size());
+  CHECK_LE(array_size, std::numeric_limits<int>::max());
+  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 * sizeof(int));
+  debug_info->SetInternalField(kWasmDebugInfoFunctionOffsets, arr);
+
+  return arr;
+}
+
+}  // namespace
+
+Handle<WasmDebugInfo> WasmDebugInfo::New(Handle<JSObject> wasm) {
+  Isolate *isolate = wasm->GetIsolate();
+  Factory *factory = isolate->factory();
+  Handle<Map> map = factory->NewMap(
+      JS_OBJECT_TYPE,
+      JSObject::kHeaderSize + kWasmDebugInfoNumInternalFields * kPointerSize);
+  Handle<JSObject> info = factory->NewJSObjectFromMap(map, TENURED);
+  info->SetInternalField(kWasmDebugInfoWasmObj, *wasm);
+  int hash = 0;
+  Handle<SeqOneByteString> wasm_bytes(GetWasmBytes(*wasm), isolate);
+  {
+    DisallowHeapAllocation no_gc;
+    hash = StringHasher::HashSequentialString(wasm_bytes->GetChars(),
+                                              wasm_bytes->length(), 0);
+  }
+  info->SetInternalField(kWasmDebugInfoWasmBytesHash,
+                         *factory->NewNumberFromInt(hash, TENURED));
+
+  // TODO(clemensh): Register the wasm module at the debugger
+
+  return Handle<WasmDebugInfo>::cast(info);
+}
+
+bool WasmDebugInfo::IsDebugInfo(Object *object) {
+  if (!object->IsJSObject()) return false;
+  JSObject *obj = JSObject::cast(object);
+  return obj->GetInternalFieldCount() == kWasmDebugInfoNumInternalFields &&
+         IsWasmObject(obj->GetInternalField(kWasmDebugInfoWasmObj)) &&
+         obj->GetInternalField(kWasmDebugInfoWasmBytesHash)->IsNumber() &&
+         (obj->GetInternalField(kWasmDebugInfoFunctionOffsets)->IsUndefined() ||
+          obj->GetInternalField(kWasmDebugInfoFunctionOffsets)->IsByteArray());
+}
+
+WasmDebugInfo *WasmDebugInfo::cast(Object *object) {
+  DCHECK(IsDebugInfo(object));
+  return static_cast<WasmDebugInfo *>(object);
+}
+
+JSObject *WasmDebugInfo::wasm_object() {
+  return JSObject::cast(GetInternalField(kWasmDebugInfoWasmObj));
+}
+
+bool WasmDebugInfo::SetBreakPoint(int byte_offset) { return false; }
+
+std::pair<int, int> WasmDebugInfo::GetFunctionOffsetAndLength(int func_index) {
+  ByteArray *arr = GetOrCreateFunctionOffsetTable(this);
+
+  if (func_index < 0 || func_index >= arr->length() / sizeof(int) / 2) {
+    return {0, 0};
+  }
+  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};
+}
+
+Handle<Object> wasm::GetFunctionOffsetTable(Isolate *isolate,
+                                            Handle<String> module_bytes) {
+  FunctionOffsetsResult function_offsets;
+  {
+    DisallowHeapAllocation no_gc;
+    DCHECK(module_bytes->IsSeqOneByteString());
+    Vector<const uint8_t> bytes_vec =
+        module_bytes->GetFlatContent().ToOneByteVector();
+    function_offsets =
+        wasm::DecodeWasmFunctionOffsets(bytes_vec.start(), bytes_vec.end());
+  }
+  if (!function_offsets.ok()) return isolate->factory()->undefined_value();
+
+  size_t array_size = 2 * function_offsets.val.size();
+  CHECK_LE(array_size, std::numeric_limits<int>::max());
+  Handle<FixedArray> arr =
+      isolate->factory()->NewFixedArray(static_cast<int>(array_size));
+  int idx = 0;
+  for (std::pair<int, int> p : function_offsets.val) {
+    arr->set(idx++, Smi::FromInt(p.first));
+    arr->set(idx++, Smi::FromInt(p.second));
+  }
+  DCHECK_EQ(arr->length(), idx);
+  return isolate->factory()->NewJSArrayWithElements(arr);
+}
+
+Handle<Object> wasm::DisassembleFunction(Isolate *isolate,
+                                         Handle<String> function_bytes,
+                                         bool get_code, bool get_table) {
+  struct NullBuf : public std::streambuf {};
+  struct LineCountingStream : public std::streambuf {
+    std::streambuf *buf;
+    uint32_t line_nr = 0;
+    uint32_t col_nr = 0;
+
+    explicit LineCountingStream(std::streambuf *buf) : buf(buf) {}
+    inline void nextChar(int_type c) {
+      ++col_nr;
+      if (c == '\n') ++line_nr, col_nr = 0;
+    }
+    int_type overflow(int_type c) override {
+      if (c != EOF) {
+        nextChar(c);
+        buf->sputc(c);
+      }
+      return c;
+    }
+    std::streamsize xsputn(const char *s, std::streamsize n) override {
+      for (const char *p = s, *e = s + n; p != e; ++p) nextChar(*p);
+      buf->sputn(s, n);
+      return n;
+    }
+  };
+
+  // The result will be put here.
+  std::stringbuf code_buf;
+  std::vector<uint32_t> offset_table;
+
+  // If get_code is set, use ostringstream. If get_table is set, use
+  // LineCountingStream. Both can be combined.
+  NullBuf nullbuf;
+  std::streambuf *selected_streambuf =
+      get_code ? &code_buf : static_cast<std::streambuf *>(&nullbuf);
+  LineCountingStream line_counting_stream(selected_streambuf);
+  std::ostream line_counting_ostream(&line_counting_stream);
+  std::function<void(int)> instruction_callback;
+  if (get_table) {
+    instruction_callback = [&](uint32_t offset) {
+      offset_table.push_back(offset);
+      offset_table.push_back(line_counting_stream.line_nr);
+      offset_table.push_back(line_counting_stream.col_nr);
+    };
+    selected_streambuf = &line_counting_stream;
+  }
+
+  {
+    DisallowHeapAllocation no_gc;
+    DCHECK(function_bytes->IsSeqOneByteString());
+    Vector<const uint8_t> bytes_vec =
+        function_bytes->GetFlatContent().ToOneByteVector();
+
+    base::AccountingAllocator allocator;
+    std::ostream os(selected_streambuf);
+    if (!PrintAst(&allocator,
+                  FunctionBody::ForTesting(bytes_vec.start(), bytes_vec.end()),
+                  os, instruction_callback)) {
+      return isolate->factory()->undefined_value();
+    }
+  }
+
+  Handle<FixedArray> return_arr = isolate->factory()->NewFixedArray(2);
+
+  if (get_code) {
+    // Unfortunately, we have to copy the string here.
+    std::string code_str = code_buf.str();
+    CHECK_LE(code_str.length(), std::numeric_limits<int>::max());
+    return_arr->set(
+        0, *isolate->factory()
+                ->NewStringFromAscii(Vector<const char>(
+                    code_str.data(), static_cast<int>(code_str.length())))
+                .ToHandleChecked());
+  }
+
+  if (get_table) {
+    DCHECK_LE(offset_table.size(), std::numeric_limits<int>::max());
+    Handle<FixedArray> offset_arr = isolate->factory()->NewFixedArray(
+        static_cast<int>(offset_table.size()));
+    int idx = 0;
+    for (uint32_t elem : offset_table) {
+      offset_arr->set(idx++, Smi::FromInt(elem));
+    }
+    DCHECK(idx % 3 == 0);
+    DCHECK_EQ(idx, offset_arr->length());
+    return_arr->set(1, *isolate->factory()->NewJSArrayWithElements(offset_arr));
+  }
+
+  return isolate->factory()->NewJSArrayWithElements(return_arr);
+}