Use a custom Struct for stack trace storage

src/runtime/runtime-internal.cc

 // Copyright 2014 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 <memory>
 
 #include "src/arguments.h"
 #include "src/ast/prettyprinter.h"
@@ skipping 99 matching lines @@
   // For wasm traps, the byte offset (a.k.a source position) can not be
   // determined from relocation info, since the explicit checks for traps
   // converge in one singe block which calls this runtime function.
   // We hence pass the byte offset explicitely, and patch it into the top-most
   // frame (a wasm frame) on the collected stack trace.
   // TODO(wasm): This implementation is temporary, see bug #5007:
   // https://bugs.chromium.org/p/v8/issues/detail?id=5007
   Handle<JSObject> error = Handle<JSObject>::cast(error_obj);
   Handle<Object> stack_trace_obj = JSReceiver::GetDataProperty(
       error, isolate->factory()->stack_trace_symbol());
+
   // Patch the stack trace (array of <receiver, function, code, position>).
   if (stack_trace_obj->IsJSArray()) {
+    using ESTF = EncodedStackTraceFrame;
+
     Handle<FixedArray> stack_elements(
         FixedArray::cast(JSArray::cast(*stack_trace_obj)->elements()));
-    DCHECK_EQ(1, stack_elements->length() % 4);
-    DCHECK(Code::cast(stack_elements->get(3))->kind() == Code::WASM_FUNCTION);
-    DCHECK(stack_elements->get(4)->IsSmi() &&
-           Smi::cast(stack_elements->get(4))->value() >= 0);
-    stack_elements->set(4, Smi::FromInt(-1 - byte_offset));
+    DCHECK_EQ(0, stack_elements->length() % ESTF::kElementsPerFrame);
+    DCHECK(Code::cast(stack_elements->get(ESTF::kCodeOffset))->kind() ==
+           Code::WASM_FUNCTION);
+    DCHECK(stack_elements->get(ESTF::kWasmFunctionIndexOffset)->IsSmi() &&
+           Smi::cast(stack_elements->get(ESTF::kWasmFunctionIndexOffset))
+                   ->value() >= 0);
+    stack_elements->set(ESTF::kOffsetOffset, Smi::FromInt(-1 - byte_offset));
   }
+
+  // Patch the detailed stack trace (array of JSObjects with various
+  // properties).
   Handle<Object> detailed_stack_trace_obj = JSReceiver::GetDataProperty(
       error, isolate->factory()->detailed_stack_trace_symbol());
-  // Patch the detailed stack trace (array of JSObjects with various
-  // properties).
   if (detailed_stack_trace_obj->IsJSArray()) {
     Handle<FixedArray> stack_elements(
         FixedArray::cast(JSArray::cast(*detailed_stack_trace_obj)->elements()));
     DCHECK_GE(stack_elements->length(), 1);
     Handle<JSObject> top_frame(JSObject::cast(stack_elements->get(0)));
     Handle<String> wasm_offset_key =
         isolate->factory()->InternalizeOneByteString(
             STATIC_CHAR_VECTOR("column"));
     LookupIterator it(top_frame, wasm_offset_key, top_frame,
                       LookupIterator::PROTOTYPE_CHAIN_SKIP_INTERCEPTOR);
@@ skipping 420 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_Typeof) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   return *Object::TypeOf(isolate, object);
 }
 
 }  // namespace internal
 }  // namespace v8