Compiling an array literal should be context-independent.

We are removing use of the debugger context. When the debugger triggers
compilation, we may not have a context from which to create a JSArray.

R=ishell@chromium.org
BUG=chromium:664577

Review-Url: https://codereview.chromium.org/2479123002
Cr-Commit-Position: refs/heads/master@{#40956}

src/ast/ast.cc

@@ -14,6 +14,7 @@
 #include "src/code-stubs.h"
 #include "src/contexts.h"
 #include "src/conversions.h"
+#include "src/elements.h"
 #include "src/property-details.h"
 #include "src/property.h"
 #include "src/string-stream.h"
@@ -580,11 +581,9 @@ void ArrayLiteral::BuildConstantElements(Isolate* isolate) {
   if (!constant_elements_.is_null()) return;
 
   int constants_length = values()->length();
-
-  // Allocate a fixed array to hold all the object literals.
-  Handle<JSArray> array = isolate->factory()->NewJSArray(
-      FAST_HOLEY_SMI_ELEMENTS, constants_length, constants_length,
-      INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE);
+  ElementsKind kind = FIRST_FAST_ELEMENTS_KIND;
+  Handle<FixedArray> fixed_array =
+      isolate->factory()->NewFixedArrayWithHoles(constants_length);
 
   // Fill in the literals.
   bool is_simple = true;
@@ -615,29 +614,34 @@ void ArrayLiteral::BuildConstantElements(Isolate* isolate) {
       is_simple = false;
     }
 
-    JSObject::AddDataElement(array, array_index, boilerplate_value, NONE)
-        .Assert();
+    kind = GetMoreGeneralElementsKind(kind,
+                                      boilerplate_value->OptimalElementsKind());
+    fixed_array->set(array_index, *boilerplate_value);
   }
 
-  JSObject::ValidateElements(array);
-  Handle<FixedArrayBase> element_values(array->elements());
+  if (is_holey) kind = GetHoleyElementsKind(kind);
 
   // Simple and shallow arrays can be lazily copied, we transform the
   // elements array to a copy-on-write array.
   if (is_simple && depth_acc == 1 && array_index > 0 &&
-      array->HasFastSmiOrObjectElements()) {
-    element_values->set_map(isolate->heap()->fixed_cow_array_map());
+      IsFastSmiOrObjectElementsKind(kind)) {
+    fixed_array->set_map(isolate->heap()->fixed_cow_array_map());
+  }
+
+  Handle<FixedArrayBase> elements = fixed_array;
+  if (IsFastDoubleElementsKind(kind)) {
+    ElementsAccessor* accessor = ElementsAccessor::ForKind(kind);
+    elements = isolate->factory()->NewFixedDoubleArray(constants_length);
+    // We are copying from non-fast-double to fast-double.
+    ElementsKind from_kind = TERMINAL_FAST_ELEMENTS_KIND;
+    accessor->CopyElements(fixed_array, from_kind, elements, constants_length);
   }
 
   // Remember both the literal's constant values as well as the ElementsKind
   // in a 2-element FixedArray.
   Handle<FixedArray> literals = isolate->factory()->NewFixedArray(2, TENURED);
-
-  ElementsKind kind = array->GetElementsKind();
-  kind = is_holey ? GetHoleyElementsKind(kind) : GetPackedElementsKind(kind);
-
   literals->set(0, Smi::FromInt(kind));
-  literals->set(1, *element_values);
+  literals->set(1, *elements);
 
   constant_elements_ = literals;
   set_is_simple(is_simple);

src/elements.cc

@@ -973,6 +973,12 @@ class ElementsAccessorBase : public ElementsAccessor {
                                packed_size, copy_size);
   }
 
+  void CopyElements(Handle<FixedArrayBase> source, ElementsKind source_kind,
+                    Handle<FixedArrayBase> destination, int size) {
+    Subclass::CopyElementsImpl(*source, 0, *destination, source_kind, 0,
+                               kPackedSizeNotKnown, size);
+  }
+
   Handle<SeededNumberDictionary> Normalize(Handle<JSObject> object) final {
     return Subclass::NormalizeImpl(object, handle(object->elements()));
   }

src/elements.h

@@ -170,6 +170,10 @@ class ElementsAccessor {
                                       Handle<Object> value, uint32_t start,
                                       uint32_t length) = 0;
 
+  virtual void CopyElements(Handle<FixedArrayBase> source,
+                            ElementsKind source_kind,
+                            Handle<FixedArrayBase> destination, int size) = 0;
+
  protected:
   friend class LookupIterator;
 

test/inspector/debugger/get-possible-breakpoints-array-literal-expected.txt

@@ -0,0 +1,27 @@
+{
+    id : <messageId>
+    result : {
+        locations : [
+            [0] : {
+                columnNumber : 0
+                lineNumber : 0
+                scriptId : <scriptId>
+            }
+            [1] : {
+                columnNumber : 6
+                lineNumber : 0
+                scriptId : <scriptId>
+            }
+            [2] : {
+                columnNumber : 7
+                lineNumber : 0
+                scriptId : <scriptId>
+            }
+            [3] : {
+                columnNumber : 8
+                lineNumber : 0
+                scriptId : <scriptId>
+            }
+        ]
+    }
+}

test/inspector/debugger/get-possible-breakpoints-array-literal.js

@@ -0,0 +1,12 @@
+// 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.
+
+Protocol.Debugger.enable();
+
+Protocol.Debugger.onceScriptParsed().then(message => message.params.scriptId)
+  .then((scriptId) => Protocol.Debugger.getPossibleBreakpoints({ start: { lineNumber: 0, columnNumber: 0, scriptId: scriptId }}))
+  .then(InspectorTest.logMessage)
+  .then(InspectorTest.completeTest);
+
+compileAndRunWithOrigin("() => []", "", 0, 0);