First implementation of fast path for instantiation of array literals composed of doubles.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 35a48b14c23759502fc0b9b632ac13fd9c04367f..2f7a943bf7c81782e5158ffcf591dd43b6a48d31 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -4461,33 +4461,53 @@ void LCodeGen::EmitDeepCopy(Handle<JSObject> object,
     }
   }
 
-  // Copy elements backing store header.
-  ASSERT(!has_elements || elements->IsFixedArray());
   if (has_elements) {
+    // Copy elements backing store header.
     __ LoadHeapObject(source, elements);
     for (int i = 0; i < FixedArray::kHeaderSize; i += kPointerSize) {

[Jakob Kummerow, 2012/03/21 10:36:47]

This should be FixedArrayBase::kHeaderSize (doesn't make a difference in
practice because FixedArray inherits kHeaderSize from FixedArrayBase, but let's
be correct here nevertheless).

       __ mov(ecx, FieldOperand(source, i));
       __ mov(FieldOperand(result, elements_offset + i), ecx);
     }
-  }
 
-  // Copy elements backing store content.
-  ASSERT(!has_elements || elements->IsFixedArray());
-  int elements_length = has_elements ? elements->length() : 0;
-  for (int i = 0; i < elements_length; i++) {
-    int total_offset = elements_offset + FixedArray::OffsetOfElementAt(i);
-    Handle<Object> value = JSObject::GetElement(object, i);
-    if (value->IsJSObject()) {
-      Handle<JSObject> value_object = Handle<JSObject>::cast(value);
-      __ lea(ecx, Operand(result, *offset));
-      __ mov(FieldOperand(result, total_offset), ecx);
-      __ LoadHeapObject(source, value_object);
-      EmitDeepCopy(value_object, result, source, offset);
-    } else if (value->IsHeapObject()) {
-      __ LoadHeapObject(ecx, Handle<HeapObject>::cast(value));
-      __ mov(FieldOperand(result, total_offset), ecx);
+    // Copy elements backing store content.
+    int elements_length = elements->length();
+    if (elements->IsFixedDoubleArray()) {
+      Handle<FixedDoubleArray> double_array =
+          Handle<FixedDoubleArray>::cast(elements);
+      for (int i = 0; i < elements_length; i++) {
+        int64_t i_value;

[Jakob Kummerow, 2012/03/21 10:36:47]

Remove the "i_". Just "value".
The same applies to i_value_low and i_value_high below.

[Sven Panne, 2012/03/21 11:04:12]

To reduce copy-n-paste, adding a method to FixedDoubleArray for getting an
int64_t from an element for a given index would be nicer IMHO. This method can
be re-used on all architectures. Not a big saving, but anyway: Redundancy is the
root of all evil. :-)

+        if (double_array->is_the_hole(i)) {
+          i_value = kHoleNanInt64;
+        } else {
+          double value = double_array->get_scalar(i);
+          i_value = BitCast<int64_t, double>(value);
+        }
+        int32_t i_value_low = i_value & 0xFFFFFFFF;
+        int32_t i_value_high = i_value >> 32;
+        int total_offset =
+            elements_offset + FixedDoubleArray::OffsetOfElementAt(i);
+        __ mov(FieldOperand(result, total_offset), Immediate(i_value_low));
+        __ mov(FieldOperand(result, total_offset + 4), Immediate(i_value_high));
+      }
+    } else if (elements->IsFixedArray()) {
+      for (int i = 0; i < elements_length; i++) {
+        int total_offset = elements_offset + FixedArray::OffsetOfElementAt(i);
+        Handle<Object> value = JSObject::GetElement(object, i);
+        if (value->IsJSObject()) {
+          Handle<JSObject> value_object = Handle<JSObject>::cast(value);
+          __ lea(ecx, Operand(result, *offset));
+          __ mov(FieldOperand(result, total_offset), ecx);
+          __ LoadHeapObject(source, value_object);
+          EmitDeepCopy(value_object, result, source, offset);
+        } else if (value->IsHeapObject()) {
+          __ LoadHeapObject(ecx, Handle<HeapObject>::cast(value));
+          __ mov(FieldOperand(result, total_offset), ecx);
+        } else {
+          __ mov(FieldOperand(result, total_offset), Immediate(value));
+        }
+      }
     } else {
-      __ mov(FieldOperand(result, total_offset), Immediate(value));
+      UNREACHABLE();
     }
   }
 }