Copy-on-write arrays.

src/arm/ic-arm.cc

Index: src/arm/ic-arm.cc
diff --git a/src/arm/ic-arm.cc b/src/arm/ic-arm.cc
index 1fd70982542a2a2058c72790d0fbbc13c7ea0040..ca7cc13c65b84e5ee8a5ebda63a298ed5150462a 100644
--- a/src/arm/ic-arm.cc
+++ b/src/arm/ic-arm.cc
@@ -414,17 +414,17 @@ void LoadIC::GenerateFunctionPrototype(MacroAssembler* masm) {
 // Falls through for regular JS object.
 static void GenerateKeyedLoadReceiverCheck(MacroAssembler* masm,
                                            Register receiver,
-                                           Register scratch1,
-                                           Register scratch2,
+                                           Register map,
+                                           Register scratch,
                                            int interceptor_bit,
                                            Label* slow) {
   // Check that the object isn't a smi.
   __ BranchOnSmi(receiver, slow);
   // Get the map of the receiver.
-  __ ldr(scratch1, FieldMemOperand(receiver, HeapObject::kMapOffset));
+  __ ldr(map, FieldMemOperand(receiver, HeapObject::kMapOffset));
   // Check bit field.
-  __ ldrb(scratch2, FieldMemOperand(scratch1, Map::kBitFieldOffset));
-  __ tst(scratch2,
+  __ ldrb(scratch, FieldMemOperand(map, Map::kBitFieldOffset));
+  __ tst(scratch,
          Operand((1 << Map::kIsAccessCheckNeeded) | (1 << interceptor_bit)));
   __ b(nz, slow);
   // Check that the object is some kind of JS object EXCEPT JS Value type.
@@ -432,13 +432,14 @@ static void GenerateKeyedLoadReceiverCheck(MacroAssembler* masm,
   // we enter the runtime system to make sure that indexing into string
   // objects work as intended.
   ASSERT(JS_OBJECT_TYPE > JS_VALUE_TYPE);
-  __ ldrb(scratch1, FieldMemOperand(scratch1, Map::kInstanceTypeOffset));
-  __ cmp(scratch1, Operand(JS_OBJECT_TYPE));
+  __ ldrb(scratch, FieldMemOperand(map, Map::kInstanceTypeOffset));
+  __ cmp(scratch, Operand(JS_OBJECT_TYPE));
   __ b(lt, slow);
 }
 
 
 // Loads an indexed element from a fast case array.
+// If not_fast_array is NULL, doesn't perform the elements map check.
 static void GenerateFastArrayLoad(MacroAssembler* masm,
                                   Register receiver,
                                   Register key,
@@ -471,11 +472,15 @@ static void GenerateFastArrayLoad(MacroAssembler* masm,
   // scratch2 - used to hold the loaded value.
 
   __ ldr(elements, FieldMemOperand(receiver, JSObject::kElementsOffset));
-  // Check that the object is in fast mode (not dictionary).
-  __ ldr(scratch1, FieldMemOperand(elements, HeapObject::kMapOffset));
-  __ LoadRoot(ip, Heap::kFixedArrayMapRootIndex);
-  __ cmp(scratch1, ip);
-  __ b(ne, not_fast_array);
+  if (not_fast_array != NULL) {
+    // Check that the object is in fast mode and writable.
+    __ ldr(scratch1, FieldMemOperand(elements, HeapObject::kMapOffset));
+    __ LoadRoot(ip, Heap::kFixedArrayMapRootIndex);
+    __ cmp(scratch1, ip);
+    __ b(ne, not_fast_array);
+  } else {
+    __ AssertFastElements(elements);
+  }
   // Check that the key (index) is within bounds.
   __ ldr(scratch1, FieldMemOperand(elements, FixedArray::kLengthOffset));
   __ cmp(key, Operand(scratch1));
@@ -1120,16 +1125,23 @@ void KeyedLoadIC::GenerateGeneric(MacroAssembler* masm) {
   GenerateKeyedLoadReceiverCheck(
       masm, receiver, r2, r3, Map::kHasIndexedInterceptor, &slow);
 
+  // Check the "has fast elements" bit in the receiver's map which is
+  // now in r2.
+  __ ldrb(r3, FieldMemOperand(r2, Map::kBitField2Offset));
+  __ tst(r3, Operand(1 << Map::kHasFastElements));
+  __ b(eq, &check_pixel_array);
+
   GenerateFastArrayLoad(
-      masm, receiver, key, r4, r3, r2, r0, &check_pixel_array, &slow);
+      masm, receiver, key, r4, r3, r2, r0, NULL, &slow);
   __ IncrementCounter(&Counters::keyed_load_generic_smi, 1, r2, r3);
   __ Ret();
 
   // Check whether the elements is a pixel array.
   // r0: key
-  // r3: elements map
-  // r4: elements
+  // r1: receiver
   __ bind(&check_pixel_array);
+  __ ldr(r4, FieldMemOperand(r1, JSObject::kElementsOffset));
+  __ ldr(r3, FieldMemOperand(r4, HeapObject::kMapOffset));
   __ LoadRoot(ip, Heap::kPixelArrayMapRootIndex);
   __ cmp(r3, ip);
   __ b(ne, &check_number_dictionary);
@@ -1690,7 +1702,7 @@ void KeyedStoreIC::GenerateGeneric(MacroAssembler* masm) {
 
   // Object case: Check key against length in the elements array.
   __ ldr(elements, FieldMemOperand(receiver, JSObject::kElementsOffset));
-  // Check that the object is in fast mode (not dictionary).
+  // Check that the object is in fast mode and writable.
   __ ldr(r4, FieldMemOperand(elements, HeapObject::kMapOffset));
   __ LoadRoot(ip, Heap::kFixedArrayMapRootIndex);
   __ cmp(r4, ip);
@@ -1748,8 +1760,8 @@ void KeyedStoreIC::GenerateGeneric(MacroAssembler* masm) {
   __ b(&fast);
 
   // Array case: Get the length and the elements array from the JS
-  // array. Check that the array is in fast mode; if it is the
-  // length is always a smi.
+  // array. Check that the array is in fast mode (and writable); if it
+  // is the length is always a smi.
   __ bind(&array);
   __ ldr(elements, FieldMemOperand(receiver, JSObject::kElementsOffset));
   __ ldr(r4, FieldMemOperand(elements, HeapObject::kMapOffset));
@@ -2217,6 +2229,8 @@ void StoreIC::GenerateArrayLength(MacroAssembler* masm) {
   __ b(ne, &miss);
 
   // Check that elements are FixedArray.
+  // We rely on StoreIC_ArrayLength below to deal with all types of
+  // fast elements (including COW).
   __ ldr(scratch, FieldMemOperand(receiver, JSArray::kElementsOffset));
   __ CompareObjectType(scratch, scratch, scratch, FIXED_ARRAY_TYPE);
   __ b(ne, &miss);