Create specialized code stubs for PixelArray loads.

src/ia32/code-stubs-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6489 matching lines @@
   __ pop(ecx);
   __ pop(eax);
   __ pop(edx);
   __ push(ecx);
 
   // Do a tail call to the rewritten stub.
   __ jmp(Operand(edi));
 }
 
 
+// Loads a indexed element from a pixel array.
+void GenerateFastPixelArrayLoad(MacroAssembler* masm,
+                                Register receiver,
+                                Register key,
+                                Register elements,
+                                Register untagged_key,
+                                Register result,
+                                Label* not_pixel_array,
+                                Label* key_not_smi,
+                                Label* out_of_range) {
+  // Register use:
+  //   receiver - holds the receiver and is unchanged.
+  //   key - holds the key and is unchanged (must be a smi).
+  //   elements - is set to the the receiver's element if
+  //       the receiver doesn't have a pixel array or the
+  //       key is not a smi, otherwise it's the elements'
+  //       external pointer.
+  //   untagged_key - is set to the untagged key
+
+  // Key must be a smi.
+  if (key_not_smi != NULL) {

[Søren Thygesen Gjesse, 2011/02/01 12:02:56]

See comments for ARM. Also on ARM you check the receiver before the key, but of
cause that does not matter.

[danno, 2011/02/03 12:53:26]

Done.

+    __ test(key, Immediate(kSmiTagMask));
+    __ j(not_zero, key_not_smi, not_taken);
+  }
+  __ mov(untagged_key, key);
+  __ SmiUntag(untagged_key);
+
+  // Verify that the receiver has pixel array elements.

[Mads Ager (chromium), 2011/02/01 12:02:12]

Perform checks in the same order on all platforms for consistency? On ARM the
pixel array check is first.

[danno, 2011/02/03 12:53:26]

Done.

+  __ mov(elements, FieldOperand(receiver, JSObject::kElementsOffset));
+  __ CheckMap(elements, Factory::pixel_array_map(), not_pixel_array, true);
+
+  // Key must be in range.
+  __ cmp(untagged_key, FieldOperand(elements, PixelArray::kLengthOffset));
+  __ j(above_equal, out_of_range);
+
+  // Perform the indexed load and tag the result as a smi.
+  __ mov(elements, FieldOperand(elements, PixelArray::kExternalPointerOffset));
+  __ movzx_b(result, Operand(elements, untagged_key, times_1, 0));
+  __ SmiTag(result);
+  __ ret(0);
+}
+
+
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32