Add pointer cache field to external string for access in generated code.

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 5071 matching lines @@
   if (never_nan_nan_ && is_equality) stream->Add("_NO_NAN");
   if (!include_number_compare_) stream->Add("_NO_NUMBER");
   if (!include_smi_compare_) stream->Add("_NO_SMI");
 }
 
 
 // -------------------------------------------------------------------------
 // StringCharCodeAtGenerator
 
 void StringCharCodeAtGenerator::GenerateFast(MacroAssembler* masm) {
-  Label flat_string;
-  Label ascii_string;
-  Label got_char_code;
-  Label sliced_string;
-
   // If the receiver is a smi trigger the non-string case.
   STATIC_ASSERT(kSmiTag == 0);
   __ JumpIfSmi(object_, receiver_not_string_);
 
   // Fetch the instance type of the receiver into result register.
   __ mov(result_, FieldOperand(object_, HeapObject::kMapOffset));
   __ movzx_b(result_, FieldOperand(result_, Map::kInstanceTypeOffset));
   // If the receiver is not a string trigger the non-string case.
   __ test(result_, Immediate(kIsNotStringMask));
   __ j(not_zero, receiver_not_string_);
 
   // If the index is non-smi trigger the non-smi case.
   STATIC_ASSERT(kSmiTag == 0);
   __ JumpIfNotSmi(index_, &index_not_smi_);
   __ bind(&got_smi_index_);
 
   // Check for index out of range.
   __ cmp(index_, FieldOperand(object_, String::kLengthOffset));
   __ j(above_equal, index_out_of_range_);
 
-  // We need special handling for non-flat strings.
-  STATIC_ASSERT(kSeqStringTag == 0);
-  __ test(result_, Immediate(kStringRepresentationMask));
-  __ j(zero, &flat_string);
+  __ SmiUntag(index_);
 
-  // Handle non-flat strings.
-  __ and_(result_, kStringRepresentationMask);
-  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
-  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
-  __ cmp(result_, kExternalStringTag);
-  __ j(greater, &sliced_string, Label::kNear);
-  __ j(equal, &call_runtime_);
+  Factory* factory = masm->isolate()->factory();
+  GenerateCharLoad(masm, factory, object_, index_, result_, &call_runtime_);
 
-  // ConsString.
-  // Check whether the right hand side is the empty string (i.e. if
-  // this is really a flat string in a cons string). If that is not
-  // the case we would rather go to the runtime system now to flatten
-  // the string.
-  Label assure_seq_string;
-  __ cmp(FieldOperand(object_, ConsString::kSecondOffset),
-         Immediate(masm->isolate()->factory()->empty_string()));
-  __ j(not_equal, &call_runtime_);
-  // Get the first of the two parts.
-  __ mov(object_, FieldOperand(object_, ConsString::kFirstOffset));
-  __ jmp(&assure_seq_string, Label::kNear);
-
-  // SlicedString, unpack and add offset.
-  __ bind(&sliced_string);
-  __ add(index_, FieldOperand(object_, SlicedString::kOffsetOffset));
-  __ mov(object_, FieldOperand(object_, SlicedString::kParentOffset));
-
-  // Assure that we are dealing with a sequential string. Go to runtime if not.
-  // Note that if the original string is a cons or slice with an external
-  // string as underlying string, we pass that unpacked underlying string with
-  // the adjusted index to the runtime function.
-  __ bind(&assure_seq_string);
-  __ mov(result_, FieldOperand(object_, HeapObject::kMapOffset));
-  __ movzx_b(result_, FieldOperand(result_, Map::kInstanceTypeOffset));
-  STATIC_ASSERT(kSeqStringTag == 0);
-  __ test(result_, Immediate(kStringRepresentationMask));
-  __ j(not_zero, &call_runtime_);
-
-  // Check for 1-byte or 2-byte string.
-  __ bind(&flat_string);
-  STATIC_ASSERT((kStringEncodingMask & kAsciiStringTag) != 0);
-  STATIC_ASSERT((kStringEncodingMask & kTwoByteStringTag) == 0);
-  __ test(result_, Immediate(kStringEncodingMask));
-  __ j(not_zero, &ascii_string, Label::kNear);
-
-  // 2-byte string.
-  // Load the 2-byte character code into the result register.
-  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
-  __ movzx_w(result_, FieldOperand(object_,
-                                   index_, times_1,  // Scratch is smi-tagged.
-                                   SeqTwoByteString::kHeaderSize));
-  __ jmp(&got_char_code, Label::kNear);
-
-  // ASCII string.
-  // Load the byte into the result register.
-  __ bind(&ascii_string);
-  __ SmiUntag(index_);
-  __ movzx_b(result_, FieldOperand(object_,
-                                   index_, times_1,
-                                   SeqAsciiString::kHeaderSize));
-  __ bind(&got_char_code);
   __ SmiTag(result_);
   __ bind(&exit_);
 }
 
 
+void StringCharCodeAtGenerator::GenerateCharLoad(MacroAssembler* masm,
+                                                 Factory* factory,
+                                                 Register string,
+                                                 Register index,
+                                                 Register result,
+                                                 Label* call_runtime) {
+  // Fetch the instance type of the receiver into result register.
+  __ mov(result, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzx_b(result, FieldOperand(result, Map::kInstanceTypeOffset));
+
+  // We need special handling for indirect strings.
+  Label check_sequential;
+  __ test(result, Immediate(kIsIndirectStringMask));
+  __ j(zero, &check_sequential);
+
+  // Dispatch on the indirect string shape: slice or cons.
+  Label cons_string;
+  __ test(result, Immediate(kSlicedNotConsMask));
+  __ j(zero, &cons_string);
+
+  // Handle slices.
+  Label indirect_string_loaded;
+  __ mov(result, FieldOperand(string, SlicedString::kOffsetOffset));
+  __ SmiUntag(result);
+  __ add(index, result);
+  __ mov(string, FieldOperand(string, SlicedString::kParentOffset));
+  __ jmp(&indirect_string_loaded);
+
+  // Handle external strings.
+  Label external_string, ascii_external, done;
+  __ bind(&external_string);
+  if (FLAG_debug_code) {
+    // Assert that we do not have a cons or slice (indirect strings) here.
+    __ test(result, Immediate(kIsIndirectStringMask));
+    __ Assert(zero, "external string expected, but not found");

[Lasse Reichstein, 2011/11/17 13:40:18]

This test checks for "indirect string" but reports "not external". Seems to
ignore sequential strings. Make a comment here if we ruled those out earlier.

+  }
+  __ mov(result, FieldOperand(string, ExternalString::kResourceDataOffset));
+  __ test(result, result);
+  __ j(zero, call_runtime);
+  __ cmp(FieldOperand(string, HeapObject::kMapOffset),
+         Immediate(factory->external_ascii_string_map()));
+  __ j(equal, &ascii_external, Label::kNear);
+  __ cmp(FieldOperand(string, HeapObject::kMapOffset),

[Lasse Reichstein, 2011/11/17 13:40:18]

Comparing against the same memory location twice in a row. Is there no register
free to load it?
Or, possibly, keep it alive since we first loaded it in line 5129?
But this'll probably not happen often enough to warrant a scratch register.

[Yang, 2011/11/17 17:06:23]

|string| is used as a temp register, so I can use it as scratch at this point.

+         Immediate(factory->external_ascii_symbol_map()));
+  __ j(equal, &ascii_external, Label::kNear);
+  // Two-byte string.
+  __ movzx_w(result, Operand(result, index, times_2, 0));
+  __ jmp(&done);
+  __ bind(&ascii_external);
+  // Ascii string.
+  __ movzx_b(result, Operand(result, index, times_1, 0));
+  __ jmp(&done);
+
+  // Handle conses.
+  // Check whether the right hand side is the empty string (i.e. if
+  // this is really a flat string in a cons string). If that is not
+  // the case we would rather go to the runtime system now to flatten
+  // the string.
+  __ bind(&cons_string);
+  __ cmp(FieldOperand(string, ConsString::kSecondOffset),
+         Immediate(factory->empty_string()));
+  __ j(not_equal, call_runtime);
+  __ mov(string, FieldOperand(string, ConsString::kFirstOffset));
+
+  __ bind(&indirect_string_loaded);
+  __ mov(result, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzx_b(result, FieldOperand(result, Map::kInstanceTypeOffset));
+
+  // Check whether the string is sequential. The only non-sequential
+  // shapes we support have just been unwrapped above.
+  // Note that if the original string is a cons or slice with an external
+  // string as underlying string, we pass that unpacked underlying string with
+  // the adjusted index to the runtime function.
+  __ bind(&check_sequential);
+  STATIC_ASSERT(kSeqStringTag == 0);
+  __ test(result, Immediate(kStringRepresentationMask));
+  __ j(not_zero, &external_string);
+
+  // Dispatch on the encoding: ASCII or two-byte.
+  Label ascii_string;
+  STATIC_ASSERT((kStringEncodingMask & kAsciiStringTag) != 0);
+  STATIC_ASSERT((kStringEncodingMask & kTwoByteStringTag) == 0);
+  __ test(result, Immediate(kStringEncodingMask));
+  __ j(not_zero, &ascii_string, Label::kNear);
+
+  // Two-byte string.
+  // Load the two-byte character code into the result register.
+  STATIC_ASSERT(kSmiTag == 0 && kSmiTagSize == 1);
+  __ movzx_w(result, FieldOperand(string,
+                                  index,
+                                  times_2,
+                                  SeqTwoByteString::kHeaderSize));
+  __ jmp(&done, Label::kNear);
+
+  // Ascii string.
+  // Load the byte into the result register.
+  __ bind(&ascii_string);
+  __ movzx_b(result, FieldOperand(string,
+                                  index,
+                                  times_1,
+                                  SeqAsciiString::kHeaderSize));
+  __ bind(&done);
+}
+
+
 void StringCharCodeAtGenerator::GenerateSlow(
     MacroAssembler* masm,
     const RuntimeCallHelper& call_helper) {
   __ Abort("Unexpected fallthrough to CharCodeAt slow case");
 
   // Index is not a smi.
   __ bind(&index_not_smi_);
   // If index is a heap number, try converting it to an integer.
   __ CheckMap(index_,
               masm->isolate()->factory()->heap_number_map(),
@@ skipping 24 matching lines @@
   __ JumpIfNotSmi(index_, index_out_of_range_);
   // Otherwise, return to the fast path.
   __ jmp(&got_smi_index_);
 
   // Call runtime. We get here when the receiver is a string and the
   // index is a number, but the code of getting the actual character
   // is too complex (e.g., when the string needs to be flattened).
   __ bind(&call_runtime_);
   call_helper.BeforeCall(masm);
   __ push(object_);
+  __ SmiTag(index_);
   __ push(index_);
   __ CallRuntime(Runtime::kStringCharCodeAt, 2);
   if (!result_.is(eax)) {
     __ mov(result_, eax);
   }
   call_helper.AfterCall(masm);
   __ jmp(&exit_);
 
   __ Abort("Unexpected fallthrough from CharCodeAt slow case");
 }
@@ skipping 1866 matching lines @@
                                  false);
   __ pop(edx);
   __ ret(0);
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32