Port r10023 to x64 (Add pointer cache field to external string).

src/x64/codegen-x64.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 349 matching lines @@
                       JSObject::kElementsOffset,
                       r11,
                       r15,
                       kDontSaveFPRegs,
                       EMIT_REMEMBERED_SET,
                       OMIT_SMI_CHECK);
   __ pop(rax);
   __ movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
 }
 
+
+void StringCharLoadGenerator::Generate(MacroAssembler* masm,
+                                       Register string,
+                                       Register index,
+                                       Register result,
+                                       Label* call_runtime) {
+  // Fetch the instance type of the receiver into result register.
+  __ movq(result, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOffset));

[Lasse Reichstein, 2011/11/24 09:21:42]

If we know that only strings get here, is it possible to expect the instance
type in one of the input registers? We have probably loaded it at some point
prior to getting here.

+
+  // We need special handling for indirect strings.
+  Label check_sequential;
+  __ testb(result, Immediate(kIsIndirectStringMask));

[Lasse Reichstein, 2011/11/24 09:21:42]

Would it make sense to have kShortExternalStringMask as part of this mask? It
is, after all, not a string that has direct access to character data.

+  __ j(zero, &check_sequential);
+
+  // Dispatch on the indirect string shape: slice or cons.
+  Label cons_string;
+  __ testb(result, Immediate(kSlicedNotConsMask));
+  __ j(zero, &cons_string, Label::kNear);
+
+  // Handle slices.
+  Label indirect_string_loaded;
+  __ SmiToInteger32(result, FieldOperand(string, SlicedString::kOffsetOffset));
+  __ addq(index, result);
+  __ movq(string, FieldOperand(string, SlicedString::kParentOffset));
+  __ jmp(&indirect_string_loaded, Label::kNear);
+
+  // 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.
+    // Sequential strings have already been ruled out.
+    __ testb(result, Immediate(kIsIndirectStringMask));
+    __ Assert(zero, "external string expected, but not found");
+  }
+  __ movq(result, FieldOperand(string, ExternalString::kResourceDataOffset));

[Lasse Reichstein, 2011/11/24 09:21:42]

Should you be testing for short external strings here, before loading the
resource?

+  // Assert that the data pointer cache is valid.
+  __ testq(result, result);
+  __ j(zero, call_runtime);

[Lasse Reichstein, 2011/11/24 09:21:42]

Not necessary?

+  Register scratch = string;
+  __ movq(scratch, FieldOperand(string, HeapObject::kMapOffset));
+  STATIC_ASSERT(kTwoByteStringTag == 0);
+  __ testb(FieldOperand(scratch, Map::kInstanceTypeOffset),
+           Immediate(kStringEncodingMask));
+  __ j(not_equal, &ascii_external, Label::kNear);
+  // Two-byte string.
+  __ movzxwl(result, Operand(result, index, times_2, 0));
+  __ jmp(&done);
+  __ bind(&ascii_external);
+  // Ascii string.
+  __ movzxbl(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);
+  __ CompareRoot(FieldOperand(string, ConsString::kSecondOffset),
+                 Heap::kEmptyStringRootIndex);
+  __ j(not_equal, call_runtime);
+  __ movq(string, FieldOperand(string, ConsString::kFirstOffset));
+
+  __ bind(&indirect_string_loaded);
+  __ movq(result, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOffset));
+
+  // Check whether the string is sequential. The only non-sequential

[Lasse Reichstein, 2011/11/24 09:21:42]

Comment seems a little off.
When we get here, we know that the string is either a sequential or an external
string. 
So perhaps write something like "Distinguish between sequential and external
strings" to make it clear what's happening.

+  // 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);
+  __ testb(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);
+  __ testb(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);
+  __ movzxwl(result, FieldOperand(string,
+                                  index,
+                                  times_2,
+                                  SeqTwoByteString::kHeaderSize));
+  __ jmp(&done, Label::kNear);
+
+  // ASCII string.
+  // Load the byte into the result register.
+  __ bind(&ascii_string);
+  __ movzxbl(result, FieldOperand(string,
+                                  index,
+                                  times_1,
+                                  SeqAsciiString::kHeaderSize));
+  __ bind(&done);
+}
+
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64