ARM: Implement StringCharAtStub.

src/arm/code-stubs-arm.cc

 // Copyright 2010 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
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@@ skipping 3685 matching lines @@
   return ConditionField::encode(static_cast<unsigned>(cc_) >> 28)
          | RegisterField::encode(lhs_.is(r0))
          | StrictField::encode(strict_)
          | NeverNanNanField::encode(cc_ == eq ? never_nan_nan_ : false)
          | IncludeNumberCompareField::encode(include_number_compare_)
          | IncludeSmiCompareField::encode(include_smi_compare_);
 }
 
 
 // StringCharCodeAtGenerator
-
 void StringCharCodeAtGenerator::GenerateFast(MacroAssembler* masm) {
   Label flat_string;
   Label ascii_string;
   Label got_char_code;
 
   // If the receiver is a smi trigger the non-string case.
   __ BranchOnSmi(object_, receiver_not_string_);
 
   // Fetch the instance type of the receiver into result register.
   __ ldr(result_, FieldMemOperand(object_, HeapObject::kMapOffset));
@@ skipping 1138 matching lines @@
   __ IncrementCounter(&Counters::string_add_native, 1, r2, r3);
   __ add(sp, sp, Operand(2 * kPointerSize));
   __ Ret();
 
   // Just jump to runtime to add the two strings.
   __ bind(&string_add_runtime);
   __ TailCallRuntime(Runtime::kStringAdd, 2, 1);
 }
 
 
+void StringCharAtStub::Generate(MacroAssembler* masm) {
+  // Expects two arguments (object, index) on the stack:
+  //  lr: return address
+  //  sp[0]: index
+  //  sp[4]: object
+  Register object = r1;
+  Register index = r0;
+  Register scratch1 = r2;
+  Register scratch2 = r3;
+  Register result = r0;
+
+  // Get object and index from the stack.
+  __ pop(index);
+  __ pop(object);
+
+  Label need_conversion;
+  Label index_out_of_range;
+  Label done;
+  StringCharAtGenerator generator(object,
+                                  index,
+                                  scratch1,
+                                  scratch2,
+                                  result,
+                                  &need_conversion,
+                                  &need_conversion,
+                                  &index_out_of_range,
+                                  STRING_INDEX_IS_NUMBER);
+  generator.GenerateFast(masm);
+  __ b(&done);
+
+  __ bind(&index_out_of_range);
+  // When the index is out of range, the spec requires us to return
+  // the empty string.
+  __ LoadRoot(result, Heap::kEmptyStringRootIndex);
+  __ jmp(&done);
+
+  __ bind(&need_conversion);
+  // Move smi zero into the result register, which will trigger
+  // conversion.
+  __ mov(result, Operand(Smi::FromInt(0)));
+  __ jmp(&done);
+
+  StubRuntimeCallHelper call_helper;

[Søren Thygesen Gjesse, 2011/01/19 11:18:03]

Control never goes here.

[Mads Ager (chromium), 2011/01/19 11:32:42]

It does but in a round-about way. |generator| has labels. There is a jump to one
of the labels generated by GenerateFast. That label is then bound by
GenerateSlow.

+  generator.GenerateSlow(masm, call_helper);
+
+  __ bind(&done);
+  __ Ret();
+}
+
+
 void ICCompareStub::GenerateSmis(MacroAssembler* masm) {
   ASSERT(state_ == CompareIC::SMIS);
   Label miss;
   __ orr(r2, r1, r0);
   __ tst(r2, Operand(kSmiTagMask));
   __ b(ne, &miss);
 
   if (GetCondition() == eq) {
     // For equality we do not care about the sign of the result.
     __ sub(r0, r0, r1, SetCC);
@@ skipping 101 matching lines @@
   __ pop(r1);
   __ Jump(r2);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM