[runtime] Remove the obsolete %_StringCharAt intrinsic.

src/full-codegen/mips64/full-codegen-mips64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_MIPS64
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 3030 matching lines @@
   __ jmp(&done);
 
   NopRuntimeCallHelper call_helper;
   generator.GenerateSlow(masm_, NOT_PART_OF_IC_HANDLER, call_helper);
 
   __ bind(&done);
   context()->Plug(result);
 }
 
 
-void FullCodeGenerator::EmitStringCharAt(CallRuntime* expr) {
-  ZoneList<Expression*>* args = expr->arguments();
-  DCHECK(args->length() == 2);
-
-  VisitForStackValue(args->at(0));
-  VisitForAccumulatorValue(args->at(1));
-  __ mov(a0, result_register());
-
-  Register object = a1;
-  Register index = a0;
-  Register scratch = a3;
-  Register result = v0;
-
-  PopOperand(object);
-
-  Label need_conversion;
-  Label index_out_of_range;
-  Label done;
-  StringCharAtGenerator generator(object,
-                                  index,
-                                  scratch,
-                                  result,
-                                  &need_conversion,
-                                  &need_conversion,
-                                  &index_out_of_range,
-                                  STRING_INDEX_IS_NUMBER);
-  generator.GenerateFast(masm_);
-  __ jmp(&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::kempty_stringRootIndex);
-  __ jmp(&done);
-
-  __ bind(&need_conversion);
-  // Move smi zero into the result register, which will trigger
-  // conversion.
-  __ li(result, Operand(Smi::FromInt(0)));
-  __ jmp(&done);
-
-  NopRuntimeCallHelper call_helper;
-  generator.GenerateSlow(masm_, NOT_PART_OF_IC_HANDLER, call_helper);
-
-  __ bind(&done);
-  context()->Plug(result);
-}
-
-
 void FullCodeGenerator::EmitCall(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   DCHECK_LE(2, args->length());
   // Push target, receiver and arguments onto the stack.
   for (Expression* const arg : *args) {
     VisitForStackValue(arg);
   }
   PrepareForBailoutForId(expr->CallId(), BailoutState::NO_REGISTERS);
   // Move target to a1.
   int const argc = args->length() - 2;
@@ skipping 853 matching lines @@
          reinterpret_cast<uint64_t>(
              isolate->builtins()->OnStackReplacement()->entry()));
   return ON_STACK_REPLACEMENT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64