[runtime] Remove the obsolete %_StringCharAt intrinsic.

src/full-codegen/s390/full-codegen-s390.cc

Index: src/full-codegen/s390/full-codegen-s390.cc
diff --git a/src/full-codegen/s390/full-codegen-s390.cc b/src/full-codegen/s390/full-codegen-s390.cc
index 0d2107d0605e2069c0ba6b5373feebd6009998aa..cd28399812a3f22615ddfebb6e4e3c85e23510f0 100644
--- a/src/full-codegen/s390/full-codegen-s390.cc
+++ b/src/full-codegen/s390/full-codegen-s390.cc
@@ -2947,47 +2947,6 @@ void FullCodeGenerator::EmitStringCharCodeAt(CallRuntime* expr) {
   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));
-
-  Register object = r3;
-  Register index = r2;
-  Register scratch = r5;
-  Register result = r2;
-
-  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_);
-  __ 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::kempty_stringRootIndex);
-  __ b(&done);
-
-  __ bind(&need_conversion);
-  // Move smi zero into the result register, which will trigger
-  // conversion.
-  __ LoadSmiLiteral(result, Smi::FromInt(0));
-  __ b(&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());