MIPS: Combine %_SubString and %_StringCharAt.

src/mips/code-stubs-mips.cc

 // Copyright 2012 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 5961 matching lines @@
   __ CallRuntime(Runtime::kCharFromCode, 1);
   __ Move(result_, v0);
 
   call_helper.AfterCall(masm);
   __ Branch(&exit_);
 
   __ Abort("Unexpected fallthrough from CharFromCode slow case");
 }
 
 
-// -------------------------------------------------------------------------
-// StringCharAtGenerator
-
-void StringCharAtGenerator::GenerateFast(MacroAssembler* masm) {
-  char_code_at_generator_.GenerateFast(masm);
-  char_from_code_generator_.GenerateFast(masm);
-}
-
-
-void StringCharAtGenerator::GenerateSlow(
-    MacroAssembler* masm,
-    const RuntimeCallHelper& call_helper) {
-  char_code_at_generator_.GenerateSlow(masm, call_helper);
-  char_from_code_generator_.GenerateSlow(masm, call_helper);
-}
-
-
 void StringHelper::GenerateCopyCharacters(MacroAssembler* masm,
                                           Register dest,
                                           Register src,
                                           Register count,
                                           Register scratch,
                                           bool ascii) {
   Label loop;
   Label done;
   // This loop just copies one character at a time, as it is only used for
   // very short strings.
@@ skipping 360 matching lines @@
 
   // Make sure first argument is a string.
   __ lw(v0, MemOperand(sp, kStringOffset));
   __ JumpIfSmi(v0, &runtime);
   __ lw(a1, FieldMemOperand(v0, HeapObject::kMapOffset));
   __ lbu(a1, FieldMemOperand(a1, Map::kInstanceTypeOffset));
   __ And(t0, a1, Operand(kIsNotStringMask));
 
   __ Branch(&runtime, ne, t0, Operand(zero_reg));
 
+  Label single_char;
+  __ Branch(&single_char, eq, a2, Operand(1));
+
   // Short-cut for the case of trivial substring.
   Label return_v0;
   // v0: original string
   // a2: result string length
   __ lw(t0, FieldMemOperand(v0, String::kLengthOffset));
   __ sra(t0, t0, 1);
   // Return original string.
   __ Branch(&return_v0, eq, a2, Operand(t0));
   // Longer than original string's length or negative: unsafe arguments.
   __ Branch(&runtime, hi, a2, Operand(t0));
@@ skipping 140 matching lines @@
       masm, a1, t1, a2, a3, t0, t2, t3, t4, DEST_ALWAYS_ALIGNED);
 
   __ bind(&return_v0);
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->sub_string_native(), 1, a3, t0);
   __ DropAndRet(3);
 
   // Just jump to runtime to create the sub string.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kSubString, 3, 1);
+
+  __ bind(&single_char);
+  // v0: original string
+  // a1: instance type
+  // a2: length
+  // a3: from index (untagged)
+  __ SmiTag(a3, a3);
+  StringCharAtGenerator generator(
+      v0, a3, a2, v0, &runtime, &runtime, &runtime, STRING_INDEX_IS_NUMBER);
+  generator.GenerateFast(masm);
+  __ DropAndRet(3);
+  generator.SkipSlow(masm, &runtime);
 }
 
 
 void StringCompareStub::GenerateFlatAsciiStringEquals(MacroAssembler* masm,
                                                       Register left,
                                                       Register right,
                                                       Register scratch1,
                                                       Register scratch2,
                                                       Register scratch3) {
   Register length = scratch1;
@@ skipping 1513 matching lines @@
   __ Pop(ra, t1, a1);
   __ Ret();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS