Improve SeqStringSetChar implementation.

src/arm/lithium-codegen-arm.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 1985 matching lines @@
     __ bind(&runtime);
     __ PrepareCallCFunction(2, scratch);
     __ mov(r1, Operand(index));
     __ CallCFunction(ExternalReference::get_date_field_function(isolate()), 2);
     __ bind(&done);
   }
 }
 
 
 void LCodeGen::DoSeqStringSetChar(LSeqStringSetChar* instr) {
-  SeqStringSetCharGenerator::Generate(masm(),
-                                      instr->encoding(),
-                                      ToRegister(instr->string()),
-                                      ToRegister(instr->index()),
-                                      ToRegister(instr->value()));
+  Register string = ToRegister(instr->string());
+  Register index = ToRegister(instr->index());
+  Register value = ToRegister(instr->value());
+  String::Encoding encoding = instr->encoding();
+
+  if (FLAG_debug_code) {
+    __ ldr(ip, FieldMemOperand(string, HeapObject::kMapOffset));
+    __ ldrb(ip, FieldMemOperand(ip, Map::kInstanceTypeOffset));
+
+    __ and_(ip, ip, Operand(kStringRepresentationMask | kStringEncodingMask));
+    static const uint32_t one_byte_seq_type = kSeqStringTag | kOneByteStringTag;
+    static const uint32_t two_byte_seq_type = kSeqStringTag | kTwoByteStringTag;
+    __ cmp(ip, Operand(encoding == String::ONE_BYTE_ENCODING
+                           ? one_byte_seq_type : two_byte_seq_type));
+    __ Check(eq, "Unexpected string type");
+  }
+
+  __ add(ip,
+         string,
+         Operand(SeqString::kHeaderSize - kHeapObjectTag));
+  if (encoding == String::ONE_BYTE_ENCODING) {
+    __ strb(value, MemOperand(ip, index));
+  } else {
+    // MemOperand with ip as the base register is not allowed for strh, so
+    // we do the address calculation explicitly.
+    __ add(ip, ip, Operand(index, LSL, 1));
+    __ strh(value, MemOperand(ip));
+  }
 }
 
 
 void LCodeGen::DoBitNotI(LBitNotI* instr) {
   Register input = ToRegister(instr->value());
   Register result = ToRegister(instr->result());
   __ mvn(result, Operand(input));
 }
 
 
@@ skipping 3901 matching lines @@
   __ sub(scratch, result, Operand::PointerOffsetFromSmiKey(index));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal