MIPS: Add new HSeqStringGetChar instruction.

src/mips/lithium-codegen-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 1738 matching lines @@
     __ Addu(scratch, string, ToRegister(index));
   } else {
     STATIC_ASSERT(kUC16Size == 2);
     __ sll(scratch, ToRegister(index), 1);
     __ Addu(scratch, string, scratch);
   }
   return FieldMemOperand(scratch, SeqString::kHeaderSize);
 }
 
 
+void LCodeGen::DoSeqStringGetChar(LSeqStringGetChar* instr) {
+  String::Encoding encoding = instr->hydrogen()->encoding();
+  Register string = ToRegister(instr->string());
+  Register result = ToRegister(instr->result());
+
+  if (FLAG_debug_code) {
+    Register scratch = scratch0();
+    __ lw(scratch, FieldMemOperand(string, HeapObject::kMapOffset));
+    __ lbu(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
+
+    __ And(scratch, scratch,
+           Operand(kStringRepresentationMask | kStringEncodingMask));
+    static const uint32_t one_byte_seq_type = kSeqStringTag | kOneByteStringTag;
+    static const uint32_t two_byte_seq_type = kSeqStringTag | kTwoByteStringTag;
+    __ Subu(at, scratch, Operand(encoding == String::ONE_BYTE_ENCODING
+                                ? one_byte_seq_type : two_byte_seq_type));
+    __ Check(eq, kUnexpectedStringType, at, Operand(zero_reg));
+  }
+
+  MemOperand operand = BuildSeqStringOperand(string, instr->index(), encoding);
+  if (encoding == String::ONE_BYTE_ENCODING) {
+    __ lbu(result, operand);
+  } else {
+    __ lhu(result, operand);
+  }
+}
+
+
 void LCodeGen::DoSeqStringSetChar(LSeqStringSetChar* instr) {
   String::Encoding encoding = instr->hydrogen()->encoding();
   Register string = ToRegister(instr->string());
   Register value = ToRegister(instr->value());
 
   if (FLAG_debug_code) {
     Register scratch = scratch0();
     __ lw(scratch, FieldMemOperand(string, HeapObject::kMapOffset));
     __ lbu(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
 
@@ skipping 4054 matching lines @@
   __ Subu(scratch, result, scratch);
   __ lw(result, FieldMemOperand(scratch,
                                 FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal