Reland r16751 with fix

src/arm/macro-assembler-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 3191 matching lines @@
     vstr(double_scratch.low(),
          FieldMemOperand(dst, (field_count - 1) * kPointerSize));
   }
 }
 
 
 void MacroAssembler::CopyBytes(Register src,
                                Register dst,
                                Register length,
                                Register scratch) {
-  Label align_loop, align_loop_1, word_loop, byte_loop, byte_loop_1, done;
+  Label align_loop_1, word_loop, byte_loop, byte_loop_1, done;
 
   // Align src before copying in word size chunks.
-  bind(&align_loop);
-  cmp(length, Operand::Zero());
-  b(eq, &done);
+  cmp(length, Operand(kPointerSize));
+  b(le, &byte_loop);
+
   bind(&align_loop_1);
   tst(src, Operand(kPointerSize - 1));
   b(eq, &word_loop);
   ldrb(scratch, MemOperand(src, 1, PostIndex));
   strb(scratch, MemOperand(dst, 1, PostIndex));
   sub(length, length, Operand(1), SetCC);
-  b(ne, &byte_loop_1);
-
+  b(&align_loop_1);
   // Copy bytes in word size chunks.
   bind(&word_loop);
   if (emit_debug_code()) {
     tst(src, Operand(kPointerSize - 1));
     Assert(eq, kExpectingAlignmentForCopyBytes);
   }
   cmp(length, Operand(kPointerSize));
   b(lt, &byte_loop);
   ldr(scratch, MemOperand(src, kPointerSize, PostIndex));
   if (CpuFeatures::IsSupported(UNALIGNED_ACCESSES)) {
@@ skipping 666 matching lines @@
 void CodePatcher::EmitCondition(Condition cond) {
   Instr instr = Assembler::instr_at(masm_.pc_);
   instr = (instr & ~kCondMask) | cond;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM