X64: Use low bits of registers in emit_sse_operand. Enable --stop-at flag.

src/x64/assembler-x64.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 142 matching lines @@
 extern MMXRegister mm15;
 
 
 struct XMMRegister {
   bool is_valid() const  { return 0 <= code_ && code_ < 16; }
   int code() const  {
     ASSERT(is_valid());
     return code_;
   }
 
+  // Return the high bit of the register code as a 0 or 1.  Used often
+  // when constructing the REX prefix byte.
+  int high_bit() const {
+    return code_ >> 3;
+  }
+  // Return the 3 low bits of the register code.  Used when encoding registers
+  // in modR/M, SIB, and opcode bytes.
+  int low_bits() const {
+    return code_ & 0x7;
+  }
+
   int code_;
 };
 
 extern XMMRegister xmm0;
 extern XMMRegister xmm1;
 extern XMMRegister xmm2;
 extern XMMRegister xmm3;
 extern XMMRegister xmm4;
 extern XMMRegister xmm5;
 extern XMMRegister xmm6;
@@ skipping 985 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_