Ensure using byte registers for byte instructions on ia32 and x64.

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.
 //
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 // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 // EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // The original source code covered by the above license above has been
 // modified significantly by Google Inc.
 // Copyright 2011 the V8 project authors. All rights reserved.

[Jakob Kummerow, 2012/02/16 12:46:02]

2012

 
 // A lightweight X64 Assembler.
 
 #ifndef V8_X64_ASSEMBLER_X64_H_
 #define V8_X64_ASSEMBLER_X64_H_
 
 #include "serialize.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 80 matching lines @@
     };
     return names[index];
   }
 
   static Register from_code(int code) {
     Register r = { code };
     return r;
   }
   bool is_valid() const { return 0 <= code_ && code_ < kNumRegisters; }
   bool is(Register reg) const { return code_ == reg.code_; }
+  // rax, rbx, rcx and rdx are byte registers, the rest are not.
+  bool is_byte_register() const { return code_ <= 3; }
   int code() const {
     ASSERT(is_valid());
     return code_;
   }
   int bit() const {
     return 1 << code_;
   }
 
   // Return the high bit of the register code as a 0 or 1.  Used often
   // when constructing the REX prefix byte.
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  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_