[PATCH] MIR Serialization: Serialize the null register operands.

[Duncan P. N. Exon Smith]

> On 2015-Jun-19, at 15:27, Alex Lorenz <arphaman at gmail.com> wrote:
> 
> Hi dexonsmith, bob.wilson, bogner,
> 
> This patch is based on a previous serialization patch that serializes immediate operands (http://reviews.llvm.org/D10573).
> 
> This patch serializes the null register machine operands. It uses the '_' keyword to represent them, but you can also refer to them in the input source by using the '%noreg' named register syntax. Example:
> 
>     - '%eax = MOV32rm %rdi, 1, _, 0, %noreg'
>     - 'RETQ %eax'
> 
> REPOSITORY
>  rL LLVM
> 
> http://reviews.llvm.org/D10580
> 
> Files:
>  lib/CodeGen/MIRParser/MILexer.cpp
>  lib/CodeGen/MIRParser/MILexer.h
>  lib/CodeGen/MIRParser/MIParser.cpp
>  lib/CodeGen/MIRPrinter.cpp
>  test/CodeGen/MIR/X86/null-register-operands.mir
> 
> EMAIL PREFERENCES
>  http://reviews.llvm.org/settings/panel/emailpreferences/
> <D10580.28054.patch>

LGTM.  I like the `_` idea instead of `%noreg`.