Re: How to eliminate redundant constant move instructions

From	Kaz Kylheku <kaz@kylheku.com>
Newsgroups	comp.compilers
Subject	Re: How to eliminate redundant constant move instructions
Date	2011-11-03 03:20 +0000
Organization	A noiseless patient Spider
Message-ID	<11-11-018@comp.compilers> (permalink)
References	<11-10-019@comp.compilers> <11-11-004@comp.compilers> <11-11-005@comp.compilers> <11-11-014@comp.compilers>

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On 2011-11-02, George Neuner <gneuner2@comcast.net> wrote:
> Yes.  But the compiler can't count on register renaming ... it can see
> only the architectural named registers.  If the code in question had
> copied Rx-> Ry then renaming would have been possible, but instead the
> code performed a constant load to each register.  No possibility of
> rename sharing there.

If the register holds a value that is used, but not clobbered, then renaming is
moot. The two blocks of code both depend on rx being zero, and so nothing is
achieved by splitting the instruction set register into two physical registers.

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Thread

How to eliminate redundant constant move instructions "Amker.Cheng" <amker.cheng@gmail.com> - 2011-10-31 17:53 +0800
  Re: How to eliminate redundant constant move instructions Kaz Kylheku <kaz@kylheku.com> - 2011-10-31 17:08 +0000
    Re: How to eliminate redundant constant move instructions amker <can.finner@gmail.com> - 2011-11-01 19:01 -0700
    Re: How to eliminate redundant constant move instructions mac <acolvin@efunct.com> - 2011-11-03 02:20 +0000
  Re: How to eliminate redundant constant move instructions George Neuner <gneuner2@comcast.net> - 2011-11-01 14:32 -0400
    Re: How to eliminate redundant constant move instructions glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2011-11-01 22:35 +0000
      Re: How to eliminate redundant constant move instructions amker <can.finner@gmail.com> - 2011-11-01 19:35 -0700
      Re: How to eliminate redundant constant move instructions amker <amker.cheng@gmail.com> - 2011-11-01 21:04 -0700
      Re: How to eliminate redundant constant move instructions George Neuner <gneuner2@comcast.net> - 2011-11-02 12:38 -0400
        Re: How to eliminate redundant constant move instructions Kaz Kylheku <kaz@kylheku.com> - 2011-11-03 03:20 +0000
          Re: How to eliminate redundant constant move instructions George Neuner <gneuner2@comcast.net> - 2011-11-04 13:27 -0400
            Re: How to eliminate redundant constant move instructions glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2011-11-04 21:19 +0000
        Re: How to eliminate redundant constant move instructions glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2011-11-03 03:32 +0000
    Re: How to eliminate redundant constant move instructions amker <can.finner@gmail.com> - 2011-11-01 19:21 -0700
      Re: How to eliminate redundant constant move instructions George Neuner <gneuner2@comcast.net> - 2011-11-04 17:26 -0400
        Re: How to eliminate redundant constant move instructions amker <amker.cheng@gmail.com> - 2011-11-07 17:33 -0800
          Re: How to eliminate redundant constant move instructions Wei-Jen Chen <chenwj@cs.NCTU.edu.tw> - 2011-11-10 08:04 +0000
          Re: How to eliminate redundant constant move instructions George Neuner <gneuner2@comcast.net> - 2011-11-10 18:18 -0500
    Re: How to eliminate redundant constant move instructions amker <amker.cheng@gmail.com> - 2011-11-01 20:58 -0700

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