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Re: Constant folding and Constant propagation

From: Joe Buck <Joe dot Buck at synopsys dot COM>
To: Jean Christophe Beyler <jean dot christophe dot beyler at gmail dot com>
Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
Date: Thu, 5 Feb 2009 13:02:41 -0800
Subject: Re: Constant folding and Constant propagation
References: <c568a2600902051234i35e77cebu23db6d54c7a0743a@mail.gmail.com> <20090205204601.GJ14209@synopsys.com>

On Thu, Feb 05, 2009 at 12:46:01PM -0800, Joe Buck wrote:
> On Thu, Feb 05, 2009 at 12:34:14PM -0800, Jean Christophe Beyler wrote:
> > I'm currently working on removing the constant folding and constant
> > propagation because, on the architecture I'm working on, it is highly
> > costly to move a constant into a register if the number is big (we can
> > say over 16 bits).
> 
> But in practice most constants that cprop deals with are values like
> -1, 0, 1, or 2.  Wouldn't it be better to be able to constrain cprop
> based on the values of the constants, than to eliminate it altogether?

I shouldn't have said "most", but small constants are common.

Follow-Ups:
- Re: Constant folding and Constant propagation
  - From: Jean Christophe Beyler

References:
- Constant folding and Constant propagation
  - From: Jean Christophe Beyler
- Re: Constant folding and Constant propagation
  - From: Joe Buck

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