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Re: A plan for eliminating cc0
- From: Ian Lance Taylor <ian at airs dot com>
- To: Paul Schlie <schlie at comcast dot net>
- Cc: <gcc at gcc dot gnu dot org>
- Date: 27 Mar 2005 11:55:53 -0500
- Subject: Re: A plan for eliminating cc0
- References: <BE6BBDA0.99D7%schlie@comcast.net>
Paul Schlie <schlie@comcast.net> writes:
> I presume that "code" can/should be optimally generated once by initially
> optimally covering the rtl representing a basic block (with minimal cost
> in either storage, cycles or some hybrid of both); where there's then no
> need to ever subsequently screw with it again (although various basic
> block partitioning resulting from various loop transformations strategies,
> etc. may require multiple mappings to determine their relative costs).
>
> Where this presumption basically ideally requires that the target be
> described as accurately as possible entirely in rtl, with no reliance
> on procedural or peephole optimization, relying entirely on GCC to
> optimally cover the program's basic-block rtl optimally with rtl
> instruction description equivalents; thereby by fully exposing all
> dependencies, an optimal instruction schedule will naturally result
> from an optimal rtl graph covering without needing to perform an
> explicit further optimization for example.
>
> (is this not feasible if the target is accurately described in rtl?)
I don't know how to respond to this. I'm discussing a way to achieve
an incremental improvement in gcc. You seem to be discussing a
different compiler. I don't think my suggestions for incremental
improvement are relevant to creating your compiler: they don't help,
and they don't hurt.
Perhaps somebody else has something to say about this, but I don't.
I'm a practical guy: I compile code with the compiler I have, not the
compiler I might want or wish to have.
Ian