Re: A plan for eliminating cc0

[Ian Lance Taylor <ian at airs dot com>]

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