Re: wide set re-implementation progress

[Gaius Mulley]

Michael Riedl <udo-michael.riedl@t-online.de> writes:

> Hallo Gaius,

Hi Michael,

> one short question on the topic - at what time is a set considered to
> be "wide" ?

wide is more than TBITSIZE (BITSET) (32 bits on most architectures).  No
change for sets <= TBITSIZE (BITSET).

> I use SYSTEM.SHIFT and SYSTEM.ROTATE and bit-wise AND/OR operations
> for index related packing/unpacking in a four-dimensional space, and
>
> it would be painful slow if this would be done within a runtime
> library for 32 or 64 bit arithmetic.

I'm aiming to make it just as efficient - the M2WIDESET module will have
<* module: inline *> (or some appropriate attribute name) which will
result in inlined trees - the same as produced internally by cc1gm2.
I'd be interested in using your library code for bench-marking - to make
sure that the new wide set performs well.  The <* module: inline *> can
also be used by your library module for example - and the M2WIDESET can
be internally optimised at m2 source level rather than lispy C code in
cc1gm2.

The M2WIDESET module provides a superset of SYSTEM.ROTATE and friends.
Currently SYSTEM.ROTATE is internally implemented as a series of 32 bit
BITSET operations (with cc1gm2 detecting whether operands are constant
and calling the appropriate routine) - this can be done with the new
wide set implementation - in effect they should produce identical trees
(in an ideal world :-).  One major benefit is maintainability of
M2WIDESET (in m2 rather than lispy trees) and it might offer the
potential for detecting more optimisation cases - maybe the answer is to
heavily benchmark both during development.  For testing purposes we
could test against a baseline gm2-14 -fm2-whole-program as a suggestion

regards,
Gaius


>
> Gruß
>
> Michael




>
> Am 09.01.24 um 17:01 schrieb Gaius Mulley:
>> Hi,
>>
>> I thought I'd post an update on the re-implementation of wide sets in
>> gm2.  The wide set re-implementation moves all of the set arithmetic
>> operators into a runtime library (removing a substantial amount of
>> complexity from the compiler).  The development version of the compiler
>> will currently bootstrap using this technique (although it does not use
>> the runtime code).  All the libraries in /libgm2 build (and many use wide
>> sets - SET OF CHAR - for example).
>>
>> Wide sets are re-implemented internally as arrays of bytes - thus
>> removing any endian portability issues.  Offloading these arithmetic
>> operators is inspired by m2r10 and when coupled with module inlining
>> should cause little if any performance penalty - and module inlining
>> would be available for general use.  I anticipate that the
>> re-implementation of wide sets would arrive in gcc master around end of
>> April (during the start of stage1 - when major changes are allowed
>> again).  At some point there should be a development branch in git
>> appear containing the wide set for testing,
>>
>> regards,
>> Gaius
>>