[Libre-soc-bugs] [Bug 558] gcc SV intrinsics concept

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Mon Jan 11 21:47:36 GMT 2021


--- Comment #39 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
right.  ok.  one area where interaction with the __attributes__ concept, which
is not going to fit precisely is: CR-based predication.

the handling, transfer in and out between INTs and CRs is one that may need
explicit intrinsics.  the crweird opcodes for example will need a data template
that is recognisably vectoriseable, bear in mind all the crweird instructions
have been designed as *scalar* not vector, but that the vectorised versions
will need special-casing


a suitable data structure will need to be defined that can recognise CRs (if
one does not already exist in gcc-ppc64), i would imagine something along the
lines of a struct containing 4 bools, eq, le, lt, so

when an array of such is marked with the standard gcc attribute vector_size
this would give a variable that can be passed around as a cr predicate, and
also passed in as a parameter to the crweird intrinsics.

how does gcc handle CRs in pp64 right now?

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