[libre-riscv-dev] [Bug 139] Add LD.X and ST.X? Strided

[bugzilla-daemon at libre-riscv.org]

http://bugs.libre-riscv.org/show_bug.cgi?id=139

--- Comment #4 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Luke Kenneth Casson Leighton from comment #3)
> Ok what format for strided LD/ST?

I/S-type? (base, src/dest, and 1 or more stride bitfields, can convert to
gather/scatter for strides that don't fit, suggest strides of n << s where n is
unsigned 7 bits and s is unsigned 5 bits though larger formats with more
immediate bits would be nice)

> 
> Not fallback to shuffle sounds good. Likewise the macro op fusion.
> 
> Also how or does SUBVL interact here?

Swizzles (different than shuffle) are usually at the intra-subvector level
(same VL index over all input/output vectors), inter-subvector swizzle would be
a separate instruction if needed (much less common, can fall back to mv.x).

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