On Wed, 30 Aug 2023, juzhe.zh...@rivai.ai wrote:
> Hi, I start to enable "vect" testsuite for RISC-V.
>
> I have a question when analyzing the 'wrapv-vect-reduc-dot-s8b.c'
> It failed at:
> FAIL: gcc.dg/vect/wrapv-vect-reduc-dot-s8b.c scan-tree-dump-times vect
> "vect_recog_dot_prod_pattern: detected" 1
> FAIL: gcc.dg/vect/wrapv-vect-reduc-dot-s8b.c scan-tree-dump-times vect
> "vect_recog_widen_mult_pattern: detected" 1
>
> They are found "2" times.
>
> Since at the first time, it failed at the vectorization of conversion:
>
> wrapv-vect-reduc-dot-s8b.c:29:14: missed: conversion not supported by
> target.
> wrapv-vect-reduc-dot-s8b.c:29:14: note: vect_is_simple_use: operand
> X[i_14], type of def: internal
> wrapv-vect-reduc-dot-s8b.c:29:14: note: vect_is_simple_use: vectype
> vector([16,16]) signed char
> wrapv-vect-reduc-dot-s8b.c:29:14: note: vect_is_simple_use: operand
> X[i_14], type of def: internal
> wrapv-vect-reduc-dot-s8b.c:29:14: note: vect_is_simple_use: vectype
> vector([16,16]) signed char
> wrapv-vect-reduc-dot-s8b.c:30:17: missed: not vectorized: relevant stmt not
> supported: _2 = (short int) _1;
> wrapv-vect-reduc-dot-s8b.c:29:14: missed: bad operation or unsupported loop
> bound.
>
> Here loop vectorizer is trying to do the conversion from char -> short with
> both same nunits.
> But we don't support 'vec_unpack' stuff in RISC-V backend since I don't see
> the case that vec_unpack can optimize the codegen of autovectorizatio for RVV.
>
> To fix it, is it necessary to support 'vec_unpack' ?
both same units would be sext, not vec_unpacks_{lo,hi} - the vectorizer
ties its hands by choosing vector types early and based on the number
of incoming/outgoing vectors it chooses one or the other method.
More precise dumping would probably help here but somewhere earlier you
should be able to see the vector type used for _2
Richard.
