I thought I'd just missed the bug fixing season of stage3, but there
appears to a little latitude in early stage4 (for vector patches), so
I'll post this now.

This patch resolves PR target/106060 by providing efficient methods for
materializing/synthesizing special "vector" constants on x86.  Currently
there are three methods of materializing a vector constant; the most
general is to load a vector from the constant pool, secondly "duplicated"
constants can be synthesized by moving an integer between units and
broadcasting (or shuffling it), and finally the special cases of the
all-zeros vector and all-ones vectors can be loaded via a single SSE
instruction.   This patch handles additional cases that can be synthesized
in two instructions, loading an all-ones vector followed by another SSE
instruction.  Following my recent patch for PR target/112992, there's
conveniently a single place in i386-expand.cc where these special cases
can be handled.

Two examples are given in the original bugzilla PR for 106060.

__m256i
should_be_cmpeq_abs ()
{
  return _mm256_set1_epi8 (1);
}

is now generated (with -O3 -march=x86-64-v3) as:

        vpcmpeqd        %ymm0, %ymm0, %ymm0
        vpabsb  %ymm0, %ymm0
        ret

and

__m256i
should_be_cmpeq_add ()
{
  return _mm256_set1_epi8 (-2);
}

is now generated as:

        vpcmpeqd        %ymm0, %ymm0, %ymm0
        vpaddb  %ymm0, %ymm0, %ymm0
        ret

This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check, both with and without --target_board=unix{-m32}
with no new failures.  Ok for mainline?


2024-01-16  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
        PR target/106060
        * config/i386/i386-expand.cc (enum ix86_vec_bcast_alg): New.
        (struct ix86_vec_bcast_map_simode_t): New type for table below.
        (ix86_vec_bcast_map_simode): Table of SImode constants that may
        be efficiently synthesized by a ix86_vec_bcast_alg method.
        (ix86_vec_bcast_map_simode_cmp): New comparator for bsearch.
        (ix86_vector_duplicate_simode_const): Efficiently synthesize
        V4SImode and V8SImode constants that duplicate special constants.
        (ix86_vector_duplicate_value): Attempt to synthesize "special"
        vector constants using ix86_vector_duplicate_simode_const.
        * config/i386/i386.cc (ix86_rtx_costs) <case ABS>: ABS of a
        vector integer mode costs with a single SSE instruction.

gcc/testsuite/ChangeLog
        PR target/106060
        * gcc.target/i386/auto-init-8.c: Update test case.
        * gcc.target/i386/avx512fp16-3.c: Likewise.
        * gcc.target/i386/pr100865-9a.c: Likewise.
        * gcc.target/i386/pr106060-1.c: New test case.
        * gcc.target/i386/pr106060-2.c: Likewise.
        * gcc.target/i386/pr106060-3.c: Likewise.
        * gcc.target/i386/pr70314-3.c: Update test case.
        * gcc.target/i386/vect-shiftv4qi.c: Likewise.
        * gcc.target/i386/vect-shiftv8qi.c: Likewise.


Thanks in advance,
Roger
--