Re: [PATCH] Fix store-merging for ~ of bswap (PR tree-optimization/83843)

[Christophe Lyon <christophe dot lyon at linaro dot org>]

On 15 January 2018 at 22:44, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> When using the bswap pass infrastructure, BIT_NOT_EXPRs aren't allowed in
> the middle, but due to the way process_store handles those it can appear
> around the value, which is something output_merged_store didn't handle.
>
> Fixed thusly, where we handle not just the case when the bswap (or nop)
> value needs inversion as whole, but also cases where only a few portions of
> it need xoring with some mask.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2018-01-15  Jakub Jelinek  <jakub@redhat.com>
>
>         PR tree-optimization/83843
>         * gimple-ssa-store-merging.c
>         (imm_store_chain_info::output_merged_store): Handle bit_not_p on
>         store_immediate_info for bswap/nop orig_stores.
>
>         * gcc.dg/store_merging_18.c: New test.
>
Hi Jakub,

I've noticed that this new test fails on arm, eg:
arm-none-linux-gnueabihf
--with-mode arm
--with-cpu cortex-a9
--with-fpu neon-fp16
FAIL: gcc.dg/store_merging_18.c scan-tree-dump-times store-merging
"Merging successful" 3 (found 0 times)

Do you want me to file a PR?

Christophe



> --- gcc/gimple-ssa-store-merging.c.jj   2018-01-04 00:43:17.629703230 +0100
> +++ gcc/gimple-ssa-store-merging.c      2018-01-15 12:29:14.105789381 +0100
> @@ -3619,6 +3619,15 @@ imm_store_chain_info::output_merged_stor
>                   gimple_seq_add_stmt_without_update (&seq, stmt);
>                   src = gimple_assign_lhs (stmt);
>                 }
> +             inv_op = invert_op (split_store, 2, int_type, xor_mask);
> +             if (inv_op != NOP_EXPR)
> +               {
> +                 stmt = gimple_build_assign (make_ssa_name (int_type),
> +                                             inv_op, src, xor_mask);
> +                 gimple_set_location (stmt, loc);
> +                 gimple_seq_add_stmt_without_update (&seq, stmt);
> +                 src = gimple_assign_lhs (stmt);
> +               }
>               break;
>             default:
>               src = ops[0];
> --- gcc/testsuite/gcc.dg/store_merging_18.c.jj  2018-01-15 12:43:49.607227365 +0100
> +++ gcc/testsuite/gcc.dg/store_merging_18.c     2018-01-15 12:43:24.882245004 +0100
> @@ -0,0 +1,51 @@
> +/* PR tree-optimization/83843 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-store-merging" } */
> +/* { dg-final { scan-tree-dump-times "Merging successful" 3 "store-merging" { target store_merge } } } */
> +
> +__attribute__((noipa)) void
> +foo (unsigned char *buf, unsigned char *tab)
> +{
> +  unsigned v = tab[1] ^ (tab[0] << 8);
> +  buf[0] = ~(v >> 8);
> +  buf[1] = ~v;
> +}
> +
> +__attribute__((noipa)) void
> +bar (unsigned char *buf, unsigned char *tab)
> +{
> +  unsigned v = tab[1] ^ (tab[0] << 8);
> +  buf[0] = (v >> 8);
> +  buf[1] = ~v;
> +}
> +
> +__attribute__((noipa)) void
> +baz (unsigned char *buf, unsigned char *tab)
> +{
> +  unsigned v = tab[1] ^ (tab[0] << 8);
> +  buf[0] = ~(v >> 8);
> +  buf[1] = v;
> +}
> +
> +int
> +main ()
> +{
> +  volatile unsigned char l1 = 0;
> +  volatile unsigned char l2 = 1;
> +  unsigned char buf[2];
> +  unsigned char tab[2] = { l1 + 1, l2 * 2 };
> +  foo (buf, tab);
> +  if (buf[0] != (unsigned char) ~1 || buf[1] != (unsigned char) ~2)
> +    __builtin_abort ();
> +  buf[0] = l1 + 7;
> +  buf[1] = l2 * 8;
> +  bar (buf, tab);
> +  if (buf[0] != 1 || buf[1] != (unsigned char) ~2)
> +    __builtin_abort ();
> +  buf[0] = l1 + 9;
> +  buf[1] = l2 * 10;
> +  baz (buf, tab);
> +  if (buf[0] != (unsigned char) ~1 || buf[1] != 2)
> +    __builtin_abort ();
> +  return 0;
> +}
>
>         Jakub