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Re: Avoid matching the same pattern statement twice
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>, richard dot sandiford at arm dot com
- Date: Tue, 3 Jul 2018 11:35:51 +0200
- Subject: Re: Avoid matching the same pattern statement twice
- References: <87h8lg92bt.fsf@arm.com>
On Tue, Jul 3, 2018 at 10:02 AM Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> r262275 allowed pattern matching on pattern statements. Testing for
> SVE on more benchmarks showed a case where this interacted badly
> with 14/n.
>
> The new over-widening detection could narrow a COND_EXPR A to another
> COND_EXPR B, which mixed_size_cond could then match. This was working
> as expected. However, we left B (now dead) in the pattern definition
> sequence with a non-null PATTERN_DEF_SEQ. mask_conversion also
> matched B, and unlike most recognisers, didn't clear PATTERN_DEF_SEQ
> before adding statements to it. This meant that the statements
> created by mixed_size_cond appeared in two supposedy separate
> sequences, causing much confusion.
>
> This patch removes pattern statements that are replaced by further
> pattern statements. As a belt-and-braces fix, it also nullifies
> PATTERN_DEF_SEQ on failure, in the same way Richard B. did recently
> for RELATED_STMT.
>
> I have patches to clean up the PATTERN_DEF_SEQ handling, but they
> only apply after the complete PR85694 sequence, whereas this needs
> to go in before 14/n.
>
> Tested on aarch64-linux-gnu, arm-linux-gnueabihf and x86_64-linux-gnu.
> OK to install?
OK.
Richard.
> Richard
>
>
> 2018-07-03 Richard Sandiford <richard.sandiford@arm.com>
>
> gcc/
> * tree-vect-patterns.c (vect_mark_pattern_stmts): Remove pattern
> statements that have been replaced by further pattern statements.
> (vect_pattern_recog_1): Clear STMT_VINFO_PATTERN_DEF_SEQ on failure.
>
> gcc/testsuite/
> * gcc.dg/vect/vect-mixed-size-cond-1.c: New test.
>
> Index: gcc/tree-vect-patterns.c
> ===================================================================
> --- gcc/tree-vect-patterns.c 2018-07-02 14:34:45.857732632 +0100
> +++ gcc/tree-vect-patterns.c 2018-07-03 08:56:56.610251460 +0100
> @@ -4295,6 +4295,9 @@ vect_mark_pattern_stmts (gimple *orig_st
> gimple_stmt_iterator gsi = gsi_for_stmt (orig_stmt, orig_def_seq);
> gsi_insert_seq_before_without_update (&gsi, def_seq, GSI_SAME_STMT);
> gsi_insert_before_without_update (&gsi, pattern_stmt, GSI_SAME_STMT);
> +
> + /* Remove the pattern statement that this new pattern replaces. */
> + gsi_remove (&gsi, false);
> }
> else
> vect_set_pattern_stmt (pattern_stmt, orig_stmt_info, pattern_vectype);
> @@ -4358,6 +4361,8 @@ vect_pattern_recog_1 (vect_recog_func *r
> if (!is_pattern_stmt_p (stmt_info))
> STMT_VINFO_RELATED_STMT (stmt_info) = NULL;
> }
> + /* Clear any half-formed pattern definition sequence. */
> + STMT_VINFO_PATTERN_DEF_SEQ (stmt_info) = NULL;
> return;
> }
>
> Index: gcc/testsuite/gcc.dg/vect/vect-mixed-size-cond-1.c
> ===================================================================
> --- /dev/null 2018-06-13 14:36:57.192460992 +0100
> +++ gcc/testsuite/gcc.dg/vect/vect-mixed-size-cond-1.c 2018-07-03 08:56:56.610251460 +0100
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +
> +int
> +f (unsigned char *restrict x, short *restrict y)
> +{
> + for (int i = 0; i < 100; ++i)
> + {
> + unsigned short a = (x[i] + 11) >> 1;
> + unsigned short b = (x[i] + 42) >> 2;
> + unsigned short cmp = y[i] == 0 ? a : b;
> + int res = cmp + 1;
> + x[i] = res;
> + }
> +}