On Tue, 3 Apr 2018, Andrey Belevantsev wrote:
> Hello,
>
> This issue ended up being fixed the way different from described in the PR.
> We do not want to walk away from the invariant "zero SCHED_TIMES -- insn
> is not scheduled" even for bookkeeping copies (testing showed it trips over
> asserts designed to catch this). Rather we choose merging exprs in the way
> the larger sched-times wins.
My understanding is this is not a "complete" solution to the problem, and a
chance for a similar blowup on some other testcase remains. Still, avoiding
picking the minimum sched-times value should be a good mitigation.
Please consider adding a comment that the average sched-times value is taken
as a compromise to thwart "endless" pipelining of bookkeeping-producing insns
available anywhere vs. pipelining of useful insns, or something like that?
OK with that considered/added.
>
> Best,
> Andrey
>
> 2018-04-03 Andrey Belevantsev <a...@ispras.ru>
>
> PR rtl-optimization/83913
>
> * sel-sched-ir.c (merge_expr_data): Choose the middle between two
> different sched-times
> when merging exprs.
>
> * gcc.dg/pr83913.c: New test.
>
> diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
> index a965d2ec42f..f6de96a7f3d 100644
> --- a/gcc/sel-sched-ir.c
> +++ b/gcc/sel-sched-ir.c
> @@ -1837,8 +1837,9 @@ merge_expr_data (expr_t to, expr_t from, insn_t
> split_point)
> if (EXPR_PRIORITY (to) < EXPR_PRIORITY (from))
> EXPR_PRIORITY (to) = EXPR_PRIORITY (from);
>
> - if (EXPR_SCHED_TIMES (to) > EXPR_SCHED_TIMES (from))
> - EXPR_SCHED_TIMES (to) = EXPR_SCHED_TIMES (from);
> + if (EXPR_SCHED_TIMES (to) != EXPR_SCHED_TIMES (from))
> + EXPR_SCHED_TIMES (to) = ((EXPR_SCHED_TIMES (from) + EXPR_SCHED_TIMES (to)
> + + 1) / 2);
>
> if (EXPR_ORIG_BB_INDEX (to) != EXPR_ORIG_BB_INDEX (from))
> EXPR_ORIG_BB_INDEX (to) = 0;
> @@ -3293,11 +3294,22 @@ has_dependence_note_mem_dep (rtx mem ATTRIBUTE_UNUSED,
>
> /* Note a dependence. */
> static void
> diff --git a/gcc/testsuite/gcc.dg/pr83913.c b/gcc/testsuite/gcc.dg/pr83913.c
> new file mode 100644
> index 00000000000..c898d71a261
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr83913.c
> @@ -0,0 +1,26 @@
> +/* { dg-do compile { target powerpc*-*-* ia64-*-* i?86-*-* x86_64-*-* } } */
> +/* { dg-options "-O2 -funroll-all-loops -fselective-scheduling
> -fsel-sched-pipelining -fschedule-insns -fno-dce -fno-forward-propagate
> -fno-rerun-cse-after-loop -fno-web" } */
> +
> +int jo, z4;
> +
> +int
> +be (long unsigned int l7, int nt)
> +{
> + int en;
> +
> + jo = l7;
> + for (en = 0; en < 24; ++en)
> + {
> + jo = (jo / z4) * (!!jo >= ((!!nt) & 2));
> + if (jo == 0)
> + nt = 0;
> + else
> + {
> + nt = z4;
> + ++z4;
> + nt = (long unsigned int) nt == (l7 + 1);
> + }
> + }
> +
> + return nt;
> +}
>
>
>
