Hello,
On 10.04.2018 17:40, Alexander Monakov wrote:
> Hi,
>
> We have this code in sel-sched.c sel_region_init():
>
> 6918 /* Init correct liveness sets on each instruction of a single-block
> loop.
> 6919 This is the only situation when we can't update liveness when
> calling
> 6920 compute_live for the first insn of the loop. */
> 6921 if (current_loop_nest)
> 6922 {
> 6923 int header =
> 6924 (sel_is_loop_preheader_p (BASIC_BLOCK_FOR_FN (cfun, BB_TO_BLOCK
> (0)))
> 6925 ? 1
> 6926 : 0);
> 6927
> 6928 if (current_nr_blocks == header + 1)
> 6929 update_liveness_on_insn
> 6930 (sel_bb_head (BASIC_BLOCK_FOR_FN (cfun, BB_TO_BLOCK
> (header))));
> 6931 }
>
> It appears it does not account for presence of empty BBs between the preheader
> and the "actual header" BB hosting the first insn of the loop. The testcase in
> the PR provides an example where we don't run update_liveness_on_insn here,
> but
> then remove the empty BB and recurse endlessly in compute_live_after_bb.
>
> This patch solves this in a brute-but-straightforward manner by invoking
> cleanup_cfg just before loop_optimizer_init.
>
> Bootstrapped/regtested on x86_64 together with the other two patches and also
> checked on a powerpc cross-compiler that the testcase is fixed. OK to apply?
OK. The comment before cleanup_cfg will not hurt but do as you wish.
Thank you,
Andrey
>
> Thanks.
> Alexander
>
> PR rtl-optimization/85659
> * sel-sched-ir.c (sel_init_pipelining): Invoke cleanup_cfg.
>
> * gcc.dg/pr84659.c: New test.
>
>
> diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
> index ee970522890..aef380a7e80 100644
> --- a/gcc/sel-sched-ir.c
> +++ b/gcc/sel-sched-ir.c
> @@ -30,6 +30,7 @@ along with GCC; see the file COPYING3. If not see
> #include "cfgrtl.h"
> #include "cfganal.h"
> #include "cfgbuild.h"
> +#include "cfgcleanup.h"
> #include "insn-config.h"
> #include "insn-attr.h"
> #include "recog.h"
> @@ -6121,6 +6122,7 @@ make_regions_from_loop_nest (struct loop *loop)
> void
> sel_init_pipelining (void)
> {
> + cleanup_cfg (0);
> /* Collect loop information to be used in outer loops pipelining. */
> loop_optimizer_init (LOOPS_HAVE_PREHEADERS
> | LOOPS_HAVE_FALLTHRU_PREHEADERS
> diff --git a/gcc/testsuite/gcc.dg/pr84659.c b/gcc/testsuite/gcc.dg/pr84659.c
> index e69de29bb2d..94c885f3869 100644
> --- a/gcc/testsuite/gcc.dg/pr84659.c
> +++ b/gcc/testsuite/gcc.dg/pr84659.c
> @@ -0,0 +1,19 @@
> +/* PR rtl-optimization/84659 */
> +/* { dg-do compile { target powerpc*-*-* ia64-*-* i?86-*-* x86_64-*-* } } */
> +/* { dg-options "-O2 -fselective-scheduling -fsel-sched-pipelining
> -fno-split-wide-types -fno-strict-aliasing -fno-tree-dce" } */
> +
> +void
> +jk (int **lq, int *k4, long long int qv, int od)
> +{
> + while (**lq < 1)
> + {
> + int uo;
> +
> + uo = ((od == 0) ? qv : *k4) != 1;
> + ++**lq;
> + }
> +
> + for (;;)
> + {
> + }
> +}
>
