On Thu, Jan 26, 2017 at 4:38 PM, Segher Boessenkool
<seg...@kernel.crashing.org> wrote:
> Scheduling should never move very expensive instructions to places they
> are executed more frequently. This patch fixes that, reducing the
> execution time of c-ray by over 40% (I tested on a BE Power7 system).
>
> Is there some existing way to test for "very expensive insn" or "very
> expensive insn we should not speculate"? Should there be a new hook?
> Is only disallowing (FP) SQRT and DIV a good solution?
Seems like it should be checking the insn cost and compare that
against some parameter. That is possibly set by the target if needed.
Thanks,
Andrew
>
>
> Segher
>
>
> ---
> gcc/sched-rgn.c | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/sched-rgn.c b/gcc/sched-rgn.c
> index 2af3a03..6ccd973 100644
> --- a/gcc/sched-rgn.c
> +++ b/gcc/sched-rgn.c
> @@ -64,6 +64,7 @@ along with GCC; see the file COPYING3. If not see
> #include "sel-sched.h"
> #include "tree-pass.h"
> #include "dbgcnt.h"
> +#include "rtl-iter.h"
> #include "pretty-print.h"
> #include "print-rtl.h"
>
> @@ -2147,12 +2148,20 @@ static int
> can_schedule_ready_p (rtx_insn *insn)
> {
> /* An interblock motion? */
> - if (INSN_BB (insn) != target_bb
> - && IS_SPECULATIVE_INSN (insn)
> - && !check_live (insn, INSN_BB (insn)))
> - return 0;
> - else
> - return 1;
> + if (INSN_BB (insn) != target_bb && IS_SPECULATIVE_INSN (insn))
> + {
> + /* Cannot schedule this insn unless all operands are live. */
> + if (!check_live (insn, INSN_BB (insn)))
> + return 0;
> +
> + /* Should not move expensive instructions speculatively. */
> + subrtx_iterator::array_type array;
> + FOR_EACH_SUBRTX (iter, array, insn, NONCONST)
> + if (*iter && GET_CODE (*iter) == SQRT)
> + return 0;
> + }
> +
> + return 1;
> }
>
> /* Updates counter and other information. Split from can_schedule_ready_p ()
> --
> 1.9.3
>
