On Fri, 21 Jan 2022, Jakub Jelinek wrote:
> Hi!
>
> cond traps can be created during ce3 after reload (and e.g. PR103028
> recently fixed some ce3 cond trap related bug, so I think often that
> works fine and we shouldn't disable cond traps after RA altogether),
> but it calls prepare_cmp_insn. This function can fail, so I don't
> see why we couldn't make it work after RA (in most cases it already
> just works). The first hunk is just an optimization which doesn't
> make sense after RA, so I've guarded it with can_create_pseudo_p.
> The second hunk is just a theoretical case, I don't have a testcase for it.
> prepare_cmp_insn has some other spots that can create pseudos, like when
> both operands have VOIDmode, or when it is BLKmode comparison, or
> not OPTAB_DIRECT, but I think none of that applies to ce3, we punt on
> BLKmode earlier, use OPTAB_DIRECT and shouldn't be comparing two
> VOIDmode CONST_INTs.
>
> Bootstrapped/regtested on x86_64-linux, i686-linux and powerpc64le-linux,
> ok for trunk?
OK.
Richard.
> 2022-01-21 Jakub Jelinek <ja...@redhat.com>
>
> PR rtl-optimization/102478
> * optabs.cc (prepare_cmp_insn): If !can_create_pseudo_p (), don't
> force_reg constants and for -fnon-call-exceptions fail if copy_to_reg
> would be needed.
>
> * gcc.dg/pr102478.c: New test.
>
> --- gcc/optabs.cc.jj 2022-01-20 11:30:45.586578023 +0100
> +++ gcc/optabs.cc 2022-01-20 16:54:35.439409550 +0100
> @@ -4398,12 +4398,14 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx
> /* If we are optimizing, force expensive constants into a register. */
> if (CONSTANT_P (x) && optimize
> && (rtx_cost (x, mode, COMPARE, 0, optimize_insn_for_speed_p ())
> - > COSTS_N_INSNS (1)))
> + > COSTS_N_INSNS (1))
> + && can_create_pseudo_p ())
> x = force_reg (mode, x);
>
> if (CONSTANT_P (y) && optimize
> && (rtx_cost (y, mode, COMPARE, 1, optimize_insn_for_speed_p ())
> - > COSTS_N_INSNS (1)))
> + > COSTS_N_INSNS (1))
> + && can_create_pseudo_p ())
> y = force_reg (mode, y);
>
> /* Don't let both operands fail to indicate the mode. */
> @@ -4472,6 +4474,8 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx
> compare and branch in different basic blocks. */
> if (cfun->can_throw_non_call_exceptions)
> {
> + if (!can_create_pseudo_p () && (may_trap_p (x) || may_trap_p (y)))
> + goto fail;
> if (may_trap_p (x))
> x = copy_to_reg (x);
> if (may_trap_p (y))
> --- gcc/testsuite/gcc.dg/pr102478.c.jj 2022-01-20 17:00:52.220192056
> +0100
> +++ gcc/testsuite/gcc.dg/pr102478.c 2022-01-20 17:00:30.917487026 +0100
> @@ -0,0 +1,29 @@
> +/* PR rtl-optimization/102478 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fno-if-conversion -Wno-div-by-zero" } */
> +
> +unsigned a, b, c;
> +
> +void
> +foo (void)
> +{
> + c |= __builtin_expect (65535 / a, 0) && 0 / 0;
> + b = 0;
> +}
> +
> +void
> +bar (void)
> +{
> + if (a <= 65535)
> + __builtin_trap ();
> + b = 0;
> +}
> +
> +void
> +baz (void)
> +{
> + if (a > 65535)
> + b = 0;
> + else
> + __builtin_trap ();
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
