On Tue, 16 Apr 2019, Jakub Jelinek wrote:
> Hi!
>
> Recently I've added an assert that if !can_alter_cfg DCE (fast DCE in that
> case) doesn't actually alter the cfg. The following testcase shows
> something where it still does. Even when a (const or pure) call doesn't
> throw, it could have EDGE_ABNORMAL{,_CALL} edges added to setjmp etc.
> The following patch makes sure we don't DCE such calls either if we can't
> alter the cfg.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2019-04-16 Jakub Jelinek <ja...@redhat.com>
>
> PR rtl-optimization/90082
> * dce.c (can_delete_call): New function.
> (deletable_insn_p, mark_insn): Use it.
>
> * gcc.dg/pr90082.c: New test.
>
> --- gcc/dce.c.jj 2019-04-12 18:19:47.134165696 +0200
> +++ gcc/dce.c 2019-04-15 12:17:40.746266503 +0200
> @@ -87,6 +87,32 @@ deletable_insn_p_1 (rtx body)
> }
> }
>
> +/* Don't delete calls that may throw if we cannot do so. */
> +
> +static bool
> +can_delete_call (rtx_insn *insn)
> +{
> + if (cfun->can_delete_dead_exceptions && can_alter_cfg)
> + return true;
> + if (!insn_nothrow_p (insn))
> + return false;
> + if (can_alter_cfg)
> + return true;
> + /* If we can't alter cfg, even when the call can't throw exceptions, it
> + might have EDGE_ABNORMAL_CALL edges and so we shouldn't delete such
> + calls. */
> + gcc_assert (CALL_P (insn));
> + if (BLOCK_FOR_INSN (insn) && BB_END (BLOCK_FOR_INSN (insn)) == insn)
> + {
> + edge e;
> + edge_iterator ei;
> +
> + FOR_EACH_EDGE (e, ei, BLOCK_FOR_INSN (insn)->succs)
> + if ((e->flags & EDGE_ABNORMAL_CALL) != 0)
> + return false;
> + }
> + return true;
> +}
>
> /* Return true if INSN is a normal instruction that can be deleted by
> the DCE pass. */
> @@ -111,8 +137,7 @@ deletable_insn_p (rtx_insn *insn, bool f
> && (RTL_CONST_OR_PURE_CALL_P (insn)
> && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))
> /* Don't delete calls that may throw if we cannot do so. */
> - && ((cfun->can_delete_dead_exceptions && can_alter_cfg)
> - || insn_nothrow_p (insn)))
> + && can_delete_call (insn))
> return find_call_stack_args (as_a <rtx_call_insn *> (insn), false,
> fast, arg_stores);
>
> @@ -206,8 +231,7 @@ mark_insn (rtx_insn *insn, bool fast)
> && !SIBLING_CALL_P (insn)
> && (RTL_CONST_OR_PURE_CALL_P (insn)
> && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))
> - && ((cfun->can_delete_dead_exceptions && can_alter_cfg)
> - || insn_nothrow_p (insn)))
> + && can_delete_call (insn))
> find_call_stack_args (as_a <rtx_call_insn *> (insn), true, fast, NULL);
> }
> }
> --- gcc/testsuite/gcc.dg/pr90082.c.jj 2019-04-15 12:22:01.662053468 +0200
> +++ gcc/testsuite/gcc.dg/pr90082.c 2019-04-15 12:22:41.638407968 +0200
> @@ -0,0 +1,13 @@
> +/* PR rtl-optimization/90082 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fnon-call-exceptions -ftrapv" } */
> +
> +void *buf[5];
> +
> +void
> +foo (int a)
> +{
> + if (__builtin_setjmp (buf) == 0)
> + __asm__ ("" : : "n" (a * 2)); /* { dg-error "impossible constraint in
> 'asm'" } */
> + /* { dg-warning "asm operand 0 probably
> doesn't match constraints" "" { target *-*-* } .-1 } */
> +}
>
> Jakub
>
--
Richard Biener <rguent...@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
