On Wed, 28 Mar 2018, Jakub Jelinek wrote:
> Hi!
>
> With the introduction of DEBUG_BEGIN_STMT/-gstatement-frontiers on by
> default, the -Wduplicated-branches warning doesn't work anymore with -g,
> because operand_equal_p in OEP_LEXICOGRAPHIC mode doesn't consider
> DEBUG_BEGIN_STMTs as equal unless they are pointer equal. For the warning
> we either need to ignore them completely (but that would need more changes,
> as the hashing doesn't ignore them), or at least what the second hunk does,
> consider them equal. The first hunk is just an optimization, if
> -Wduplicated-branches is used on extremely deeply nested STATEMENT_LISTs,
> then for -fchecking we'd be computing the hashes etc. at the level of every
> stmt of every STATEMENT_LIST; we need to do that just once at the toplevel.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2018-03-28 Jakub Jelinek <ja...@redhat.com>
>
> PR c/85094
> * fold-const.c (operand_equal_p): Handle DEBUG_BEGIN_STMT.
> For STATEMENT_LIST, pass down OEP_LEXICOGRAPHIC and maybe
> OEP_NO_HASH_CHECK for recursive call, to avoid exponential
> checking.
>
> * c-c++-common/Wduplicated-branches-14.c: New test.
>
> --- gcc/fold-const.c.jj 2018-03-27 12:54:43.657242009 +0200
> +++ gcc/fold-const.c 2018-03-28 16:20:40.024574216 +0200
> @@ -3479,7 +3479,8 @@ operand_equal_p (const_tree arg0, const_
> if (tsi_end_p (tsi1) && tsi_end_p (tsi2))
> return 1;
> if (!operand_equal_p (tsi_stmt (tsi1), tsi_stmt (tsi2),
> - OEP_LEXICOGRAPHIC))
> + flags & (OEP_LEXICOGRAPHIC
> + | OEP_NO_HASH_CHECK)))
> return 0;
> }
> }
> @@ -3492,6 +3493,10 @@ operand_equal_p (const_tree arg0, const_
> if (flags & OEP_LEXICOGRAPHIC)
> return OP_SAME_WITH_NULL (0);
> return 0;
> + case DEBUG_BEGIN_STMT:
> + if (flags & OEP_LEXICOGRAPHIC)
> + return 1;
> + return 0;
> default:
> return 0;
> }
> --- gcc/testsuite/c-c++-common/Wduplicated-branches-14.c.jj 2018-03-28
> 16:20:00.966553266 +0200
> +++ gcc/testsuite/c-c++-common/Wduplicated-branches-14.c 2018-03-28
> 16:19:07.264524448 +0200
> @@ -0,0 +1,16 @@
> +/* PR c/85094 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -Wduplicated-branches -g" } */
> +
> +extern int g;
> +
> +void
> +foo (int r)
> +{
> + if (r < 64)
> + g -= 48;
> + else if (r < 80) /* { dg-warning "this condition has identical branches"
> } */
> + g -= 64 - 45;
> + else
> + g -= 80 - 61;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
