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Re: [patch] Fix failure of ACATS cc3601a
- From: Richard Guenther <richard dot guenther at gmail dot com>
- To: Eric Botcazou <ebotcazou at adacore dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Thu, 31 Mar 2011 17:34:53 +0200
- Subject: Re: [patch] Fix failure of ACATS cc3601a
- References: <201103311725.40432.ebotcazou@adacore.com>
On Thu, Mar 31, 2011 at 5:25 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> Hi,
>
> the ACATS test cc3601a started to fail recently at -O2 after the various tweaks
> to the optimizer. ?This is an assertion failure in the gimplifier invoked from
> PRE because of a dangling PLACEHOLDER_EXPR in operand #2 of an ARRAY_REF.
>
> CCP2 turns the ARRAY_REF:
>
> ?D.2774_394 = MEM[(boolean[(size_type) <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->LB0:<PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->UB0 >= <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->LB0 ? (size_type) <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->UB0 : (size_type) <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->LB0 + -1] *)&ab1][D.2776_392]{lb: D.2758_393 sz:
> 1};
>
> into:
>
> ?D.2774_394 = MEM[(boolean[(size_type) <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->LB0:<PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->UB0 >= <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->LB0 ? (size_type) <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->UB0 : (size_type) <PLACEHOLDER_EXPR struct
> opt16__ab___XUP>.P_BOUNDS->LB0 + -1] *)&ab1][D.2776_392]{lb: 0 sz: 1};
>
> i.e. it computes that operand #2 is 0. ?Later PRE re-creates the reference "by
> pieces" and explicitly drops the 0:
>
> ? ? ? ?if (genop2)
> ? ? ? ? ?{
> ? ? ? ? ? ?/* Drop zero minimum index. ?*/
> ? ? ? ? ? ?if (tree_int_cst_equal (genop2, integer_zero_node))
> ? ? ? ? ? ? ?genop2 = NULL_TREE;
>
> so the gimplifier re-populates it, bringing back the PLACEHOLDER_EXPR.
>
> Fixed by not dropping the 0 in PRE. ?Tested on i586-suse-linux, OK for the
> mainline?
Ok.
Thanks,
Richard.
>
> 2011-03-31 ?Eric Botcazou ?<ebotcazou@adacore.com>
>
> ? ? ? ?* tree-ssa-pre.c (create_component_ref_by_pieces_1) <ARRAY_REF>:
> ? ? ? ?Drop a zero minimum index only if it is redundant.
>
>
> 2011-03-31 ?Eric Botcazou ?<ebotcazou@adacore.com>
>
> ? ? ? ?* gnat.dg/opt16.adb: New test.
>
>
> --
> Eric Botcazou
>