[Bug debug/94281] [8/9/10 Regression] g++: error: hash.cpp: ‘-fcompare-debug’ failure (length) since r8-5241-g8697bf9f46f36168

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94281

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:10ea09ee846eaa345161a3a3f519b3780d6101fa

commit r10-7395-g10ea09ee846eaa345161a3a3f519b3780d6101fa
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Mar 26 10:10:21 2020 +0100

    gimplify: Fix -fcompare-debug differences caused by gimplify_body [PR94281]

    The following testcase FAILs, because gimplify_body adds a GIMPLE_NOP only
    when there are no statements in the function and with -g there is a
    DEBUG_BEGIN_STMT, so it doesn't add it and due to -fno-tree-dce that never
    gets removed afterwards.  Similarly, if the body seq after gimplification
    contains some DEBUG_BEGIN_STMTs plus a single gbind, then we could behave
    differently between -g0 and -g, by using that gbind as the body in the -g0
    case and not in the -g case.
    This patch fixes that by ignoring DEBUG_BEGIN_STMTs (other debug stmts
can't
    appear at this point yet thankfully) during decisions and if we pick the
    single gbind and there are DEBUG_BEGIN_STMTs next to it, it moves them into
    the gbind.
    While debugging this, I found also a bug in the
gimple_seq_last_nondebug_stmt
    function, for a seq that has a single non-DEBUG_BEGIN_STMT statement
    followed by one or more DEBUG_BEGIN_STMTs it would return NULL rather than
    the first statement.

    2020-03-26  Jakub Jelinek  <jakub@redhat.com>

            PR debug/94281
            * gimple.h (gimple_seq_first_nondebug_stmt): New function.
            (gimple_seq_last_nondebug_stmt): Don't return NULL if seq contains
            a single non-debug stmt followed by one or more debug stmts.
            * gimplify.c (gimplify_body): Use gimple_seq_first_nondebug_stmt
            instead of gimple_seq_first_stmt, use
gimple_seq_first_nondebug_stmt
            and gimple_seq_last_nondebug_stmt instead of gimple_seq_first and
            gimple_seq_last to check if outer_stmt gbind could be reused and
            if yes and it is surrounded by any debug stmts, move them into the
            gbind body.

            * g++.dg/debug/pr94281.C: New test.