[Bug debug/95343] New: IPA-SRA can result in bad debug info about removed function arguments

[Bug debug/95343] New: IPA-SRA can result in bad debug info about removed function arguments

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95343

            Bug ID: 95343
           Summary: IPA-SRA can result in bad debug info about removed
                    function arguments
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

Created attachment 48608
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48608&action=edit
Testcase

ipa_param_adjustments::modify_call does not properly account for extra
arguments left over from clone materialization when recording debug
info.  Therefore, when the attached testcase is compiled with -O2 or
higher and run in gdb with a breakpoint is set at line 20 where we
examine the value of parameter i, it incorrectly reports 4, even
though it should be 2.

[Bug debug/95343] IPA-SRA can result in wrong debug info about removed function arguments

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95343

Martin Jambor <jamborm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |jamborm at gcc dot gnu.org
            Summary|IPA-SRA can result in bad   |IPA-SRA can result in wrong
                   |debug info about removed    |debug info about removed
                   |function arguments          |function arguments
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2020-05-26
     Ever confirmed|0                           |1

--- Comment #1 from Martin Jambor <jamborm at gcc dot gnu.org> ---
The simplest fix which will make i reported as "optimized out" is the
following.  But I am testing a patch which can make gdb actually show
the correct 4.  Still, the following is usable for gcc 10 if the full
patch is deemed too risky:

diff --git a/gcc/ipa-param-manipulation.c b/gcc/ipa-param-manipulation.c
index 978916057f0..2a04f7b3ce5 100644
--- a/gcc/ipa-param-manipulation.c
+++ b/gcc/ipa-param-manipulation.c
@@ -787,7 +787,12 @@ ipa_param_adjustments::modify_call (gcall *stmt,
          if (!is_gimple_reg (old_parm) || kept[i])
            continue;
          tree origin = DECL_ORIGIN (old_parm);
-         tree arg = gimple_call_arg (stmt, i);
+         int index;
+         if (transitive_remapping)
+           index = index_map[i];
+         else
+           index = i;
+         tree arg = gimple_call_arg (stmt, index);

          if (!useless_type_conversion_p (TREE_TYPE (origin), TREE_TYPE (arg)))
            {

[Bug debug/95343] IPA-SRA can result in wrong debug info about removed function arguments

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95343

--- Comment #2 from Martin Jambor <jamborm at gcc dot gnu.org> ---
(In reply to Martin Jambor from comment #1)
> ...I am testing a patch which can make gdb actually show
> the correct 4. 

I meant the correct value 2, of course.

[Bug debug/95343] IPA-SRA can result in wrong debug info about removed function arguments

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95343

--- Comment #3 from Martin Jambor <jamborm at gcc dot gnu.org> ---
I have proposed a patch series on the mailing list to address PR 93385 and the
last patch in it also addresses this issue and allows gdb to print the correct
value of the removed parameter:

https://gcc.gnu.org/pipermail/gcc-patches/2020-May/546705.html

[Bug debug/95343] IPA-SRA can result in wrong debug info about removed function arguments

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95343

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Jambor <jamborm@gcc.gnu.org>:

https://gcc.gnu.org/g:053c88093a45f175f446eda009f3312e4e508514

commit r11-1787-g053c88093a45f175f446eda009f3312e4e508514
Author: Martin Jambor <mjambor@suse.cz>
Date:   Thu Jul 2 14:30:50 2020 +0200

    ipa-sra: Prevent constructing debug info from wrong argument

    The mechanism generating debug info for removed parameters did not
    adjust index of the argument in the call statement to take into
    account extra arguments IPA-SRA might have produced when splitting a
    strucutre.  This patch addresses that omission and stops gdb from
    showing incorrect value for the removed parameter and says "value
    optimized out" instead.  The guality testcase will end up as
    UNSUPPORTED in the results which is how Richi told me on IRC we deal
    with this.

    It is possible to generate debug info to actually show the value of
    the removed parameter but so far my approaches to do just that seem
    toocontroversial
    (https://gcc.gnu.org/pipermail/gcc-patches/2020-May/546705.html), so
    before I come up with something better I'd like to push this to master
    and the gcc-10 branch in time for the GCC 10.2 release.

    gcc/ChangeLog:

    2020-07-01  Martin Jambor  <mjambor@suse.cz>

            PR debug/95343
            * ipa-param-manipulation.c (ipa_param_adjustments::modify_call):
Adjust
            argument index if necessary.

    gcc/testsuite/ChangeLog:

    2020-07-01  Martin Jambor  <mjambor@suse.cz>

            PR debug/95343
            * gcc.dg/guality/pr95343.c: New test.

[Bug debug/95343] IPA-SRA can result in wrong debug info about removed function arguments

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95343

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Martin Jambor
<jamborm@gcc.gnu.org>:

https://gcc.gnu.org/g:61e4ee3f2c0e3d77602c87866cd5c0cfb81d5da2

commit r10-8421-g61e4ee3f2c0e3d77602c87866cd5c0cfb81d5da2
Author: Martin Jambor <mjambor@suse.cz>
Date:   Fri Jul 3 14:51:02 2020 +0200

    ipa-sra: Prevent constructing debug info from wrong argument

    The mechanism generating debug info for removed parameters did not
    adjust index of the argument in the call statement to take into
    account extra arguments IPA-SRA might have produced when splitting a
    strucutre.  This patch addresses that omission and stops gdb from
    showing incorrect value for the removed parameter and says "value
    optimized out" instead.  The guality testcase will end up as
    UNSUPPORTED in the results which is how Richi told me on IRC we deal
    with this.

    It is possible to generate debug info to actually show the value of
    the removed parameter but so far my approaches to do just that seem
    toocontroversial
    (https://gcc.gnu.org/pipermail/gcc-patches/2020-May/546705.html), so
    before I come up with something better I'd like to push this to master
    and the gcc-10 branch in time for the GCC 10.2 release.

    gcc/ChangeLog:

    2020-07-01  Martin Jambor  <mjambor@suse.cz>

            PR debug/95343
            * ipa-param-manipulation.c (ipa_param_adjustments::modify_call):
Adjust
            argument index if necessary.

    gcc/testsuite/ChangeLog:

    2020-07-01  Martin Jambor  <mjambor@suse.cz>

            PR debug/95343
            * gcc.dg/guality/pr95343.c: New test.

    (cherry picked from commit 053c88093a45f175f446eda009f3312e4e508514)

[Bug debug/95343] IPA-SRA can result in wrong debug info about removed function arguments

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95343

Martin Jambor <jamborm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #6 from Martin Jambor <jamborm at gcc dot gnu.org> ---
This bug is fixed, the debug info is no longer wrong, just also missing in
cases where we could actually provide it.  But that is a different thing, so
let me close this one.