[Bug tree-optimization/110434] New: tree-nrv introduces incorrect CLOBBER(eol)

[Bug tree-optimization/110434] New: tree-nrv introduces incorrect CLOBBER(eol)

[kristerw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110434

            Bug ID: 110434
           Summary: tree-nrv introduces incorrect CLOBBER(eol)
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kristerw at gcc dot gnu.org
  Target Milestone: ---

The tree-nrv pass may introduce incorrect CLOBBER(eol) of the form
  <retval> ={v} {CLOBBER(eol)};
  return <retval>;

One example of this can be seen by compiling gcc.c-torture/execute/921204-1.c
for x86 using the flags "-O -m32", where it changes the IR

  union bu o;
  ...
  o = i;
  MEM[(union  *)&o].b18 = _11;
  MEM[(union  *)&o].b20 = _11;
  <retval> = o;
  o ={v} {CLOBBER(eol)};
  return <retval>;

to just use <retval> instead of o

  union bu o [value-expr: <retval>];
  ...
  <retval> = i;
  MEM[(union  *)&<retval>].b18 = _11;
  MEM[(union  *)&<retval>].b20 = _11;
  <retval> ={v} {CLOBBER(eol)};
  return <retval>;

so the CLOBBER(eol) now refers to <retval>.

[Bug tree-optimization/110434] tree-nrv introduces incorrect CLOBBER(eol)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110434

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-06-28

[Bug tree-optimization/110434] tree-nrv introduces incorrect CLOBBER(eol)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110434

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:4bf76b5b6db8e68755788ec91012c5a686440720

commit r14-2164-g4bf76b5b6db8e68755788ec91012c5a686440720
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Jun 28 11:27:45 2023 +0200

    tree-optimization/110434 - avoid <retval> ={v} {CLOBBER} from NRV

    When NRV replaces a local variable with <retval> it also replaces
    occurences in clobbers.  This leads to <retval> being clobbered
    before the return of it which is strictly invalid but harmless in
    practice since there's no pass after NRV which would remove
    earlier stores.

    The following fixes this nevertheless.

            PR tree-optimization/110434
            * tree-nrv.cc (pass_nrv::execute): Remove CLOBBERs of
            VAR we replace with <retval>.

[Bug tree-optimization/110434] tree-nrv introduces incorrect CLOBBER(eol)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110434

Richard Biener <rguenth at gcc dot gnu.org> changed:

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

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.  Thanks for reporting.