[Bug tree-optimization/105801] New: Missed CCP with -ftrivial-auto-var-init=zero

[Bug tree-optimization/105801] New: Missed CCP with -ftrivial-auto-var-init=zero

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105801

            Bug ID: 105801
           Summary: Missed CCP with -ftrivial-auto-var-init=zero
           Product: gcc
           Version: 12.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

int foo (int flag)
{
  int i;
  if (flag)
    i = 1;
  return i;
}

CCP used to optimize this to 'return 1;' but with -ftrivial-auto-var-init=zero
only FRE does this now.

[Bug tree-optimization/105801] Missed CCP with -ftrivial-auto-var-init=zero

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105801

--- 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:8f4634fb82d5670183d0ee42de9dae3b55ab5087

commit r13-4678-g8f4634fb82d5670183d0ee42de9dae3b55ab5087
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Dec 13 14:24:02 2022 +0100

    tree-optimization/105801 - CCP and .DEFERRED_INIT

    This makes sure we treat .DEFERRED_INIT as producing UNDEFINED so
    we can continue optimizing uninitialized uses the same as without
    -ftrivial-auto-var-init=zero.  For the testcase this means we
    catch the return 1 optimization opportunity at CCP rather than
    only at FRE which already does the right thing here.

            PR tree-optimization/105801
            * tree-ssa-ccp.cc (likely_value): .DEFERRED_INIT produces
            UNDEFINED.
            * doc/invoke.texi (ftrivial-auto-var-init): Explicitely
            mention we treat variables without an initializer as
            undefined also for optimization purposes.

            * gcc.dg/tree-ssa/ssa-ccp-43.c: New testcase.

[Bug tree-optimization/105801] Missed CCP with -ftrivial-auto-var-init=zero

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105801

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |13.0
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed for GCC 13.