https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126316
Drea Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Known to fail| |12.1.0
Ever confirmed|0 |1
Keywords| |wrong-code
Last reconfirmed| |2026-07-18
--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
The problem is there is a call to insert_clobbers_for_var which finds the
ccp1 does:
saved_stack.5_4 = __builtin_stack_save ();
saved_stack.2_5 = __builtin_stack_save ();
vla2.7 ={v} {CLOBBER(eos)};
__builtin_stack_restore (saved_stack.2_5);
vla2.4_7 = &vla2.7;
doNothing (vla2.4_7);
__builtin_stack_restore (saved_stack.5_4);
Which is wrong. Because it inserts the clobber at the one before the usage.
It should have skipped the saved_stack.2_5 save/restore.
So what insert_clobbers_for_var needs to do is when it reaches a
__builtin_stack_restore, mark that argument as needing to skipped and then go
to the next previous statement. And then when looking at __builtin_stack_save,
skip the ones the marked as needing to be skipped.
