[Bug tree-optimization/103489] [12 Regression] ICE with -O3 in operator[], at vec.h:889

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103489

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=101636

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
So we BB vectorize sth we should use bool patterns to fixup.  We get

t.c:8:1: note:   using normal nonmask vectors for a_I_lsm.24_70 = PHI
<_54(D)(2), _208(4)>
t.c:8:1: note:   using boolean precision 16 for _208 = _207 != 0;

but fail to add compensation on the PHI arg def because that's not supported
right now.  See also PR101636 for another bool pattern issue (but probably
unrelated).

So in this case the store is outside of a vectorized cycle (store motion is
applied) and thus defined by a loop closed PHI node.  check_bool_pattern
doesn't handle this and thus we get to see we have a normal nonmask vector
for the LC PHI:

t.c:8:1: note:   using normal nonmask vectors for a_I_lsm.24_20 = PHI
<a_I_lsm.24_70(5)>

but since we do not have patterns for PHIs the first nonmask use cannot
get compensation code.

The precision determining code in this case is broken since it does not handle
cycles properly, we first visit the loop PHI having an external def and not
yet visited backedge argument.

I'm going to produce a fix for the ICE and think about fixing bool pattern
detection for GCC 13.