[Bug tree-optimization/101267] [12 Regression] ICE in vect_is_simple_use when building 521.wrf_r with -Ofast -march=znver2

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101267

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

           What    |Removed                     |Added
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                 CC|                            |rsandifo at gcc dot gnu.org

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
So we're having

(gdb) p debug (slp_node)
t.f90:1:21: note: node 0x39fbbc0 (max_nunits=2, refcnt=1)
t.f90:1:21: note: op template: _144 = .MASK_LOAD (_143, 32B, _142);
t.f90:1:21: note:       stmt 0 _144 = .MASK_LOAD (_143, 32B, _142);
t.f90:1:21: note:       stmt 1 _146 = .MASK_LOAD (_145, 32B, _142);
t.f90:1:21: note:       children 0x39fbc48

where vectorizable_load invokes

8500              if (!vect_check_scalar_mask (vinfo, stmt_info, mask,
&mask_dt,
8501                                           &mask_vectype))
8502                return false;

but the SLP child is

(gdb) p debug ((slp_tree)0x39fbc48)
t.f90:1:21: note: node (external) 0x39fbc48 (max_nunits=1, refcnt=1)
t.f90:1:21: note:       { _142, _142 }

so it won't have a vector type set.  In fact vect_check_scalar_mask doesn't
seem to be prepared for SLP at all - we're lucky it "works" but then most
definitely it won't for externals.  You'll note that the SLP variant for
vect_is_simple_use won't be applicable here since we only have SLP
representations for the mask operand which isn't even the first one.

The SLP "support" for masked loads was added by Alejandro Martinez it seems,
CCing other ARM folks.

A possible fix is to simply give up for external SLP defs above, the internal
def case was probably working by chance.  I'm testing such a fix.