[Bug ipa/103073] [12 Regression] ICE in insert_access, at ipa-modref-tree.h:578 since r12-4401-gfecd145359fc981b

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103073

--- Comment #7 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 4 Nov 2021, hubicka at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103073
> 
> Jan Hubicka <hubicka at gcc dot gnu.org> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |rguenther at suse dot de
> 
> --- Comment #5 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
> OK, after some inlining we produce an access past the end of array which makes
> get_base_ref_and_extend to produce an access with size==8 and max_size==0.
> Modref access merging is built on an assumption that max_size>size (if both are
> known).
> 
> The access is (*g_18(D))[3][_207];:
>  <array_ref 0x7ffff756f0e0
>     type <boolean_type 0x7ffff73ebb28 bool public unsigned type_6 QI
>         size <integer_cst 0x7ffff73ed030 constant 8>
>         unit-size <integer_cst 0x7ffff73ed048 constant 1>
>         align:8 warn_if_not_align:0 symtab:0 alias-set 1 canonical-type
> 0x7ffff73ebb28 precision:1 min <integer_cst 0x7ffff73ed288 0> max <integer_cst
> 0x7ffff73ed2b8 1>
>         pointer_to_this <pointer_type 0x7ffff7534bd0>>
> 
>     arg:0 <array_ref 0x7ffff756f118
>         type <array_type 0x7ffff7534dc8 type <boolean_type 0x7ffff73ebb28 bool>
>             type_6 BLK
>             size <integer_cst 0x7ffff7541ae0 constant 168>
>             unit-size <integer_cst 0x7ffff7541ab0 constant 21>
>             align:8 warn_if_not_align:0 symtab:0 alias-set 1 canonical-type
> 0x7ffff7534dc8 domain <integer_type 0x7ffff7534d20>>
> 
>         arg:0 <mem_ref 0x7ffff7566cd0 type <array_type 0x7ffff7534f18>
> 
>             arg:0 <ssa_name 0x7ffff754d630 type <pointer_type 0x7ffff7534348>
>                 visited var <parm_decl 0x7ffff7548180 g>
>                 def_stmt GIMPLE_NOP
>                 version:18
>                 ptr-info 0x7ffff7541f60>
>             arg:1 <integer_cst 0x7ffff7541e88 constant 0>
>             tt.C:5:14 start: tt.C:5:11 finish: tt.C:5:14>
>         arg:1 <integer_cst 0x7ffff73ed300 constant 3>
>         tt.C:5:17 start: tt.C:5:11 finish: tt.C:5:17>
>     arg:1 <ssa_name 0x7ffff756eca8
>         type <integer_type 0x7ffff73eb690 unsigned int sizes-gimplified public
> unsigned SI
>             size <integer_cst 0x7ffff73ed180 constant 32>
>             unit-size <integer_cst 0x7ffff73ed198 constant 4>
>             align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
> 0x7ffff73eb690 precision:32 min <integer_cst 0x7ffff73ed1b0 0> max <integer_cst
> 0x7ffff73ed168 4294967295>
>             pointer_to_this <pointer_type 0x7ffff73fb498>>
>         visited
>         def_stmt _207 = _293 + 21;
>         version:207
>         ptr-info 0x7ffff7567860>
>     tt.C:5:24 start: tt.C:5:11 finish: tt.C:5:24>
> 
> and we get maxsize reduced based on value range info:
> 582                                           TYPE_PRECISION (sizetype));
> 583                             woffset *= wi::to_offset (unit_size);
> 584                             woffset <<= LOG2_BITS_PER_UNIT;
> 585                             bit_offset += woffset;
> 586                             if (known_size_p (maxsize))
> 587                               maxsize -= woffset;
> 588                           }
> 589                       }
> 590                   }
> (gdb) p woffset
> $114 = {<poly_int_pod<1, generic_wide_int<fixed_wide_int_storage<128> > >> =
> {coeffs = {{<fixed_wide_int_storage<128>> = {val = {168, 0, 140737488345944},
> len = 1}, static is_sign_extended = true}}}, <No data fields>}
> (gdb) p maxsize
> $115 = {<poly_int_pod<1, generic_wide_int<fixed_wide_int_storage<128> > >> =
> {coeffs = {{<fixed_wide_int_storage<128>> = {val = {168, 0, 140737488346016},
> len = 1}, static is_sign_extended = true}}}, <No data fields>}
> 
> I suppose we can ignore such paradoxical range becuase executing that code
> undefined.  But I think we may want to handle this in alias oracle as well?

Well, the usual thing to do is to check max_size_known_p () and
if maybe_ne (max_size, size) then use [offset, max_size] for 
disambiguation.  I think for modref you can do the same - if max size
is known then use [offset, max_size], otherwise you have to punt.  You
shouldn't need 'size' at all, 'size' is when you are looking for
must-defs.