https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110237
--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> --- On Tue, 20 Jun 2023, crazylht at gmail dot com wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110237 > > --- Comment #4 from Hongtao.liu <crazylht at gmail dot com> --- > (In reply to Richard Biener from comment #3) > > This looks like the same issue as PR110309. We have > > > > (insn 38 35 39 3 (set (mem:V16SI (plus:DI (reg:DI 40 r12 [orig:90 _22 ] > > [90]) > > (const:DI (plus:DI (symbol_ref:DI ("b") [flags 0x2] > > <var_decl 0x7ffff6e28d80 b>) > > (const_int -4 [0xfffffffffffffffc])))) [1 MEM > > <vector(16) int> [(int *)vectp_b.12_28]+0 S64 A32]) > > (vec_merge:V16SI (reg:V16SI 20 xmm0 [118]) > > (mem:V16SI (plus:DI (reg:DI 40 r12 [orig:90 _22 ] [90]) > > (const:DI (plus:DI (symbol_ref:DI ("b") [flags 0x2] > > <var_decl 0x7ffff6e28d80 b>) > > (const_int -4 [0xfffffffffffffffc])))) [1 MEM > > <vector(16) int> [(int *)vectp_b.12_28]+0 S64 A32]) > > > > so instead of a masked load we see a vec_merge with a (mem:V16SI ...) > > based on the vectp_b.12_28 pointer that has full size but the load of b[1] > > we try disambiguate against refers to int b[10] which is too small for > > a load of 64 bytes so we disambiguate based on that. > > > /* If the pointer based access is bigger than the variable they cannot > alias. This is similar to the check below where we use TBAA to > increase the size of the pointer based access based on the dynamic > type of a containing object we can infer from it. */ > poly_int64 dsize2; > if (known_size_p (size1) --- should be unknown?? > && poly_int_tree_p (DECL_SIZE (base2), &dsize2) > && known_lt (dsize2, size1)) > return false; > > Should we set MEM_SIZE_KNOWN_P to false for maskstore/maskload? > It seems to me maxsize should be 64bytes, but real size should be unknown. Yes, you shouldn't have MEM_ATTRs that indicate the size is known.
