https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104550
--- Comment #16 from rguenther at suse dot de <rguenther at suse dot de> --- On Thu, 17 Feb 2022, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104550 > > --- Comment #15 from Jakub Jelinek <jakub at gcc dot gnu.org> --- > (In reply to qinzhao from comment #11) > > (In reply to Jakub Jelinek from comment #10) > > > Even in that case, filling the memory with pattern & mask instead of > > > filling > > > the memory with pattern + __builtin_clear_padding afterwards seems like a > > > win. > > > > So, you mean It's better to do the following for pattern init: > > > > 1. add call to .DEFERRED_INIT(, pattern, ) during gimplification; > > 2. during RTL expansion, fill the memory with pattern & mask if the variable > > is in memory. > > > > how to implement "fill the memory with pattern & mask" during RTL expansion? > > currently, we use memset to fill the memory when the variable is in memory, > > pattern & mask might not fit to a BYTE-repeatable pattern that can be used > > for memset? > > You can populate a buffer with the pattern and then > clear_type_padding_in_mask. > Then you can create a STRING_CST out from that array and store_expr > (the_STRING_CST, DECL_RTL (var), false, false, false) - at least when DECL_RTL > (var) is a MEM. It would of course be _highly_ desirable to _not_ need to build a STRING_CST here. The problematical cases are all when DECL_RTL isn't a MEM, of course.
