https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87984
--- Comment #30 from rguenther at suse dot de <rguenther at suse dot de> --- On Fri, 29 Mar 2019, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87984 > > --- Comment #29 from Jakub Jelinek <jakub at gcc dot gnu.org> --- > (In reply to Richard Biener from comment #28) > > Any comments? > > > --- gcc/gimple.c (revision 270012) > > +++ gcc/gimple.c (working copy) > > @@ -2727,11 +2738,16 @@ gimple_asm_clobbers_memory_p (const gasm > > { > > unsigned i; > > > > + /* While strictly speaking only a "memory" clobber denotes clobbering > > + memory in GIMPLE we also treat local hard-register variables as > > + memory so simply treat all clobbers as memory. The only exception > > + is the special clobber "cc". */ > > for (i = 0; i < gimple_asm_nclobbers (stmt); i++) > > { > > tree op = gimple_asm_clobber_op (stmt, i); > > - if (strcmp (TREE_STRING_POINTER (TREE_VALUE (op)), "memory") == 0) > > - return true; > > + if (strcmp (TREE_STRING_POINTER (TREE_VALUE (op)), "cc") == 0) > > + continue; > > + return true; > > } > > > > /* Non-empty basic ASM implicitly clobbers memory. */ > > This will affect not just tree-ssa-operands.c, where it is ok I guess, as it > will just mean a vdef and the alias oracle then can figure out if something > aliases or not, but also ipa-pure-const.c and sanopt. Do we want to say that > functions with register clobbers are no longer pure/const and for sanopt > consider them to be potential spots to free memory? For ipa-pure-const definitely - the calls need to be barriers for local reg sets. For sanopt a memory clobber isn't a very good indication for a spot to free memory anyways... Btw, getting back optimization for cases with hardreg clobbers would need to be put into the alias oracle then.
