Re: [PATCH] tree-optimization/103168 - Improve VN of pure function calls
> > Yes, note that we don't have callused unless IPA PTA is enabled, > but it might be salveagable from IPA reference info? What we're > missing is a stmt_clobbers_pt_solution_p, or rather a reasonably > cheap way to construct an ao_ref covering all of a points-to > solution. The not-so-cheap way to do that is > > tree tem = make_ssa_name (ptr_type_node); > ptr_info_def *pi = get_ptr_info (p); > pt->pt = *gimple_call_use_set (call_stmt); > tree ref = build2 (MEM_REF, void_type_node /* ?? */, tem, build_zero_cst > (ptr_type_node /* that effectively is ref-all */)); > ao_ref_init (&r, ref); > r->base = ref; > r->ref = NULL_TREE; > r->offset = 0; > r->alias_set = 0; > r->base_alias_set = 0; > > and if we come from IPA reference we first have to build a > points-to bitmap as well. > > What would be a bit more convenient is probably adding > a pt_solution * member to ao_ref. Maybe also avoiding Having a way to add additional pt_solution to the ref looks like a good idea, since then it could do through the common path in tree-ssa-alias.c. I will look into that next year :) Honza > the MEM_REF build we already do in some cases and overload > the base field using a union and a designator ... > > But yes, sth for next stage1. > > Richard.
Re: [PATCH] tree-optimization/103168 - Improve VN of pure function calls
On Wed, 24 Nov 2021, Jan Hubicka wrote: > > This improves value-numbering of calls that read memory, calls > > to const functions with aggregate arguments and calls to > > pure functions where the latter include const functions we > > demoted to pure for the fear of interposing with a less > > optimized version. Note that for pure functions we do not > > handle functions that access global memory. > > Thank you! I am happy we finally undid some of the pessimization caused > by the interposition panic. I was wondering if I should try next stage1 > start tracking eliminated reads in functions, but that is tricky to do > since things like if (*global_var == *globa_var) is folded already in > frontend. > > I was thinking a bit what to do abou global accesses and I think we > still can do something (also next stage1). > > Currently we disambiguate using > if (stmt_may_clobber_ref_p_1 (def, &ref, true)) > where ref is the REF is a ao_ref we built from the summary of STMT and > DEF is another statement. This is fine but we ignore info we have from > PTA on STMT (the statement we try to optimize). > > I we could look at DEF, and try to disambiguate all memory it > writes against STMT using PTA oracle and that would let us to handle > global memory well (we don't need REF for that) because we will work out > that some accesses are not escaping to STMT becaue they are not in > CALLUSED. Somewhat anoying is that we don't have predicate in > tree-ssa-alias for that (stmt_clobber_stmt_p :) Yes, note that we don't have callused unless IPA PTA is enabled, but it might be salveagable from IPA reference info? What we're missing is a stmt_clobbers_pt_solution_p, or rather a reasonably cheap way to construct an ao_ref covering all of a points-to solution. The not-so-cheap way to do that is tree tem = make_ssa_name (ptr_type_node); ptr_info_def *pi = get_ptr_info (p); pt->pt = *gimple_call_use_set (call_stmt); tree ref = build2 (MEM_REF, void_type_node /* ?? */, tem, build_zero_cst (ptr_type_node /* that effectively is ref-all */)); ao_ref_init (&r, ref); r->base = ref; r->ref = NULL_TREE; r->offset = 0; r->alias_set = 0; r->base_alias_set = 0; and if we come from IPA reference we first have to build a points-to bitmap as well. What would be a bit more convenient is probably adding a pt_solution * member to ao_ref. Maybe also avoiding the MEM_REF build we already do in some cases and overload the base field using a union and a designator ... But yes, sth for next stage1. Richard.
Re: [PATCH] tree-optimization/103168 - Improve VN of pure function calls
> This improves value-numbering of calls that read memory, calls > to const functions with aggregate arguments and calls to > pure functions where the latter include const functions we > demoted to pure for the fear of interposing with a less > optimized version. Note that for pure functions we do not > handle functions that access global memory. Thank you! I am happy we finally undid some of the pessimization caused by the interposition panic. I was wondering if I should try next stage1 start tracking eliminated reads in functions, but that is tricky to do since things like if (*global_var == *globa_var) is folded already in frontend. I was thinking a bit what to do abou global accesses and I think we still can do something (also next stage1). Currently we disambiguate using if (stmt_may_clobber_ref_p_1 (def, &ref, true)) where ref is the REF is a ao_ref we built from the summary of STMT and DEF is another statement. This is fine but we ignore info we have from PTA on STMT (the statement we try to optimize). I we could look at DEF, and try to disambiguate all memory it writes against STMT using PTA oracle and that would let us to handle global memory well (we don't need REF for that) because we will work out that some accesses are not escaping to STMT becaue they are not in CALLUSED. Somewhat anoying is that we don't have predicate in tree-ssa-alias for that (stmt_clobber_stmt_p :) Honza
