On Sun, 25 Sep 2011, Tom de Vries wrote: > On 09/25/2011 10:57 AM, Richard Guenther wrote: > > On Sat, Sep 24, 2011 at 5:29 PM, Eric Botcazou <ebotca...@adacore.com> > > wrote: > >>> This is an updated version of the patch. I have 2 new patches and an > >>> updated testcase which I will sent out individually. > >>> > >>> Patch set was bootstrapped and reg-tested on x86_64. > >>> > >>> Ok for trunk? > >>> > >>> Thanks, > >>> - Tom > >>> > >>> 2011-07-30 Tom de Vries <t...@codesourcery.com> > >>> > >>> PR middle-end/43513 > >>> * Makefile.in (tree-ssa-ccp.o): Add $(PARAMS_H) to rule. > >>> * tree-ssa-ccp.c (params.h): Include. > >>> (fold_builtin_alloca_for_var): New function. > >>> (ccp_fold_stmt): Use fold_builtin_alloca_for_var. > >> > >> We have detected another fallout on some Ada code: the transformation > >> replaces > >> a call to __builtin_alloca with &var, i.e. it introduces an aliased > >> variable, > >> which invalidates the points-to information of some subsequent call, > >> fooling > >> DSE into thinking that it can eliminate a live store. > > > > Ugh, yeah. I suppose PTA assigned a HEAP var as pointed-to object for the > > original pointer, even if the transformed stmt > > > > orig_ptr_1 = &a; > > > > has the points-to information preserved for orig_ptr_1 further propagation > > of > > &a will make accesses through orig_ptr_1 have different alias properties. > > > > What should work in this special case of a singleton points-to set of > > orig_ptr_1 > > (might want to check that) is, do > > > > SET_DECL_PT_UID (decl-of-a, DECL_UID (pointed-to orig_ptr_1)); > > > > The brute force approach is not acceptable (it'll wreck IPA points-to info). > > > > A helper like pt_solution_singleton_p (struct pt_solution *pt, unsigned > > *uid) > > whould be nice to have for this. > > > > Note that we don't have points-to information computed during the first > > CCP pass, so the above should be conditional on SSA_NAME_PTR_INFO > > being present and not ! ->anything (but then assert that we actually do have > > a singleton, or fail the folding). > > > > I tried to implement the approach you describe above in attached patch. > Currently testing on x86_64.
Looks good to me (with a changelog entry). Thanks, Richard. > Thanks, > - Tom > > > Richard. > > > >> The brute force approach > >> > >> Index: tree-ssa-ccp.c > >> =================================================================== > >> --- tree-ssa-ccp.c (revision 179038) > >> +++ tree-ssa-ccp.c (working copy) > >> @@ -2014,7 +2014,10 @@ do_ssa_ccp (void) > >> ccp_initialize (); > >> ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node); > >> if (ccp_finalize ()) > >> - return (TODO_cleanup_cfg | TODO_update_ssa | > >> TODO_remove_unused_locals); > >> + return (TODO_cleanup_cfg > >> + | TODO_update_ssa > >> + | TODO_rebuild_alias > >> + | TODO_remove_unused_locals); > >> else > >> return 0; > >> } > >> > >> works, but we might want to be move clever. Thoughts? > >> > >> -- > >> Eric Botcazou > >> > > -- Richard Guenther <rguent...@suse.de> SUSE / SUSE Labs SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer
