On Wed, Nov 5, 2014 at 5:06 PM, Martin Jambor <mjam...@suse.cz> wrote: > On Tue, Oct 28, 2014 at 03:57:43PM +0100, Richard Biener wrote: >> On Tue, Oct 28, 2014 at 1:00 AM, Aldy Hernandez <al...@redhat.com> wrote: >> > Gentlemen! >> > >> > My apologies for the big patch. In getting locals emitted early >> > (parameters >> > and locally scoped variables), I ran into many things which were in need of >> > surgery, many of which couldn't happen without the other. Consequently, I >> > ended up fixing everything such that we are now back to no guality.exp >> > failures for any language. >> > >> > [Curiously, I hadn't noticed locals were not being dumped early because >> > they >> > were being picked up by the late dwarf pass. Fixing this oversight is what >> > caused this entire patch.] >> > >> > There are a lot of changes here, and I would greatly appreciate feedback, >> > so >> > let me at least explain what's going on at a high level... >> > >> > 1. Changes to gen_subprogram_die() to handle early generation of locals, >> > and >> > amending location information on the second pass. Everything else in this >> > patch, basically stems from this change. >> > >> > 2. Changes to gen_variable_die() to handle multiple passes (early/late >> > dwarf >> > generation). >> > >> > A lot of this is complicated by the fact that old_die's are cached and >> > keyed >> > by `tree', but an abstract instance and an inline instance share trees, >> > while dwarf2out_abstract_function() sets DECL_ABSTRACT_P behind the scenes. >> > >> > The current support (and my changes) maintain this shared and delicate >> > design. I wonder whether we could simplify a lot of this code by unsharing >> > these trees, but this may be beyond the scope of this work. Richi perhaps >> > you can comment? >> >> I think that the abstract and inline instances are cases that are _only_ >> generated "early" - that is, they don't contain any locations or whatever >> and thus do not need to ameded in the late dwarf pass. So I'd simply >> generate dwarf for them and not remember their DIEs. > > Please have a look at PR 63722, which is a complaint I got from people > exploring possiblities of using dwarf to analyze what gcc did to Linux > kernel and they discovered that DIEs of abstract origins do not have > their DW_AT_inline set correctly for functions that were IPA-SRAed but > not inlined. On the original testcase before reduction I've seen the > same problem also when using -fno-ipa-sra -fno-ipa-cp so it is not > just my passes but also probably ipa-split ;-) > > In any case, if we want abstract origins to have this field set > correctly in abstract origins, we need to have the possibility to > modify it after IPA.
My point is we don't need the abstract origins at all - they are a DWARF bytecode space optimization. Richard. > Martin
