On Wed, 28 Dec 2016, Andreas Tobler wrote:
> On 28.12.16 19:24, Richard Biener wrote:
> > On December 27, 2016 11:17:00 PM GMT+01:00, Andreas Tobler
> > <andreast-l...@fgznet.ch> wrote:
> > > On 16.09.16 13:30, Richard Biener wrote:
> > > > On Thu, 15 Sep 2016, Richard Biener wrote:
> > > >
> > > > >
> > > > > This addresses sth I needed to address with the early LTO debug
> > > patches
> > > > > (you might now figure I'm piecemail merging stuff from that patch).
> > > > >
> > > > > When the cgraph code optimizes out a global we call the
> > > late_global_decl
> > > > > debug hook to eventually add a DW_AT_const_value to its DIE (we
> > > don't
> > > > > really expect a location as that will be invalid after optimizing
> > > out
> > > > > and will be pruned).
> > > > >
> > > > > With the early LTO debug patches I have introduced a
> > > early_dwarf_finished
> > > > > flag (mainly for consistency checking) and I figured I can use that
> > > to
> > > > > detect the call to the late hook during the early phase and provide
> > > > > the following cleaned up variant of avoiding to create locations
> > > that
> > > > > require later pruning (which doesn't work with emitting the early
> > > DIEs).
> > > > >
> > > > > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
> > > > >
> > > > > I verified it does the correct thing for a unit like
> > > > >
> > > > > static const int i = 2;
> > > > >
> > > > > (but ISTR we do have at least one testcase in the testsuite as
> > > well).
> > > > >
> > > > > Will commit if testing finishes successfully.
> > > >
> > > > Ok, so it showed issues when merging that back to early-LTO-debug.
> > > > Turns out in LTO we never call early_finish and thus
> > > early_dwarf_finished
> > > > was never set. Also dwarf2out_late_global_decl itself is a better
> > > > place to constrain generating locations.
> > > >
> > > > The following variant is in very late stage of testing.
> > > >
> > > > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
> > > > LTO bootstrap on x86_64-unknown-linux-gnu in stage3. LTO bootstrap
> > > > with early-LTO-debug in stage3, bootstraped with early-LTO-debug,
> > > > testing in progress.
> > >
> > > Any chance to backport this commit (r240228) to 6.x?
> > > It fixes a bootstrap comparison issue on aarch64-*-freebsd*.
> > > The aarch64-*-freebsd* port is not yet merged to 6.x and 5.4.x due to
> > > the bootstrap comparison failure I faced.
> >
> > Did you analyze the bootstrap miscompare? I suspect the patch merely papers
> > over the problem.
>
> gcc/contrib/compare-debug -p prev-gcc/ipa-icf.o gcc/ipa-icf.o
> prev-gcc/ipa-icf.o.stripped. gcc/ipa-icf.o.stripped. differ: char 52841, line
> 253
>
>
> The objdump -dSx diff on the non stripped object looked always more or less
> the same, a rodata offset which was different.
>
> - 1448: R_AARCH64_ADD_ABS_LO12_NC .rodata+0x1d8
> + 1448: R_AARCH64_ADD_ABS_LO12_NC .rodata+0x410
Hmm, sounds like a constant pool entry was created by -g at a different
time (and thus offset) from regular compilation. So yes, the patch
in question should have the affect to "fix" this.
Note that I later changed the fix with
2016-10-20 Richard Biener <rguent...@suse.de>
* cgraphunit.c (analyze_functions): Set node->definition to
false to signal symbol removal to debug_hooks->late_global_decl.
* ipa.c (symbol_table::remove_unreachable_nodes): When not in
WPA signal symbol removal to the debuginfo machinery.
* dwarf2out.c (dwarf2out_late_global_decl): Instead of
using early_finised to guard the we're called for symbol
removal case look at the symtabs definition flag.
(gen_variable_die): Remove redundant check.
(the dwarf2out_late_global_decl and analyze_functions part are
relevant).
That should be the fix to backport (avoiding the early_dwarf_finished
part).
Richard.
> > Was that regular bootstrap (with or without compare-debug)?
>
> Hm, regular bootstrap, --with-build-config=bootstrap-debug?
>
> Or do you have something else in mind?
>
> I rerun on 6.x w/o 'patch' now. Hopefully in 12h I have something.
>
> Btw, I bisected on trunk, r240227 was nok, the next, r240228 was ok. Then I
> took the part from r240228 to the 6.x branch and my comparison issue was gone.
>
> If I miss something you need to know pls let me know.
>
> TIA,
> Andreas
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
