Re: Something wrong with bootstrap-lto, or lto itself:

[Trevor Saunders <tsaunders at mozilla dot com>]

On Tue, Nov 05, 2013 at 12:56:39PM +0100, Richard Biener wrote:
> On Tue, Nov 5, 2013 at 6:42 AM, Trevor Saunders <tsaunders@mozilla.com> wrote:
> > On Mon, Nov 04, 2013 at 01:29:10PM +0100, Richard Biener wrote:
> >> On Wed, Oct 30, 2013 at 8:17 PM, Toon Moene <toon@moene.org> wrote:
> >> > Consider this:
> >> >
> >> > http://gcc.gnu.org/ml/gcc-testresults/2013-10/msg02329.html
> >> >
> >> > and
> >> >
> >> > http://gcc.gnu.org/ml/gcc-testresults/2013-10/msg02258.html
> >> >
> >> > /scratch/toon/bd5894/./prev-gcc/xg++ -B/scratch/toon/bd5894/./prev-gcc/
> >> > -B/home/toon/compilers/install/x86_64-unknown-linux-gnu/bin/ -nostdinc++
> >> > -B/scratch/toon/bd5894/prev-x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs
> >> > -B/scratch/toon/bd5894/prev-x86_64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs
> >> > -I/scratch/toon/bd5894/prev-x86_64-unknown-linux-gnu/libstdc++-v3/include/x86_64-unknown-linux-gnu
> >> > -I/scratch/toon/bd5894/prev-x86_64-unknown-linux-gnu/libstdc++-v3/include
> >> > -I/home/toon/compilers/gcc/libstdc++-v3/libsupc++
> >> > -L/scratch/toon/bd5894/prev-x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs
> >> > -L/scratch/toon/bd5894/prev-x86_64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs
> >> > -g -O2 -flto=jobserver -frandom-seed=1 -DIN_GCC    -fno-exceptions -fno-rtti
> >> > -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
> >> > -Wcast-qual -Wmissing-format-attribute -pedantic -Wno-long-long
> >> > -Wno-variadic-macros -Wno-overlength-strings -Werror -fno-common
> >> > -DHAVE_CONFIG_H -static-libstdc++ -static-libgcc  -o cc1plus \
> >> >               cp/cp-lang.o c-family/stub-objc.o cp/call.o cp/decl.o
> >> > cp/expr.o cp/pt.o cp/typeck2.o cp/class.o cp/decl2.o cp/error.o cp/lex.o
> >> > cp/parser.o cp/ptree.o cp/rtti.o cp/typeck.o cp/cvt.o cp/except.o
> >> > cp/friend.o cp/init.o cp/method.o cp/search.o cp/semantics.o cp/tree.o
> >> > cp/repo.o cp/dump.o cp/optimize.o cp/mangle.o cp/cp-objcp-common.o
> >> > cp/name-lookup.o cp/cxx-pretty-print.o cp/cp-gimplify.o
> >> > cp/cp-array-notation.o cp/lambda.o cp/vtable-class-hierarchy.o attribs.o
> >> > incpath.o c-family/c-common.o c-family/c-cppbuiltin.o c-family/c-dump.o
> >> > c-family/c-format.o c-family/c-gimplify.o c-family/c-lex.o c-family/c-omp.o
> >> > c-family/c-opts.o c-family/c-pch.o c-family/c-ppoutput.o c-family/c-pragma.o
> >> > c-family/c-pretty-print.o c-family/c-semantics.o c-family/c-ada-spec.o
> >> > c-family/array-notation-common.o c-family/c-ubsan.o i386-c.o glibc-c.o
> >> > cc1plus-checksum.o libbackend.a main.o tree-browser.o libcommon-target.a
> >> > libcommon.a ../libcpp/libcpp.a ../libdecnumber/libdecnumber.a libcommon.a
> >> > ../libcpp/libcpp.a   ../libbacktrace/.libs/libbacktrace.a
> >> > ../libiberty/libiberty.a ../libdecnumber/libdecnumber.a  -lcloog-isl -lisl
> >> > -lmpc -lmpfr -lgmp -rdynamic -ldl  -L../zlib -lz
> >> > In function 'release',
> >> >     inlined from '_ZN7va_heap7reserveIbEEvRP3vecIT_S_8vl_embedEjb.part.95'
> >> > at /home/toon/compilers/gcc/gcc/vec.h:288:7,
> >> >     inlined from 'reserve',
> >> >     inlined from '_ZN3vecIb7va_heap6vl_ptrE7reserveEjb.part.96' at
> >> > /home/toon/compilers/gcc/gcc/vec.h:1367:3,
> >> >     inlined from 'reserve.constprop',
> >> >     inlined from 'reserve_exact' at
> >> > /home/toon/compilers/gcc/gcc/vec.h:1387:45,
> >> >     inlined from 'safe_grow' at /home/toon/compilers/gcc/gcc/vec.h:1515:3,
> >> >     inlined from 'safe_grow_cleared' at
> >> > /home/toon/compilers/gcc/gcc/vec.h:1529:3,
> >> >     inlined from 'vect_bb_vectorization_profitable_p' at
> >> > /home/toon/compilers/gcc/gcc/tree-vect-slp.c:2027:0,
> >> >     inlined from 'vect_slp_analyze_bb_1' at
> >> > /home/toon/compilers/gcc/gcc/tree-vect-slp.c:2174:55,
> >> >     inlined from 'vect_slp_analyze_bb' at
> >> > /home/toon/compilers/gcc/gcc/tree-vect-slp.c:2229:44:
> >> > /home/toon/compilers/gcc/gcc/vec.h:316:3: error: attempt to free a non-heap
> >> > object 'life' [-Werror=free-nonheap-object]
> >> >    ::free (v);
> >> >    ^
> >> > lto1: all warnings being treated as errors
> >>
> >> Obviously fallout of the stack-vector rewrite.
> >>
> >>       stack_vec<bool, 20> life;
> >>       life.safe_grow_cleared (SLP_INSTANCE_GROUP_SIZE (instance));
> >>
> >> doesn't make much sense anyway ...  why is the initial size only
> >> allowed as a template parameter?  But then safe_grow shouldn't free
> >> the stack storage.
> >
> > So, I'm still confused how exactly this happens, presumably we must be
> > trying to reserve a vector of length zero and consequently hit that code
> > in va_heap::reserve to free the vector if we're supposed to reserve 0
> > elements, but that doesn't make sense because the first check in
> > vec::reserve should have failed if that was the case.  Unfortunately I
> > have no clue how to get dumps for optimization happening during lto or
> > otherwise debug the compiler during lto.
> 
> The backtrace suggests that the error may be from expanding code
> that is dead at runtime but was not detected as so.  IPA-CP likely
> propagated the storage object and partial inlining obfuscated the code
> enough to hide the fact that it is dead ...

ah, good point

> > However I think I've convinced myself this code to have
> > vec_prefix::calculate_allocation return 0 if !prefix & !reserve should
> > never be hit, so I think we can remove it and infact that seems to get
> > me through atleast one round of lto.
> >
> > I'll run a full lto bootstrap and standard bootstrap on x86_64-linux-gnu
> > with test suite, assuming those are ok is the below ok?
> 
> Ok.

everything checked out over night so I committed this as r204392

Trev

> 
> Thanks,
> Richard.
> 
> > Trev
> >
> > 2013-11-4  Trevor Saunders  <tsaunders@mozilla.com>
> >
> >         * vec.c (vec_prefix::calculate_allocation): Don't try to handle the
> >         case of no prefix and reserving zero slots, because when that's the
> >         case we'll never get here.
> >         * vec.h (va_heap::reserve): Don't try and handle
> >         vec_prefix::calculate_allocation returning zero because that should
> >         never happen.
> >
> > diff --git a/gcc/vec.c b/gcc/vec.c
> > index f3c3315..78252e0 100644
> > --- a/gcc/vec.c
> > +++ b/gcc/vec.c
> > @@ -187,9 +187,7 @@ vec_prefix::calculate_allocation (vec_prefix *pfx, unsigned reserve,
> >        num = pfx->m_num;
> >      }
> >    else if (!reserve)
> > -    /* If there's no vector, and we've not requested anything, then we
> > -       will create a NULL vector.  */
> > -    return 0;
> > +    gcc_unreachable ();
> >
> >    /* We must have run out of room.  */
> >    gcc_assert (alloc - num < reserve);
> > diff --git a/gcc/vec.h b/gcc/vec.h
> > index f97e022..b1ebda4 100644
> > --- a/gcc/vec.h
> > +++ b/gcc/vec.h
> > @@ -283,11 +283,7 @@ va_heap::reserve (vec<T, va_heap, vl_embed> *&v, unsigned reserve, bool exact
> >  {
> >    unsigned alloc
> >      = vec_prefix::calculate_allocation (v ? &v->m_vecpfx : 0, reserve, exact);
> > -  if (!alloc)
> > -    {
> > -      release (v);
> > -      return;
> > -    }
> > +  gcc_assert (alloc);
> >
> >    if (GATHER_STATISTICS && v)
> >      v->m_vecpfx.release_overhead ();
> > --
> > 1.8.4.2
> >
> >>
> >> Richard.
> >>
> >> > --
> >> > Toon Moene - e-mail: toon@moene.org - phone: +31 346 214290
> >> > Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
> >> > At home: http://moene.org/~toon/; weather: http://moene.org/~hirlam/
> >> > Progress of GNU Fortran: http://gcc.gnu.org/wiki/GFortran#news