> On Wed, Aug 20, 2014 at 9:28 AM, Venkataramanan Kumar > <venkataramanan.ku...@linaro.org> wrote: > > Hi Honza, > > > > After discussing with Richard Beiner via > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62077, it look like it is > > an existing problem in trunk and is masked due the fact that stage1 > > and stage2 compilers in trunk are built with enable-checking and hence > > same garbage collection tuning parameters. > > Note that it works on trunk with --enable-checking=release for > whatever reason.
Strange, do you know how the IR is affected by garbage collection? Honza > > > In release branches, stage 1 is built with some checks like "gc" but > > stage 2 is not. > > These gc parameters affect the LTO IR and it gets streamed differently. > > > > Currently for release branches we have workaround of setting same gc > > parameters for stage1 and stage2 builds (or) build stage1 with > > ---enable-checking=release. > > > > regards, > > Venkat > > > > > > On 11 August 2014 16:20, Venkataramanan Kumar > > <venkataramanan.ku...@linaro.org> wrote: > >> Hi Honza, > >> > >> I did not find any differences in tree level dumps. These are the dump > >> differences in IPA > >> > >> In gimple-fold.c.000i.cgraph > >> > >> (--Snip--) > >> < _Z25gimple_build_omp_continueP9tree_nodeS0_/761 > >> (gimple_build_omp_continue(tree_node*, tree_node*)) @0x3ff7ebda548 > >> --- > >>> _Z25gimple_build_omp_continueP9tree_nodeS0_/761 > >>> (gimple_build_omp_continue(tree_node*, tree_node*)) @0x3ff92b5a548 > >> 28865c28865 > >> < _Z26gimple_build_omp_taskgroupP21gimple_statement_base/760 > >> (gimple_build_omp_taskgroup(gimple_statement_base*)) @0x3ff7ebda400 > >> --- > >>> _Z26gimple_build_omp_taskgroupP21gimple_statement_base/760 > >>> (gimple_build_omp_taskgroup(gimple_statement_base*)) @0x3ff92b5a400 > >> 28875c28875 > >> < _Z23gimple_build_omp_masterP21gimple_statement_base/759 > >> (gimple_build_omp_master(gimple_statement_base*)) @0x3ff7ebda2b8 > >> --- > >>> _Z23gimple_build_omp_masterP21gimple_statement_base/759 > >>> (gimple_build_omp_master(gimple_statement_base*)) @0x3ff92b5a2b8 > >> 28885c28885 > >> < _Z24gimple_build_omp_sectionP21gimple_statement_base/758 > >> (gimple_build_omp_section(gimple_statement_base*)) @0x3ff7ebda170 > >> --- > >>> _Z24gimple_build_omp_sectionP21gimple_statement_base/758 > >>> (gimple_build_omp_section(gimple_statement_base*)) @0x3ff92b5a170 > >> (--Snip--) > >> > >> > >> In gimple.c.044i.profile_estimate > >> > >> (--Snip--) > >> > >> 1987c1987 > >> < vec<tree_node*, va_heap, vl_ptr>::qsort(int (*)(void const*, void > >> const*)) (struct vec * const this, int (*<T10f9>) (const void *, const > >> void *) cmp) > >> --- > >>> vec<tree_node*, va_heap, vl_ptr>::qsort(int (*)(void const*, void > >>> const*)) (struct vec * const this, int (*<T10fb>) (const void *, const > >>> void *) cmp) > >> (--Snip--) > >> > >> gimple.c.048i.inline > >> > >> (--Snip--) > >> > >> < min size: 6 > >> --- > >>> min size: 0 > >> 6590c6590 > >> < min size: 14 > >> --- > >>> min size: 0 > >> 6607c6607 > >> < min size: 28 > >> (--Snip--) > >> > >> On 7 August 2014 19:14, Jan Hubicka <hubi...@ucw.cz> wrote: > >>>> > >>>> As a First step I compared the "objump -D" dump between > >>>> "stage2-gcc/gimple.o" and "stage3-gcc/gimple.o". Differences are in > >>>> LTO sections .gnu.lto_.decls.0, .gnu.lto_.symtab. > >>>> Ref: http://paste.ubuntu.com/7949238/ > >>> > >>> If you see the differences already in .o files (i.e. at compile time), I > >>> think the next > >>> step is to produce -fdump-tree-all -fdump-ipa-all dumps of > >>> stage2-gcc/gimple.o > >>> and stage3-gcc/gimple.o and see how they differ. > >>> > >>> Debugging misoptimization of LTO stage2 compiler will be interesting - I > >>> guess we can > >>> first try to identify what is wrong rahter than usual bisecting method... > >>> > >>> Honza > >>>> > >>>> No differences when when using "objdump -d". > >>>> > >>>> Next I passed "-save-temps" to stage2 and stage3 builds and compared > >>>> the assembly files. The differences are in strings dumped via .ascii > >>>> and ,string directives. > >>>> > >>>> Next I checked the flags passed to the stage 2 and stage 3 builds. It > >>>> is same and below is the flag set being passed. > >>>> > >>>> -save-temps -O2 -g -flto -flto=jobserver -frandom-seed=1 > >>>> -ffat-lto-objects -DIN_GCC -fno-exceptions -fno-rtti > >>>> -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings > >>>> -Wcast-qual -Wmissing-forma t-attribute -pedantic > >>>> -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings > >>>> > >>>> Can you please suggest on how to fix/debug further these comparison > >>>> failures in GCC 4.9? > >>>> > >>>> regards, > >>>> Venkat.
