Re: RFA: patch to fix IRA degradation on SPEC2006 calculix

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Tue, Nov 18, 2008 at 10:30 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Tue, Nov 18, 2008 at 7:45 PM, Vladimir Makarov <vmakarov@redhat.com> wrote:
>> H.J. reported huge degradation of IRA on calculix on x86_64
>>
>> http://gcc.gnu.org/ml/gcc-patches/2008-11/msg00812.html
>>
>> Calculix has one hot function (about 80% of all program time) e_c3d
>> with small most frequently executed loop.  One accidental spill in the
>> loop results in 30% degradation.  The degradation occurred after
>> submitting patch introducing bad spills processing.  I missed another
>> checks of bad spills in allocno comparison when all previous high
>> priority criteria are the same (see
>> ira-color.c::push_allocnos_to_stack).
>>
>> I also found that the hot function in calculix has more 50 loops,
>> therefore IRA decides to use one region allocation.  Instead of such
>> approach, I change the code to make no more ira-max-loops-num regions
>> (most frequenly used ones) instead of one region.  I also changed
>> ira-max-loops-num value to 100 (there are still functions in calculix
>> which contains more 100 loops) because it looks like fortran functions
>> have many implicit loops (from vector operations).  It permits to
>> improve calculix score a bit more.
>>
>> The rest of the patch is a code printing more info which I used for
>> debugging.
>>
>> The patch was successfully bootstrapped on x86_64.
>>
>> Is it ok to commit?
>
> It doesn't bootstrap Linux/x86-64:
>
> [hjl@gnu-27 src]$ /export/build/gnu/gcc/build-x86_64-linux/./gcc/xgcc
> -shared-libgcc -B/export/build/gnu/gcc/build-x86_64-linux/./gcc
> -nostdinc++ -L/export/build/gnu/gcc/build-x86_64-linux/x86_64-unknown-linux-gnu/libstdc++-v3/src
> -L/export/build/gnu/gcc/build-x86_64-linux/x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs
> -B/usr/gcc-4.4/x86_64-unknown-linux-gnu/bin/
> -B/usr/gcc-4.4/x86_64-unknown-linux-gnu/lib/ -isystem
> /usr/gcc-4.4/x86_64-unknown-linux-gnu/include -isystem
> /usr/gcc-4.4/x86_64-unknown-linux-gnu/sys-include
> -I/export/build/gnu/gcc/build-x86_64-linux/x86_64-unknown-linux-gnu/libstdc++-v3/include/x86_64-unknown-linux-gnu
> -I/export/build/gnu/gcc/build-x86_64-linux/x86_64-unknown-linux-gnu/libstdc++-v3/include
> -I/net/gnu-13/export/gnu/src/gcc/gcc/libstdc++-v3/libsupc++
> -fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual
> -fdiagnostics-show-location=once -ffunction-sections -fdata-sections
> -g -O2 -D_GNU_SOURCE -c
> /net/gnu-13/export/gnu/src/gcc/gcc/libstdc++-v3/src/bitmap_allocator.cc
>  -fPIC -DPIC -o .libs/bitmap_allocator.o
> /net/gnu-13/export/gnu/src/gcc/gcc/libstdc++-v3/src/bitmap_allocator.cc:
> In member function âsize_t* __gnu_cxx::free_list::_M_get(size_t)â:
> /net/gnu-13/export/gnu/src/gcc/gcc/libstdc++-v3/src/bitmap_allocator.cc:103:
> internal compiler error: Segmentation fault
> Please submit a full bug report,
> with preprocessed source if appropriate.
> See <http://gcc.gnu.org/bugs.html> for instructions.
> [hjl@gnu-27 src]$
>
> I used "--enable-clocale=gnu --with-system-zlib
> --enable-checking=assert --with-demangler-in-ld --enable-shared
> --enable-threads=posix --enable-haifa --prefix=/usr/gcc-4.4
> --with-local-prefix=/usr/local" to configure gcc.
>

Valgrind reports:

==666== Conditional jump or move depends on uninitialised value(s)
==666==    at 0xA260CF: ira_build (ira-build.c:1697)
==666==    by 0xA21673: rest_of_handle_ira (ira.c:1788)
==666==    by 0x6387D8: execute_one_pass (passes.c:1279)
==666==    by 0x638A04: execute_pass_list (passes.c:1328)
==666==    by 0x638A1C: execute_pass_list (passes.c:1329)
==666==    by 0x708166: tree_rest_of_compilation (tree-optimize.c:418)
==666==    by 0x8260C3: cgraph_expand_function (cgraphunit.c:1047)
==666==    by 0x8277A4: cgraph_optimize (cgraphunit.c:1106)
==666==    by 0x450B1C: cp_write_global_declarations (decl2.c:3615)
==666==    by 0x6CE146: toplev_main (toplev.c:979)
==666==    by 0x50448B3: (below main) (in /lib64/libc-2.5.so)
==666==
==666== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 1)
==666== malloc/free: in use at exit: 993,009 bytes in 7,944 blocks.
==666== malloc/free: 373,081 allocs, 365,137 frees, 225,318,650 bytes allocated.
==666== For counts of detected errors, rerun with: -v
==666== searching for pointers to 7,944 not-freed blocks.
==666== checked 21,004,136 bytes.
==666==
==666== LEAK SUMMARY:
==666==    definitely lost: 144 bytes in 14 blocks.
==666==      possibly lost: 0 bytes in 0 blocks.
==666==    still reachable: 992,865 bytes in 7,930 blocks.
==666==         suppressed: 0 bytes in 0 blocks.


>> 2008-11-18  Vladimir Makarov  <vmakarov@redhat.com>
>>
>>   * doc/invoke.texi (ira-max-loops-num): Change semantics.
>>
>>   * ira-int.h (struct ira_loop_tree_node): New member to_remove_p.
>>
>>   * ira-color.c (allocno_spill_priority): New function.
>>   (remove_allocno_from_bucket_and_push, push_allocno_to_spill):
>>   Print more info about the spilled allocno.
>>   (push_allocnos_to_stack): Use allocno_spill_priority.  Add more
>>   checks on bad spill.
>>
>>   * ira-build.c (loop_node_to_be_removed_p): Remove.
>>   (loop_compare_func, mark_loops_for_removal): New functions.
>>   (remove_uneccesary_loop_nodes_from_loop_t): Use member
>>   to_remove_p.
>>   (remove_unnecessary_allocnos): Call mark_loops_for_removal.
>>
>>   * ira.c (ira): Don't change flag_ira_algorithm.
>>
>>   * params.def (ira-max-loops-num): Change the value.
>>

-- 
H.J.