Re: Massive performance regression from switching to gcc 4.5

[Jan Hubicka <hubicka at ucw dot cz>]

> > Jan Hubicka wrote:
> >>> On Fri, 25 Jun 2010, it was written:
> >>> There sure is something in 4.5. I've seen a 1-10% slowdown at the GiNaC
> >>> (a computer algebra library) benchmark suite after switching from 4.4 to
> >>> 4.5 on x86_64 when compiling with -O2. And there hasn't been a measurable
> >>> performance differences between 4.3 and 4.4.
> >>
> >> FP intensive code could be also affected by:
> >
> > This code isn't using floating-point.
> 
> Hmm, building ginac with current 4.5 branch I get:
> /bin/sh ../libtool --tag=CXX   --mode=compile /abuild/jh/gcc-4.5-nopatch/bin/g++ -DHAVE_CONFIG_H -I. -I../../ginac -I../config   -I/usr/local/include    -g -O2 -MT function.lo -MD -MP -MF .deps/function.Tpo -c -o function.lo ../../ginac/function.cpp
> libtool: compile:  /abuild/jh/gcc-4.5-nopatch/bin/g++ -DHAVE_CONFIG_H -I. -I../../ginac -I../config -I/usr/local/include -g -O2 -MT function.lo -MD -MP -MF .deps/function.Tpo -c ../../ginac/function.cpp  -fPIC -DPIC -o .libs/function.o
> ../../ginac/function.cpp: In member function â??GiNaC::ex GiNaC::function::power(const GiNaC::ex&) constâ??:
> ../../ginac/function.cpp:1800:15: error: expected type-specifier
> ../../ginac/function.cpp:1800:15: error: expected â??)â??
> ../../ginac/function.cpp:1801:72: error: conversion from â??int*â?? to â??GiNaC::exâ?? is ambiguous
> ../../ginac/ex.h:279:1: note: candidates are: GiNaC::ex::ex(long unsigned int) <near match>
> ../../ginac/ex.h:273:1: note:                 GiNaC::ex::ex(long int) <near match>
> ../../ginac/ex.h:267:1: note:                 GiNaC::ex::ex(unsigned int) <near match>
> ../../ginac/ex.h:261:1: note:                 GiNaC::ex::ex(int) <near match>

Hi,
I got arround by just replacing the offending line by abort() that seems to get me far enough
to build the testsuite.  One thing I noticed is that compile time prolonged excessively to about
10 minutes.  It seems to be var tracking

39609    11.3093  cc1plus                  canonicalize_values_star
33469     9.5562  cc1plus                  loc_cmp
22206     6.3403  cc1plus                  set_slot_part
15798     4.5107  cc1plus                  rtx_equal_p
14479     4.1341  cc1plus                  htab_find_with_hash
10461     2.9869  cc1plus                  htab_find_slot_with_hash
7268      2.0752  cc1plus                  find_loc_in_1pdv
6718      1.9181  cc1plus                  cselib_expand_value_rtx_1
6619      1.8899  libc-2.11.1.so           strcmp
6193      1.7682  cc1plus                  htab_expand
6020      1.7188  cc1plus                  check_changed_vars_0
5797      1.6552  cc1plus                  htab_traverse_noresize
5615      1.6032  cc1plus                  htab_find_with_hash
4757      1.3582  cc1plus                  vt_expand_loc_callback
4529      1.2931  libginac-1.5.so.0.1.2    GiNaC::basic::compare(GiNaC::basic const&) const
4497      1.2840  libc-2.11.1.so           _int_malloc
3879      1.1075  as                       /usr/bin/as
3703      1.0573  cc1plus                  variable_htab_eq
3698      1.0559  cc1plus                  insert_into_intersection
3287      0.9385  cc1plus                  emit_note_insn_var_location

Honza