2.5X slowdown with g++ 3.4 (probably 3.3 also) over 3.2

[P Ruetz]

I hope this issue has not been discussed before.  My search on this topic
did not turn up anything pertinent.

I have been compiling a computationally bound C++ program with MS Visual C++
and various GNU g++ versions for some time.

Normally, g++ and MSVC produce similar run times with optimized code.
However when moving from g++ 3.2 to 3.4 (and, I think, this also happened
with 3.3 when I tried it some time ago), the run times increase about 2.5x.
With 3.2 my regressions run in 2 hours (3.0G Pentium D using both cores),
but run in over 5 hours with 3.4.  I can not find anything in particular 
that is
causing the slowdown.

Both were compiled with identical flags.  An example of all flags is shown
below.

g++ -I 
/sw/dev/tcl/include -O3 -pedantic -Wpointer-arith -Wsign-compare 
-Wredundant-decls
 -Wwrite-strings -Wconversion -Wall -W -Wshadow -Wno-unused -Wundef 
-Wchar-subscripts
  -Wno-long-long -Wformat -ffloat-store -DWIN32 -D__BORLANDC__=0 -DNEW_HEADER
  -DTURQUOISE -DARCH="\"x86-win\""  -c  ../../../dev/src/build.cpp

The link command is:

g++ dp.a  -lm -ltcl84 -ltk84   -o dp

dp.a contains all of the compiled objects

The code is c++ code but does not use any standard library objects.

Here are the detailed g++ versions for the test I performed.  I used Windows
XP/Intel as the test environment.

g++ (GCC) 3.2 20020927 (prerelease)

g++ (GCC) 3.4.4 (cygming special) (gdc 0.12, using dmd 0.125)

Thanks for any help and suggestions,
Peter

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