Benchmark results of Build Time optimisation flags + LTO

[sheepdestroyer]

Hi, first post here for me

I did a small scale benchmarking of diffrent compile flags with git from October 2nd.
My system is a SandyBridge core i7 2620 dual core + HT so 4 threads ; I run fedora 20 64bit + gcc 4.9.1 from rawhide

Standard build is -O3, targets general arch x64 (I think?) and without LTO.
I was interested in finding out what would be the effect of -Ofast instead of -O3, -march=native (equivalent to -march=corei7-avx on my cpu) and LTO with recent gcc.

I used the povray.elf benchmark found on this forum

---------------------------------------Run1------ ------Run2--------------Run3
Standard----------------------------15min 43s------- 15min 43s------- 15min 44s
-Ofast-------------------------------15min 43s--------15min 42s
march=native----------------------15min 42s--------15min 44s
march=native & -Ofast------------15min 44s -------15min 44s
LTO----------------------------------15min 42s--------15min 42s
LTO & -Ofast------------------------15min 43s--------15min 44s
LTO & march=native---------------15min 44s--------15min 42s
LTO & march=native & -Ofast-----15min 42s--------15min 42s

As you can see, this is quite unconcluant and I would be tempted to think that neither optimization flags nor LTO matter.
But I only tried one synthethic benchmark and would like your advice on how to bench real games in a reproducible way.
Thanks for your comments