Chris Lattner wrote:
On May 12, 2009, at 6:56 AM, Vladimir Makarov wrote:
A few people asked me to do a new comparison of GCC releases and LLVM
as the new GCC release and LLVM were out recently.
You can find the comparison on http://vmakarov.fedorapeople.org/spec/
The comparison for x86 (32-bit mode) was done on Pentium4 and for
x86_64 (64-bit mode) on Core I7.
Some changes in the performance were big since GCC 3.2 and it is
sometimes hard to see small changes on the posted graphs. Therefore
I put original tables used to generate the graphs.
Looking at the llvm 2.5 vs gcc 4.4 comparison is very interesting,
thank you for putting this together Vladimir! I find these numbers
particularly interesting because you're comparing simple options like
-O2 and -O3 instead of the crazy spec tuning mix :). This is much
more likely to be representative of what real users will get on their
apps.
Some random thoughts:
1. I have a hard time understanding the code size numbers. Does 10%
mean that GCC is generating 10% bigger or 10% smaller code than llvm?
The change is reported relative to LLVM. So 10% means that GCC
generates 10% bigger code than LLVM and -10% means that GCC generates
10% less code.
2. You change two variables in your configurations: micro architecture
and pointer size. Would you be willing to run x86-32 Core i7 numbers
as well? LLVM in particular is completely untuned for the (really old
and quirky) "netburst" architecture, but I'm interested to see how it
runs for you on more modern Core i7 or Core2 processors in 32-bit mode.
I used the same processor (P4) and options for x86 as for the GCC
release comparison. I did not know that LLVM is badly tuned for P4,
sorry. I could do the same comparison for x86 on Core i7 without
specific tuning (there is no tuning for i7 yet) but it takes a lot of
time. May be it will be ready on next week.
3. Your SPEC FP benchmarks tell me two things: GCC 4.4's fortran
support is dramatically better than 4.2's (which llvm 2.5 uses), and
your art/mgrid hacks apparently do great stuff :).
4. Your SPEC INT numbers are more interesting to me. It looks like
you guys have some significant wins in 175.vpr, 197.crafty, and other
benchmarks. At some point, I'll have to see what you guys are doing :)
Thanks for the info, great stuff!
-Chris
