On 09/07/2011 11:28 AM, Duncan Sands wrote:
Hi Vladimir, thanks for doing this.
The above said about compilation speed is true when GCC front-end is
used for LLVM.
It's not clear to me which GCC front-end you mean. There is llvm-gcc
(based on gcc-4.2) and the dragonegg plugin (the 2.9 version works with
gcc-4.5; the development version works also with gcc-4.6). Can you
please clarify.
This is not dragonegg. It was llvm-gcc4.2-2.9-x86_64-linux.
By the way, some highly unscientific experiments I did
suggest that the GCC tree optimizers are (almost) as fast as the LLVM IR
optimizers while doing a better job;
That is probably not only tree optimizers. RTL optimizers seem not slow
as well.
while at -O3 the LLVM code generators
are significantly faster than the GCC code generators and do a comparable
and sometimes better job. Unfortunately I haven't had time to do a
serious
study, so this might just be an accident of the benchmarks I looked at
and
the options I happened to use rather than anything meaningful.
I frequently see that on small benchmarks some optimizations (I mostly
work on RA) look better than on bigger benchmarks. It would be
interesting to run SPEC2006 for comparison because it contains even
bigger benchmarks. Unfortunately, it will take 2 weeks on my machine to
run SPEC2006 for the same # of option sets.
