[llvm-commits] [patch] Switch LTO to use MC

[Rafael Ávila de Espíndola]

 > Very nice Rafael!  Do you have a breakdown of how much of that 6:30
> is spent reading bitcode files, doing IR linking, doing optimization,
> doing codegen, and doing native linking?  I'm just curious where the
> time is going.  I would not have expected 30s for the asmprinter +
> native assembler :)

I did some basic experiments, but they have to be updated. I remember
the assembler taking about 12s and llvm-mc being a bit faster going from
.s to .o. I was also surprised when the final time reduction was 30s.

Doing llvm-link of all the IL files is about 3m if I remember correctly.

There is also some overhead just in managing so much memory. The largest
speedup I go so far was just by merging modules as we read them. Another
thing on these lines is trying to reuse gold mmaps. Right now we map the
files again or malloc+read them (in the case of archive members).

I will try to upload a "small" test with all the .o files, both elf and
IL so that it is easy to redo just link.

> -Chris

Cheers,
Rafael