On 08/20/2017 09:19 PM, Zachary Turner via dev-platform wrote:
On Monday, August 14, 2017 at 1:47:02 PM UTC-7, Hans Wennborg wrote:
Yes, we want to do LTO+PGO builds eventually. (In particular, we'd
like to use ThinLTO for more manageable build times.) That requires
switching to using the lld linker, which in turn is requires adding
support for writing pdb files, an area that's been making lots of
progress lately.
Cheers,
Hans
A quick update on this, but I wrote a blog post about the state of PDBs in lld
today.
http://blog.llvm.org/2017/08/llvm-on-windows-now-supports-pdb-debug.html
TL;DR is that all the hard stuff is done, PDBs are happening, and now it's just
a matter of finding debug quality issues. I haven't tried linking Chromium
with lld yet, but I have tried linking clang with lld and I'm seeing
/DEBUG:FULL link times with /Z7 being similar to MSVC /DEBUG:FASTLINK times
with /Zi.
(With all the obvious disclaimers about how as we find / fix debug quality
issues, things could slow down, since PDB generation without /Zi is a pretty
big contributor to link time).
If anyone here is up for dogfooding, I would love to have bug reports against
LLD's PDB debug info quality.
This is great news! For those who are interested in the very young
project to port Firefox to link with lld,
https://bugzilla.mozilla.org/show_bug.cgi?id=linker-lld tracks that work.
Cheers,
Ehsan
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