[llvm-dev] Making LLD PDB generation faster

Zachary Turner via llvm-dev llvm-dev at lists.llvm.org
Sat Feb 23 22:19:31 PST 2019

+Reid and Alexandre, who have been doing work in this area recently

On Sat, Feb 23, 2019 at 4:07 AM Leonardo Santagada via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi,
> Is anyone working on making the PDB generation on LLD faster? Looking
> of a trace for linking one of our binaries (it takes 1min6s-1min20s) I
> see two things:
> 1) LookupBucketFor(Val, ConstFoundBucket); takes 35s so almost half of
> the time of linking, mostly finding duplicates
> 2) There is no parallelization inside of addObjectsToPDB
> Is anyone working on those? Also has anyone thought about merging .obj
> files to deduplicate type infomation so we can do the linking on
> projects to generate something like a lib file, but deduplicated debug
> information (as far as I know actual .lib just put all pdbs or /Z7
> debug info inside a file without dedup).
> Just looking at the code it seems it is much more mature and also the
> choice of SHA1_8 seems interesting (still don't know why not use
> xxHash64).
> ps: My code to add ghashes to msvc compiled .obj files is almost ready
> to be pushed as an option for llvm-objcopy.
> --
> Leonardo Santagada
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