Re: Optimizing PostgreSQL with LLVM's PGO+LTO

Hi,

On 2023-01-30 10:24:02 -0700, João Paulo Labegalini de Carvalho wrote:
> > What compiler / version / flags / OS did you try?
> >
>
> I am running experiment on a machine with:
>
> - Intel(R) Xeon(R) Platinum 8268 CPU @ 2.90GHz
> - Ubuntu 18.04.6 LTS
> - LLVM/Clang 15.0.6 (build from source)
>
> These are the flags I am using:
>
> CFLAGS = -O3 -fuse-ld=lld -gline-tables-only -fprofile-instr-generate
> LDFLAGS = -fuse-ld=lld -Wl,-q

For some reason my notes for using LTO include changing RANLIB to point to
gcc/llvm-ranlib of the appropriate version. Won't even be used on HEAD, but
before that it can make a difference.

Depending on how you built clang, it could be that the above recipe ends up
using the system lld, which might be too old.

What are the crashes you're getting?

Greetings,

Andres Freund