Re: JIT compiling with LLVM v9.0

Hi,

On 2018-01-30 13:46:37 -0500, Robert Haas wrote:
> On Mon, Jan 29, 2018 at 1:40 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > It's an optional dependency, and it doesn't increase build time that
> > much... If we were to move the llvm interfacing code to a .so, there'd
> > not even be a packaging issue, you can just package that .so separately
> > and get errors if somebody tries to enable LLVM without that .so being
> > installed.
>
> I suspect that would be really valuable. If 'yum install
> postgresql-server' (or your favorite equivalent) sucks down all of
> LLVM, some people are going to complain, either because they are
> trying to build little tiny machine images or because they are subject
> to policies which preclude the presence of a compiler on a production
> server. If you can do 'yum install postgresql-server' without
> additional dependencies and 'yum install postgresql-server-jit' to
> make it go faster, that issue is solved.

So, I'm working on that now. In the course of this I'll be
painfully rebase and rename a lot of code, which I'd like not to repeat
unnecessarily.

Right now there primarily is:

src/backend/lib/llvmjit.c - infrastructure, optimization, error handling
src/backend/lib/llvmjit_{error,wrap,inline}.cpp - expose more stuff to C
src/backend/executor/execExprCompile.c - emit LLVM IR for expressions
src/backend/access/common/heaptuple.c - emit LLVM IR for deforming

Given that we need a shared library it'll be best buildsystem wise if
all of this is in a directory, and there's a separate file containing
the stubs that call into it.

I'm not quite sure where to put the code. I'm a bit inclined to add a
new
src/backend/jit/
because we're dealing with code from across different categories? There
we could have a pgjit.c with the stubs, and llvmjit/ with the llvm
specific code?

Alternatively I'd say we put the stub into src/backend/executor/pgjit.c,
and the actual llvm using code into src/backend/executor/llvmjit/?

Comments?

Andres Freund