Date: Fri, 13 Oct 2023 11:06:21 +0200
From: Dmitry Dolgov <9erthalion6@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Thomas Munro <thomas.munro@gmail.com>,
	Devrim =?utf-8?B?R8O8bmTDvHo=?= <devrim@gunduz.org>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Fabien COELHO <coelho@cri.ensmp.fr>,
	Ronan Dunklau <ronan.dunklau@aiven.io>
Subject: Re: LLVM 16 (opaque pointers)
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> On Thu, Oct 12, 2023 at 04:31:20PM -0700, Andres Freund wrote:
> Hi,
>
> On 2023-10-11 21:59:50 +1300, Thomas Munro wrote:
> > +#else
> > +	LLVMPassBuilderOptionsRef options;
> > +	LLVMErrorRef err;
> > +	int			compile_optlevel;
> > +	char	   *passes;
> > +
> > +	if (context->base.flags & PGJIT_OPT3)
> > +		compile_optlevel = 3;
> > +	else
> > +		compile_optlevel = 0;
> > +
> > +	passes = psprintf("default<O%d>,mem2reg,function(no-op-function),no-op-module",
> > +					  compile_optlevel);
>
> I don't think the "function(no-op-function),no-op-module" bit does something
> particularly useful?

Right, looks like leftovers after verifying which passes were actually
applied. My bad, could be removed.

> I also don't think we should add the mem2reg pass outside of -O0 - running it
> after a real optimization pipeline doesn't seem useful and might even make the
> code worse? mem2reg is included in default<O1> (and obviously also in O3).

My understanding was that while mem2reg is included everywhere above
-O0, this set of passes won't hurt. But yeah, if you say it could
degrade the final result, it's better to not do this. I'll update this
part.