Re: [PATCH] lto: pass through -funwind-tables and -fasynchronous-unwind-tables

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Jan 18, 2023 at 01:39:18PM +0100, Andreas Schwab wrote:
> On Jan 18 2023, Jakub Jelinek wrote:
> 
> > With LTO each function has the DECL_FUNCTION_SPECIFIC_OPTIMIZATION
> > (and _TARGET), for functions with optimize attribute obviously as without
> > LTO specific to what options have been overridden (but with defaults from
> > TU's command line etc.), for functions without that simply with what
> > options has the TU.
> 
> Sorry, I cannot parse that sentence.  Could you please try again?

After parsing options GCC creates an OPTIMIZATION_NODE tree with all the
PerFunction/Optimization option state recorded in it (and more).
That node is then when writing LTO attached to each function (different
node if a function has optimize attribute etc.).
That is streamed in by lto1 back and on each set_cfun such saved options
are stored into global_options{,_set}.

> > lto1 then streams in those options and when switching functions switches
> > the global options.
> 
> Why does that not work then?

I don't know what doesn't work.  You haven't mentioned what kind of PR
you're trying to fix or what problem you are seeing.

	Jakub