Re: [PATCH] tree-optimization/106912 - IPA profile and pure/const

[Richard Biener <rguenther@suse.de>]

On Fri, 17 Mar 2023, Jakub Jelinek wrote:

> On Fri, Mar 17, 2023 at 08:40:34PM +0100, Jan Hubicka wrote:
> > > +		/* Drop the const attribute from the call type (the pure
> > > +		   attribute is not available on types).  */
> > > +		tree fntype = gimple_call_fntype (call);
> > > +		if (fntype && TYPE_READONLY (fntype))
> > > +		  gimple_call_set_fntype
> > > +		    (call, build_qualified_type (fntype, (TYPE_QUALS (fntype)
> > > +							  & ~TYPE_QUAL_CONST)));
> > 
> > Sorry, now I am bit confused on why Jakub's fix did not need similar
> > fixup.  The flag is only set during the profiling stage and thus I would
> > expect it to still run into the problem that VOPs are missing.
> > Is it only becuase we do not sanity check?
> 
> My patch started from this point ignoring all TYPE_READONLY bits on
> all FUNCTION_TYPE/METHOD_TYPEs, while Richi's patch instead makes it
> explicit in the IL, TYPE_READONLY is honored as before but it shouldn't
> show up in any of the gimple_call_fntype types unless it is a direct
> call to a const function for which we don't have a body.
> 
> In either case, vops are added on the update_stmt a few lines later.
> 
> > Here is a testcase that shows the problem:
> > 
> > include <math.h>
> > float c;
> > 
> > __attribute__ ((const))
> > float
> > instrument(float v)
> > {
> >         return sin (v);
> > }
> > __attribute__ ((no_profile_instrument_function,const,noinline))
> > float noinstrument (float v)
> > {
> >         return instrument (v);
> > }
> > 
> > m()
> > {
> >         c+=instrument(c);
> >         if (!__builtin_expect (c,1))
> >         {
> >           c+=noinstrument (c);
> >         }
> >         c+=instrument(c);
> > }
> > main()
> > {
> >         m();
> > }
> > 
> > Compiling 
> > gcc -O0 t.c -fprofile-arcs -fno-early-inlining --coverage -lm -ftest-coverage -S ; gcc t.s -ftest-coverage -lm -fprofile-arcs
> > makes gcov to report 3 executions on instrument while with -O3 it is 2.

With my proposed patch it works fine and reports 3 executions on
'instrument' with both -O0 and -O3.  I checked it indeed reports only
2 executions with GCC 12.

So it seems the patch is a progression in general?

Thus, OK?

Thanks,
Richard.