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

[Jan Hubicka <hubicka@ucw.cz>]

> 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?
OK,
thanks!
Honza
> 
> Thanks,
> Richard.