RE: Ping^3 [PATCH V2] Add attribute hot judgement for INLINE_HINT_known_hot hint.

["Cui, Lili" <lili.cui@intel.com>]

> 
> On 10/20/22 19:52, Cui, Lili via Gcc-patches wrote:
> > Hi Honza,
> >
> > Gentle ping
> > https://gcc.gnu.org/pipermail/gcc-patches/2022-September/601934.html
> >
> > gcc/ChangeLog
> >
> >    * ipa-inline-analysis.cc (do_estimate_edge_time): Add function attribute
> >    judgement for INLINE_HINT_known_hot hint.
> >
> > gcc/testsuite/ChangeLog:
> >
> >    * gcc.dg/ipa/inlinehint-6.c: New test.
> > ---
> >   gcc/ipa-inline-analysis.cc              | 13 ++++---
> >   gcc/testsuite/gcc.dg/ipa/inlinehint-6.c | 47
> +++++++++++++++++++++++++
> >   2 files changed, 56 insertions(+), 4 deletions(-)
> >   create mode 100644 gcc/testsuite/gcc.dg/ipa/inlinehint-6.c
> >
> > diff --git a/gcc/ipa-inline-analysis.cc b/gcc/ipa-inline-analysis.cc
> > index 1ca685d1b0e..7bd29c36590 100644
> > --- a/gcc/ipa-inline-analysis.cc
> > +++ b/gcc/ipa-inline-analysis.cc
> > @@ -48,6 +48,7 @@ along with GCC; see the file COPYING3.  If not see
> >   #include "ipa-utils.h"
> >   #include "cfgexpand.h"
> >   #include "gimplify.h"
> > +#include "attribs.h"
> >
> >   /* Cached node/edge growths.  */
> >   fast_call_summary<edge_growth_cache_entry *, va_heap>
> > *edge_growth_cache = NULL; @@ -249,15 +250,19 @@
> do_estimate_edge_time (struct cgraph_edge *edge, sreal
> *ret_nonspec_time)
> >         hints = estimates.hints;
> >       }
> >
> > -  /* When we have profile feedback, we can quite safely identify hot
> > -     edges and for those we disable size limits.  Don't do that when
> > -     probability that caller will call the callee is low however, since it
> > +  /* When we have profile feedback or function attribute, we can quite
> safely
> > +     identify hot edges and for those we disable size limits.  Don't do that
> > +     when probability that caller will call the callee is low
> > + however, since it
> >        may hurt optimization of the caller's hot path.  */
> > -  if (edge->count.ipa ().initialized_p () && edge->maybe_hot_p ()
> > +  if ((edge->count.ipa ().initialized_p () && edge->maybe_hot_p ()
> >         && (edge->count.ipa () * 2
> >   	  > (edge->caller->inlined_to
> >   	     ? edge->caller->inlined_to->count.ipa ()
> >   	     : edge->caller->count.ipa ())))
> > +      || (lookup_attribute ("hot", DECL_ATTRIBUTES (edge->caller->decl))
> > +	  != NULL
> > +	 && lookup_attribute ("hot", DECL_ATTRIBUTES (edge->callee->decl))
> > +	  != NULL))
> >       hints |= INLINE_HINT_known_hot;
> 
> Is the theory here that if the user has marked the caller and callee as hot,
> then we're going to assume an edge between them is hot too?  That's not
> necessarily true, it could be they're both hot, but via other call chains.  But it's
> probably a reasonable heuristic in practice.
> 
Yes,  thanks Jeff.

Lili.
> 
> OK
> 
> 
> jeff
>