Re: [PATCH 8/9] ipa-sra: Make scan_expr_access bail out on uninteresting expressions

[Jan Hubicka <hubicka@ucw.cz>]

> > Hi,
> > 
> > I'm re-posting patches which I have posted at the end of stage 1 but
> > which have not passed review yet.
> > 
> > 8<--------------------------------------------------------------------
> > 
> > I have noticed that scan_expr_access passes all the expressions it
> > gets to get_ref_base_and_extent even when we are really only
> > interested in memory accesses.  So bail out when the expression is
> > something clearly uninteresting.
> > 
> > Bootstrapped and tested individually when I originally posted it and
> > now bootstrapped and LTO-bootstrapped and tested as part of the whole
> > series.  OK for master?
> > 
> > 
> > gcc/ChangeLog:
> > 
> > 2021-12-14  Martin Jambor  <mjambor@suse.cz>
> > 
> > 	* ipa-sra.c (scan_expr_access): Bail out early if expr is something we
> > 	clearly do not need to pass to get_ref_base_and_extent.
> > ---
> >  gcc/ipa-sra.cc | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/gcc/ipa-sra.cc b/gcc/ipa-sra.cc
> > index 93fceeafc73..3646d71468c 100644
> > --- a/gcc/ipa-sra.cc
> > +++ b/gcc/ipa-sra.cc
> > @@ -1748,6 +1748,11 @@ scan_expr_access (tree expr, gimple *stmt, isra_scan_context ctx,
> >        || TREE_CODE (expr) == REALPART_EXPR)
> >      expr = TREE_OPERAND (expr, 0);
> >  
> > +  if (!handled_component_p (expr)
> > +      && !DECL_P (expr)
> > +      && TREE_CODE (expr) != MEM_REF)
> > +    return;
> Is this needed because get_ref_base_and_extend crashes if given SSA_NAME
> or something else or is it just optimization?
> Perhaps Richi will know if there is better test for this.
Looking at:

static inline bool
gimple_assign_load_p (const gimple *gs)
{
  tree rhs;
  if (!gimple_assign_single_p (gs))
    return false;
  rhs = gimple_assign_rhs1 (gs);
  if (TREE_CODE (rhs) == WITH_SIZE_EXPR)
    return true;
  rhs = get_base_address (rhs);
  return (DECL_P (rhs)
          || TREE_CODE (rhs) == MEM_REF || TREE_CODE (rhs) == TARGET_MEM_REF);
} 

I wonder if we don't want to avoid get_base_address (which is loopy) and
use same check and move it into a new predicate that is more convenient
to use?

Honza
> 
> Honza
> > +
> >    base = get_ref_base_and_extent (expr, &poffset, &psize, &pmax_size, &reverse);
> >  
> >    if (TREE_CODE (base) == MEM_REF)
> > -- 
> > 2.38.1
> >