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

[Richard Biener <rguenther@suse.de>]

> Am 12.12.2022 um 22:59 schrieb Jan Hubicka via Gcc-patches <gcc-patches@gcc.gnu.org>:
> 
> 
>> 
>>> 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?

We can simplify the above to a single stripping of a handled component and considering another handled component as load (register ops are always single)

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