Re: [PATCH] Implement ipa_vr hashing.

[Martin Jambor <mjambor@suse.cz>]

Hi,

On Mon, May 22 2023, Aldy Hernandez via Gcc-patches wrote:
> Implement hashing for ipa_vr.  When all is said and done, all these
> patches incurr a 7.64% slowdown for ipa-cp, with is entirely covered by
> the similar 7% increase in this area last week.  So we get type agnostic
> ranges with "infinite" range precision close to free.

Do you know why/where this slow-down happens?  Do we perhaps want to
limit the "infiniteness" a little somehow?

Also, jump functions live for a long time, have you looked at how memory
hungry they become?  I hope that the hashing would be good at preventing
any issues.

Generally, I think I OK with the patches if the impact on memory is not
too bad, though I guess they depend on the one I looked at last week, so
we may focus on that one first.

Thanks,

Martin

>
> There is no change in overall compilation.
>
> OK?
>
> gcc/ChangeLog:
>
> 	* ipa-prop.cc (struct ipa_vr_ggc_hash_traits): Adjust for use with
> 	ipa_vr instead of value_range.
> 	(gt_pch_nx): Same.
> 	(gt_ggc_mx): Same.
> 	(ipa_get_value_range): Same.
> 	* value-range.cc (gt_pch_nx): Move to ipa-prop.cc and adjust for
> 	ipa_vr.
> 	(gt_ggc_mx): Same.
> ---
>  gcc/ipa-prop.cc    | 76 +++++++++++++++++++++++++++-------------------
>  gcc/value-range.cc | 15 ---------
>  2 files changed, 45 insertions(+), 46 deletions(-)
>
> diff --git a/gcc/ipa-prop.cc b/gcc/ipa-prop.cc
> index c46a89f1b49..6383bc11e0a 100644
> --- a/gcc/ipa-prop.cc
> +++ b/gcc/ipa-prop.cc
> @@ -109,53 +109,53 @@ struct ipa_bit_ggc_hash_traits : public ggc_cache_remove <ipa_bits *>
>  /* Hash table for avoid repeated allocations of equal ipa_bits.  */
>  static GTY ((cache)) hash_table<ipa_bit_ggc_hash_traits> *ipa_bits_hash_table;
>  
> -/* Traits for a hash table for reusing value_ranges used for IPA.  Note that
> -   the equiv bitmap is not hashed and is expected to be NULL.  */
> +/* Traits for a hash table for reusing ranges.  */
>  
> -struct ipa_vr_ggc_hash_traits : public ggc_cache_remove <value_range *>
> +struct ipa_vr_ggc_hash_traits : public ggc_cache_remove <ipa_vr *>
>  {
> -  typedef value_range *value_type;
> -  typedef value_range *compare_type;
> +  typedef ipa_vr *value_type;
> +  typedef const vrange *compare_type;
>    static hashval_t
> -  hash (const value_range *p)
> +  hash (const ipa_vr *p)
>      {
> -      tree min, max;
> -      value_range_kind kind = get_legacy_range (*p, min, max);
> -      inchash::hash hstate (kind);
> -      inchash::add_expr (min, hstate);
> -      inchash::add_expr (max, hstate);
> +      // This never get called, except in the verification code, as
> +      // ipa_get_value_range() calculates the hash itself.  This
> +      // function is mostly here for completness' sake.
> +      Value_Range vr;
> +      p->get_vrange (vr);
> +      inchash::hash hstate;
> +      add_vrange (vr, hstate);
>        return hstate.end ();
>      }
>    static bool
> -  equal (const value_range *a, const value_range *b)
> +  equal (const ipa_vr *a, const vrange *b)
>      {
> -      return (types_compatible_p (a->type (), b->type ())
> -	      && *a == *b);
> +      return a->equal_p (*b);
>      }
>    static const bool empty_zero_p = true;
>    static void
> -  mark_empty (value_range *&p)
> +  mark_empty (ipa_vr *&p)
>      {
>        p = NULL;
>      }
>    static bool
> -  is_empty (const value_range *p)
> +  is_empty (const ipa_vr *p)
>      {
>        return p == NULL;
>      }
>    static bool
> -  is_deleted (const value_range *p)
> +  is_deleted (const ipa_vr *p)
>      {
> -      return p == reinterpret_cast<const value_range *> (1);
> +      return p == reinterpret_cast<const ipa_vr *> (1);
>      }
>    static void
> -  mark_deleted (value_range *&p)
> +  mark_deleted (ipa_vr *&p)
>      {
> -      p = reinterpret_cast<value_range *> (1);
> +      p = reinterpret_cast<ipa_vr *> (1);
>      }
>  };
>  
> -/* Hash table for avoid repeated allocations of equal value_ranges.  */
> +/* Hash table for avoid repeated allocations of equal ranges.  */
>  static GTY ((cache)) hash_table<ipa_vr_ggc_hash_traits> *ipa_vr_hash_table;
>  
>  /* Holders of ipa cgraph hooks: */
> @@ -265,6 +265,22 @@ ipa_vr::dump (FILE *out) const
>      fprintf (out, "NO RANGE");
>  }
>  
> +// ?? These stubs are because we use an ipa_vr in a hash_traits and
> +// hash-traits.h defines an extern of gt_ggc_mx (T &) instead of
> +// picking up the gt_ggc_mx (T *) version.
> +void
> +gt_pch_nx (ipa_vr *&x)
> +{
> +  return gt_pch_nx ((ipa_vr *) x);
> +}
> +
> +void
> +gt_ggc_mx (ipa_vr *&x)
> +{
> +  return gt_ggc_mx ((ipa_vr *) x);
> +}
> +
> +
>  /* Return true if DECL_FUNCTION_SPECIFIC_OPTIMIZATION of the decl associated
>     with NODE should prevent us from analyzing it for the purposes of IPA-CP.  */
>  
> @@ -2284,27 +2300,25 @@ ipa_set_jfunc_bits (ipa_jump_func *jf, const widest_int &value,
>    jf->bits = ipa_get_ipa_bits_for_value (value, mask);
>  }
>  
> -/* Return a pointer to a value_range just like *TMP, but either find it in
> -   ipa_vr_hash_table or allocate it in GC memory.  TMP->equiv must be NULL.  */
> +/* Return a pointer to an ipa_vr just like TMP, but either find it in
> +   ipa_vr_hash_table or allocate it in GC memory.  */
>  
>  static ipa_vr *
>  ipa_get_value_range (const vrange &tmp)
>  {
> -  /* FIXME: Add hashing support.
> -  value_range **slot = ipa_vr_hash_table->find_slot (tmp, INSERT);
> +  inchash::hash hstate;
> +  inchash::add_vrange (tmp, hstate);
> +  hashval_t hash = hstate.end ();
> +  ipa_vr **slot = ipa_vr_hash_table->find_slot_with_hash (&tmp, hash, INSERT);
>    if (*slot)
>      return *slot;
>  
> -  value_range *vr = new (ggc_alloc<value_range> ()) value_range;
> -  *vr = *tmp;
> -  *slot = vr;
> -  */
>    ipa_vr *vr = new (ggc_alloc<ipa_vr> ()) ipa_vr (tmp);
> -
> +  *slot = vr;
>    return vr;
>  }
>  
> -/* Assign to JF a pointer to a value_range just like TMP but either fetch a
> +/* Assign to JF a pointer to a range just like TMP but either fetch a
>     copy from ipa_vr_hash_table or allocate a new on in GC memory.  */
>  
>  static void
> diff --git a/gcc/value-range.cc b/gcc/value-range.cc
> index 45b1e655967..7b81025357b 100644
> --- a/gcc/value-range.cc
> +++ b/gcc/value-range.cc
> @@ -2008,21 +2008,6 @@ gt_pch_nx (vrange *x, gt_pointer_operator op, void *cookie)
>      gcc_unreachable ();
>  }
>  
> -// ?? These stubs are for ipa-prop.cc which use a value_range in a
> -// hash_traits.  hash-traits.h defines an extern of gt_ggc_mx (T &)
> -// instead of picking up the gt_ggc_mx (T *) version.
> -void
> -gt_pch_nx (int_range<2> *&x)
> -{
> -  return gt_pch_nx ((irange *) x);
> -}
> -
> -void
> -gt_ggc_mx (int_range<2> *&x)
> -{
> -  return gt_ggc_mx ((irange *) x);
> -}
> -
>  #define DEFINE_INT_RANGE_INSTANCE(N)					\
>    template int_range<N>::int_range(tree_node *,				\
>  				   const wide_int &,			\
> -- 
> 2.40.1