On Mon, May 29, 2023 at 6:20 PM Martin Jambor <mjam...@suse.cz> wrote:
>
> Hi,
>
> there have been concerns that linear searches through DECL_ARGUMENTS
> that are often necessary to compute the index of a particular
> PARM_DECL which is the key to results of IPA-CP can happen often
> enough to be a compile time issue, especially if we plug the results
> into value numbering, as I intend to do with a follow-up patch.
>
> This patch creates a hash map to do the look-up for all functions
> which have some information discovered by IPA-CP and which have 32
> parameters or more. 32 is a hard-wired magical constant here to
> capture the trade-off between the memory allocation overhead and
> length of the linear search. I do not think it is worth making it a
> --param but if people think it appropriate, I can turn it into one.
Since ipcp_transformation is short-lived (is it?) is it worth the trouble?
Comments below ...
> Bootstrapped, tested and LTO bootstrapped on x86_64-linux, both as-is
> and with themagical constant dropped to 4 so that the has lookup path
> is also well excercised. OK for master?
>
> Thanks,
>
> Martin
>
>
> gcc/ChangeLog:
>
> 2023-05-26 Martin Jambor <mjam...@suse.cz>
>
> * ipa-prop.h (struct ipcp_transformation): Rearrange members
> according to C++ class coding convention, add m_tree_to_idx,
> get_param_index and maybe_create_parm_idx_map.
> * ipa-cp.cc (ipcp_transformation::get_param_index): New function.
> (ipcp_transformation::maype_create_parm_idx_map): Likewise.
> * ipa-prop.cc (ipcp_get_parm_bits): Use get_param_index.
> (ipcp_update_bits): Accept TS as a parameter, assume it is not NULL.
> (ipcp_update_vr): Likewise.
> (ipcp_transform_function): Call, maybe_create_parm_idx_map of TS, bail
> out quickly if empty, pass it to ipcp_update_bits and ipcp_update_vr.
> ---
> gcc/ipa-cp.cc | 45 +++++++++++++++++++++++++++++++++++++++++++++
> gcc/ipa-prop.cc | 44 +++++++++++++++++++-------------------------
> gcc/ipa-prop.h | 33 +++++++++++++++++++++++++--------
> 3 files changed, 89 insertions(+), 33 deletions(-)
>
> diff --git a/gcc/ipa-cp.cc b/gcc/ipa-cp.cc
> index 0f37bb5e336..9f8b07b2398 100644
> --- a/gcc/ipa-cp.cc
> +++ b/gcc/ipa-cp.cc
> @@ -6761,3 +6761,48 @@ ipa_cp_cc_finalize (void)
> orig_overall_size = 0;
> ipcp_free_transformation_sum ();
> }
> +
> +/* Given PARAM which must be a parameter of function FNDECL described by
> THIS,
> + return its index in the DECL_ARGUMENTS chain, using a pre-computed hash
> map
> + if avialable (which is pre-computed only if there are many parameters).
> Can
> + return -1 if param is static chain not represented among DECL_ARGUMENTS.
> */
> +
> +int
> +ipcp_transformation::get_param_index (const_tree fndecl, const_tree param)
> const
> +{
> + gcc_assert (TREE_CODE (param) == PARM_DECL);
> + if (m_tree_to_idx)
> + {
> + unsigned *pr = m_tree_to_idx->get(param);
> + if (!pr)
> + {
> + gcc_assert (DECL_STATIC_CHAIN (fndecl));
> + return -1;
> + }
> + return (int) *pr;
> + }
> +
> + unsigned index = 0;
> + for (tree p = DECL_ARGUMENTS (fndecl); p; p = DECL_CHAIN (p), index++)
> + if (p == param)
> + return (int) index;
> +
> + gcc_assert (DECL_STATIC_CHAIN (fndecl));
> + return -1;
> +}
> +
> +/* Assuming THIS describes FNDECL and it has sufficiently many parameters to
> + justify the overhead, creat a has map from parameter trees to their
> + indices. */
> +void
> +ipcp_transformation::maybe_create_parm_idx_map (tree fndecl)
> +{
> + int c = count_formal_params (fndecl);
> + if (c < 32)
> + return;
> +
> + m_tree_to_idx = hash_map<const_tree, unsigned>::create_ggc (c);
> + unsigned index = 0;
> + for (tree p = DECL_ARGUMENTS (fndecl); p; p = DECL_CHAIN (p), index++)
> + m_tree_to_idx->put (p, index);
I think allocating the hash-map with 'c' for some numbers (depending
on the "prime"
chosen) will necessarily cause re-allocation of the hash since we keep a load
factor of at most 3/4 upon insertion.
But - I wonder if a UID sorted array isn't a very much better data
structure for this?
That is, a vec<std::pair<int, unsigned> >?
> +}
> diff --git a/gcc/ipa-prop.cc b/gcc/ipa-prop.cc
> index ab6de9f10da..f0976e363f7 100644
> --- a/gcc/ipa-prop.cc
> +++ b/gcc/ipa-prop.cc
> @@ -5776,16 +5776,9 @@ ipcp_get_parm_bits (tree parm, tree *value, widest_int
> *mask)
> if (!ts || vec_safe_length (ts->bits) == 0)
> return false;
>
> - int i = 0;
> - for (tree p = DECL_ARGUMENTS (current_function_decl);
> - p != parm; p = DECL_CHAIN (p))
> - {
> - i++;
> - /* Ignore static chain. */
> - if (!p)
> - return false;
> - }
> -
> + int i = ts->get_param_index (current_function_decl, parm);
> + if (i < 0)
> + return false;
> clone_info *cinfo = clone_info::get (cnode);
> if (cinfo && cinfo->param_adjustments)
> {
> @@ -5802,16 +5795,12 @@ ipcp_get_parm_bits (tree parm, tree *value,
> widest_int *mask)
> return true;
> }
>
> -
> -/* Update bits info of formal parameters as described in
> - ipcp_transformation. */
> +/* Update bits info of formal parameters of NODE as described in TS. */
>
> static void
> -ipcp_update_bits (struct cgraph_node *node)
> +ipcp_update_bits (struct cgraph_node *node, ipcp_transformation *ts)
> {
> - ipcp_transformation *ts = ipcp_get_transformation_summary (node);
> -
> - if (!ts || vec_safe_length (ts->bits) == 0)
> + if (vec_safe_is_empty (ts->bits))
> return;
> vec<ipa_bits *, va_gc> &bits = *ts->bits;
> unsigned count = bits.length ();
> @@ -5913,14 +5902,12 @@ ipcp_update_bits (struct cgraph_node *node)
> }
> }
>
> -/* Update value range of formal parameters as described in
> - ipcp_transformation. */
> +/* Update value range of formal parameters of NODE as described in TS. */
>
> static void
> -ipcp_update_vr (struct cgraph_node *node)
> +ipcp_update_vr (struct cgraph_node *node, ipcp_transformation *ts)
> {
> - ipcp_transformation *ts = ipcp_get_transformation_summary (node);
> - if (!ts || vec_safe_length (ts->m_vr) == 0)
> + if (vec_safe_is_empty (ts->m_vr))
> return;
> const vec<ipa_vr, va_gc> &vr = *ts->m_vr;
> unsigned count = vr.length ();
> @@ -5996,10 +5983,17 @@ ipcp_transform_function (struct cgraph_node *node)
> fprintf (dump_file, "Modification phase of node %s\n",
> node->dump_name ());
>
> - ipcp_update_bits (node);
> - ipcp_update_vr (node);
> ipcp_transformation *ts = ipcp_get_transformation_summary (node);
> - if (!ts || vec_safe_is_empty (ts->m_agg_values))
> + if (!ts
> + || (vec_safe_is_empty (ts->m_agg_values)
> + && vec_safe_is_empty (ts->bits)
> + && vec_safe_is_empty (ts->m_vr)))
> + return 0;
> +
> + ts->maybe_create_parm_idx_map (cfun->decl);
> + ipcp_update_bits (node, ts);
> + ipcp_update_vr (node, ts);
> + if (vec_safe_is_empty (ts->m_agg_values))
> return 0;
> param_count = count_formal_params (node->decl);
> if (param_count == 0)
> diff --git a/gcc/ipa-prop.h b/gcc/ipa-prop.h
> index f306f8a377e..211b12ff6b3 100644
> --- a/gcc/ipa-prop.h
> +++ b/gcc/ipa-prop.h
> @@ -925,16 +925,10 @@ ipa_is_param_used_by_polymorphic_call (class
> ipa_node_params *info, int i)
>
> struct GTY(()) ipcp_transformation
> {
> - /* Known aggregate values. */
> - vec<ipa_argagg_value, va_gc> *m_agg_values;
> - /* Known bits information. */
> - vec<ipa_bits *, va_gc> *bits;
> - /* Value range information. */
> - vec<ipa_vr, va_gc> *m_vr;
> -
> /* Default constructor. */
> ipcp_transformation ()
> - : m_agg_values (NULL), bits (NULL), m_vr (NULL)
> + : m_agg_values (nullptr), bits (nullptr), m_vr (nullptr),
> + m_tree_to_idx (nullptr)
> { }
>
> /* Default destructor. */
> @@ -944,6 +938,29 @@ struct GTY(()) ipcp_transformation
> vec_free (bits);
> vec_free (m_vr);
> }
> +
> + /* Given PARAM which must be a parameter of function FNDECL described by
> + THIS, return its index in the DECL_ARGUMENTS chain, using a pre-computed
> + hash map if avialable (which is pre-computed only if there are many
> + parameters). Can return -1 if param is static chain not represented
> among
> + DECL_ARGUMENTS. */
> + int get_param_index (const_tree fndecl, const_tree param) const;
> +
> + /* Assuming THIS describes FUNC and it has sufficiently many parameters to
> + justify the overhead, creat a has map from parameter trees to their
> + indices. */
> +
> + void maybe_create_parm_idx_map (tree fndecl);
> +
> + /* Known aggregate values. */
> + vec<ipa_argagg_value, va_gc> *m_agg_values;
> + /* Known bits information. */
> + vec<ipa_bits *, va_gc> *bits;
> + /* Value range information. */
> + vec<ipa_vr, va_gc> *m_vr;
> + /* If there are many parameters, a hash map to speed-up look-ups of their
> + indices. */
> + hash_map<const_tree, unsigned> *m_tree_to_idx;
> };
>
> inline
> --
> 2.40.1
>
