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Re: [RFC][IPA-VRP] Add support for IPA VRP in ipa-cp/ipa-prop
> Maybe it is better to separate value range and alignment summary
> writing/reading to different functions. Here is another updated
> version which does this.
Makes sense to me. Note that the alignment summary propagation can be either
handled by doing bitwise constant propagation and/or extending our value ranges
by stride (as described in
http://www.lighterra.com/papers/valuerangeprop/Patterson1995-ValueRangeProp.pdf
I would like it to go eventually away in favour of more generic solution.
> -/* If DEST_PLATS already has aggregate items, check that aggs_by_ref matches
> +/* Propagate value range across jump function JFUNC that is associated with
> + edge CS and update DEST_PLATS accordingly. */
> +
> +static bool
> +propagate_vr_accross_jump_function (cgraph_edge *cs,
> + ipa_jump_func *jfunc,
> + struct ipcp_param_lattices *dest_plats)
> +{
> + struct ipcp_param_lattices *src_lats;
> + ipcp_vr_lattice *dest_lat = &dest_plats->m_value_range;
> +
> + if (dest_lat->bottom_p ())
> + return false;
> +
> + if (jfunc->type == IPA_JF_PASS_THROUGH)
> + {
> + struct ipa_node_params *caller_info = IPA_NODE_REF (cs->caller);
> + int src_idx = ipa_get_jf_pass_through_formal_id (jfunc);
> + src_lats = ipa_get_parm_lattices (caller_info, src_idx);
> +
> + if (ipa_get_jf_pass_through_operation (jfunc) == NOP_EXPR)
> + return dest_lat->meet_with (src_lats->m_value_range);
Clearly we can propagate thorugh expressions here (PLUS_EXPR). I have run
into similar issue in loop code that builds simple generic expresisons
(like (int)ssa_name+10) and it would be nice to have easy way to deterine
their value range based on the knowledge of SSA_NAME's valur range.
Bit this is fine for initial implementaiotn for sure.
>
> +/* Look up all VR information that we have discovered and copy it over
> + to the transformation summary. */
> +
> +static void
> +ipcp_store_vr_results (void)
> +{
> + cgraph_node *node;
> +
> + FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (node)
> + {
> + ipa_node_params *info = IPA_NODE_REF (node);
> + bool found_useful_result = false;
> +
> + if (!opt_for_fn (node->decl, flag_ipa_vrp))
> + {
> + if (dump_file)
> + fprintf (dump_file, "Not considering %s for VR discovery "
> + "and propagate; -fipa-ipa-vrp: disabled.\n",
> + node->name ());
> + continue;
I belive you need to also prevent propagation through functions copmiled with
-fno-ipa-vrp, not only prevent any transformations.
> +/* Update value range of formal parameters as described in
> + ipcp_transformation_summary. */
> +
> +static void
> +ipcp_update_vr (struct cgraph_node *node)
> +{
> + tree fndecl = node->decl;
> + tree parm = DECL_ARGUMENTS (fndecl);
> + tree next_parm = parm;
> + ipcp_transformation_summary *ts = ipcp_get_transformation_summary (node);
> + if (!ts || vec_safe_length (ts->m_vr) == 0)
> + return;
> + const vec<ipa_vr, va_gc> &vr = *ts->m_vr;
> + unsigned count = vr.length ();
> +
> + for (unsigned i = 0; i < count; ++i, parm = next_parm)
> + {
> + if (node->clone.combined_args_to_skip
> + && bitmap_bit_p (node->clone.combined_args_to_skip, i))
> + continue;
> + gcc_checking_assert (parm);
> + next_parm = DECL_CHAIN (parm);
> + tree ddef = ssa_default_def (DECL_STRUCT_FUNCTION (node->decl), parm);
> +
> + if (!ddef || !is_gimple_reg (parm))
> + continue;
> +
> + if (cgraph_local_p (node)
The test of cgraph_local_p seems redundant here. The analysis phase should not determine
anything if function is reachable non-locally.
> +/* Info about value ranges. */
> +
> +struct GTY(()) ipa_vr
> +{
> + /* The data fields below are valid only if known is true. */
> + bool known;
> + enum value_range_type type;
> + tree min;
> + tree max;
What is the point of representing range as trees rather than wide ints. Can they
be non-constant integer?
The patch looks good to me otherwise!
Honza