Hi Honza,

Here is a re-based version which also addresses the review comments.

On 21/07/16 22:54, Jan Hubicka wrote:
>> 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.

Indeed. I will do this as a follow up.

>>
>> +/* 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.

Do you mean the following, I was following other implementations.

@@ -2264,6 +2430,11 @@ propagate_constants_accross_call (struct
cgraph_edge *cs)
        &dest_plats->bits_lattice);
   ret |= propagate_aggs_accross_jump_function (cs, jump_func,
        dest_plats);
+  if (opt_for_fn (callee->decl, flag_ipa_vrp))
+    ret |= propagate_vr_accross_jump_function (cs,
+       jump_func, dest_plats);
+  else
+    ret |= dest_plats->m_value_range.set_to_bottom ();

>> +/* 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.

Removed it.

>> +/* 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?

Changed to wide_int after adding that support.

LTO Bootstrapped and regression tested on x86_64-linux-gnu with no new
regressions, is this OK?

Thanks
Kugan