Detect unused parameters in ipa-modref

[Jan Hubicka]

Hi,
ipa-modref tracks only parameters with SSA_NAMES.  This makes completely
unused parameters to get no flags, while EAF_UNUSED should be right one.
This patch implements it.  I also noticed that EAF_UNUSED implies all
other flags, but we set only EAF_UNUSED.  This measn that we should
special case it in lattice merge operations as implemented.

Bootstrapped/regtested x86_64-linux, comitted.

Honza

        * ipa-modref.c (modref_lattice::merge): Do nothing if F is EAF_UNUSED.
        (analyze_parms): Detect unused params.
        (modref_merge_call_site_flags): Merge correct EAF_UNUSED.
diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index d1d4ba786a4..5ba8ff000f0 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -1437,6 +1437,8 @@ modref_lattice::add_escape_point (gcall *call, int arg, 
int min_flags,
 bool
 modref_lattice::merge (int f)
 {
+  if (f & EAF_UNUSED)
+    return false;
   if ((flags & f) != flags)
     {
       flags &= f;
@@ -1825,8 +1827,26 @@ analyze_parms (modref_summary *summary, 
modref_summary_lto *summary_lto,
        parm = TREE_CHAIN (parm))
     {
       tree name = ssa_default_def (cfun, parm);
-      if (!name)
-       continue;
+      if (!name || has_zero_uses (name))
+       {
+         /* We do not track non-SSA parameters,
+            but we want to track unused gimple_regs.  */
+         if (!is_gimple_reg (parm))
+           continue;
+         if (summary)
+           {
+             if (parm_index >= summary->arg_flags.length ())
+               summary->arg_flags.safe_grow_cleared (count, true);
+             summary->arg_flags[parm_index] = EAF_UNUSED;
+           }
+         else if (summary_lto)
+           {
+             if (parm_index >= summary_lto->arg_flags.length ())
+               summary_lto->arg_flags.safe_grow_cleared (count, true);
+             summary_lto->arg_flags[parm_index] = EAF_UNUSED;
+           }
+         continue;
+       }
       analyze_ssa_name_flags (name, lattice, 0, ipa);
       int flags = lattice[SSA_NAME_VERSION (name)].flags;
 
@@ -3636,7 +3656,8 @@ modref_merge_call_site_flags (escape_summary *sum,
        }
       flags |= ee->min_flags;
       flags_lto |= ee->min_flags;
-      if (cur_summary && ee->parm_index < cur_summary->arg_flags.length ())
+      if (!(flags & EAF_UNUSED)
+         && cur_summary && ee->parm_index < cur_summary->arg_flags.length ())
        {
          int f = cur_summary->arg_flags[ee->parm_index];
          if ((f & flags) != f)
@@ -3648,7 +3669,8 @@ modref_merge_call_site_flags (escape_summary *sum,
              changed = true;
            }
        }
-      if (cur_summary_lto
+      if (!(flags_lto & EAF_UNUSED)
+         && cur_summary_lto
          && ee->parm_index < cur_summary_lto->arg_flags.length ())
        {
          int f = cur_summary_lto->arg_flags[ee->parm_index];