[PATCH v2] [autofdo] Annotate empty bb with all debug_stmt with location of phi in the single_succ.

[liuhongt]

From: "hongtao.liu" <hongtao....@intel.com>

> I think the comment is a bit off, it should be "For an empty BB ..." since
> we should not change behavior on whether there are debug stmts or not.
Changed.

For an empty BB with all debug_stmt, it will be ignored by
afdo_set_bb_count, but it can be set with count of single successors
PHIs which edge from the BB.

gcc/ChangeLog:

        PR gcov-profile/118581
        * auto-profile.cc (autofdo_source_profile::get_count_info):
        Overload the function with parameter gimple location instead
        of stmt.
        (afdo_set_bb_count): For !has_annotated BB, Check single
        successors PHIs corresponding to the block and use those
        count.
---
 gcc/auto-profile.cc | 53 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/gcc/auto-profile.cc b/gcc/auto-profile.cc
index 2d2d4a428f2..326b07e6336 100644
--- a/gcc/auto-profile.cc
+++ b/gcc/auto-profile.cc
@@ -303,6 +303,10 @@ public:
      in INFO and return true; otherwise return false.  */
   bool get_count_info (gimple *stmt, count_info *info) const;
 
+  /* Find count_info for a given gimple location GIMPLE_LOC. If found,
+     store the count_info in INFO and return true; otherwise return false.  */
+  bool get_count_info (location_t gimple_loc, count_info *info) const;
+
   /* Find total count of the callee of EDGE.  */
   gcov_type get_callsite_total_count (struct cgraph_edge *edge) const;
 
@@ -724,11 +728,18 @@ autofdo_source_profile::get_function_instance_by_decl 
(tree decl) const
 bool
 autofdo_source_profile::get_count_info (gimple *stmt, count_info *info) const
 {
-  if (LOCATION_LOCUS (gimple_location (stmt)) == cfun->function_end_locus)
+  return get_count_info (gimple_location (stmt), info);
+}
+
+bool
+autofdo_source_profile::get_count_info (location_t gimple_loc,
+                                       count_info *info) const
+{
+  if (LOCATION_LOCUS (gimple_loc) == cfun->function_end_locus)
     return false;
 
   inline_stack stack;
-  get_inline_stack (gimple_location (stmt), &stack);
+  get_inline_stack (gimple_loc, &stack);
   if (stack.length () == 0)
     return false;
   function_instance *s = get_function_instance_by_inline_stack (stack);
@@ -1132,7 +1143,43 @@ afdo_set_bb_count (basic_block bb, const stmt_set 
&promoted)
     }
 
   if (!has_annotated)
-    return false;
+    {
+      /* For an empty BB with all debug stmt which assigne a value with
+        constant, check successors PHIs corresponding to the block and
+        use those counts.  */
+      edge tmp_e;
+      edge_iterator tmp_ei;
+      FOR_EACH_EDGE (tmp_e, tmp_ei, bb->succs)
+       {
+         basic_block bb_succ = tmp_e->dest;
+         for (gphi_iterator gpi = gsi_start_phis (bb_succ);
+              !gsi_end_p (gpi);
+              gsi_next (&gpi))
+           {
+             gphi *phi = gpi.phi ();
+             size_t i;
+             for (i = 0; i < gimple_phi_num_args (phi); i++)
+               {
+                 edge e = gimple_phi_arg_edge (phi, i);
+                 if (e->src != bb)
+                   continue;
+                 location_t phi_loc = gimple_phi_arg_location (phi, i);
+                 inline_stack stack;
+                 count_info info;
+                 if (afdo_source_profile->get_count_info (phi_loc, &info)
+                     && info.count != 0)
+                   {
+                     if (info.count > max_count)
+                       max_count = info.count;
+                     has_annotated = true;
+                   }
+               }
+           }
+       }
+
+      if (!has_annotated)
+       return false;
+    }
 
   for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
     afdo_source_profile->mark_annotated (gimple_location (gsi_stmt (gsi)));
-- 
2.34.1