dse.c (struct insn_info): Add 'frame_read' field.

	* dse.c (struct insn_info): Add 'frame_read' field.
	(scan_insn): For the call to a const function, set frame_read if
	reload has been run.
	If the insn reads the frame, kill the frame related stores.
	(scan_reads_nospill): Likewise.

From-SVN: r129312

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e45535d349a56990e4a2fecfd53e1ef8ebb38268..41969ade4320dc8232cae54b1b1ad3a14691574e 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2007-10-15  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+       * dse.c (struct insn_info): Add 'frame_read' field.
+       (scan_insn): For the call to a const function, set frame_read if
+       reload has been run.
+       If the insn reads the frame, kill the frame related stores.
+       (scan_reads_nospill): Likewise.
+
 2007-10-14  Jason Merrill  <jason@redhat.com>
 
        * tree-eh.c (optimize_double_finally): Don't assume that the

diff --git a/gcc/dse.c b/gcc/dse.c
index a5244e114142a955738b6ba03d7c13041de68415..764c3359d1bc0b622b84477850db60c3bf50e545 100644 (file)
--- a/gcc/dse.c
+++ b/gcc/dse.c
@@ -286,8 +286,26 @@ struct insn_info
 
   /* This field is only used for the processing of const functions.
      These functions cannot read memory, but they can read the stack
-     because that is where they may get their parms.  It is set to
-     true if the insn may contain a stack pointer based store.  */
+     because that is where they may get their parms.  We need to be
+     this conservative because, like the store motion pass, we don't
+     consider CALL_INSN_FUNCTION_USAGE when processing call insns.
+     Moreover, we need to distinguish two cases:
+     1. Before reload (register elimination), the stores related to
+       outgoing arguments are stack pointer based and thus deemed
+       of non-constant base in this pass.  This requires special
+       handling but also means that the frame pointer based stores
+       need not be killed upon encountering a const function call.
+     2. After reload, the stores related to outgoing arguments can be
+       either stack pointer or hard frame pointer based.  This means
+       that we have no other choice than also killing all the frame
+       pointer based stores upon encountering a const function call.
+     This field is set after reload for const function calls.  Having
+     this set is less severe than a wild read, it just means that all
+     the frame related stores are killed rather than all the stores.  */
+  bool frame_read;
+
+  /* This field is only used for the processing of const functions.
+     It is set if the insn may contain a stack pointer based store.  */
   bool stack_pointer_based;
 
   /* This is true if any of the sets within the store contains a
@@ -1967,10 +1985,36 @@ scan_insn (bb_info_t bb_info, rtx insn)
          if (dump_file)
            fprintf (dump_file, "const call %d\n", INSN_UID (insn));
 
+         /* See the head comment of the frame_read field.  */
+         if (reload_completed)
+           insn_info->frame_read = true;
+
+         /* Loop over the active stores and remove those which are
+            killed by the const function call.  */
          while (i_ptr)
            {
-             /* Remove the stack pointer based stores.  */
+             bool remove_store = false;
+
+             /* The stack pointer based stores are always killed.  */
              if (i_ptr->stack_pointer_based)
+               remove_store = true;
+
+             /* If the frame is read, the frame related stores are killed.  */
+             else if (insn_info->frame_read)
+               {
+                 store_info_t store_info = i_ptr->store_rec;
+
+                 /* Skip the clobbers.  */
+                 while (!store_info->is_set)
+                   store_info = store_info->next;
+
+                 if (store_info->group_id >= 0
+                     && VEC_index (group_info_t, rtx_group_vec,
+                                   store_info->group_id)->frame_related)
+                   remove_store = true;
+               }
+
+             if (remove_store)
                {
                  if (dump_file)
                    dump_insn_info ("removing from active", i_ptr);
@@ -1982,6 +2026,7 @@ scan_insn (bb_info_t bb_info, rtx insn)
                }
              else
                last = i_ptr;
+
              i_ptr = i_ptr->next_local_store;
            }
        }
@@ -2491,6 +2536,18 @@ scan_reads_nospill (insn_info_t insn_info, bitmap gen, bitmap kill)
   int i;
   group_info_t group;
 
+  /* If this insn reads the frame, kill all the frame related stores.  */
+  if (insn_info->frame_read)
+    {
+      for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)
+       if (group->process_globally && group->frame_related)
+         {
+           if (kill)
+             bitmap_ior_into (kill, group->group_kill);
+           bitmap_and_compl_into (gen, group->group_kill); 
+         }
+    }
+
   while (read_info)
     {
       for (i = 0; VEC_iterate (group_info_t, rtx_group_vec, i, group); i++)