2012-04-02 Richard Guenther <rguenther@suse.de>

	PR tree-optimization/52756
	* tree-ssa-threadupdate.c (def_split_header_continue_p): New function.
	(thread_through_loop_header): After threading through the loop latch
	remove the split part from the loop and clear further threading
	opportunities that would create a multiple entry loop.

	* gcc.dg/torture/pr52756.c: New testcase.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@186085 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a020c70..2d4fb1d 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,13 @@
 2012-04-02  Richard Guenther  <rguenther@suse.de>
 
+       PR tree-optimization/52756
+       * tree-ssa-threadupdate.c (def_split_header_continue_p): New function.
+       (thread_through_loop_header): After threading through the loop latch
+       remove the split part from the loop and clear further threading
+       opportunities that would create a multiple entry loop.
+
+2012-04-02  Richard Guenther  <rguenther@suse.de>
+
        PR rtl-optimization/52800
        * cprop.c (execute_rtl_cprop): Call cleanup_cfg with
        CLEANUP_CFG_CHANGED.

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2d95e0e..a10bea7 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2012-04-02  Richard Guenther  <rguenther@suse.de>
 
+       PR tree-optimization/52756
+       * gcc.dg/torture/pr52756.c: New testcase.
+
+2012-04-02  Richard Guenther  <rguenther@suse.de>
+
        PR middle-end/52803
        * gcc.dg/pr52803.c: New testcase.
 

diff --git a/gcc/testsuite/gcc.dg/torture/pr52756.c b/gcc/testsuite/gcc.dg/torture/pr52756.c
new file mode 100644 (file)
index 0000000..175b414
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr52756.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+
+void Env_FetchObj0AttrOffset (unsigned int NumFields,  int *Status)
+{
+  int Found = 0;
+  if (NumFields)      
+    while ((*Status == 0) && NumFields-- > 0 && Found == 0)       
+      Found = 1;
+}

diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c
index 4532886..000bd3f 100644 (file)
--- a/gcc/tree-ssa-threadupdate.c
+++ b/gcc/tree-ssa-threadupdate.c
@@ -826,6 +826,17 @@ determine_bb_domination_status (struct loop *loop, basic_block bb)
   return (bb_reachable ? DOMST_DOMINATING : DOMST_LOOP_BROKEN);
 }
 
+/* Return true if BB is part of the new pre-header that is created
+   when threading the latch to DATA.  */
+
+static bool
+def_split_header_continue_p (const_basic_block bb, const void *data)
+{
+  const_basic_block new_header = (const_basic_block) data;
+  return (bb->loop_father == new_header->loop_father
+         && bb != new_header);
+}
+
 /* Thread jumps through the header of LOOP.  Returns true if cfg changes.
    If MAY_PEEL_LOOP_HEADERS is false, we avoid threading from entry edges
    to the inside of the loop.  */
@@ -990,11 +1001,46 @@ thread_through_loop_header (struct loop *loop, bool may_peel_loop_headers)
 
   if (latch->aux)
     {
+      basic_block *bblocks;
+      unsigned nblocks, i;
+
       /* First handle the case latch edge is redirected.  */
       loop->latch = thread_single_edge (latch);
       gcc_assert (single_succ (loop->latch) == tgt_bb);
       loop->header = tgt_bb;
 
+      /* Remove the new pre-header blocks from our loop.  */
+      bblocks = XCNEWVEC (basic_block, loop->num_nodes);
+      nblocks = dfs_enumerate_from (header, 0, def_split_header_continue_p,
+                                   bblocks, loop->num_nodes, tgt_bb);
+      for (i = 0; i < nblocks; i++)
+       {
+         remove_bb_from_loops (bblocks[i]);
+         add_bb_to_loop (bblocks[i], loop_outer (loop));
+       }
+      free (bblocks);
+
+      /* Cancel remaining threading requests that would make the
+        loop a multiple entry loop.  */
+      FOR_EACH_EDGE (e, ei, header->preds)
+       {
+         edge e2;
+         if (e->aux == NULL)
+           continue;
+
+         if (THREAD_TARGET2 (e))
+           e2 = THREAD_TARGET2 (e);
+         else
+           e2 = THREAD_TARGET (e);
+
+         if (e->src->loop_father != e2->dest->loop_father
+             && e2->dest != loop->header)
+           {
+             free (e->aux);
+             e->aux = NULL;
+           }
+       }
+
       /* Thread the remaining edges through the former header.  */
       thread_block (header, false);
     }