re PR tree-optimization/50204 (Missed fully redundant load found in crafty (SPEC 2k))

2011-10-11  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/50204
	* tree-ssa-alias.c (get_continuation_for_phi_1): Split out
	two argument handling from ...
	(get_continuation_for_phi): ... here.  Handle arbitrary number
	of PHI args.

	* gcc.dg/tree-ssa/ssa-fre-36.c: New testcase.

From-SVN: r179799

gcc/ChangeLog

+2011-10-11  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/50204
+	* tree-ssa-alias.c (get_continuation_for_phi_1): Split out
+	two argument handling from ...
+	(get_continuation_for_phi): ... here.  Handle arbitrary number
+	of PHI args.
+
 2011-10-11  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/33067

gcc/testsuite/ChangeLog

+2011-10-11  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/50204
+	* gcc.dg/tree-ssa/ssa-fre-36.c: New testcase.
+
 2011-10-11  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
 
 	* gcc.target/s390/20090223-1.c: Add -Wno-attributes.

gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-36.c

+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-fre1-details" } */
+
+extern int opening;
+extern int middle_game;
+int s;
+extern int d[1];
+void PreEvaluate(int wtm)
+{
+  int i, j;
+  if (opening) {
+      d[0]=1;
+  }
+  else if (middle_game) {
+      d[0]=-1;
+  }
+  if (4 != opening) {
+      return;
+  }
+  s = 1;
+}
+
+/* We should be able to CSE the second load of opening.  */
+
+/* { dg-final { scan-tree-dump "Replaced opening" "fre1" } } */
+/* { dg-final { cleanup-tree-dump "fre1" } } */

gcc/tree-ssa-alias.c

@@ -1875,27 +1875,14 @@ maybe_skip_until (gimple phi, tree target, ao_ref *ref,
   return true;
 }
 
-/* Starting from a PHI node for the virtual operand of the memory reference
-   REF find a continuation virtual operand that allows to continue walking
-   statements dominating PHI skipping only statements that cannot possibly
-   clobber REF.  Returns NULL_TREE if no suitable virtual operand can
-   be found.  */
+/* For two PHI arguments ARG0 and ARG1 try to skip non-aliasing code
+   until we hit the phi argument definition that dominates the other one.
+   Return that, or NULL_TREE if there is no such definition.  */
 
-tree
-get_continuation_for_phi (gimple phi, ao_ref *ref, bitmap *visited)
+static tree
+get_continuation_for_phi_1 (gimple phi, tree arg0, tree arg1,
+			    ao_ref *ref, bitmap *visited)
 {
-  unsigned nargs = gimple_phi_num_args (phi);
-
-  /* Through a single-argument PHI we can simply look through.  */
-  if (nargs == 1)
-    return PHI_ARG_DEF (phi, 0);
-
-  /* For two arguments try to skip non-aliasing code until we hit
-     the phi argument definition that dominates the other one.  */
-  if (nargs == 2)
-    {
-      tree arg0 = PHI_ARG_DEF (phi, 0);
-      tree arg1 = PHI_ARG_DEF (phi, 1);
   gimple def0 = SSA_NAME_DEF_STMT (arg0);
   gimple def1 = SSA_NAME_DEF_STMT (arg1);
   tree common_vuse;
@@ -1937,6 +1924,44 @@ get_continuation_for_phi (gimple phi, ao_ref *ref, bitmap *visited)
 	  && !stmt_may_clobber_ref_p_1 (def1, ref))
 	return common_vuse;
     }
+
+  return NULL_TREE;
+}
+
+
+/* Starting from a PHI node for the virtual operand of the memory reference
+   REF find a continuation virtual operand that allows to continue walking
+   statements dominating PHI skipping only statements that cannot possibly
+   clobber REF.  Returns NULL_TREE if no suitable virtual operand can
+   be found.  */
+
+tree
+get_continuation_for_phi (gimple phi, ao_ref *ref, bitmap *visited)
+{
+  unsigned nargs = gimple_phi_num_args (phi);
+
+  /* Through a single-argument PHI we can simply look through.  */
+  if (nargs == 1)
+    return PHI_ARG_DEF (phi, 0);
+
+  /* For two or more arguments try to pairwise skip non-aliasing code
+     until we hit the phi argument definition that dominates the other one.  */
+  else if (nargs >= 2)
+    {
+      tree arg0 = PHI_ARG_DEF (phi, 0);
+      tree arg1;
+      unsigned i = 1;
+      do
+	{
+	  arg1 = PHI_ARG_DEF (phi, i);
+	  arg0 = get_continuation_for_phi_1 (phi, arg0, arg1, ref, visited);
+	  if (!arg0)
+	    return NULL_TREE;
+
+	}
+      while (++i < nargs);
+
+      return arg0;
     }
 
   return NULL_TREE;