re PR tree-optimization/56812 (Simple loop is not SLP-vectorized after r196872)

2013-04-03  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/56812
	* tree-vect-data-refs.c (vect_slp_analyze_data_ref_dependence):
	DRs of the same interleaving chain are independent.

	* g++.dg/vect/slp-pr56812.cc: New testcase.

From-SVN: r197390

gcc/ChangeLog

+2013-04-03  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/56812
+	* tree-vect-data-refs.c (vect_slp_analyze_data_ref_dependence):
+	DRs of the same interleaving chain are independent.
+
 2013-04-02  Jason Merrill  <jason@redhat.com>
 
 	* gdbinit.in (pbb): Use debug fn.

gcc/testsuite/ChangeLog

+2013-04-03  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/56812
+	* g++.dg/vect/slp-pr56812.cc: New testcase.
+
 2013-04-03  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/56284

gcc/testsuite/g++.dg/vect/slp-pr56812.cc

+/* { dg-do compile } */
+/* { dg-require-effective-target vect_float } */
+/* { dg-options "-O3 -funroll-loops -fdump-tree-slp-details" } */
+
+class mydata {
+public:
+    mydata() {Set(-1.0);}
+    void Set (float);
+    static int upper() {return 8;}
+    float data[8];
+};
+
+void mydata::Set (float x)
+{
+  for (int i=0; i<upper(); i++)
+    data[i] = x;
+}
+
+/* { dg-final { scan-tree-dump-times "basic block vectorized using SLP" 1 "slp" } } */
+/* { dg-final { cleanup-tree-dump "slp" } } */

gcc/tree-vect-data-refs.c

@@ -484,6 +484,13 @@ vect_slp_analyze_data_ref_dependence (struct data_dependence_relation *ddr)
   if (DR_IS_READ (dra) && DR_IS_READ (drb))
     return false;
 
+  /* If dra and drb are part of the same interleaving chain consider
+     them independent.  */
+  if (STMT_VINFO_GROUPED_ACCESS (vinfo_for_stmt (DR_STMT (dra)))
+      && (GROUP_FIRST_ELEMENT (vinfo_for_stmt (DR_STMT (dra)))
+	  == GROUP_FIRST_ELEMENT (vinfo_for_stmt (DR_STMT (drb)))))
+    return false;
+
   /* Unknown data dependence.  */
   if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
     {