re PR tree-optimization/60012 (Vectorizer generates unnecessary loop versioning for alias)

2014-02-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/60012
	* tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Apply
	TBAA disambiguation to all DDRs.

	* gcc.dg/vect/pr60012.c: New testcase.

From-SVN: r207455

gcc/ChangeLog

+2014-02-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/60012
+	* tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Apply
+	TBAA disambiguation to all DDRs.
+
 2014-02-04  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	PR target/59788

gcc/testsuite/ChangeLog

+2014-02-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/60012
+	* gcc.dg/vect/pr60012.c: New testcase.
+
 2014-02-04  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	PR target/59788

gcc/testsuite/gcc.dg/vect/pr60012.c

+/* { dg-do compile } */
+/* { dg-additional-options "--param vect-max-version-for-alias-checks=0" } */
+
+typedef struct
+{
+  short real;
+  short imag;
+} complex16_t;
+
+void
+libvector_AccSquareNorm_ref (unsigned long long  *acc,
+			     const complex16_t *x, unsigned len)
+{
+  unsigned i;
+  for (i = 0; i < len; i++)
+    acc[i] += ((unsigned long long)((int)x[i].real * x[i].real))
+	+ ((unsigned long long)((int)x[i].imag * x[i].imag));
+}
+
+/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
+/* { dg-final { cleanup-tree-dump "vect" } } */

gcc/tree-vect-data-refs.c

@@ -235,6 +235,18 @@ vect_analyze_data_ref_dependence (struct data_dependence_relation *ddr,
       || (DR_IS_READ (dra) && DR_IS_READ (drb)))
     return false;
 
+  /* Even if we have an anti-dependence then, as the vectorized loop covers at
+     least two scalar iterations, there is always also a true dependence.
+     As the vectorizer does not re-order loads and stores we can ignore
+     the anti-dependence if TBAA can disambiguate both DRs similar to the
+     case with known negative distance anti-dependences (positive
+     distance anti-dependences would violate TBAA constraints).  */
+  if (((DR_IS_READ (dra) && DR_IS_WRITE (drb))
+       || (DR_IS_WRITE (dra) && DR_IS_READ (drb)))
+      && !alias_sets_conflict_p (get_alias_set (DR_REF (dra)),
+				 get_alias_set (DR_REF (drb))))
+    return false;
+
   /* Unknown data dependence.  */
   if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
     {