Fix PR46928: handle "A[p] == A[p]" in data dep analysis with p a parameter of the loop.

2010-12-14  Sebastian Pop  <sebastian.pop@amd.com>

	PR tree-optimization/46928
	* tree-data-ref.c (analyze_overlapping_iterations): Handle "A[p] == A[p]"
	in data dependence analysis with p a parameter of the loop.

	* gcc.dg/tree-ssa/ldist-17.c: New.

From-SVN: r167843

gcc/ChangeLog

 2010-12-14  Sebastian Pop  <sebastian.pop@amd.com>
 
+	PR tree-optimization/46928
+	* tree-data-ref.c (analyze_overlapping_iterations): Handle "A[p] == A[p]"
+	in data dependence analysis with p a parameter of the loop.
+
+2010-12-14  Sebastian Pop  <sebastian.pop@amd.com>
+
 	PR tree-optimization/45948
 	* tree-loop-distribution.c (ssa_name_has_uses_outside_loop_p): New.
 	(stmt_has_scalar_dependences_outside_loop): New.

gcc/testsuite/ChangeLog

 2010-12-14  Sebastian Pop  <sebastian.pop@amd.com>
 
+	PR tree-optimization/46928
+	* gcc.dg/tree-ssa/ldist-17.c: New.
+
+2010-12-14  Sebastian Pop  <sebastian.pop@amd.com>
+
 	PR tree-optimization/45948
 	* gcc.dg/tree-ssa/ldist-pr45948.c: New.
 

gcc/testsuite/gcc.dg/tree-ssa/ldist-17.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-loop-distribution -fdump-tree-ldist-details" } */
+
+typedef int mad_fixed_t;
+struct mad_pcm
+{
+  unsigned int samplerate;
+  unsigned short channels;
+  unsigned short length;
+  mad_fixed_t samples[2][1152];
+};
+struct mad_synth
+{
+  mad_fixed_t filter[2][2][2][16][8];
+  unsigned int phase;
+  struct mad_pcm pcm;
+};
+void mad_synth_mute (struct mad_synth *synth);
+void
+mad_synth_mute (struct mad_synth *synth)
+{
+  unsigned int ch;
+  unsigned int s;
+  unsigned int v;
+
+  ch = 0U;
+  while (ch < 2U)
+    {
+      s = 0U;
+      while (s < 16U)
+	{
+	  v = 0U;
+	  while (v < 8U)
+	    {
+	      synth->filter[ch][1][1][s][v] = 0;
+	      synth->filter[ch][1][0][s][v] = 0;
+	      synth->filter[ch][0][1][s][v] = 0;
+	      synth->filter[ch][0][0][s][v] = 0;
+	      v++;
+	    }
+	  s++;
+	}
+      ch++;
+    }
+  return;
+}
+
+/* { dg-final { scan-tree-dump "distributed: split to 4" "ldist" } } */
+/* { dg-final { scan-tree-dump-times "__builtin_memset" 8 "ldist" } } */
+/* { dg-final { cleanup-tree-dump "ldist" } } */

gcc/tree-data-ref.c

@@ -2653,7 +2653,8 @@ analyze_overlapping_iterations (tree chrec_a,
   /* If they are the same chrec, and are affine, they overlap
      on every iteration.  */
   else if (eq_evolutions_p (chrec_a, chrec_b)
-	   && evolution_function_is_affine_multivariate_p (chrec_a, lnn))
+	   && (evolution_function_is_affine_multivariate_p (chrec_a, lnn)
+	       || operand_equal_p (chrec_a, chrec_b, 0)))
     {
       dependence_stats.num_same_subscript_function++;
       *overlap_iterations_a = conflict_fn (1, affine_fn_cst (integer_zero_node));
@@ -2662,7 +2663,7 @@ analyze_overlapping_iterations (tree chrec_a,
     }
 
   /* If they aren't the same, and aren't affine, we can't do anything
-     yet. */
+     yet.  */
   else if ((chrec_contains_symbols (chrec_a)
 	    || chrec_contains_symbols (chrec_b))
 	   && (!evolution_function_is_affine_multivariate_p (chrec_a, lnn)