4 files changed, 47 insertions, 23 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5de0010c69c..a9275fac580 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,12 @@
 2005-08-23  Sebastian Pop  <pop@cri.ensmp.fr>
 
+	* lambda-code.c (lambda_vector_lexico_pos): Moved...
+	* lambda.h (lambda_vector_lexico_pos): ... here.
+	* tree-data-ref.c (build_classic_dist_vector): Return false when
+	the distance vector is lexicographically negative.
+
+2005-08-23  Sebastian Pop  <pop@cri.ensmp.fr>
+
 	PR tree-optimization/23511
 	* tree-ssa-loop-niter.c (infer_loop_bounds_from_undefined): Don't 
 	handle cases where TYPE_MIN_VALUE or TYPE_MAX_VALUE are NULL_TREE.
diff --git a/gcc/lambda-code.c b/gcc/lambda-code.c
index 29b3e5ae708..cf995a3f9f4 100644
--- a/gcc/lambda-code.c
+++ b/gcc/lambda-code.c
@@ -2010,27 +2010,6 @@ lambda_loopnest_to_gcc_loopnest (struct loop *old_loopnest,
   VEC_free (tree, heap, new_ivs);
 }
 
-/* Returns true when the vector V is lexicographically positive, in
-   other words, when the first nonzero element is positive.  */
-
-static bool
-lambda_vector_lexico_pos (lambda_vector v, 
-			  unsigned n)
-{
-  unsigned i;
-  for (i = 0; i < n; i++)
-    {
-      if (v[i] == 0)
-	continue;
-      if (v[i] < 0)
-	return false;
-      if (v[i] > 0)
-	return true;
-    }
-  return true;
-}
-
-
 /* Return TRUE if this is not interesting statement from the perspective of
    determining if we have a perfect loop nest.  */
 
diff --git a/gcc/lambda.h b/gcc/lambda.h
index dea12ef6098..9855b6f73ed 100644
--- a/gcc/lambda.h
+++ b/gcc/lambda.h
@@ -376,5 +376,26 @@ print_lambda_vector (FILE * outfile, lambda_vector vector, int n)
     fprintf (outfile, "%3d ", vector[i]);
   fprintf (outfile, "\n");
 }
+
+/* Returns true when the vector V is lexicographically positive, in
+   other words, when the first nonzero element is positive.  */
+
+static inline bool
+lambda_vector_lexico_pos (lambda_vector v, 
+			  unsigned n)
+{
+  unsigned i;
+  for (i = 0; i < n; i++)
+    {
+      if (v[i] == 0)
+	continue;
+      if (v[i] < 0)
+	return false;
+      if (v[i] > 0)
+	return true;
+    }
+  return true;
+}
+
 #endif /* LAMBDA_H  */
 
diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index 54494c2e986..d7a4253320c 100644
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -3030,8 +3030,8 @@ subscript_dependence_tester (struct data_dependence_relation *ddr)
    NB_LOOPS is the total number of loops we are considering.
    FIRST_LOOP_DEPTH is the loop->depth of the first loop in the analyzed
    loop nest.  
-   Return FALSE if the dependence relation is outside of the loop nest
-   starting at FIRST_LOOP_DEPTH. 
+   Return FALSE when fail to represent the data dependence as a distance
+   vector.
    Return TRUE otherwise.  */
 
 static bool
@@ -3196,6 +3196,23 @@ build_classic_dist_vector (struct data_dependence_relation *ddr,
   
   DDR_DIST_VECT (ddr) = dist_v;
   DDR_SIZE_VECT (ddr) = nb_loops;
+
+  /* Verify a basic constraint: classic distance vectors should always
+     be lexicographically positive.  */
+  if (!lambda_vector_lexico_pos (DDR_DIST_VECT (ddr),
+				 DDR_SIZE_VECT (ddr)))
+    {
+      if (DDR_SIZE_VECT (ddr) == 1)
+	/* This one is simple to fix, and can be fixed.
+	   Multidimensional arrays cannot be fixed that simply.  */
+	lambda_vector_negate (DDR_DIST_VECT (ddr), DDR_DIST_VECT (ddr),
+			      DDR_SIZE_VECT (ddr));
+      else
+	/* This is not valid: we need the delta test for properly
+	   fixing all this.  */
+	return false;
+    }
+
   return true;
 }