isl_map.c: parameter_compute_divs: extract out first_parameter_equality

We will be able to reuse this function in the next commit.

Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>

diff --git a/isl_map.c b/isl_map.c
index a74324b..6eb1a1a 100644 (file)
--- a/isl_map.c
+++ b/isl_map.c
@@ -6377,6 +6377,32 @@ error:
        return NULL;
 }
 
+/* Given a basic set "bset" that only involves parameters and existentially
+ * quantified variables, return the index of the first equality
+ * that only involves parameters.  If there is no such equality then
+ * return bset->n_eq.
+ *
+ * This function assumes that isl_basic_set_gauss has been called on "bset".
+ */
+static int first_parameter_equality(__isl_keep isl_basic_set *bset)
+{
+       int i, j;
+       unsigned nparam, n_div;
+
+       if (!bset)
+               return -1;
+
+       nparam = isl_basic_set_dim(bset, isl_dim_param);
+       n_div = isl_basic_set_dim(bset, isl_dim_div);
+
+       for (i = 0, j = n_div - 1; i < bset->n_eq && j >= 0; --j) {
+               if (!isl_int_is_zero(bset->eq[i][1 + nparam + j]))
+                       ++i;
+       }
+
+       return i;
+}
+
 /* Project the given basic set onto its parameter domain, possibly introducing
  * new, explicit, existential variables in the constraints.
  * The input has parameters and (possibly implicit) existential variables.
@@ -6391,11 +6417,11 @@ error:
  */
 static struct isl_set *parameter_compute_divs(struct isl_basic_set *bset)
 {
-       int i, j;
+       int i;
        struct isl_mat *eq;
        struct isl_mat *T, *T2;
        struct isl_set *set;
-       unsigned nparam, n_div;
+       unsigned nparam;
 
        bset = isl_basic_set_cow(bset);
        if (!bset)
@@ -6410,16 +6436,11 @@ static struct isl_set *parameter_compute_divs(struct isl_basic_set *bset)
        if (isl_basic_set_plain_is_empty(bset))
                return isl_set_from_basic_set(bset);
 
-       nparam = isl_basic_set_dim(bset, isl_dim_param);
-       n_div = isl_basic_set_dim(bset, isl_dim_div);
-
-       for (i = 0, j = n_div - 1; i < bset->n_eq && j >= 0; --j) {
-               if (!isl_int_is_zero(bset->eq[i][1 + nparam + j]))
-                       ++i;
-       }
+       i = first_parameter_equality(bset);
        if (i == bset->n_eq)
                return isl_basic_set_lexmin(bset);
 
+       nparam = isl_basic_set_dim(bset, isl_dim_param);
        eq = isl_mat_sub_alloc6(bset->ctx, bset->eq, i, bset->n_eq - i,
                0, 1 + nparam);
        eq = isl_mat_cow(eq);