isl_aff_floor: reduce coefficients of newly created div

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

diff --git a/isl_aff.c b/isl_aff.c
index f1ec212..e226377 100644 (file)
--- a/isl_aff.c
+++ b/isl_aff.c
@@ -11,6 +11,7 @@
  * Universiteit Leiden, Niels Bohrweg 1, 2333 CA Leiden, The Netherlands
  */
 
+#include <isl_ctx_private.h>
 #include <isl_map_private.h>
 #include <isl_aff_private.h>
 #include <isl_dim_private.h>
@@ -460,12 +461,16 @@ __isl_give isl_aff *isl_aff_neg(__isl_take isl_aff *aff)
 
 /* Given f, return floor(f).
  * If f is an integer expression, then just return f.
- * Otherwise, create a new div d = [f] and return the expression d.
+ * Otherwise, if f = g/m, write g = q m + r,
+ * create a new div d = [r/m] and return the expression q + d.
+ * The coefficients in r are taken to lie between -m/2 and m/2.
  */
 __isl_give isl_aff *isl_aff_floor(__isl_take isl_aff *aff)
 {
+       int i;
        int size;
        isl_ctx *ctx;
+       isl_vec *div;
 
        if (!aff)
                return NULL;
@@ -477,15 +482,29 @@ __isl_give isl_aff *isl_aff_floor(__isl_take isl_aff *aff)
        if (!aff)
                return NULL;
 
-       aff->ls = isl_local_space_add_div(aff->ls, isl_vec_copy(aff->v));
-       if (!aff->ls)
+       aff->v = isl_vec_cow(aff->v);
+       div = isl_vec_copy(aff->v);
+       div = isl_vec_cow(div);
+       if (!div)
                return isl_aff_free(aff);
 
        ctx = isl_aff_get_ctx(aff);
+       isl_int_fdiv_q(aff->v->el[0], aff->v->el[0], ctx->two);
+       for (i = 1; i < aff->v->size; ++i) {
+               isl_int_fdiv_r(div->el[i], div->el[i], div->el[0]);
+               isl_int_fdiv_q(aff->v->el[i], aff->v->el[i], div->el[0]);
+               if (isl_int_gt(div->el[i], aff->v->el[0])) {
+                       isl_int_sub(div->el[i], div->el[i], div->el[0]);
+                       isl_int_add_ui(aff->v->el[i], aff->v->el[i], 1);
+               }
+       }
+
+       aff->ls = isl_local_space_add_div(aff->ls, div);
+       if (!aff->ls)
+               return isl_aff_free(aff);
+
        size = aff->v->size;
-       isl_vec_free(aff->v);
-       aff->v = isl_vec_alloc(ctx, size + 1);
-       aff->v = isl_vec_clr(aff->v);
+       aff->v = isl_vec_extend(aff->v, size + 1);
        if (!aff->v)
                return isl_aff_free(aff);
        isl_int_set_si(aff->v->el[0], 1);