add isl_basic_set_preimage_multi_aff

[platform/upstream/isl.git] / isl_aff.c

diff --git a/isl_aff.c b/isl_aff.c
index 499298c..9174069 100644 (file)
--- a/isl_aff.c
+++ b/isl_aff.c
@@ -3417,6 +3417,77 @@ __isl_give isl_pw_multi_aff *isl_pw_multi_aff_substitute(
        return res;
 }
 
+/* Compute the preimage of the affine expression "src" under "ma"
+ * and put the result in "dst".  If "has_denom" is set (to one),
+ * then "src" and "dst" have an extra initial denominator.
+ * "n_div_ma" is the number of existentials in "ma"
+ * "n_div_bset" is the number of existentials in "src"
+ * The resulting "dst" (which is assumed to have been allocated by
+ * the caller) contains coefficients for both sets of existentials,
+ * first those in "ma" and then those in "src".
+ * f, c1, c2 and g are temporary objects that have been initialized
+ * by the caller.
+ *
+ * Let src represent the expression
+ *
+ *     (a(p) + b x + c(divs))/d
+ *
+ * and let ma represent the expressions
+ *
+ *     x_i = (r_i(p) + s_i(y) + t_i(divs'))/m_i
+ *
+ * We start out with the following expression for dst:
+ *
+ *     (a(p) + 0 y + 0 divs' + f \sum_i b_i x_i + c(divs))/d
+ *
+ * with the multiplication factor f initially equal to 1.
+ * For each x_i that we substitute, we multiply the numerator
+ * (and denominator) of dst by c_1 = m_i and add the numerator
+ * of the x_i expression multiplied by c_2 = f b_i,
+ * after removing the common factors of c_1 and c_2.
+ * The multiplication factor f also needs to be multiplied by c_1
+ * for the next x_j, j > i.
+ */
+void isl_seq_preimage(isl_int *dst, isl_int *src,
+       __isl_keep isl_multi_aff *ma, int n_div_ma, int n_div_bset,
+       isl_int f, isl_int c1, isl_int c2, isl_int g, int has_denom)
+{
+       int i;
+       int n_param, n_in, n_out;
+       int o_div_bset;
+
+       n_param = isl_multi_aff_dim(ma, isl_dim_param);
+       n_in = isl_multi_aff_dim(ma, isl_dim_in);
+       n_out = isl_multi_aff_dim(ma, isl_dim_out);
+
+       o_div_bset = has_denom + 1 + n_param + n_in + n_div_ma;
+
+       isl_seq_cpy(dst, src, has_denom + 1 + n_param);
+       isl_seq_clr(dst + has_denom + 1 + n_param, n_in + n_div_ma);
+       isl_seq_cpy(dst + o_div_bset,
+                   src + has_denom + 1 + n_param + n_out, n_div_bset);
+
+       isl_int_set_si(f, 1);
+
+       for (i = 0; i < n_out; ++i) {
+               if (isl_int_is_zero(src[has_denom + 1 + n_param + i]))
+                       continue;
+               isl_int_set(c1, ma->p[i]->v->el[0]);
+               isl_int_mul(c2, f, src[has_denom + 1 + n_param + i]);
+               isl_int_gcd(g, c1, c2);
+               isl_int_divexact(c1, c1, g);
+               isl_int_divexact(c2, c2, g);
+
+               isl_int_mul(f, f, c1);
+               isl_seq_combine(dst + has_denom, c1, dst + has_denom,
+                               c2, ma->p[i]->v->el + 1, ma->p[i]->v->size - 1);
+               isl_seq_scale(dst + o_div_bset,
+                               dst + o_div_bset, c1, n_div_bset);
+               if (has_denom)
+                       isl_int_mul(dst[0], dst[0], c1);
+       }
+}
+
 /* Extend the local space of "dst" to include the divs
  * in the local space of "src".
  */