isl_qpolynomial_substitute_equalities: ignore constant when removing factors

The constant term of the affine expression inside an integer division
should not be taking to account when trying to remove common factors
between numerator and denominator.  For example, [(1 + 2 x)/4]
should be simplified to [x/2].

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

diff --git a/isl_polynomial.c b/isl_polynomial.c
index 68e5e19..db73fdc 100644 (file)
--- a/isl_polynomial.c
+++ b/isl_polynomial.c
@@ -1940,6 +1940,27 @@ __isl_give struct isl_upoly *isl_upoly_from_affine(isl_ctx *ctx, isl_int *f,
        return up;
 }
 
+/* Remove common factor of non-constant terms and denominator.
+ */
+static void normalize_div(__isl_keep isl_qpolynomial *qp, int div)
+{
+       isl_ctx *ctx = qp->div->ctx;
+       unsigned total = qp->div->n_col - 2;
+
+       isl_seq_gcd(qp->div->row[div] + 2, total, &ctx->normalize_gcd);
+       isl_int_gcd(ctx->normalize_gcd,
+                   ctx->normalize_gcd, qp->div->row[div][0]);
+       if (isl_int_is_one(ctx->normalize_gcd))
+               return;
+
+       isl_seq_scale_down(qp->div->row[div] + 2, qp->div->row[div] + 2,
+                           ctx->normalize_gcd, total);
+       isl_int_divexact(qp->div->row[div][0], qp->div->row[div][0],
+                           ctx->normalize_gcd);
+       isl_int_fdiv_q(qp->div->row[div][1], qp->div->row[div][1],
+                           ctx->normalize_gcd);
+}
+
 __isl_give isl_qpolynomial *isl_qpolynomial_substitute_equalities(
        __isl_take isl_qpolynomial *qp, __isl_take isl_basic_set *eq)
 {
@@ -1976,8 +1997,7 @@ __isl_give isl_qpolynomial *isl_qpolynomial_substitute_equalities(
                                continue;
                        isl_seq_elim(qp->div->row[k] + 1, eq->eq[i], j, total,
                                        &qp->div->row[k][0]);
-                       isl_seq_normalize(qp->div->ctx,
-                                         qp->div->row[k], 1 + total);
+                       normalize_div(qp, k);
                }
 
                if (isl_int_is_pos(eq->eq[i][j]))