isl_qpolynomial_add: replace 0-degree polynomials by their constant terms

diff --git a/isl_polynomial.c b/isl_polynomial.c
index 0b063ad..e0f5adb 100644 (file)
--- a/isl_polynomial.c
+++ b/isl_polynomial.c
@@ -416,6 +416,27 @@ static __isl_give struct isl_upoly *replace_by_zero(
        return isl_upoly_zero(ctx);
 }
 
+static __isl_give struct isl_upoly *replace_by_constant_term(
+       __isl_take struct isl_upoly *up)
+{
+       struct isl_upoly_rec *rec;
+       struct isl_upoly *cst;
+
+       if (!up)
+               return NULL;
+
+       rec = isl_upoly_as_rec(up);
+       if (!rec)
+               goto error;
+       isl_assert(up->ctx, rec->n == 1, goto error);
+       cst = isl_upoly_copy(rec->p[0]);
+       isl_upoly_free(up);
+       return cst;
+error:
+       isl_upoly_free(up);
+       return NULL;
+}
+
 __isl_give struct isl_upoly *isl_upoly_sum(__isl_take struct isl_upoly *up1,
        __isl_take struct isl_upoly *up2)
 {
@@ -459,8 +480,8 @@ __isl_give struct isl_upoly *isl_upoly_sum(__isl_take struct isl_upoly *up1,
                if (!rec)
                        goto error;
                rec->p[0] = isl_upoly_sum(rec->p[0], up2);
-               if (rec->n == 1 && isl_upoly_is_zero(rec->p[0]))
-                       up1 = replace_by_zero(up1);
+               if (rec->n == 1)
+                       up1 = replace_by_constant_term(up1);
                return up1;
        }
 
@@ -493,6 +514,8 @@ __isl_give struct isl_upoly *isl_upoly_sum(__isl_take struct isl_upoly *up1,
 
        if (rec1->n == 0)
                up1 = replace_by_zero(up1);
+       else if (rec1->n == 1)
+               up1 = replace_by_constant_term(up1);
 
        isl_upoly_free(up2);