From aa6c06612cec721cca434cbc63febcdc501a400a Mon Sep 17 00:00:00 2001
From: Sven Verdoolaege <skimo@kotnet.org>
Date: Thu, 12 May 2011 15:55:15 +0200
Subject: [PATCH] add isl_equality_from_aff

Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>
---
 doc/user.pod             |  6 ++++++
 include/isl/constraint.h |  1 +
 isl_constraint.c         | 27 +++++++++++++++++++++++++++
 3 files changed, 34 insertions(+)

diff --git a/doc/user.pod b/doc/user.pod
index bec4f9df..7528d14b 100644
--- a/doc/user.pod
+++ b/doc/user.pod
@@ -2049,6 +2049,12 @@ a non-zero coefficient for the specified dimension.
 		__isl_keep isl_constraint *constraint,
 		enum isl_dim_type type, int pos);
 
+Conversely, an equality constraint can be constructed, equating
+the affine expression to zero, using
+
+	__isl_give isl_constraint *isl_equality_from_aff(
+		__isl_take isl_aff *aff);
+
 The expression can be inspected using
 
 	#include <isl/aff.h>
diff --git a/include/isl/constraint.h b/include/isl/constraint.h
index 7d20bab6..39c5c3b0 100644
--- a/include/isl/constraint.h
+++ b/include/isl/constraint.h
@@ -113,6 +113,7 @@ struct isl_basic_set *isl_basic_set_from_constraint(
 
 __isl_give isl_aff *isl_constraint_get_bound(
 	__isl_keep isl_constraint *constraint, enum isl_dim_type type, int pos);
+__isl_give isl_constraint *isl_equality_from_aff(__isl_take isl_aff *aff);
 
 __isl_give isl_printer *isl_printer_print_constraint(__isl_take isl_printer *p,
 	__isl_keep isl_constraint *c);
diff --git a/isl_constraint.c b/isl_constraint.c
index ecc1a0d6..5d55c81b 100644
--- a/isl_constraint.c
+++ b/isl_constraint.c
@@ -1004,3 +1004,30 @@ __isl_give isl_aff *isl_constraint_get_bound(
 
 	return aff;
 }
+
+/* Construct an equality constraint equating the given affine expression
+ * to zero.
+ */
+__isl_give isl_constraint *isl_equality_from_aff(__isl_take isl_aff *aff)
+{
+	int k;
+	isl_basic_set *bset;
+
+	if (!aff)
+		return NULL;
+
+	bset = isl_basic_set_from_local_space(isl_aff_get_local_space(aff));
+	bset = isl_basic_set_extend_constraints(bset, 1, 0);
+	k = isl_basic_set_alloc_equality(bset);
+	if (k < 0)
+		goto error;
+
+	isl_seq_cpy(bset->eq[k], aff->v->el + 1, aff->v->size - 1);
+	isl_aff_free(aff);
+
+	return isl_basic_set_constraint(bset, &bset->eq[k]);
+error:
+	isl_aff_free(aff);
+	isl_basic_set_free(bset);
+	return NULL;
+}
-- 
2.11.4.GIT