From 6841be4175bf922931a601706deaf39b1779aefb Mon Sep 17 00:00:00 2001
From: Sven Verdoolaege <skimo@kotnet.org>
Date: Fri, 27 Feb 2009 11:18:01 +0100
Subject: [PATCH] isl_basic_map_intersect: reuse sample value of either basic
 map if possible

If the sample value stored in one of the two basic maps is an element
of both basic maps, then we can keep it as sample value for the intersection.
---
 isl_map.c | 84 ++++++++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 51 insertions(+), 33 deletions(-)

diff --git a/isl_map.c b/isl_map.c
index a9898c8..afb2ab1 100644
--- a/isl_map.c
+++ b/isl_map.c
@@ -1550,9 +1550,44 @@ error:
 	return NULL;
 }
 
+static int basic_map_contains(struct isl_basic_map *bmap, struct isl_vec *vec)
+{
+	int i;
+	unsigned total;
+	isl_int s;
+
+	total = 1 + isl_basic_map_total_dim(bmap);
+	if (total != vec->size)
+		return -1;
+
+	isl_int_init(s);
+
+	for (i = 0; i < bmap->n_eq; ++i) {
+		isl_seq_inner_product(vec->block.data, bmap->eq[i], total, &s);
+		if (!isl_int_is_zero(s)) {
+			isl_int_clear(s);
+			return 0;
+		}
+	}
+
+	for (i = 0; i < bmap->n_ineq; ++i) {
+		isl_seq_inner_product(vec->block.data, bmap->ineq[i], total, &s);
+		if (isl_int_is_neg(s)) {
+			isl_int_clear(s);
+			return 0;
+		}
+	}
+
+	isl_int_clear(s);
+
+	return 1;
+}
+
 struct isl_basic_map *isl_basic_map_intersect(
 		struct isl_basic_map *bmap1, struct isl_basic_map *bmap2)
 {
+	struct isl_vec *sample = NULL;
+
 	if (!bmap1 || !bmap2)
 		goto error;
 
@@ -1569,15 +1604,31 @@ struct isl_basic_map *isl_basic_map_intersect(
 		isl_assert(bmap1->ctx,
 			    isl_dim_equal(bmap1->dim, bmap2->dim), goto error);
 
+	if (bmap1->sample &&
+	    basic_map_contains(bmap1, bmap1->sample) > 0 &&
+	    basic_map_contains(bmap2, bmap1->sample) > 0)
+		sample = isl_vec_copy(bmap1->ctx, bmap1->sample);
+	else if (bmap2->sample &&
+	    basic_map_contains(bmap1, bmap2->sample) > 0 &&
+	    basic_map_contains(bmap2, bmap2->sample) > 0)
+		sample = isl_vec_copy(bmap2->ctx, bmap2->sample);
+
 	bmap1 = isl_basic_map_extend_dim(bmap1, isl_dim_copy(bmap1->dim),
 			bmap2->n_div, bmap2->n_eq, bmap2->n_ineq);
 	if (!bmap1)
 		goto error;
 	bmap1 = add_constraints(bmap1, bmap2, 0, 0);
 
+	if (sample) {
+		isl_vec_free(bmap1->ctx, bmap1->sample);
+		bmap1->sample = sample;
+	}
+
 	bmap1 = isl_basic_map_simplify(bmap1);
 	return isl_basic_map_finalize(bmap1);
 error:
+	if (sample)
+		isl_vec_free(bmap1->ctx, sample);
 	isl_basic_map_free(bmap1);
 	isl_basic_map_free(bmap2);
 	return NULL;
@@ -3341,39 +3392,6 @@ int isl_basic_map_is_strict_subset(
 	return !is_subset;
 }
 
-static int basic_map_contains(struct isl_basic_map *bmap, struct isl_vec *vec)
-{
-	int i;
-	unsigned total;
-	isl_int s;
-
-	total = 1 + isl_basic_map_total_dim(bmap);
-	if (total != vec->size)
-		return -1;
-
-	isl_int_init(s);
-
-	for (i = 0; i < bmap->n_eq; ++i) {
-		isl_seq_inner_product(vec->block.data, bmap->eq[i], total, &s);
-		if (!isl_int_is_zero(s)) {
-			isl_int_clear(s);
-			return 0;
-		}
-	}
-
-	for (i = 0; i < bmap->n_ineq; ++i) {
-		isl_seq_inner_product(vec->block.data, bmap->ineq[i], total, &s);
-		if (isl_int_is_neg(s)) {
-			isl_int_clear(s);
-			return 0;
-		}
-	}
-
-	isl_int_clear(s);
-
-	return 1;
-}
-
 int isl_basic_map_is_universe(struct isl_basic_map *bmap)
 {
 	if (!bmap)
-- 
2.7.4