From 230c927e6e9c6af47b3aa6e2af96941cca9f7a5c Mon Sep 17 00:00:00 2001
From: Sven Verdoolaege <skimo@kotnet.org>
Date: Mon, 15 Mar 2010 14:22:22 +0100
Subject: [PATCH] iscc: add inverse operation

---
 doc/isl.tex |  2 ++
 iscc.c      | 37 ++++++++++++++++++++++++++++++++-----
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/doc/isl.tex b/doc/isl.tex
index 1b38e6a..ca117ef 100644
--- a/doc/isl.tex
+++ b/doc/isl.tex
@@ -171,6 +171,8 @@ of the set $s$ and return a piecewise quasipolynomial
 mapping each of the individual elements to the resulting
 constant
 \\
+$m_2$ := $m_1$\ai[\tt]{\^{}-1} & inverse of $m_1$
+\\
 $l$ := $m$\ai[\tt]{\^{}+} &
 compute an overapproximation of the transitive closure
 of $m$ and return a list containing the overapproximation
diff --git a/iscc.c b/iscc.c
index eb0cad8..61a3f56 100644
--- a/iscc.c
+++ b/iscc.c
@@ -501,6 +501,35 @@ error:
 	return obj;
 }
 
+static struct isl_obj power(struct isl_stream *s, struct isl_obj obj)
+{
+	struct isl_token *tok;
+
+	if (isl_stream_eat_if_available(s, '+'))
+		return transitive_closure(s->ctx, obj);
+
+	tok = isl_stream_next_token(s);
+	if (!tok || tok->type != ISL_TOKEN_VALUE || isl_int_cmp_si(tok->u.v, -1)) {
+		isl_stream_error(s, tok, "expecting -1");
+		if (tok)
+			isl_stream_push_token(s, tok);
+		goto error;
+	}
+	isl_token_free(tok);
+	isl_assert(s->ctx, obj.type == isl_obj_map, goto error);
+
+	obj.v = isl_map_reverse(obj.v);
+	if (!obj.v)
+		goto error;
+
+	return obj;
+error:
+	free_obj(obj);
+	obj.type = isl_obj_none;
+	obj.v = NULL;
+	return obj;
+}
+
 static struct isl_obj read_obj(struct isl_stream *s,
 	struct isl_hash_table *table)
 {
@@ -526,11 +555,9 @@ static struct isl_obj read_obj(struct isl_stream *s,
 		}
 	}
 
-	if (isl_stream_eat_if_available(s, '^')) {
-		if (isl_stream_eat(s, '+'))
-			goto error;
-		obj = transitive_closure(s->ctx, obj);
-	} else if (obj.type == isl_obj_list && isl_stream_eat_if_available(s, '['))
+	if (isl_stream_eat_if_available(s, '^'))
+		obj = power(s, obj);
+	else if (obj.type == isl_obj_list && isl_stream_eat_if_available(s, '['))
 		obj = obj_at_index(s, obj);
 
 	return obj;
-- 
2.11.4.GIT