From 8c0888fbe138d5f30842361a3b7af369ebfc3a0b Mon Sep 17 00:00:00 2001
From: Sven Verdoolaege <sven@cerebras.net>
Date: Thu, 24 Oct 2019 15:46:38 +0200
Subject: [PATCH] add exported isl_aff_domain_reverse

This complements the already exported isl_space_domain_reverse.

Signed-off-by: Sven Verdoolaege <sven@cerebras.net>
---
 doc/user.pod      |  4 ++++
 include/isl/aff.h |  2 ++
 isl_aff.c         | 38 ++++++++++++++++++++++++++++++++++++++
 isl_test2.cc      |  9 +++++++++
 4 files changed, 53 insertions(+)

diff --git a/doc/user.pod b/doc/user.pod
index 274a01a3..8684fd3e 100644
--- a/doc/user.pod
+++ b/doc/user.pod
@@ -5425,6 +5425,10 @@ earlier dimensions before those that involve later dimensions.
 	__isl_give isl_space *isl_space_range_reverse(
 		__isl_take isl_space *space);
 
+	#include <isl/aff.h>
+	__isl_give isl_aff *isl_aff_domain_reverse(
+		__isl_take isl_aff *aff);
+
 	#include <isl/map.h>
 	__isl_give isl_basic_map *isl_basic_map_reverse(
 		__isl_take isl_basic_map *bmap);
diff --git a/include/isl/aff.h b/include/isl/aff.h
index f7044b2d..e6a166ea 100644
--- a/include/isl/aff.h
+++ b/include/isl/aff.h
@@ -134,6 +134,8 @@ __isl_overload
 __isl_give isl_aff *isl_aff_scale_down_val(__isl_take isl_aff *aff,
 	__isl_take isl_val *v);
 
+__isl_export
+__isl_give isl_aff *isl_aff_domain_reverse(__isl_take isl_aff *aff);
 __isl_give isl_aff *isl_aff_insert_dims(__isl_take isl_aff *aff,
 	enum isl_dim_type type, unsigned first, unsigned n);
 __isl_give isl_aff *isl_aff_add_dims(__isl_take isl_aff *aff,
diff --git a/isl_aff.c b/isl_aff.c
index 0c17cf39..937abb66 100644
--- a/isl_aff.c
+++ b/isl_aff.c
@@ -2819,6 +2819,44 @@ __isl_give isl_aff *isl_aff_move_dims(__isl_take isl_aff *aff,
 	return aff;
 }
 
+/* Given an affine function on a domain (A -> B),
+ * interchange A and B in the wrapped domain
+ * to obtain a function on the domain (B -> A).
+ *
+ * Since this may change the position of some variables,
+ * it may also change the normalized order of the local variables.
+ * Restore this order.  Since sort_divs assumes the input
+ * has a single reference, an explicit isl_aff_cow is required.
+ */
+__isl_give isl_aff *isl_aff_domain_reverse(__isl_take isl_aff *aff)
+{
+	isl_space *space;
+	isl_local_space *ls;
+	isl_vec *v;
+	isl_size n_in, n_out;
+	unsigned offset;
+
+	space = isl_aff_peek_domain_space(aff);
+	offset = isl_space_offset(space, isl_dim_set);
+	n_in = isl_space_wrapped_dim(space, isl_dim_set, isl_dim_in);
+	n_out = isl_space_wrapped_dim(space, isl_dim_set, isl_dim_out);
+	if (n_in < 0 || n_out < 0)
+		return isl_aff_free(aff);
+
+	v = isl_aff_take_rat_aff(aff);
+	v = isl_vec_move_els(v, 1 + 1 + offset, 1 + 1 + offset + n_in, n_out);
+	aff = isl_aff_restore_rat_aff(aff, v);
+
+	ls = isl_aff_take_domain_local_space(aff);
+	ls = isl_local_space_wrapped_reverse(ls);
+	aff = isl_aff_restore_domain_local_space(aff, ls);
+
+	aff = isl_aff_cow(aff);
+	aff = sort_divs(aff);
+
+	return aff;
+}
+
 /* Return a zero isl_aff in the given space.
  *
  * This is a helper function for isl_pw_*_as_* that ensures a uniform
diff --git a/isl_test2.cc b/isl_test2.cc
index 5a4ad407..2ec134a9 100644
--- a/isl_test2.cc
+++ b/isl_test2.cc
@@ -458,6 +458,15 @@ static void test_project(isl::ctx ctx)
  */
 static void test_reverse(isl::ctx ctx)
 {
+	C(&isl::aff::domain_reverse, {
+	{ "{ T[A[] -> B[*]] -> [0] }",
+	  "{ [B[*] -> A[]] -> [0] }" },
+	{ "{ T[A[] -> A[]] -> [0] }",
+	  "{ T[A[] -> A[]] -> [0] }" },
+	{ "{ [A[x] -> B[y]] -> [5*(x // 2) + 7*(y // 3)] }",
+	  "{ [B[y] -> A[x]] -> [5*(x // 2) + 7*(y // 3)] }" },
+	});
+
 	C(&isl::union_map::range_reverse, {
 	{ "{ A[] -> [B[] -> C[]]; A[] -> B[]; A[0] -> N[B[1] -> B[2]] }",
 	  "{ A[] -> [C[] -> B[]]; A[0] -> N[B[2] -> B[1]] }" },
-- 
2.11.4.GIT