From cbf7ae8fef4d40248f9b0ff9f2b56546395eebb6 Mon Sep 17 00:00:00 2001
From: Tobias Grosser <tobias@grosser.es>
Date: Mon, 21 Dec 2015 22:45:53 +0000
Subject: [PATCH] ScopInfo: Polish the implementation of mapToDimension

Besides improving the documentation and the code we now assert in case the input
is invalid (N < 0) and also do not any more return a nullptr in case USet is
empty. This should make the code more readable.

llvm-svn: 256208
---
 polly/lib/Analysis/ScopInfo.cpp | 52 +++++++++++++++++++++++++----------------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/polly/lib/Analysis/ScopInfo.cpp b/polly/lib/Analysis/ScopInfo.cpp
index 71c180d..0714c37 100644
--- a/polly/lib/Analysis/ScopInfo.cpp
+++ b/polly/lib/Analysis/ScopInfo.cpp
@@ -3353,14 +3353,13 @@ struct MapToDimensionDataTy {
 };
 
 // @brief Create a function that maps the elements of 'Set' to its N-th
-//        dimension.
+//        dimension and add it to User->Res.
 //
-// The result is added to 'User->Res'.
+// @param Set        The input set.
+// @param User->N    The dimension to map to.
+// @param User->Res  The isl_union_pw_multi_aff to which to add the result.
 //
-// @param Set The input set.
-// @param N   The dimension to map to.
-//
-// @returns   Zero if no error occurred, non-zero otherwise.
+// @returns   isl_stat_ok if no error occured, othewise isl_stat_error.
 static isl_stat mapToDimension_AddSet(__isl_take isl_set *Set, void *User) {
   struct MapToDimensionDataTy *Data = (struct MapToDimensionDataTy *)User;
   int Dim;
@@ -3380,28 +3379,41 @@ static isl_stat mapToDimension_AddSet(__isl_take isl_set *Set, void *User) {
   return isl_stat_ok;
 }
 
-// @brief Create a function that maps the elements of Domain to their Nth
-//        dimension.
+// @brief Create an isl_multi_union_aff that defines an identity mapping
+//        from the elements of USet to their N-th dimension.
+//
+// # Example:
+//
+//            Domain: { A[i,j]; B[i,j,k] }
+//                 N: 1
 //
-// @param Domain The set of elements to map.
+// Resulting Mapping: { {A[i,j] -> [(j)]; B[i,j,k] -> [(j)] }
+//
+// @param USet   A union set describing the elements for which to generate a
+//               mapping.
 // @param N      The dimension to map to.
+// @returns      A mapping from USet to its N-th dimension.
 static __isl_give isl_multi_union_pw_aff *
-mapToDimension(__isl_take isl_union_set *Domain, int N) {
-  if (N <= 0 || isl_union_set_is_empty(Domain)) {
-    isl_union_set_free(Domain);
+mapToDimension(__isl_take isl_union_set *USet, int N) {
+  assert(N >= 0);
+
+  if (!USet)
     return nullptr;
-  }
+
+  assert(!isl_union_set_is_empty(USet));
 
   struct MapToDimensionDataTy Data;
-  isl_space *Space;
 
-  Space = isl_union_set_get_space(Domain);
-  Data.N = N;
-  Data.Res = isl_union_pw_multi_aff_empty(Space);
-  if (isl_union_set_foreach_set(Domain, &mapToDimension_AddSet, &Data) < 0)
-    Data.Res = isl_union_pw_multi_aff_free(Data.Res);
+  auto *Space = isl_union_set_get_space(USet);
+  auto *PwAff = isl_union_pw_multi_aff_empty(Space);
 
-  isl_union_set_free(Domain);
+  Data = {N, PwAff};
+
+  auto Res = isl_union_set_foreach_set(USet, &mapToDimension_AddSet, &Data);
+
+  assert(Res == isl_stat_ok);
+
+  isl_union_set_free(USet);
   return isl_multi_union_pw_aff_from_union_pw_multi_aff(Data.Res);
 }
 
-- 
2.7.4