Do not intersect with AssumedContext in calculateMinMaxAccess

Originally, we intersected the iteration space with the AssumedContext before
computing the minimal/maximal memory offset in our run-time alias checks. With
this patch we drop this intersection as the AssumedContext can - for larger or
more complex scops - become very complicated (contain many disjuncts). When
intersecting an object with many disjuncts with other objects, the number of
disjuncts in these other objects also increases quickly. As a result, the
compile time is unnecessarily increased. This patch now drops the intersection
with the assumed context to ensure we do not pay unnecessary compile time
costs.

With this patch we see -3.17% reduction in compile time for 3mm with default
flags and -17.87% when compiling 3mm with -DPOLYBENCH_USE_C99_PROTO flag. We
did not observe any regressions in LNT.

Contributed-by: Pratik Bhatu <cs12b1010@iith.ac.in>

Reviewers: grosser

Differential Revision: http://reviews.llvm.org/D12198

llvm-svn: 245617

1 files changed, 4 insertions, 6 deletions

diff --git a/polly/lib/Analysis/ScopInfo.cpp b/polly/lib/Analysis/ScopInfo.cpp
index d5e43970faf..28df84b0c24 100644
--- a/polly/lib/Analysis/ScopInfo.cpp
+++ b/polly/lib/Analysis/ScopInfo.cpp
@@ -1339,12 +1339,10 @@ static __isl_give isl_set *getAccessDomain(MemoryAccess *MA) {
 /// @brief Wrapper function to calculate minimal/maximal accesses to each array.
 static bool calculateMinMaxAccess(__isl_take isl_union_map *Accesses,
                                   __isl_take isl_union_set *Domains,
-                                  __isl_take isl_set *AssumedContext,
                                   Scop::MinMaxVectorTy &MinMaxAccesses) {
 
   Accesses = isl_union_map_intersect_domain(Accesses, Domains);
   isl_union_set *Locations = isl_union_map_range(Accesses);
-  Locations = isl_union_set_intersect_params(Locations, AssumedContext);
   Locations = isl_union_set_coalesce(Locations);
   Locations = isl_union_set_detect_equalities(Locations);
   bool Valid = (0 == isl_union_set_foreach_set(Locations, buildMinMaxAccess,
@@ -1497,8 +1495,8 @@ bool Scop::buildAliasGroups(AliasAnalysis &AA) {
     for (MemoryAccess *MA : AG)
       Accesses = isl_union_map_add_map(Accesses, MA->getAccessRelation());
 
-    bool Valid = calculateMinMaxAccess(
-        Accesses, getDomains(), getAssumedContext(), MinMaxAccessesNonReadOnly);
+    bool Valid = calculateMinMaxAccess(Accesses, getDomains(),
+                                       MinMaxAccessesNonReadOnly);
 
     // Bail out if the number of values we need to compare is too large.
     // This is important as the number of comparisions grows quadratically with
@@ -1515,8 +1513,8 @@ bool Scop::buildAliasGroups(AliasAnalysis &AA) {
       for (MemoryAccess *MA : ReadOnlyPair.second)
         Accesses = isl_union_map_add_map(Accesses, MA->getAccessRelation());
 
-    Valid = calculateMinMaxAccess(Accesses, getDomains(), getAssumedContext(),
-                                  MinMaxAccessesReadOnly);
+    Valid =
+        calculateMinMaxAccess(Accesses, getDomains(), MinMaxAccessesReadOnly);
 
     if (!Valid)
       return false;