[ADT] IntervalMap: add overlaps(a, b) method

Summary:
This function checks whether the mappings in the interval map overlap
with the given range [a;b]. The motivation is to enable checking for
overlap before inserting a new interval into the map.

Reviewers: vsk, dblaikie

Subscribers: dexonsmith, kristina, llvm-commits

Differential Revision: https://reviews.llvm.org/D55760

llvm-svn: 349898

2 files changed, 57 insertions, 0 deletions

diff --git a/llvm/include/llvm/ADT/IntervalMap.h b/llvm/include/llvm/ADT/IntervalMap.h
index b75c4920a82..2af61049e5a 100644
--- a/llvm/include/llvm/ADT/IntervalMap.h
+++ b/llvm/include/llvm/ADT/IntervalMap.h
@@ -1134,6 +1134,19 @@ public:
     I.find(x);
     return I;
   }
+
+  /// overlaps(a, b) - Return true if the intervals in this map overlap with the
+  /// interval [a;b].
+  bool overlaps(KeyT a, KeyT b) {
+    assert(Traits::nonEmpty(a, b));
+    const_iterator I = find(a);
+    if (!I.valid())
+      return false;
+    // [a;b] and [x;y] overlap iff x<=b and a<=y. The find() call guarantees the
+    // second part (y = find(a).stop()), so it is sufficient to check the first
+    // one.
+    return !Traits::stopLess(b, I.start());
+  }
 };
 
 /// treeSafeLookup - Return the mapped value at x or NotFound, assuming a
diff --git a/llvm/unittests/ADT/IntervalMapTest.cpp b/llvm/unittests/ADT/IntervalMapTest.cpp
index 11f13752f31..513c063a7b6 100644
--- a/llvm/unittests/ADT/IntervalMapTest.cpp
+++ b/llvm/unittests/ADT/IntervalMapTest.cpp
@@ -611,6 +611,50 @@ TEST(IntervalMapTest, RandomCoalescing) {
 
 }
 
+TEST(IntervalMapTest, Overlaps) {
+  UUMap::Allocator allocator;
+  UUMap map(allocator);
+  map.insert(10, 20, 0);
+  map.insert(30, 40, 0);
+  map.insert(50, 60, 0);
+
+  EXPECT_FALSE(map.overlaps(0, 9));
+  EXPECT_TRUE(map.overlaps(0, 10));
+  EXPECT_TRUE(map.overlaps(0, 15));
+  EXPECT_TRUE(map.overlaps(0, 25));
+  EXPECT_TRUE(map.overlaps(0, 45));
+  EXPECT_TRUE(map.overlaps(10, 45));
+  EXPECT_TRUE(map.overlaps(30, 45));
+  EXPECT_TRUE(map.overlaps(35, 36));
+  EXPECT_TRUE(map.overlaps(40, 45));
+  EXPECT_FALSE(map.overlaps(45, 45));
+  EXPECT_TRUE(map.overlaps(60, 60));
+  EXPECT_TRUE(map.overlaps(60, 66));
+  EXPECT_FALSE(map.overlaps(66, 66));
+}
+
+TEST(IntervalMapTest, OverlapsHalfOpen) {
+  UUHalfOpenMap::Allocator allocator;
+  UUHalfOpenMap map(allocator);
+  map.insert(10, 20, 0);
+  map.insert(30, 40, 0);
+  map.insert(50, 60, 0);
+
+  EXPECT_FALSE(map.overlaps(0, 9));
+  EXPECT_FALSE(map.overlaps(0, 10));
+  EXPECT_TRUE(map.overlaps(0, 15));
+  EXPECT_TRUE(map.overlaps(0, 25));
+  EXPECT_TRUE(map.overlaps(0, 45));
+  EXPECT_TRUE(map.overlaps(10, 45));
+  EXPECT_TRUE(map.overlaps(30, 45));
+  EXPECT_TRUE(map.overlaps(35, 36));
+  EXPECT_FALSE(map.overlaps(40, 45));
+  EXPECT_FALSE(map.overlaps(45, 46));
+  EXPECT_FALSE(map.overlaps(60, 61));
+  EXPECT_FALSE(map.overlaps(60, 66));
+  EXPECT_FALSE(map.overlaps(66, 67));
+}
+
 TEST(IntervalMapOverlapsTest, SmallMaps) {
   typedef IntervalMapOverlaps<UUMap,UUMap> UUOverlaps;
   UUMap::Allocator allocator;