Add more checks to IntervalMapOverlaps::advance() to ensure that advanceTo sees

monotonic keys.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122093 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/IntervalMap.h

@@ -2040,6 +2040,21 @@ class IntervalMapOverlaps {
   void advance() {
     if (!valid())
       return;
+
+    if (Traits::stopLess(posA.stop(), posB.start())) {
+      // A ends before B begins. Catch up.
+      posA.advanceTo(posB.start());
+      if (!posA.valid() || !Traits::stopLess(posB.stop(), posA.start()))
+        return;
+    } else if (Traits::stopLess(posB.stop(), posA.start())) {
+      // B ends before A begins. Catch up.
+      posB.advanceTo(posA.start());
+      if (!posB.valid() || !Traits::stopLess(posA.stop(), posB.start()))
+        return;
+    } else
+      // Already overlapping.
+      return;
+
     for (;;) {
       // Make a.end > b.start.
       posA.advanceTo(posB.start());
@@ -2076,7 +2091,7 @@ public:
     return Traits::startLess(ak, bk) ? bk : ak;
   }
 
-  /// stop - End of the overlaping interval.
+  /// stop - End of the overlapping interval.
   KeyType stop() const {
     KeyType ak = a().stop();
     KeyType bk = b().stop();
@@ -2086,20 +2101,12 @@ public:
   /// skipA - Move to the next overlap that doesn't involve a().
   void skipA() {
     ++posA;
-    if (!posA.valid() || !Traits::stopLess(posB.stop(), posA.start()))
-      return;
-    // Second half-loop of advance().
-    posB.advanceTo(posA.start());
-    if (!posB.valid() || !Traits::stopLess(posA.stop(), posB.start()))
-      return;
     advance();
   }
 
   /// skipB - Move to the next overlap that doesn't involve b().
   void skipB() {
     ++posB;
-    if (!posB.valid() || !Traits::stopLess(posA.stop(), posB.start()))
-      return;
     advance();
   }
 
@@ -2116,7 +2123,12 @@ public:
   /// advanceTo - Move to the first overlapping interval with
   /// stopLess(x, stop()).
   void advanceTo(KeyType x) {
+    if (!valid())
+      return;
+    // Make sure advanceTo sees monotonic keys.
+    if (Traits::stopLess(posA.stop(), x))
       posA.advanceTo(x);
+    if (Traits::stopLess(posB.stop(), x))
       posB.advanceTo(x);
     advance();
   }

unittests/ADT/IntervalMapTest.cpp

@@ -659,6 +659,19 @@ TEST(IntervalMapOverlapsTest, BigMaps) {
   ++AB;
   EXPECT_FALSE(AB.valid());
 
+  // Test advanceTo.
+  UUOverlaps AB2(mapA, mapB);
+  AB2.advanceTo(410);
+  ASSERT_TRUE(AB2.valid());
+  EXPECT_EQ(410u, AB2.a().start());
+  EXPECT_EQ(402u, AB2.b().start());
+
+  // It is valid to advanceTo with any monotonic sequence.
+  AB2.advanceTo(411);
+  ASSERT_TRUE(AB2.valid());
+  EXPECT_EQ(410u, AB2.a().start());
+  EXPECT_EQ(402u, AB2.b().start());
+
   // Check reversed maps.
   UUOverlaps BA(mapB, mapA);
   ASSERT_TRUE(BA.valid());
@@ -686,6 +699,18 @@ TEST(IntervalMapOverlapsTest, BigMaps) {
   EXPECT_EQ(600u, BA.a().start());
   ++BA;
   EXPECT_FALSE(BA.valid());
+
+  // Test advanceTo.
+  UUOverlaps BA2(mapB, mapA);
+  BA2.advanceTo(410);
+  ASSERT_TRUE(BA2.valid());
+  EXPECT_EQ(410u, BA2.b().start());
+  EXPECT_EQ(402u, BA2.a().start());
+
+  BA2.advanceTo(411);
+  ASSERT_TRUE(BA2.valid());
+  EXPECT_EQ(410u, BA2.b().start());
+  EXPECT_EQ(402u, BA2.a().start());
 }
 
 } // namespace