From 328eb0d3282a34b7a96bdc18df463227b98f25fc Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Fri, 19 Nov 2010 23:28:53 +0000
Subject: [PATCH] Support backwards iteration starting from end().

llvm-svn: 119871
---
 include/llvm/ADT/IntervalMap.h    |  2 +-
 unittests/ADT/IntervalMapTest.cpp | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/llvm/ADT/IntervalMap.h b/include/llvm/ADT/IntervalMap.h
index b128f31a8d2..dd4eec3c63c 100644
--- a/include/llvm/ADT/IntervalMap.h
+++ b/include/llvm/ADT/IntervalMap.h
@@ -1235,7 +1235,7 @@ public:
     if (!branched()) {
       assert(rootOffset && "Cannot decrement begin()");
       --rootOffset;
-    } else if (treeLeafOffset())
+    } else if (valid() && treeLeafOffset())
       --treeLeafOffset();
     else
       treeDecrement();
diff --git a/unittests/ADT/IntervalMapTest.cpp b/unittests/ADT/IntervalMapTest.cpp
index 5c8b61f278d..c7def84340a 100644
--- a/unittests/ADT/IntervalMapTest.cpp
+++ b/unittests/ADT/IntervalMapTest.cpp
@@ -352,6 +352,16 @@ TEST(IntervalMapTest, Branched) {
   EXPECT_FALSE(I.valid());
   EXPECT_TRUE(I == map.end());
 
+  // Backwards iteration.
+  for (unsigned i = 99; i; --i) {
+    --I;
+    ASSERT_TRUE(I.valid());
+    EXPECT_EQ(10*i, I.start());
+    EXPECT_EQ(10*i+5, I.stop());
+    EXPECT_EQ(i, *I);
+  }
+  EXPECT_TRUE(I == map.begin());
+
 }
 
 } // namespace