[STLExtras] Add distance() for ranges, pred_size(), and succ_size()

This commit adds a wrapper for std::distance() which works with ranges.
As it would be a common case to write `distance(predecessors(BB))`, this
also introduces `pred_size()` and `succ_size()` helpers to make that
easier to write.

Differential Revision: https://reviews.llvm.org/D46668

llvm-svn: 332057

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/IteratorTest.cpp b/llvm/unittests/ADT/IteratorTest.cpp
index 5b9320e80a3..69033bbf593 100644
--- a/llvm/unittests/ADT/IteratorTest.cpp
+++ b/llvm/unittests/ADT/IteratorTest.cpp
@@ -365,4 +365,12 @@ TEST(ZipIteratorTest, Reverse) {
   EXPECT_TRUE(all_of(ascending, [](unsigned n) { return (n & 0x01) == 0; }));
 }
 
+TEST(RangeTest, Distance) {
+  std::vector<int> v1;
+  std::vector<int> v2{1, 2, 3};
+
+  EXPECT_EQ(std::distance(v1.begin(), v1.end()), distance(v1));
+  EXPECT_EQ(std::distance(v2.begin(), v2.end()), distance(v2));
+}
+
 } // anonymous namespace