Reapply "Add reverse(ContainerTy) range adapter."

This reverts commit r243567, which ultimately reapplies r243563.

The fix here was to use std::enable_if for overload resolution.  Thanks to David
Blaikie for lots of help on this, and for the extra tests!

Original commit message follows:

For cases where we needed a foreach loop in reverse over a container,
we had to do something like

 for (const GlobalValue *GV : make_range(TypeInfos.rbegin(),
                                         TypeInfos.rend())) {

This provides a convenience method which shortens this to

 for (const GlobalValue *GV : reverse(TypeInfos)) {

There are 2 versions of this, with a preference to the rbegin() version.

The first uses rbegin() and rend() to construct an iterator_range.

The second constructs an iterator_range from the begin() and end() methods
wrapped in std::reverse_iterator's.

Reviewed by David Blaikie.

llvm-svn: 243581

1 files changed, 83 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/RangeAdapterTest.cpp b/llvm/unittests/ADT/RangeAdapterTest.cpp
new file mode 100644
index 00000000000..634f5bb990d
--- /dev/null
+++ b/llvm/unittests/ADT/RangeAdapterTest.cpp
@@ -0,0 +1,83 @@
+//===- RangeAdapterTest.cpp - Unit tests for range adapters  --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/iterator_range.h"
+#include "llvm/ADT/STLExtras.h"
+#include "gtest/gtest.h"
+
+#include <iterator>
+#include <list>
+#include <vector>
+
+using namespace llvm;
+
+namespace {
+
+// A wrapper around vector which exposes rbegin(), rend().
+class ReverseOnlyVector {
+  std::vector<int> Vec;
+
+public:
+  ReverseOnlyVector(std::initializer_list<int> list) : Vec(list) {}
+
+  typedef std::vector<int>::reverse_iterator reverse_iterator;
+  reverse_iterator rbegin() { return Vec.rbegin(); }
+  reverse_iterator rend() { return Vec.rend(); }
+};
+
+// A wrapper around vector which exposes begin(), end(), rbegin() and rend().
+// begin() and end() don't have implementations as this ensures that we will
+// get a linker error if reverse() chooses begin()/end() over rbegin(), rend().
+class BidirectionalVector {
+  std::vector<int> Vec;
+
+public:
+  BidirectionalVector(std::initializer_list<int> list) : Vec(list) {}
+
+  typedef std::vector<int>::iterator iterator;
+  iterator begin();
+  iterator end();
+
+  typedef std::vector<int>::reverse_iterator reverse_iterator;
+  reverse_iterator rbegin() { return Vec.rbegin(); }
+  reverse_iterator rend() { return Vec.rend(); }
+};
+
+template <typename R> void TestRev(const R &r) {
+  int counter = 3;
+  for (int i : r)
+    EXPECT_EQ(i, counter--);
+}
+
+// Test fixture
+template <typename T> class RangeAdapterLValueTest : public ::testing::Test {};
+
+typedef ::testing::Types<std::vector<int>, std::list<int>, int[4]>
+    RangeAdapterLValueTestTypes;
+TYPED_TEST_CASE(RangeAdapterLValueTest, RangeAdapterLValueTestTypes);
+
+TYPED_TEST(RangeAdapterLValueTest, TrivialOperation) {
+  TypeParam v = {0, 1, 2, 3};
+  TestRev(reverse(v));
+
+  const TypeParam c = {0, 1, 2, 3};
+  TestRev(reverse(c));
+}
+
+template <typename T> struct RangeAdapterRValueTest : testing::Test {};
+
+typedef ::testing::Types<std::vector<int>, std::list<int>, ReverseOnlyVector,
+                         BidirectionalVector> RangeAdapterRValueTestTypes;
+TYPED_TEST_CASE(RangeAdapterRValueTest, RangeAdapterRValueTestTypes);
+
+TYPED_TEST(RangeAdapterRValueTest, TrivialOperation) {
+  TestRev(reverse(TypeParam({0, 1, 2, 3})));
+}
+
+} // anonymous namespace