Few more cherry-picks to prep for reverse iterator changes (#5386)

Cherry-picks to get some good changes, specifically in STLExtras

---------

Co-authored-by: Pete Cooper <[email protected]>
Co-authored-by: Duncan P. N. Exon Smith <[email protected]>

include/llvm/ADT/STLExtras.h

@@ -200,6 +200,54 @@ inline mapped_iterator<ItTy, FuncTy> map_iterator(const ItTy &I, FuncTy F) {
   return mapped_iterator<ItTy, FuncTy>(I, F);
 }
 
+/// Helper to determine if type T has a member called rbegin().
+template <typename Ty> class has_rbegin_impl {
+  typedef char yes[1];
+  typedef char no[2];
+
+  template <typename Inner>
+  static yes& test(Inner *I, decltype(I->rbegin()) * = nullptr);
+
+  template <typename>
+  static no& test(...);
+
+public:
+  static const bool value = sizeof(test<Ty>(nullptr)) == sizeof(yes);
+};
+
+/// Metafunction to determine if T& or T has a member called rbegin().
+template <typename Ty>
+struct has_rbegin : has_rbegin_impl<typename std::remove_reference<Ty>::type> {
+};
+
+// Returns an iterator_range over the given container which iterates in reverse.
+// Note that the container must have rbegin()/rend() methods for this to work.
+template <typename ContainerTy>
+auto reverse(ContainerTy &&C,
+             typename std::enable_if<has_rbegin<ContainerTy>::value>::type * =
+                 nullptr) -> decltype(make_range(C.rbegin(), C.rend())) {
+  return make_range(C.rbegin(), C.rend());
+}
+
+// Returns a std::reverse_iterator wrapped around the given iterator.
+template <typename IteratorTy>
+std::reverse_iterator<IteratorTy> make_reverse_iterator(IteratorTy It) {
+  return std::reverse_iterator<IteratorTy>(It);
+}
+
+// Returns an iterator_range over the given container which iterates in reverse.
+// Note that the container must have begin()/end() methods which return
+// bidirectional iterators for this to work.
+template <typename ContainerTy>
+auto reverse(
+    ContainerTy &&C,
+    typename std::enable_if<!has_rbegin<ContainerTy>::value>::type * = nullptr)
+    -> decltype(make_range(make_reverse_iterator(std::end(C)),
+                           make_reverse_iterator(std::begin(C)))) {
+  return make_range(make_reverse_iterator(std::end(C)),
+                    make_reverse_iterator(std::begin(C)));
+}
+
 //===----------------------------------------------------------------------===//
 //     Extra additions to <utility>
 //===----------------------------------------------------------------------===//

lib/CodeGen/AsmPrinter/ARMException.cpp

@@ -115,9 +115,7 @@ void ARMException::emitTypeInfos(unsigned TTypeEncoding) {
     Entry = TypeInfos.size();
   }
 
-  for (std::vector<const GlobalValue *>::const_reverse_iterator
-         I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
-    const GlobalValue *GV = *I;
+  for (const GlobalValue *GV : reverse(TypeInfos)) {
     if (VerboseAsm)
       Asm->OutStreamer->AddComment("TypeInfo " + Twine(Entry--));
     Asm->EmitTTypeReference(GV, TTypeEncoding);

unittests/ADT/CMakeLists.txt

@@ -28,6 +28,7 @@ set(ADTSources
   PointerIntPairTest.cpp
   PointerUnionTest.cpp
   PostOrderIteratorTest.cpp
+  RangeAdapterTest.cpp
   SCCIteratorTest.cpp
   SmallPtrSetTest.cpp
   SmallStringTest.cpp

unittests/ADT/RangeAdapterTest.cpp

@@ -0,0 +1,172 @@
+//===- 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;
+  typedef std::vector<int>::const_reverse_iterator const_reverse_iterator;
+  reverse_iterator rbegin() { return Vec.rbegin(); }
+  reverse_iterator rend() { return Vec.rend(); }
+  const_reverse_iterator rbegin() const { return Vec.rbegin(); }
+  const_reverse_iterator rend() const { 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 {
+  mutable std::vector<int> Vec;
+
+public:
+  BidirectionalVector(std::initializer_list<int> list) : Vec(list) {}
+
+  typedef std::vector<int>::iterator iterator;
+  iterator begin() const;
+  iterator end() const;
+
+  typedef std::vector<int>::reverse_iterator reverse_iterator;
+  reverse_iterator rbegin() const { return Vec.rbegin(); }
+  reverse_iterator rend() const { return Vec.rend(); }
+};
+
+/// This is the same as BidirectionalVector but with the addition of const
+/// begin/rbegin methods to ensure that the type traits for has_rbegin works.
+class BidirectionalVectorConsts {
+  std::vector<int> Vec;
+
+public:
+  BidirectionalVectorConsts(std::initializer_list<int> list) : Vec(list) {}
+
+  typedef std::vector<int>::iterator iterator;
+  typedef std::vector<int>::const_iterator const_iterator;
+  iterator begin();
+  iterator end();
+  const_iterator begin() const;
+  const_iterator end() const;
+
+  typedef std::vector<int>::reverse_iterator reverse_iterator;
+  typedef std::vector<int>::const_reverse_iterator const_reverse_iterator;
+  reverse_iterator rbegin() { return Vec.rbegin(); }
+  reverse_iterator rend() { return Vec.rend(); }
+  const_reverse_iterator rbegin() const { return Vec.rbegin(); }
+  const_reverse_iterator rend() const { return Vec.rend(); }
+};
+
+/// Check that types with custom iterators work.
+class CustomIteratorVector {
+  mutable std::vector<int> V;
+
+public:
+  CustomIteratorVector(std::initializer_list<int> list) : V(list) {}
+
+  typedef std::vector<int>::iterator iterator;
+  class reverse_iterator {
+    std::vector<int>::iterator I;
+
+  public:
+    reverse_iterator() = default;
+    reverse_iterator(const reverse_iterator &) = default;
+    reverse_iterator &operator=(const reverse_iterator &) = default;
+
+    explicit reverse_iterator(std::vector<int>::iterator I) : I(I) {}
+
+    reverse_iterator &operator++() {
+      --I;
+      return *this;
+    }
+    reverse_iterator &operator--() {
+      ++I;
+      return *this;
+    }
+    int &operator*() const { return *std::prev(I); }
+    int *operator->() const { return &*std::prev(I); }
+    friend bool operator==(const reverse_iterator &L,
+                           const reverse_iterator &R) {
+      return L.I == R.I;
+    }
+    friend bool operator!=(const reverse_iterator &L,
+                           const reverse_iterator &R) {
+      return !(L == R);
+    }
+  };
+
+  iterator begin() const { return V.begin(); }
+  iterator end()  const { return V.end(); }
+  reverse_iterator rbegin() const { return reverse_iterator(V.end()); }
+  reverse_iterator rend() const { return reverse_iterator(V.begin()); }
+};
+
+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>, CustomIteratorVector,
+                         ReverseOnlyVector, BidirectionalVector,
+                         BidirectionalVectorConsts>
+    RangeAdapterRValueTestTypes;
+TYPED_TEST_CASE(RangeAdapterRValueTest, RangeAdapterRValueTestTypes);
+
+TYPED_TEST(RangeAdapterRValueTest, TrivialOperation) {
+  TestRev(reverse(TypeParam({0, 1, 2, 3})));
+}
+
+TYPED_TEST(RangeAdapterRValueTest, HasRbegin) {
+  static_assert(has_rbegin<TypeParam>::value, "rbegin() should be defined");
+}
+
+TYPED_TEST(RangeAdapterRValueTest, RangeType) {
+  static_assert(
+      std::is_same<
+          decltype(reverse(*static_cast<TypeParam *>(nullptr)).begin()),
+          decltype(static_cast<TypeParam *>(nullptr)->rbegin())>::value,
+      "reverse().begin() should have the same type as rbegin()");
+  static_assert(
+      std::is_same<
+          decltype(reverse(*static_cast<const TypeParam *>(nullptr)).begin()),
+          decltype(static_cast<const TypeParam *>(nullptr)->rbegin())>::value,
+      "reverse().begin() should have the same type as rbegin() [const]");
+}
+
+} // anonymous namespace