[LLVMSupport] Re-import LLVMSupport .cpp and .h files from 9ff3a9759b7c2f146e7f46e4aebc60453c577c5a from apple/llvm-project

Done via the following commands, while having llvm-project checked out at 9ff3a9759b7c2f146e7f46e4aebc60453c577c5a, a
commit on the stable/20210726 branch of apple/llvm-project, <swiftlang/llvm-project@9ff3a97>:

for i in swift/stdlib/public/LLVMSupport/*.cpp ; do cp llvm-project/llvm/lib/Support/$(basename $i) $i ; done
for i in swift/stdlib/include/llvm/ADT/*.h; do cp llvm-project/llvm/include/llvm/ADT/$(basename $i) $i ; done
for i in swift/stdlib/include/llvm/Support/*.h; do cp llvm-project/llvm/include/llvm/Support/$(basename $i) $i ; done
cp llvm-project/llvm/include/llvm/ADT/ScopeExit.h swift/stdlib/include/llvm/ADT/ScopeExit.h
cp llvm-project/llvm/include/llvm/ADT/Twine.h swift/stdlib/include/llvm/ADT/Twine.h
cp llvm-project/llvm/include/llvm/Support/raw_ostream.h swift/stdlib/include/llvm/Support/raw_ostream.h

Author: kubamracek

stdlib/include/llvm/ADT/ArrayRef.h

@@ -24,9 +24,10 @@
 #include <type_traits>
 #include <vector>
 
-inline namespace __swift { inline namespace __runtime {
 namespace llvm {
 
+  template<typename T> struct DenseMapInfo;
+
   /// ArrayRef - Represent a constant reference to an array (0 or more elements
   /// consecutively in memory), i.e. a start pointer and a length.  It allows
   /// various APIs to take consecutive elements easily and conveniently.
@@ -41,10 +42,17 @@ namespace llvm {
   template<typename T>
   class LLVM_GSL_POINTER LLVM_NODISCARD ArrayRef {
   public:
-    using iterator = const T *;
-    using const_iterator = const T *;
-    using size_type = size_t;
+    using value_type = T;
+    using pointer = value_type *;
+    using const_pointer = const value_type *;
+    using reference = value_type &;
+    using const_reference = const value_type &;
+    using iterator = const_pointer;
+    using const_iterator = const_pointer;
     using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using size_type = size_t;
+    using difference_type = ptrdiff_t;
 
   private:
     /// The start of the array, in an external buffer.
@@ -298,8 +306,17 @@ namespace llvm {
   template<typename T>
   class LLVM_NODISCARD MutableArrayRef : public ArrayRef<T> {
   public:
-    using iterator = T *;
+    using value_type = T;
+    using pointer = value_type *;
+    using const_pointer = const value_type *;
+    using reference = value_type &;
+    using const_reference = const value_type &;
+    using iterator = pointer;
+    using const_iterator = const_pointer;
     using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using size_type = size_t;
+    using difference_type = ptrdiff_t;
 
     /// Construct an empty MutableArrayRef.
     /*implicit*/ MutableArrayRef() = default;
@@ -554,7 +571,35 @@ namespace llvm {
     return hash_combine_range(S.begin(), S.end());
   }
 
+  // Provide DenseMapInfo for ArrayRefs.
+  template <typename T> struct DenseMapInfo<ArrayRef<T>> {
+    static inline ArrayRef<T> getEmptyKey() {
+      return ArrayRef<T>(
+          reinterpret_cast<const T *>(~static_cast<uintptr_t>(0)), size_t(0));
+    }
+
+    static inline ArrayRef<T> getTombstoneKey() {
+      return ArrayRef<T>(
+          reinterpret_cast<const T *>(~static_cast<uintptr_t>(1)), size_t(0));
+    }
+
+    static unsigned getHashValue(ArrayRef<T> Val) {
+      assert(Val.data() != getEmptyKey().data() &&
+             "Cannot hash the empty key!");
+      assert(Val.data() != getTombstoneKey().data() &&
+             "Cannot hash the tombstone key!");
+      return (unsigned)(hash_value(Val));
+    }
+
+    static bool isEqual(ArrayRef<T> LHS, ArrayRef<T> RHS) {
+      if (RHS.data() == getEmptyKey().data())
+        return LHS.data() == getEmptyKey().data();
+      if (RHS.data() == getTombstoneKey().data())
+        return LHS.data() == getTombstoneKey().data();
+      return LHS == RHS;
+    }
+  };
+
 } // end namespace llvm
-}} // namespace swift::runtime
 
 #endif // LLVM_ADT_ARRAYREF_H