[ADT] Add hash_combine_range that takes a range (NFC)

The new function will allow us to replace:

  hash_combine_range(Ops.begin(), Ops.end())

with:

  hash_combine_range(Ops)

Author: kazutakahirata

llvm/include/llvm/ADT/Hashing.h

@@ -44,6 +44,7 @@
 #ifndef LLVM_ADT_HASHING_H
 #define LLVM_ADT_HASHING_H
 
+#include "llvm/ADT/ADL.h"
 #include "llvm/Config/abi-breaking.h"
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -469,6 +470,10 @@ hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) {
   return ::llvm::hashing::detail::hash_combine_range_impl(first, last);
 }
 
+// A wrapper for hash_combine_range above.
+template <typename RangeT> hash_code hash_combine_range(RangeT &&R) {
+  return hash_combine_range(adl_begin(R), adl_end(R));
+}
 
 // Implementation details for hash_combine.
 namespace hashing {

llvm/unittests/ADT/HashingTest.cpp

@@ -166,15 +166,19 @@ TEST(HashingTest, HashCombineRangeBasicTest) {
   hash_code arr1_hash = hash_combine_range(begin(arr1), end(arr1));
   EXPECT_NE(dummy_hash, arr1_hash);
   EXPECT_EQ(arr1_hash, hash_combine_range(begin(arr1), end(arr1)));
+  EXPECT_EQ(arr1_hash, hash_combine_range(arr1));
 
   const std::vector<int> vec(begin(arr1), end(arr1));
   EXPECT_EQ(arr1_hash, hash_combine_range(vec.begin(), vec.end()));
+  EXPECT_EQ(arr1_hash, hash_combine_range(vec));
 
   const std::list<int> list(begin(arr1), end(arr1));
   EXPECT_EQ(arr1_hash, hash_combine_range(list.begin(), list.end()));
+  EXPECT_EQ(arr1_hash, hash_combine_range(list));
 
   const std::deque<int> deque(begin(arr1), end(arr1));
   EXPECT_EQ(arr1_hash, hash_combine_range(deque.begin(), deque.end()));
+  EXPECT_EQ(arr1_hash, hash_combine_range(deque));
 
   const int arr2[] = { 3, 2, 1 };
   hash_code arr2_hash = hash_combine_range(begin(arr2), end(arr2));