[libc++] Add regression test for std::hash implementation in ABI v1

[Mordante]

Thanks, LGTM when the CI is happy.

[ldionne]

Trigger AIX ci

[ldionne]

Fix CI on AIX

[ldionne]

CI's passing, red bots are flakes.

libcxx/test/libcxx/utilities/utility/__murmur2_or_cityhash.abi-v1.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// Test the CityHash implementation is correct.
-
 // UNSUPPORTED: c++03
 
-// In ABI v1, our CityHash implementation is incorrect and fixing it would
-// be an ABI break.
-// REQUIRES: libcpp-abi-version=2
+// Test that the CityHash implementation returns the results we expect.
+//
+// Note that this implementation is technically incorrect, however changing it is
+// an ABI break. This test ensures that we don't unintentionally break the ABI v1
+// by "fixing" the hash implementation.
+// REQUIRES: libcpp-abi-version=1
 
 #include <cassert>
 #include <string>
 #include <utility>
 
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 #  define CHOOSE_BY_ENDIANESS(little, big) (little)
 #else
 #  define CHOOSE_BY_ENDIANESS(little, big) (big)
 #endif
 
 std::string CityHash[] = {
     {/* "abcdefgh" */ "\x61\x62\x63\x64\x65\x66\x67\x68"},
     {/* "abcDefgh" */ "\x61\x62\x63\x44\x65\x66\x67\x68"},
     {/* "CityHash" */ "\x43\x69\x74\x79\x48\x61\x73\x68"},
     {/* "CitYHash" */ "\x43\x69\x74\x59\x48\x61\x73\x68"},
 };
 
 int main(int, char**) {
   const std::pair<std::string, uint64_t> TestCases[] = {
-      {CityHash[0], CHOOSE_BY_ENDIANESS(0x4382a8d0fe8edb17ULL, 0xca84e809bef16fbcULL)},
-      {CityHash[1], CHOOSE_BY_ENDIANESS(0xecefb080a6854061ULL, 0xd7feb824250272dcULL)},
-      {CityHash[2], CHOOSE_BY_ENDIANESS(0x169ea3aebf908d6dULL, 0xea8cef3ca6f6e368ULL)},
-      {CityHash[3], CHOOSE_BY_ENDIANESS(0xe18298a2760f09faULL, 0xf33a7700bb7a94a8ULL)},
+      {CityHash[0], CHOOSE_BY_ENDIANESS(0x87c69099911bab7eULL, 0x7eab1b919990c687ULL)},
+      {CityHash[1], CHOOSE_BY_ENDIANESS(0x87c69099911bab7eULL, 0x7eab1b919990c687ULL)},
+      {CityHash[2], CHOOSE_BY_ENDIANESS(0x85322632e188694aULL, 0x4a6988e132263285ULL)},
+      {CityHash[3], CHOOSE_BY_ENDIANESS(0x85322632e188694aULL, 0x4a6988e132263285ULL)},
   };
 
   std::__murmur2_or_cityhash<uint64_t> h64;
   for (const auto& test_case : TestCases) {
     assert(h64(test_case.first.data(), test_case.first.size()) == test_case.second);
   }
   return 0;
 }

libcxx/test/libcxx/utilities/utility/__murmur2_or_cityhash.abi-v2.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// Test the CityHash implementation is correct.
-
 // UNSUPPORTED: c++03
 
+// Test that the CityHash implementation is correct.
+//
 // In ABI v1, our CityHash implementation is incorrect and fixing it would
 // be an ABI break.
 // REQUIRES: libcpp-abi-version=2
 
 #include <cassert>
 #include <string>
 #include <utility>