With the patch:
root@adelaide:~/llvm-project# ./build/libcxx/benchmarks/unordered_set_operations.libcxx.out --benchmark_filter='BM_Rehash' --benchmark_min_time=3.0
2022-06-17T23:50:20+00:00
Running ./build/libcxx/benchmarks/unordered_set_operations.libcxx.out
Run on (4 X 2394.37 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x4)
  L1 Instruction 32 KiB (x4)
  L2 Unified 4096 KiB (x4)
  L3 Unified 16384 KiB (x2)
Load Average: 0.94, 1.60, 0.91
----------------------------------------------------------------------------------
Benchmark                                        Time             CPU   Iterations
----------------------------------------------------------------------------------
BM_Rehash/unordered_set_string_arg/1024      44848 ns        44846 ns        96172

On main:
root@adelaide:~/llvm-project# ./build/libcxx/benchmarks/unordered_set_operations.libcxx.out --benchmark_filter='BM_Rehash' --benchmark_min_time=3.0
2022-06-17T23:56:19+00:00
Running ./build/libcxx/benchmarks/unordered_set_operations.libcxx.out
Run on (4 X 2394.37 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x4)
  L1 Instruction 32 KiB (x4)
  L2 Unified 4096 KiB (x4)
  L3 Unified 16384 KiB (x2)
Load Average: 2.41, 2.44, 1.47
----------------------------------------------------------------------------------
Benchmark                                        Time             CPU   Iterations
----------------------------------------------------------------------------------
BM_Rehash/unordered_set_string_arg/1024      55711 ns        55706 ns        74198