Have just optimized some of the code and pushed another change as 69dce1c552.

ran both master and 69dce1c552 using pyperformance with PGO:

➜  ~ python3.8 -m perf compare_to master.json 69dce1c552.json --table 
+-------------------------+---------+-----------------------------+
| Benchmark               | master  | 69dce1c552                  |
+=========================+=========+=============================+
| 2to3                    | 432 ms  | 426 ms: 1.02x faster (-2%)  |
+-------------------------+---------+-----------------------------+
| chaos                   | 157 ms  | 155 ms: 1.01x faster (-1%)  |
+-------------------------+---------+-----------------------------+
| crypto_pyaes            | 154 ms  | 153 ms: 1.00x faster (-0%)  |
+-------------------------+---------+-----------------------------+
| dulwich_log             | 123 ms  | 124 ms: 1.00x slower (+0%)  |
+-------------------------+---------+-----------------------------+
| fannkuch                | 603 ms  | 600 ms: 1.01x faster (-1%)  |
+-------------------------+---------+-----------------------------+
| float                   | 153 ms  | 154 ms: 1.01x slower (+1%)  |
+-------------------------+---------+-----------------------------+
| go                      | 323 ms  | 326 ms: 1.01x slower (+1%)  |
+-------------------------+---------+-----------------------------+
| hexiom                  | 13.6 ms | 13.5 ms: 1.01x faster (-1%) |
+-------------------------+---------+-----------------------------+
| json_dumps              | 18.1 ms | 17.9 ms: 1.01x faster (-1%) |
+-------------------------+---------+-----------------------------+
| logging_format          | 13.2 us | 13.8 us: 1.05x slower (+5%) |
+-------------------------+---------+-----------------------------+
| logging_silent          | 266 ns  | 280 ns: 1.05x slower (+5%)  |
+-------------------------+---------+-----------------------------+
| logging_simple          | 12.4 us | 13.1 us: 1.06x slower (+6%) |
+-------------------------+---------+-----------------------------+
| meteor_contest          | 145 ms  | 132 ms: 1.10x faster (-9%)  |
+-------------------------+---------+-----------------------------+
| nbody                   | 179 ms  | 172 ms: 1.04x faster (-4%)  |
+-------------------------+---------+-----------------------------+
| nqueens                 | 138 ms  | 134 ms: 1.03x faster (-3%)  |
+-------------------------+---------+-----------------------------+
| pathlib                 | 56.4 ms | 55.6 ms: 1.01x faster (-1%) |
+-------------------------+---------+-----------------------------+
| pickle                  | 15.0 us | 15.4 us: 1.03x slower (+3%) |
+-------------------------+---------+-----------------------------+
| pickle_pure_python      | 620 us  | 617 us: 1.01x faster (-1%)  |
+-------------------------+---------+-----------------------------+
| raytrace                | 696 ms  | 691 ms: 1.01x faster (-1%)  |
+-------------------------+---------+-----------------------------+
| regex_compile           | 242 ms  | 243 ms: 1.00x slower (+0%)  |
+-------------------------+---------+-----------------------------+
| scimark_monte_carlo     | 140 ms  | 143 ms: 1.02x slower (+2%)  |
+-------------------------+---------+-----------------------------+
| scimark_sparse_mat_mult | 5.90 ms | 5.94 ms: 1.01x slower (+1%) |
+-------------------------+---------+-----------------------------+
| spectral_norm           | 194 ms  | 196 ms: 1.01x slower (+1%)  |
+-------------------------+---------+-----------------------------+
| sympy_str               | 246 ms  | 245 ms: 1.00x faster (-0%)  |
+-------------------------+---------+-----------------------------+
| telco                   | 8.42 ms | 8.31 ms: 1.01x faster (-1%) |
+-------------------------+---------+-----------------------------+
| unpack_sequence         | 59.2 ns | 59.7 ns: 1.01x slower (+1%) |
+-------------------------+---------+-----------------------------+
| unpickle                | 21.2 us | 21.4 us: 1.01x slower (+1%) |
+-------------------------+---------+-----------------------------+
| unpickle_list           | 5.73 us | 5.81 us: 1.01x slower (+1%) |
+-------------------------+---------+-----------------------------+
| unpickle_pure_python    | 471 us  | 467 us: 1.01x faster (-1%)  |
+-------------------------+---------+-----------------------------+
| xml_etree_iterparse     | 142 ms  | 143 ms: 1.01x slower (+1%)  |
+-------------------------+---------+-----------------------------+
| xml_etree_generate      | 139 ms  | 137 ms: 1.02x faster (-2%)  |
+-------------------------+---------+-----------------------------+
| xml_etree_process       | 109 ms  | 108 ms: 1.01x faster (-1%)  |
+-------------------------+---------+-----------------------------+

Not significant (21): deltablue; django_template; html5lib; json_loads; mako; pickle_dict; pickle_list; pidigits; python_startup; python_startup_no_site; regex_dna; regex_effbot; regex_v8; richards; scimark_fft; scimark_lu; scimark_sor; sympy_expand; sympy_integrate; sympy_sum; xml_etree_parse

I'd like to look at the way range object LengthHint works, it looks like the path for those is not ideal and could use some optimization. Also, BUILD_LIST_PREALLOC uses the Iterator, not the actual object, so you can't use the much faster _HasLen and PyObject_Length().

I'm going to look at how __length_hint__ could be optimized for iterators that would make the smaller range cases more efficient.

meteor_contest uses a lot of list comprehensions, so should show the impact for the patch.