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py/qstr: Add support for MICROPY_QSTR_BYTES_IN_HASH=0.

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This disables using qstr hashes altogether, which saves RAM and flash
(two bytes per interned string on a typical build) as well as code size.
On PYBV11 this is worth over 3k flash.

qstr comparison will now be done just by length then data. This affects
qstr_find_strn although this has a negligible performance impact as, for a
given comparison, the length and first character will ~usually be
different anyway.

String hashing (e.g. builtin `hash()` and map.c) now need to compute the
hash dynamically, and for the map case this does come at a performance
cost.

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
This commit is contained in:
Jim Mussared
2023-02-03 16:42:03 +11:00
parent 307ecc5707
commit 7ea503929a
4 changed files with 66 additions and 23 deletions
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27
tools/mpy-tool.py
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@@ -1473,21 +1473,20 @@ def freeze_mpy(firmware_qstr_idents, compiled_modules):
raw_code_count = 0
raw_code_content = 0
print()
print("const qstr_hash_t mp_qstr_frozen_const_hashes[] = {")
qstr_size = {"metadata": 0, "data": 0}
for _, _, _, qbytes in new:
qhash = qstrutil.compute_hash(qbytes, config.MICROPY_QSTR_BYTES_IN_HASH)
print(" %d," % qhash)
print("};")
if config.MICROPY_QSTR_BYTES_IN_HASH:
print()
print("const qstr_hash_t mp_qstr_frozen_const_hashes[] = {")
for _, _, _, qbytes in new:
qhash = qstrutil.compute_hash(qbytes, config.MICROPY_QSTR_BYTES_IN_HASH)
print(" %d," % qhash)
qstr_content += config.MICROPY_QSTR_BYTES_IN_HASH
print("};")
print()
print("const qstr_len_t mp_qstr_frozen_const_lengths[] = {")
for _, _, _, qbytes in new:
print(" %d," % len(qbytes))
qstr_size["metadata"] += (
config.MICROPY_QSTR_BYTES_IN_LEN + config.MICROPY_QSTR_BYTES_IN_HASH
)
qstr_size["data"] += len(qbytes)
qstr_content += config.MICROPY_QSTR_BYTES_IN_LEN
qstr_content += len(qbytes) + 1 # include NUL
print("};")
print()
print("extern const qstr_pool_t mp_qstr_const_pool;")
@@ -1497,14 +1496,12 @@ def freeze_mpy(firmware_qstr_idents, compiled_modules):
print(" true, // is_sorted")
print(" %u, // allocated entries" % qstr_pool_alloc)
print(" %u, // used entries" % len(new))
print(" (qstr_hash_t *)mp_qstr_frozen_const_hashes,")
if config.MICROPY_QSTR_BYTES_IN_HASH:
print(" (qstr_hash_t *)mp_qstr_frozen_const_hashes,")
print(" (qstr_len_t *)mp_qstr_frozen_const_lengths,")
print(" {")
for _, _, qstr, qbytes in new:
print(' "%s",' % qstrutil.escape_bytes(qstr, qbytes))
qstr_content += (
config.MICROPY_QSTR_BYTES_IN_LEN + config.MICROPY_QSTR_BYTES_IN_HASH + len(qbytes) + 1
)
print(" },")
print("};")