There were two issues with the existing code:
1. "1 << i" is computed as a 32-bit number so would overflow when
executed on 64-bit machines (when mp_uint_t is 64-bit). This meant that
*args beyond 32 positions would not be handled correctly.
2. star_args must fit as a positive small int so that it is encoded
correctly in the emitted code. MP_SMALL_INT_BITS is too big because it
overflows a small int by 1 bit. MP_SMALL_INT_BITS - 1 does not work
because it produces a signed small int which is then sign extended when
extracted (even by mp_obj_get_int_truncated), and this sign extension
means that any position arg after *args is also treated as a star-arg.
So the maximum bit position is MP_SMALL_INT_BITS - 2. This means that
MP_OBJ_SMALL_INT_VALUE() can be used instead of
mp_obj_get_int_truncated() to get the value of star_args.
These issues are fixed by this commit, and a test added.
Signed-off-by: Damien George <damien@micropython.org>
This commit introduces changes:
- All jump opcodes are changed to have variable length arguments, of either
1 or 2 bytes (previously they were fixed at 2 bytes). In most cases only
1 byte is needed to encode the short jump offset, saving bytecode size.
- The bytecode emitter now selects 1 byte jump arguments when the jump
offset is guaranteed to fit in 1 byte. This is achieved by checking if
the code size changed during the last pass and, if it did (if it shrank),
then requesting that the compiler make another pass to get the correct
offsets of the now-smaller code. This can continue multiple times until
the code stabilises. The code can only ever shrink so this iteration is
guaranteed to complete. In most cases no extra passes are needed, the
original 4 passes are enough to get it right by the 4th pass (because the
2nd pass computes roughly the correct labels and the 3rd pass computes
the correct size for the jump argument).
This change to the jump opcode encoding reduces .mpy files and RAM usage
(when bytecode is in RAM) by about 2% on average.
The performance of the VM is not impacted, at least within measurment of
the performance benchmark suite.
Code size is reduced for builds that include a decent amount of frozen
bytecode. ARM Cortex-M builds without any frozen code increase by about
350 bytes.
Signed-off-by: Damien George <damien@micropython.org>
This adds the Python files in the tests/ directory to be formatted with
./tools/codeformat.py. The basics/ subdirectory is excluded for now so we
aren't changing too much at once.
In a few places `# fmt: off`/`# fmt: on` was used where the code had
special formatting for readability or where the test was actually testing
the specific formatting.
Keeping all the stress related tests in one place makes it easier to
stress-test a given port, and to also not run such tests on ports that
can't handle them.
There is a finite list of ascending primes used for the size of a hash
table, and this test tests that the code can handle a dict larger than the
maximum value in that list of primes. Adding this tests gets py/map.c to
100% coverage.
