25ff5b52d9
Allows optimisation of cases like:
import micropython
_DEBUG = micropython.const(False)
if _DEBUG:
print('Debugging info')
Previously the 'if' statement was only optimised out if the type of the
const() argument was integer.
The change is implemented in a way that makes the compiler slightly smaller
(-16 bytes on PYBV11) but compilation will also be very slightly slower.
As a bonus, if const support is enabled then the compiler can now optimise
const truthy/falsey expressions of other types, like:
while "something":
pass
... unclear if that is useful, but perhaps it could be.
Signed-off-by: Angus Gratton <angus@redyak.com.au>
70 lines
1.5 KiB
Python
70 lines
1.5 KiB
Python
# cmdline: -v -v
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# Test constant-related bytecode optimisations
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# (constant folding, compile-time if/while evaluation, etc.)
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from micropython import const
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import sys
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try:
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sys.settrace
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# if MICROPY_PY_SYS_SETTRACE is enabled, compile-time const optimizations
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# are disabled so the bytecode output is very different
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print("SKIP")
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raise SystemExit
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except AttributeError:
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pass
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_STR = const("foo")
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_EMPTY_TUPLE = const(())
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_TRUE = const(True)
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_FALSE = const(False)
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_SMALLINT = const(33)
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_ZERO = const(0)
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# Bytecode generated for these if/while statements should contain no JUMP_IF
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# and no instances of string 'Eliminated'
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if _STR or _EMPTY_TUPLE:
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print("Kept")
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if _STR and _EMPTY_TUPLE:
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print("Eliminated")
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if _TRUE:
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print("Kept")
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if _SMALLINT:
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print("Kept")
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if _ZERO and _SMALLINT:
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print("Eliminated")
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if _FALSE:
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print("Eliminated")
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while _SMALLINT:
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print("Kept")
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break
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while _ZERO:
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print("Eliminated")
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while _FALSE:
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print("Eliminated")
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# These values are stored in variables, and therefore bytecode will contain JUMP_IF
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a = _EMPTY_TUPLE or _STR
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if a == _STR:
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print("Kept")
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b = _SMALLINT and _STR
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if b == _STR:
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print("Kept")
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# The compiler is also unable to optimise these expressions, even though the arguments are const,
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# so these also contain JUMP_IF
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if (_EMPTY_TUPLE or _STR) == _STR:
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print("Kept")
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if (_EMPTY_TUPLE and _STR) == _STR:
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print("Not Eliminated")
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if (not _STR) == _FALSE:
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print("Kept")
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assert True
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