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d38f9f8bee
Estimated hours taken: 1 Change the bit shift functions to perform checking to avoid implementation defined behaviour. library/int.m: Add checking to `int:<<' and `int:>>'. Add `int:unchecked_left_shift' and `int:unchecked_right_shift' which do not perform any checking. compiler/code_util.m: Replace `int:<<' and `int:>>' with `int:unchecked_left_shift' and `int:unchecked_right_shift' in the builtin table. NEWS: Mention the changes to int.m. tests/hard_coded/Mmakefile: tests/hard_coded/shift_test.m: tests/hard_coded/shift_test.exp: Test the shift functions.
31 lines
666 B
Plaintext
31 lines
666 B
Plaintext
64 << 0 = 64 (64)
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64 << 2 = 256 (256)
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-64 << 2 = -256 (-256)
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64 << -2 = 16 (16)
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-64 << -2 = -16 (-16)
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64 << -256 = 0 (0)
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-64 << -256 = -1 (-1)
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25 << 3 = 200 (200)
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-25 << 3 = -200 (-200)
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25 << -3 = 3 (3)
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-25 << -3 = -4 (-4)
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64 >> 0 = 64 (64)
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64 >> 2 = 16 (16)
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-64 >> 2 = -16 (-16)
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64 >> -2 = 256 (256)
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-64 >> -2 = -256 (-256)
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64 >> 256 = 0 (0)
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-64 >> 256 = -1 (-1)
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25 >> 3 = 3 (3)
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-25 >> 3 = -4 (-4)
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25 >> -3 = 200 (200)
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-25 >> -3 = -200 (-200)
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64 unchecked_left_shift 2 = 256 (256)
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-64 unchecked_right_shift 2 = -16 (-16)
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The following cases test undefined behaviour
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(they cause overflow):
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64 << 256 = 0 (0)
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-64 << 256 = 0 (0)
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64 >> -256 = 0 (0)
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-64 >> -256 = 0 (0)
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