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py: Remove BITS_PER_WORD definition.

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It's only used in one location, to test if << or >> will overflow when
shifting mp_uint_t.  For such a test it's clearer to use sizeof(lhs_val),
which will be valid even if the type of lhs_val changes.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George
2021-02-04 15:27:53 +11:00
parent 7c44354592
commit 8a41ee19c2
2 changed files with 5 additions and 4 deletions
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8
py/runtime.c
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@@ -387,7 +387,9 @@ mp_obj_t mp_binary_op(mp_binary_op_t op, mp_obj_t lhs, mp_obj_t rhs) {
if (rhs_val < 0) {
// negative shift not allowed
mp_raise_ValueError(MP_ERROR_TEXT("negative shift count"));
} else if (rhs_val >= (mp_int_t)BITS_PER_WORD || lhs_val > (MP_SMALL_INT_MAX >> rhs_val) || lhs_val < (MP_SMALL_INT_MIN >> rhs_val)) {
} else if (rhs_val >= (mp_int_t)(sizeof(lhs_val) * BITS_PER_BYTE)
|| lhs_val > (MP_SMALL_INT_MAX >> rhs_val)
|| lhs_val < (MP_SMALL_INT_MIN >> rhs_val)) {
// left-shift will overflow, so use higher precision integer
lhs = mp_obj_new_int_from_ll(lhs_val);
goto generic_binary_op;
@@ -404,10 +406,10 @@ mp_obj_t mp_binary_op(mp_binary_op_t op, mp_obj_t lhs, mp_obj_t rhs) {
mp_raise_ValueError(MP_ERROR_TEXT("negative shift count"));
} else {
// standard precision is enough for right-shift
if (rhs_val >= (mp_int_t)BITS_PER_WORD) {
if (rhs_val >= (mp_int_t)(sizeof(lhs_val) * BITS_PER_BYTE)) {
// Shifting to big amounts is underfined behavior
// in C and is CPU-dependent; propagate sign bit.
rhs_val = BITS_PER_WORD - 1;
rhs_val = sizeof(lhs_val) * BITS_PER_BYTE - 1;
}
lhs_val >>= rhs_val;
}