8000 Expose inline versions of _PyLong_IsCompact & _PyLong_CompactValue by encukou · Pull Request #16 · faster-cpython/cpython · GitHub
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Expose inline versions of _PyLong 8000 _IsCompact & _PyLong_CompactValue #16

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Merged
merged 5 commits into from
May 19, 2023
Merged

Expose inline versions of _PyLong_IsCompact & _PyLong_CompactValue #16

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3d43ba5
Expose inline versions of _PyLong_IsCompact & _PyLong_CompactValue in…
encukou May 15, 2023
3bd2019
PyLong, not PyInt
encukou May 15, 2023
73708ea
Add docs
encukou May 15, 2023
9d98ac5
Add blurb
encukou May 18, 2023
d30c1cb
Add tests
encukou May 18, 2023
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Expose inline versions of _PyLong_IsCompact & _PyLong_CompactValue in… 
… unstable API.
  • Loading branch information
@encukou
encukou committed May 15, 2023
commit 3d43ba5836fded6a136752472fa1127d63fe5909
26 changes: 26 additions & 0 deletions Include/cpython/longintrepr.h
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Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,32 @@ PyAPI_FUNC(PyLongObject *)
_PyLong_FromDigits(int negative, Py_ssize_t digit_count, digit *digits);


/* Inline some internals for speed. These should be in pycore_long.h
* if user code didn't need them inlined. */

#define _PyLong_SIGN_MASK 3
#define _PyLong_NON_SIZE_BITS 3

static inline int
_PyLong_IsCompact(const PyLongObject* op) {
assert(PyLong_Check(op));
return op->long_value.lv_tag < (2 << _PyLong_NON_SIZE_BITS);
}

#define PyUnstable_Int_IsCompact _PyLong_IsCompact

static inline Py_ssize_t
_PyLong_CompactValue(const PyLongObject *op)
{
assert(PyLong_Check(op));
assert(PyUnstable_Int_IsCompact(op));
Py_ssize_t sign = 1 - (op->long_value.lv_tag & _PyLong_SIGN_MASK);
return sign * (Py_ssize_t)op->long_value.ob_digit[0];
}

#define PyUnstable_Int_CompactValue _PyLong_CompactValue


#ifdef __cplusplus
}
#endif
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39 changes: 15 additions & 24 deletions Include/internal/pycore_long.h
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Expand Up @@ -118,6 +118,21 @@ PyAPI_FUNC(char*) _PyLong_FormatBytesWriter(
#define SIGN_NEGATIVE 2
#define NON_SIZE_BITS 3

/* The functions _PyLong_IsCompact and _PyLong_CompactValue are defined
* in Include/cpython/longobject.h, since they need to be inline.
*
* "Compact" values have at least one bit to spare,
* so that addition and subtraction can be performed on the values
* without risk of overflow.
*
* The inline functions need tag bits.
* For readability, rather than do `#define SIGN_MASK _PyLong_SIGN_MASK`
* we define them to the numbers in both places and then assert that
* they're the same.
*/
static_assert(SIGN_MASK == _PyLong_SIGN_MASK);
static_assert(NON_SIZE_BITS == _PyLong_NON_SIZE_BITS);

/* All *compact" values are guaranteed to fit into
* a Py_ssize_t with at least one bit to spare.
* In other words, for 64 bit machines, compact
Expand All @@ -131,13 +146,6 @@ _PyLong_IsNonNegativeCompact(const PyLongObject* op) {
return op->long_value.lv_tag <= (1 << NON_SIZE_BITS);
}

static inline int
_PyLong_IsCompact(const PyLongObject* op) {
assert(PyLong_Check(op));
return op->long_value.lv_tag < (2 << NON_SIZE_BITS);
}

#define PyUnstable_Int_IsCompact _PyLong_IsCompact

static inline int
_PyLong_BothAreCompact(const PyLongObject* a, const PyLongObject* b) {
Expand All @@ -146,23 +154,6 @@ _PyLong_BothAreCompact(const PyLongObject* a, const PyLongObject* b) {
return (a->long_value.lv_tag | b->long_value.lv_tag) < (2 << NON_SIZE_BITS);
}

/* Returns a *compact* value, iff `_PyLong_IsCompact` is true for `op`.
*
* "Compact" values have at least one bit to spare,
* so that addition and subtraction can be performed on the values
* without risk of overflow.
*/
static inline Py_ssize_t
_PyLong_CompactValue(const PyLongObject *op)
{
assert(PyLong_Check(op));
assert(_PyLong_IsCompact(op));
Py_ssize_t sign = 1 - (op->long_value.lv_tag & SIGN_MASK);
return sign * (Py_ssize_t)op->long_value.ob_digit[0];
}

#define PyUnstable_Int_CompactValue _PyLong_CompactValue

static inline bool
_PyLong_IsZero(const PyLongObject *op)
{
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