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bpo-29882: Add _Py_popcount32() function (GH-20518)

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* Rename pycore_byteswap.h to pycore_bitutils.h.
* Move popcount_digit() to pycore_bitutils.h as _Py_popcount32().
* _Py_popcount32() uses GCC and clang builtin function if available.
* Add unit tests to _Py_popcount32().
This commit is contained in:
Victor Stinner 2020-06-08 16:30:33 +02:00 • committed by GitHub
parent 301f0d4ff9
commit c6b292cdee
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11 changed files with 108 additions and 39 deletions
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42
Modules/_testinternalcapi.c
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@ -12,7 +12,7 @@
#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "pycore_byteswap.h" // _Py_bswap32()
#include "pycore_bitutils.h" // _Py_bswap32()
#include "pycore_initconfig.h" // _Py_GetConfigsAsDict()
#include "pycore_hashtable.h" // _Py_hashtable_new()
#include "pycore_gc.h" // PyGC_Head
@ -63,6 +63,45 @@ test_bswap(PyObject *self, PyObject *Py_UNUSED(args))
}
static int
check_popcount(uint32_t x, int expected)
{
// Use volatile to prevent the compiler to optimize out the whole test
volatile uint32_t u = x;
int bits = _Py_popcount32(u);
if (bits != expected) {
PyErr_Format(PyExc_AssertionError,
"_Py_popcount32(%lu) returns %i, expected %i",
(unsigned long)x, bits, expected);
return -1;
}
return 0;
}
static PyObject*
test_popcount(PyObject *self, PyObject *Py_UNUSED(args))
{
#define CHECK(X, RESULT) \
do { \
if (check_popcount(X, RESULT) < 0) { \
return NULL; \
} \
} while (0)
CHECK(0, 0);
CHECK(1, 1);
CHECK(0x08080808, 4);
CHECK(0x10101010, 4);
CHECK(0x10204080, 4);
CHECK(0xDEADCAFE, 22);
CHECK(0xFFFFFFFF, 32);
Py_RETURN_NONE;
#undef CHECK
}
#define TO_PTR(ch) ((void*)(uintptr_t)ch)
#define FROM_PTR(ptr) ((uintptr_t)ptr)
#define VALUE(key) (1 + ((int)(key) - 'a'))
@ -157,6 +196,7 @@ static PyMethodDef TestMethods[] = {
{"get_configs", get_configs, METH_NOARGS},
{"get_recursion_depth", get_recursion_depth, METH_NOARGS},
{"test_bswap", test_bswap, METH_NOARGS},
{"test_popcount", test_popcount, METH_NOARGS},
{"test_hashtable", test_hashtable, METH_NOARGS},
{NULL, NULL} /* sentinel */
};