diff options
| -rw-r--r-- | Include/internal/pycore_long.h | 19 | ||||
| -rw-r--r-- | Python/bytecodes.c | 8 | ||||
| -rw-r--r-- | Python/generated_cases.c.h | 8 |
3 files changed, 25 insertions, 10 deletions
diff --git a/Include/internal/pycore_long.h b/Include/internal/pycore_long.h index 30c97b7..8c1d017 100644 --- a/Include/internal/pycore_long.h +++ b/Include/internal/pycore_long.h @@ -110,6 +110,25 @@ PyAPI_FUNC(char*) _PyLong_FormatBytesWriter( int base, int alternate); +/* Return 1 if the argument is positive single digit int */ +static inline int +_PyLong_IsPositiveSingleDigit(PyObject* sub) { + /* For a positive single digit int, the value of Py_SIZE(sub) is 0 or 1. + + We perform a fast check using a single comparison by casting from int + to uint which casts negative numbers to large positive numbers. + For details see Section 14.2 "Bounds Checking" in the Agner Fog + optimization manual found at: + https://www.agner.org/optimize/optimizing_cpp.pdf + + The function is not affected by -fwrapv, -fno-wrapv and -ftrapv + compiler options of GCC and clang + */ + assert(PyLong_CheckExact(sub)); + Py_ssize_t signed_size = Py_SIZE(sub); + return ((size_t)signed_size) <= 1; +} + #ifdef __cplusplus } #endif diff --git a/Python/bytecodes.c b/Python/bytecodes.c index b29e16e..c0b625b 100644 --- a/Python/bytecodes.c +++ b/Python/bytecodes.c @@ -391,8 +391,7 @@ dummy_func( DEOPT_IF(!PyList_CheckExact(list), BINARY_SUBSCR); // Deopt unless 0 <= sub < PyList_Size(list) - Py_ssize_t signed_magnitude = Py_SIZE(sub); - DEOPT_IF(((size_t)signed_magnitude) > 1, BINARY_SUBSCR); + DEOPT_IF(!_PyLong_IsPositiveSingleDigit(sub), BINARY_SUBSCR); assert(((PyLongObject *)_PyLong_GetZero())->ob_digit[0] == 0); Py_ssize_t index = ((PyLongObject*)sub)->ob_digit[0]; DEOPT_IF(index >= PyList_GET_SIZE(list), BINARY_SUBSCR); @@ -410,8 +409,7 @@ dummy_func( DEOPT_IF(!PyTuple_CheckExact(tuple), BINARY_SUBSCR); // Deopt unless 0 <= sub < PyTuple_Size(list) - Py_ssize_t signed_magnitude = Py_SIZE(sub); - DEOPT_IF(((size_t)signed_magnitude) > 1, BINARY_SUBSCR); + DEOPT_IF(!_PyLong_IsPositiveSingleDigit(sub), BINARY_SUBSCR); assert(((PyLongObject *)_PyLong_GetZero())->ob_digit[0] == 0); Py_ssize_t index = ((PyLongObject*)sub)->ob_digit[0]; DEOPT_IF(index >= PyTuple_GET_SIZE(tuple), BINARY_SUBSCR); @@ -508,7 +506,7 @@ dummy_func( DEOPT_IF(!PyList_CheckExact(list), STORE_SUBSCR); // Ensure nonnegative, zero-or-one-digit ints. - DEOPT_IF(((size_t)Py_SIZE(sub)) > 1, STORE_SUBSCR); + DEOPT_IF(!_PyLong_IsPositiveSingleDigit(sub), STORE_SUBSCR); Py_ssize_t index = ((PyLongObject*)sub)->ob_digit[0]; // Ensure index < len(list) DEOPT_IF(index >= PyList_GET_SIZE(list), STORE_SUBSCR); diff --git a/Python/generated_cases.c.h b/Python/generated_cases.c.h index 6d84a64..42b7ca0 100644 --- a/Python/generated_cases.c.h +++ b/Python/generated_cases.c.h @@ -491,8 +491,7 @@ DEOPT_IF(!PyList_CheckExact(list), BINARY_SUBSCR); // Deopt unless 0 <= sub < PyList_Size(list) - Py_ssize_t signed_magnitude = Py_SIZE(sub); - DEOPT_IF(((size_t)signed_magnitude) > 1, BINARY_SUBSCR); + DEOPT_IF(!_PyLong_IsPositiveSingleDigit(sub), BINARY_SUBSCR); assert(((PyLongObject *)_PyLong_GetZero())->ob_digit[0] == 0); Py_ssize_t index = ((PyLongObject*)sub)->ob_digit[0]; DEOPT_IF(index >= PyList_GET_SIZE(list), BINARY_SUBSCR); @@ -517,8 +516,7 @@ DEOPT_IF(!PyTuple_CheckExact(tuple), BINARY_SUBSCR); // Deopt unless 0 <= sub < PyTuple_Size(list) - Py_ssize_t signed_magnitude = Py_SIZE(sub); - DEOPT_IF(((size_t)signed_magnitude) > 1, BINARY_SUBSCR); + DEOPT_IF(!_PyLong_IsPositiveSingleDigit(sub), BINARY_SUBSCR); assert(((PyLongObject *)_PyLong_GetZero())->ob_digit[0] == 0); Py_ssize_t index = ((PyLongObject*)sub)->ob_digit[0]; DEOPT_IF(index >= PyTuple_GET_SIZE(tuple), BINARY_SUBSCR); @@ -642,7 +640,7 @@ DEOPT_IF(!PyList_CheckExact(list), STORE_SUBSCR); // Ensure nonnegative, zero-or-one-digit ints. - DEOPT_IF(((size_t)Py_SIZE(sub)) > 1, STORE_SUBSCR); + DEOPT_IF(!_PyLong_IsPositiveSingleDigit(sub), STORE_SUBSCR); Py_ssize_t index = ((PyLongObject*)sub)->ob_digit[0]; // Ensure index < len(list) DEOPT_IF(index >= PyList_GET_SIZE(list), STORE_SUBSCR); |