From 97a1eddde6b3ca2c9f7d9383e64c6f71ccecb5d6 Mon Sep 17 00:00:00 2001
From: Sergey Fedoseev <fedoseev.sergey@gmail.com>
Date: Tue, 20 Aug 2019 22:28:27 +0500
Subject: [PATCH 1/2] bpo-37907: Slightly improve performance of
 PyLong_AsSsize_t() with large longs

---
 .../2019-08-21-21-19-38.bpo-37907.0SNcSw.rst  |  3 ++
 Objects/longobject.c                          | 29 +++++++++----------
 2 files changed, 16 insertions(+), 16 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2019-08-21-21-19-38.bpo-37907.0SNcSw.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-08-21-21-19-38.bpo-37907.0SNcSw.rst b/Misc/NEWS.d/next/Core and Builtins/2019-08-21-21-19-38.bpo-37907.0SNcSw.rst
new file mode 100644
index 00000000000000..2237c905365936
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-08-21-21-19-38.bpo-37907.0SNcSw.rst	
@@ -0,0 +1,3 @@
+Slightly improve performance of :c:func:`PyLong_AsSsize_t`,
+:c:func:`PyLong_AsSize_t`, :c:func:`PyLong_AsLong` and
+:c:func:`PyLong_AsUnsignedLong` with large longs. Patch by Sergey Fedoseev.
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 90ed02b8c27a19..b1997e0b62b086 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -484,7 +484,7 @@ PyLong_AsLongAndOverflow(PyObject *vv, int *overflow)
 {
     /* This version by Tim Peters */
     PyLongObject *v;
-    unsigned long x, prev;
+    unsigned long x;
     long res;
     Py_ssize_t i;
     int sign;
@@ -527,12 +527,11 @@ PyLong_AsLongAndOverflow(PyObject *vv, int *overflow)
             i = -(i);
         }
         while (--i >= 0) {
-            prev = x;
-            x = (x << PyLong_SHIFT) | v->ob_digit[i];
-            if ((x >> PyLong_SHIFT) != prev) {
+            if (x > (unsigned long)-1 >> PyLong_SHIFT) {
                 *overflow = sign;
                 goto exit;
             }
+            x = (x << PyLong_SHIFT) | v->ob_digit[i];
         }
         /* Haven't lost any bits, but casting to long requires extra
          * care (see comment above).
@@ -596,7 +595,7 @@ _PyLong_AsInt(PyObject *obj)
 Py_ssize_t
 PyLong_AsSsize_t(PyObject *vv) {
     PyLongObject *v;
-    size_t x, prev;
+    size_t x;
     Py_ssize_t i;
     int sign;
 
@@ -623,10 +622,10 @@ PyLong_AsSsize_t(PyObject *vv) {
         i = -(i);
     }
     while (--i >= 0) {
-        prev = x;
-        x = (x << PyLong_SHIFT) | v->ob_digit[i];
-        if ((x >> PyLong_SHIFT) != prev)
+        if (x > (size_t)-1 >> PyLong_SHIFT) {
             goto overflow;
+        }
+        x = (x << PyLong_SHIFT) | v->ob_digit[i];
     }
     /* Haven't lost any bits, but casting to a signed type requires
      * extra care (see comment above).
@@ -652,7 +651,7 @@ unsigned long
 PyLong_AsUnsignedLong(PyObject *vv)
 {
     PyLongObject *v;
-    unsigned long x, prev;
+    unsigned long x;
     Py_ssize_t i;
 
     if (vv == NULL) {
@@ -677,14 +676,13 @@ PyLong_AsUnsignedLong(PyObject *vv)
     case 1: return v->ob_digit[0];
     }
     while (--i >= 0) {
-        prev = x;
-        x = (x << PyLong_SHIFT) | v->ob_digit[i];
-        if ((x >> PyLong_SHIFT) != prev) {
+        if (x > (unsigned long)-1 >> PyLong_SHIFT) {
             PyErr_SetString(PyExc_OverflowError,
                             "Python int too large to convert "
                             "to C unsigned long");
             return (unsigned long) -1;
         }
+        x = (x << PyLong_SHIFT) | v->ob_digit[i];
     }
     return x;
 }
@@ -696,7 +694,7 @@ size_t
 PyLong_AsSize_t(PyObject *vv)
 {
     PyLongObject *v;
-    size_t x, prev;
+    size_t x;
     Py_ssize_t i;
 
     if (vv == NULL) {
@@ -721,13 +719,12 @@ PyLong_AsSize_t(PyObject *vv)
     case 1: return v->ob_digit[0];
     }
     while (--i >= 0) {
-        prev = x;
-        x = (x << PyLong_SHIFT) | v->ob_digit[i];
-        if ((x >> PyLong_SHIFT) != prev) {
+        if (x > (size_t)-1 >> PyLong_SHIFT) {
             PyErr_SetString(PyExc_OverflowError,
                 "Python int too large to convert to C size_t");
             return (size_t) -1;
         }
+        x = (x << PyLong_SHIFT) | v->ob_digit[i];
     }
     return x;
 }

From 99ab95dada65f90ecc02ea6ba48f5d2b4ae61ecb Mon Sep 17 00:00:00 2001
From: Sergey Fedoseev <fedoseev.sergey@gmail.com>
Date: Sat, 27 Aug 2022 13:42:21 +0500
Subject: [PATCH 2/2] use limits consts

---
 Objects/longobject.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Objects/longobject.c b/Objects/longobject.c
index b1997e0b62b086..f3c74a4fe1b5f9 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -527,7 +527,7 @@ PyLong_AsLongAndOverflow(PyObject *vv, int *overflow)
             i = -(i);
         }
         while (--i >= 0) {
-            if (x > (unsigned long)-1 >> PyLong_SHIFT) {
+            if (x > ULONG_MAX >> PyLong_SHIFT) {
                 *overflow = sign;
                 goto exit;
             }
@@ -622,7 +622,7 @@ PyLong_AsSsize_t(PyObject *vv) {
         i = -(i);
     }
     while (--i >= 0) {
-        if (x > (size_t)-1 >> PyLong_SHIFT) {
+        if (x > SIZE_MAX >> PyLong_SHIFT) {
             goto overflow;
         }
         x = (x << PyLong_SHIFT) | v->ob_digit[i];
@@ -676,7 +676,7 @@ PyLong_AsUnsignedLong(PyObject *vv)
     case 1: return v->ob_digit[0];
     }
     while (--i >= 0) {
-        if (x > (unsigned long)-1 >> PyLong_SHIFT) {
+        if (x > ULONG_MAX >> PyLong_SHIFT) {
             PyErr_SetString(PyExc_OverflowError,
                             "Python int too large to convert "
                             "to C unsigned long");
@@ -719,7 +719,7 @@ PyLong_AsSize_t(PyObject *vv)
     case 1: return v->ob_digit[0];
     }
     while (--i >= 0) {
-        if (x > (size_t)-1 >> PyLong_SHIFT) {
+        if (x > SIZE_MAX >> PyLong_SHIFT) {
             PyErr_SetString(PyExc_OverflowError,
                 "Python int too large to convert to C size_t");
             return (size_t) -1;