From 3166603dfd61ff09d8c47547e1f848206d9742c4 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Fri, 1 Sep 2023 22:34:15 -0700
Subject: [PATCH] Optimise math.ceil for known exact float
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This matches a similar optimisation done for math.floor in
https://github.com/python/cpython/pull/21072

Before:
```
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=3.14' 'ceil(x)'
20000000 loops, best of 11: 13.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=0.0' 'ceil(x)'
20000000 loops, best of 11: 13.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-3.14E32' 'ceil(x)'
10000000 loops, best of 11: 35.3 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-323452345.14' 'ceil(x)'
10000000 loops, best of 11: 21.8 nsec per loop
```

After:
```
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=3.14' 'ceil(x)'
20000000 loops, best of 11: 11.8 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=0.0' 'ceil(x)'
20000000 loops, best of 11: 11.7 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-3.14E32' 'ceil(x)'
10000000 loops, best of 11: 32.7 nsec per loop
λ ./python.exe -m timeit -r 11 -s 'from math import ceil' -s 'x=-323452345.14' 'ceil(x)'
10000000 loops, best of 11: 20.1 nsec per loop
```
---
 Modules/mathmodule.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index d929dcf65a7e32a..3c6d6d8b38828f3 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -1125,8 +1125,13 @@ static PyObject *
 math_ceil(PyObject *module, PyObject *number)
 /*[clinic end generated code: output=6c3b8a78bc201c67 input=2725352806399cab]*/
 {
+    double x;
 
-    if (!PyFloat_CheckExact(number)) {
+    if (PyFloat_CheckExact(number)) {
+        x = PyFloat_AS_DOUBLE(number);
+    }
+    else
+    {
         math_module_state *state = get_math_module_state(module);
         PyObject *method = _PyObject_LookupSpecial(number, state->str___ceil__);
         if (method != NULL) {
@@ -1136,11 +1141,10 @@ math_ceil(PyObject *module, PyObject *number)
         }
         if (PyErr_Occurred())
             return NULL;
+        x = PyFloat_AsDouble(number);
+        if (x == -1.0 && PyErr_Occurred())
+            return NULL;
     }
-    double x = PyFloat_AsDouble(number);
-    if (x == -1.0 && PyErr_Occurred())
-        return NULL;
-
     return PyLong_FromDouble(ceil(x));
 }