commit 2942b909d9a428e6683d90b3436cfa4a81bd5d8a
author INADA Naoki <methane@users.noreply.github.com> Wed Feb 07 19:09:36 2018 +0900
committer GitHub <noreply@github.com> Wed Feb 07 19:09:36 2018 +0900
tree e05b4e4314a71e4b915c0814b6d41c7a1184cedd
parent 0a18422b31e0d7549da5ddbf62194f8c583c2091

bpo-32616: Disable computed gotos by default for clang < 5 (GH-5574)

Python/ceval.c

diff --git a/Python/ceval.c b/Python/ceval.c
index 4e4adc2..bae158d 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -689,11 +689,19 @@
 PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
 {
 #ifdef DYNAMIC_EXECUTION_PROFILE
-  #undef USE_COMPUTED_GOTOS
+    #undef USE_COMPUTED_GOTOS
 #endif
 #ifdef HAVE_COMPUTED_GOTOS
     #ifndef USE_COMPUTED_GOTOS
-    #define USE_COMPUTED_GOTOS 1
+        #if defined(__clang__) && (__clang_major__ < 5)
+            /* Computed gotos caused significant performance regression
+             * with clang < 5.0.
+             * https://bugs.python.org/issue32616
+             */
+            #define USE_COMPUTED_GOTOS 0
+        #else
+            #define USE_COMPUTED_GOTOS 1
+        #endif
     #endif
 #else
     #if defined(USE_COMPUTED_GOTOS) && USE_COMPUTED_GOTOS