Autoconf detection

Author: Fidget-Spinner

Include/Python.h

@@ -8,8 +8,6 @@
 // Since this is a "meta-include" file, "#ifdef __cplusplus / extern "C" {"
 // is not needed.
 
-#define Py_TAIL_CALL_INTERP 1
-
 // Include Python header files
 #include "patchlevel.h"
 #include "pyconfig.h"

configure

@@ -1717,22 +1717,6 @@ then
   ABI_THREAD="t"
 fi
 
-# Check for --enable-tail-call-interp
-# --enable-tail-call-interp
-AC_MSG_CHECKING([for --enable-tail-call-interp])
-AC_ARG_ENABLE([tail-call-interp],
-  [AS_HELP_STRING([--enable-tail-call-interp], [enable tail calling interpreter]) ],
-[
-if test "$enableval" != no
-then
-  AC_MSG_RESULT([yes]);
-  AC_DEFINE([Py_TAIL_CALL_INTERP], [1],
-            [Define if you want to enable tail calling interpreter])
-else
-  AC_MSG_RESULT([no]);
-fi],
-[AC_MSG_RESULT([no])])
-
 # Check for --with-pydebug
 AC_MSG_CHECKING([for --with-pydebug])
 AC_ARG_WITH([pydebug],
@@ -7013,6 +6997,60 @@ case "$ac_cv_computed_gotos" in yes*)
   [Define if the C compiler supports computed gotos.])
 esac
 
+# Check for --with-tail-calling-interp
+AC_MSG_CHECKING([for --with-tail-calling-interp])
+AC_ARG_WITH(
+  [tail-calling-interp],
+  [AS_HELP_STRING(
+    [--tail-calling-interp],
+    [enable tail-calling interpreter in evaluation loop and rest of CPython (enabled by default on supported compilers)]
+  )],
+[
+if test "$withval" = yes
+then
+  AC_DEFINE([Py_TAIL_CALLING_INTERP], [1],
+  [Define if you want to use tail-calling interpreters in CPython.])
+  AC_MSG_RESULT([yes])
+fi
+if test "$withval" = no
+then
+  AC_DEFINE([Py_TAIL_CALLING_INTERP], [0],
+  [Define if you want to use tail-calling interpreters in CPython.])
+  AC_MSG_RESULT([no])
+fi
+],
+[AC_MSG_RESULT([no value specified])])
+
+
+AC_CACHE_CHECK([whether $CC supports efficient proper tail calls], [ac_cv_tail_call],
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[[
+
+#if __has_attribute(musttail)
+#   if __has_attribute(preserve_none)
+// Only allowlist x86_64 and AArch64. Add more architectures as compilers gain support for them.
+#       if defined(__x86_64__) || defined(__aarch64__)
+#           define PROPER_TAIL_CALLS 1
+#       endif
+#   endif
+#endif
+
+#ifndef PROPER_TAIL_CALLS
+#   error "No proper tail calls"
+#endif
+
+]]])],
+[ac_cv_tail_call=yes],
+[ac_cv_tail_call=no],
+[if test "${with_tail_calling_interp+set}" = set; then
+   ac_cv_tail_call="$with_tail_calling_interp -- configured --with(out)-tail-calling-interp"
+ else
+   ac_cv_tail_call=no
+ fi]))
+case "$ac_cv_tail_call" in yes*)
+  AC_DEFINE([Py_TAIL_CALLING_INTERP], [1],
+  [Define if the C compiler supports efficient proper tail calls.])
+esac
+
 case $ac_sys_system in
 AIX*)
   AC_DEFINE([HAVE_BROKEN_PIPE_BUF], [1],

configure.ac

@@ -1718,8 +1718,8 @@
 /* The version of SunOS/Solaris as reported by `uname -r' without the dot. */
 #undef Py_SUNOS_VERSION
 
-/* Define if you want to enable tail calling interpreter */
-#undef Py_TAIL_CALL_INTERP
+/* Define if the C compiler supports efficient proper tail calls. */
+#undef Py_TAIL_CALLING_INTERP
 
 /* Define if you want to enable tracing references for debugging purpose */
 #undef Py_TRACE_REFS