Add configure infrastructure to detect support for C99's restrict.

Will be used in later commits improving performance for a few key
routines where information about aliasing allows for significantly
better code generation.

This allows to use the C99 'restrict' keyword without breaking C89, or
for that matter C++, compilers. If not supported it's defined to be
empty.

Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de

diff --git a/configure b/configure
index 98cb8b2881475ab8ef1d7f2205339b9d560d5fc3..910f0fc3736992697485358c651241c3c4742091 100755 (executable)
--- a/configure
+++ b/configure
@@ -11545,6 +11545,52 @@ _ACEOF
     ;;
 esac
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword" >&5
+$as_echo_n "checking for C/C++ restrict keyword... " >&6; }
+if ${ac_cv_c_restrict+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_cv_c_restrict=no
+   # The order here caters to the fact that C++ does not require restrict.
+   for ac_kw in __restrict __restrict__ _Restrict restrict; do
+     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+typedef int * int_ptr;
+       int foo (int_ptr $ac_kw ip) {
+       return ip[0];
+       }
+int
+main ()
+{
+int s[1];
+       int * $ac_kw t = s;
+       t[0] = 0;
+       return foo(t)
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_c_restrict=$ac_kw
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+     test "$ac_cv_c_restrict" != no && break
+   done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_restrict" >&5
+$as_echo "$ac_cv_c_restrict" >&6; }
+
+ case $ac_cv_c_restrict in
+   restrict) ;;
+   no) $as_echo "#define restrict /**/" >>confdefs.h
+ ;;
+   *)  cat >>confdefs.h <<_ACEOF
+#define restrict $ac_cv_c_restrict
+_ACEOF
+ ;;
+ esac
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for printf format archetype" >&5
 $as_echo_n "checking for printf format archetype... " >&6; }
 if ${pgac_cv_printf_archetype+:} false; then :

diff --git a/configure.in b/configure.in
index 4548db0dd3c8961b2830491d15718db6d1bd13f0..ab990d69f4cb5fc134265ec34fc9e0fa79bbd5e3 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -1299,6 +1299,7 @@ fi
 m4_defun([AC_PROG_CC_STDC], []) dnl We don't want that.
 AC_C_BIGENDIAN
 AC_C_INLINE
+AC_C_RESTRICT
 PGAC_PRINTF_ARCHETYPE
 AC_C_FLEXIBLE_ARRAY_MEMBER
 PGAC_C_SIGNED

diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index b0298cca19c93435584c7d110627e1b2c53ed618..80ee37dd622636fa6ed45a7d422278c83c65a963 100644 (file)
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -923,6 +923,20 @@
    if such a type exists, and if the system does not define it. */
 #undef intptr_t
 
+/* Define to the equivalent of the C99 'restrict' keyword, or to
+   nothing if this is not supported.  Do not define if restrict is
+   supported directly.  */
+#undef restrict
+/* Work around a bug in Sun C++: it does not support _Restrict or
+   __restrict__, even though the corresponding Sun C compiler ends up with
+   "#define restrict _Restrict" or "#define restrict __restrict__" in the
+   previous line.  Perhaps some future version of Sun C++ will work with
+   restrict; if so, hopefully it defines __RESTRICT like Sun C does.  */
+#if defined __SUNPRO_CC && !defined __RESTRICT
+# define _Restrict
+# define __restrict__
+#endif
+
 /* Define to empty if the C compiler does not understand signed types. */
 #undef signed
 

diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index b76aad02676e6270d755b33ece944fb616f585b7..3be1c235aaa3f4b8d9c074239f00487a1cf7df9a 100644 (file)
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -681,6 +681,17 @@
 #define inline __inline
 #endif
 
+/* Define to the equivalent of the C99 'restrict' keyword, or to
+   nothing if this is not supported.  Do not define if restrict is
+   supported directly.  */
+/* Visual Studio 2008 and upwards */
+#if (_MSC_VER >= 1500)
+/* works for C and C++ in msvc */
+#define restrict __restrict
+#else
+#define restrict
+#endif
+
 /* Define to empty if the C compiler does not understand signed types. */
 /* #undef signed */