From 8122e1437e332e156d971a0274879b0ee76e488a Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Fri, 20 Mar 2015 10:26:17 +0100
Subject: [PATCH] Add, optional, support for 128bit integers.
We will, for the foreseeable future, not expose 128 bit datatypes to
SQL. But being able to use 128bit math will allow us, in a later patch,
to use 128bit accumulators for some aggregates; leading to noticeable
speedups over using numeric.
So far we only detect a gcc/clang extension that supports 128bit math,
but no 128bit literals, and no *printf support. We might want to expand
this in the future to further compilers; if there are any that that
provide similar support.
Discussion: 544BB5F1.50709@proxel.se
Author: Andreas Karlsson, with significant editorializing by me
Reviewed-By: Peter Geoghegan, Oskari Saarenmaa
---
config/c-compiler.m4 | 37 +++++++++++++++++++++++++
configure | 52 +++++++++++++++++++++++++++++++++++
configure.in | 3 ++
src/include/c.h | 11 ++++++++
src/include/pg_config.h.in | 3 ++
src/include/pg_config.h.win32 | 3 ++
6 files changed, 109 insertions(+)
diff --git a/config/c-compiler.m4 b/config/c-compiler.m4
index 509f96139ff..38aab11bc65 100644
--- a/config/c-compiler.m4
+++ b/config/c-compiler.m4
@@ -125,6 +125,43 @@ undefine([Ac_cachevar])dnl
])# PGAC_TYPE_64BIT_INT
+# PGAC_TYPE_128BIT_INT
+# ---------------------
+# Check if __int128 is a working 128 bit integer type, and if so
+# define PG_INT128_TYPE to that typename. This currently only detects
+# a GCC/clang extension, but support for different environments may be
+# added in the future.
+#
+# For the moment we only test for support for 128bit math; support for
+# 128bit literals and snprintf is not required.
+AC_DEFUN([PGAC_TYPE_128BIT_INT],
+[AC_CACHE_CHECK([for __int128], [pgac_cv__128bit_int],
+[AC_LINK_IFELSE([AC_LANG_PROGRAM([
+/*
+ * These are globals to discourage the compiler from folding all the
+ * arithmetic tests down to compile-time constants. We do not have
+ * convenient support for 64bit literals at this point...
+ */
+__int128 a = 48828125;
+__int128 b = 97656255;
+],[
+__int128 c,d;
+a = (a << 12) + 1; /* 200000000001 */
+b = (b << 12) + 5; /* 400000000005 */
+/* use the most relevant arithmetic ops */
+c = a * b;
+d = (c + b) / b;
+/* return different values, to prevent optimizations */
+if (d != a+1)
+ return 0;
+return 1;
+])],
+[pgac_cv__128bit_int=yes],
+[pgac_cv__128bit_int=no])])
+if test x"$pgac_cv__128bit_int" = xyes ; then
+ AC_DEFINE(PG_INT128_TYPE, __int128, [Define to the name of a signed 128-bit integer type.])
+fi])# PGAC_TYPE_128BIT_INT
+
# PGAC_C_FUNCNAME_SUPPORT
# -----------------------
diff --git a/configure b/configure
index 379dab16ab9..2c9b3a7c710 100755
--- a/configure
+++ b/configure
@@ -13803,6 +13803,58 @@ _ACEOF
fi
+# Check for extensions offering the integer scalar type __int128.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __int128" >&5
+$as_echo_n "checking for __int128... " >&6; }
+if ${pgac_cv__128bit_int+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+/*
+ * These are globals to discourage the compiler from folding all the
+ * arithmetic tests down to compile-time constants. We do not have
+ * convenient support for 64bit literals at this point...
+ */
+__int128 a = 48828125;
+__int128 b = 97656255;
+
+int
+main ()
+{
+
+__int128 c,d;
+a = (a << 12) + 1; /* 200000000001 */
+b = (b << 12) + 5; /* 400000000005 */
+/* use the most relevant arithmetic ops */
+c = a * b;
+d = (c + b) / b;
+/* return different values, to prevent optimizations */
+if (d != a+1)
+ return 0;
+return 1;
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+ pgac_cv__128bit_int=yes
+else
+ pgac_cv__128bit_int=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+ conftest$ac_exeext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__128bit_int" >&5
+$as_echo "$pgac_cv__128bit_int" >&6; }
+if test x"$pgac_cv__128bit_int" = xyes ; then
+
+$as_echo "#define PG_INT128_TYPE __int128" >>confdefs.h
+
+fi
+
# Check for various atomic operations now that we have checked how to declare
# 64bit integers.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for builtin __sync char locking functions" >&5
diff --git a/configure.in b/configure.in
index ca29e93eee1..b2c1ce71d23 100644
--- a/configure.in
+++ b/configure.in
@@ -1771,6 +1771,9 @@ AC_CHECK_TYPES([int8, uint8, int64, uint64], [], [],
# C, but is missing on some old platforms.
AC_CHECK_TYPES(sig_atomic_t, [], [], [#include <signal.h>])
+# Check for extensions offering the integer scalar type __int128.
+PGAC_TYPE_128BIT_INT
+
# Check for various atomic operations now that we have checked how to declare
# 64bit integers.
PGAC_HAVE_GCC__SYNC_CHAR_TAS
diff --git a/src/include/c.h b/src/include/c.h
index a2d4a2c5c5d..744721860c5 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -293,6 +293,17 @@ typedef unsigned long long int uint64;
#define HAVE_INT64_TIMESTAMP
#endif
+/*
+ * 128-bit signed and unsigned integers
+ * There currently is only a limited support for the type. E.g. 128bit
+ * literals and snprintf are not supported; but math is.
+ */
+#if defined(PG_INT128_TYPE)
+#define HAVE_INT128
+typedef PG_INT128_TYPE int128;
+typedef unsigned PG_INT128_TYPE uint128;
+#endif
+
/* sig_atomic_t is required by ANSI C, but may be missing on old platforms */
#ifndef HAVE_SIG_ATOMIC_T
typedef int sig_atomic_t;
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index ece57c81ccf..202c51a34a5 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -711,6 +711,9 @@
/* Define to the version of this package. */
#undef PACKAGE_VERSION
+/* Define to the name of a signed 128-bit integer type. */
+#undef PG_INT128_TYPE
+
/* Define to the name of a signed 64-bit integer type. */
#undef PG_INT64_TYPE
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index 3f858c658b9..1baf64f0056 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -562,6 +562,9 @@
/* Define to the version of this package. */
#define PACKAGE_VERSION "9.5devel"
+/* Define to the name of a signed 128-bit integer type. */
+#undef PG_INT128_TYPE
+
/* Define to the name of a signed 64-bit integer type. */
#define PG_INT64_TYPE long long int
--
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