configure.ac: add SIMD detection capabilities
This change adds a check whether compiler supports some SIMD
(Single Instruction, Multiple Data) instructions. It is enabled
by default, and can be disabled by configure option --disable-simd.
The check macro is based on the AX_EXT from autoconf-archive:
www.gnu.org/software/autoconf-archive/ax_ext.html
And depends on the ax_check_compile_flag macro:
www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
Currently only the following SIMD extensions are being checked:
AVX2, SSE3, SSE4.1, but adding others is also possible. All found
extensions are being defined in the 'config.h' header.
Change-Id: Idf8fff984bd936a75c7c307338df88ba4b005817
diff --git a/m4/ax_check_simd.m4 b/m4/ax_check_simd.m4
new file mode 100644
index 0000000..d07d706
--- /dev/null
+++ b/m4/ax_check_simd.m4
@@ -0,0 +1,82 @@
+# ===========================================================================
+# http://www.gnu.org/software/autoconf-archive/ax_ext.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+# AX_EXT
+#
+# DESCRIPTION
+#
+# Find supported SIMD extensions by requesting cpuid. When an SIMD
+# extension is found, the -m"simdextensionname" is added to SIMD_FLAGS if
+# compiler supports it. For example, if "sse2" is available, then "-msse2"
+# is added to SIMD_FLAGS.
+#
+# This macro calls:
+#
+# AC_SUBST(SIMD_FLAGS)
+#
+# And defines:
+#
+# HAVE_AVX3 / HAVE_SSE3 / HAVE_SSE4.1
+#
+# LICENSE
+#
+# Copyright (c) 2007 Christophe Tournayre <turn3r@users.sourceforge.net>
+# Copyright (c) 2013 Michael Petch <mpetch@capp-sysware.com>
+#
+# Copying and distribution of this file, with or without modification, are
+# permitted in any medium without royalty provided the copyright notice
+# and this notice are preserved. This file is offered as-is, without any
+# warranty.
+#
+# NOTE: The functionality that requests the cpuid has been stripped because
+# this project detects the CPU capabilities during runtime. However, we
+# still need to check if the compiler supports the requested SIMD flag.
+
+#serial 12
+
+AC_DEFUN([AX_CHECK_SIMD],
+[
+ AC_REQUIRE([AC_CANONICAL_HOST])
+
+ case $host_cpu in
+ i[[3456]]86*|x86_64*|amd64*)
+ AX_CHECK_COMPILE_FLAG(-mavx2, ax_cv_support_avx2_ext=yes, [])
+ if test x"$ax_cv_support_avx2_ext" = x"yes"; then
+ SIMD_FLAGS="$SIMD_FLAGS -mavx2"
+ AC_DEFINE(HAVE_AVX2,,
+ [Support AVX2 (Advanced Vector Extensions 2) instructions])
+ AM_CONDITIONAL(HAVE_AVX2, true)
+ else
+ AC_MSG_WARN([Your compiler does not support AVX2 instructions])
+ AM_CONDITIONAL(HAVE_AVX2, false)
+ fi
+
+ AX_CHECK_COMPILE_FLAG(-msse3, ax_cv_support_sse3_ext=yes, [])
+ if test x"$ax_cv_support_sse3_ext" = x"yes"; then
+ SIMD_FLAGS="$SIMD_FLAGS -msse3"
+ AC_DEFINE(HAVE_SSE3,,
+ [Support SSE3 (Streaming SIMD Extensions 3) instructions])
+ AM_CONDITIONAL(HAVE_SSE3, true)
+ else
+ AC_MSG_WARN([Your compiler does not support SSE3 instructions])
+ AM_CONDITIONAL(HAVE_SSE3, false)
+ fi
+
+ AX_CHECK_COMPILE_FLAG(-msse4.1, ax_cv_support_sse41_ext=yes, [])
+ if test x"$ax_cv_support_sse41_ext" = x"yes"; then
+ SIMD_FLAGS="$SIMD_FLAGS -msse4.1"
+ AC_DEFINE(HAVE_SSE4_1,,
+ [Support SSE4.1 (Streaming SIMD Extensions 4.1) instructions])
+ AM_CONDITIONAL(HAVE_SSE4_1, true)
+ else
+ AC_MSG_WARN([Your compiler does not support SSE4.1 instructions])
+ AM_CONDITIONAL(HAVE_SSE4_1, false)
+ fi
+ ;;
+ esac
+
+ AC_SUBST(SIMD_FLAGS)
+])