Merge branch 'simd-runtime-detection' into 'master'

Support for runtime detection of SIMD

This merge request adds support for runtime SIMD detection. The idea is that you would build gf-complete with full SIMD support, and gf_init will select the appropriate function at runtime based on the capabilities of the target machine. This would eliminate the need to build different versions of the code for different processors (you still need to build for different archs). Ceph for example has 3-4 flavors of jerasure on Intel (and does not support PCLMUL optimizations as a result of using to many binaries). Numerous libraries have followed as similar approach include zlib.

When reviewing this merge request I recommend that you look at each of the 5 commits independently. The first 3 commits don't change the existing logic. Instead they add debugging functions and test scripts that facilitate testing of the 4th and commit. The 4th commit is where all the new logic goes along with tests. The 5th commit fixes build scripts.

I've tested this on x86_64, arm, and aarch64 using QEMU. Numerous tests have been added that help this code and could help with future testing of gf-complete. Also I've compared the functions selected with the old code (prior to runtime SIMD support) with the new code and all functions are identical. Here's a gist with the test results prior to SIMD extensions: https://gist.github.com/bassamtabbara/d9a6dcf0a749b7ab01bc2953a359edec.

See merge request !18

1 files changed, 0 insertions, 79 deletions

diff --git a/m4/ax_gcc_x86_avx_xgetbv.m4 b/m4/ax_gcc_x86_avx_xgetbv.m4
deleted file mode 100644
index 0624eeb..0000000
--- a/m4/ax_gcc_x86_avx_xgetbv.m4
+++ /dev/null
@@ -1,79 +0,0 @@
-# ===========================================================================
-#   http://www.gnu.org/software/autoconf-archive/ax_gcc_x86_avx_xgetbv.html
-# ===========================================================================
-#
-# SYNOPSIS
-#
-#   AX_GCC_X86_AVX_XGETBV
-#
-# DESCRIPTION
-#
-#   On later x86 processors with AVX SIMD support, with gcc or a compiler
-#   that has a compatible syntax for inline assembly instructions, run a
-#   small program that executes the xgetbv instruction with input OP. This
-#   can be used to detect if the OS supports AVX instruction usage.
-#
-#   On output, the values of the eax and edx registers are stored as
-#   hexadecimal strings as "eax:edx" in the cache variable
-#   ax_cv_gcc_x86_avx_xgetbv.
-#
-#   If the xgetbv instruction fails (because you are running a
-#   cross-compiler, or because you are not using gcc, or because you are on
-#   a processor that doesn't have this instruction),
-#   ax_cv_gcc_x86_avx_xgetbv_OP is set to the string "unknown".
-#
-#   This macro mainly exists to be used in AX_EXT.
-#
-# LICENSE
-#
-#   Copyright (c) 2013 Michael Petch <mpetch@capp-sysware.com>
-#
-#   This program is free software: you can redistribute it and/or modify it
-#   under the terms of the GNU General Public License as published by the
-#   Free Software Foundation, either version 3 of the License, or (at your
-#   option) any later version.
-#
-#   This program is distributed in the hope that it will be useful, but
-#   WITHOUT ANY WARRANTY; without even the implied warranty of
-#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
-#   Public License for more details.
-#
-#   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
-#
-#   As a special exception, the respective Autoconf Macro's copyright owner
-#   gives unlimited permission to copy, distribute and modify the configure
-#   scripts that are the output of Autoconf when processing the Macro. You
-#   need not follow the terms of the GNU General Public License when using
-#   or distributing such scripts, even though portions of the text of the
-#   Macro appear in them. The GNU General Public License (GPL) does govern
-#   all other use of the material that constitutes the Autoconf Macro.
-#
-#   This special exception to the GPL applies to versions of the Autoconf
-#   Macro released by the Autoconf Archive. When you make and distribute a
-#   modified version of the Autoconf Macro, you may extend this special
-#   exception to the GPL to apply to your modified version as well.
-
-#serial 1
-
-AC_DEFUN([AX_GCC_X86_AVX_XGETBV],
-[AC_REQUIRE([AC_PROG_CC])
-AC_LANG_PUSH([C])
-AC_CACHE_CHECK(for x86-AVX xgetbv $1 output, ax_cv_gcc_x86_avx_xgetbv_$1,
- [AC_RUN_IFELSE([AC_LANG_PROGRAM([#include <stdio.h>], [
-     int op = $1, eax, edx;
-     FILE *f;
-      /* Opcodes for xgetbv */
-      __asm__(".byte 0x0f, 0x01, 0xd0"
-        : "=a" (eax), "=d" (edx)
-        : "c" (op));
-     f = fopen("conftest_xgetbv", "w"); if (!f) return 1;
-     fprintf(f, "%x:%x\n", eax, edx);
-     fclose(f);
-     return 0;
-])],
-     [ax_cv_gcc_x86_avx_xgetbv_$1=`cat conftest_xgetbv`; rm -f conftest_xgetbv],
-     [ax_cv_gcc_x86_avx_xgetbv_$1=unknown; rm -f conftest_xgetbv],
-     [ax_cv_gcc_x86_avx_xgetbv_$1=unknown])])
-AC_LANG_POP([C])
-])