From 534e0774e37ee8faebfda0ae785567ac26d2d6ac Mon Sep 17 00:00:00 2001
From: Ilya Maykov <ivmaykov@gmail.com>
Date: Wed, 3 Aug 2016 16:49:21 -0700
Subject: [PATCH] Better AVX2 detection for GCC compilers

---
 configure.ac | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index e3132364..1b24bf50 100644
--- a/configure.ac
+++ b/configure.ac
@@ -398,10 +398,15 @@ AS_IF([test "x$EMSCRIPTEN" = "x" -a "$host_os" != "pnacl"], [
 #endif
 #pragma GCC target("avx2")
 #include <immintrin.h>
-]], [[ __m256i x = _mm256_abs_epi8(_mm256_setzero_si256()); ]])],
+]], [[
+__m256i x = _mm256_abs_epi8(_mm256_setzero_si256());
+#ifdef __GNUC__
+__asm__ __volatile__ ("vpermq $1,%ymm1,%ymm2");
+#endif
+]])],
     [AC_MSG_RESULT(yes)
      AC_DEFINE([HAVE_AVX2INTRIN_H], [1], [AVX2 is available])
-     AX_CHECK_COMPILE_FLAG([-mavx2], [CFLAGS_AVX="-mavx2"])
+     AX_CHECK_COMPILE_FLAG([-mavx2], [CFLAGS_AVX2="-mavx2"])
      AC_MSG_CHECKING(if _mm256_broadcastsi128_si256 is correctly defined)
      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 #ifdef __native_client__