dev-python/pyblake2: select implementation using compiler macros

This eliminates the need for the cpu_flags_x86 USE flags, and resolves
a build failure if CFLAGS and cpu_flags_x86 are mismatched.

Package-Manager: Portage-2.3.11_p4, Repoman-2.3.3_p62

dev-python/pyblake2/pyblake2-0.9.3.ebuild

@@ -4,7 +4,7 @@
 EAPI=6
 
 PYTHON_COMPAT=( python{2_7,3_4,3_5,3_6} pypy )
-inherit distutils-r1 flag-o-matic
+inherit distutils-r1 flag-o-matic toolchain-funcs
 
 DESCRIPTION="BLAKE2 hash function extension module"
 HOMEPAGE="https://github.com/dchest/pyblake2 https://pypi.python.org/pypi/pyblake2"
@@ -13,18 +13,35 @@ SRC_URI="mirror://pypi/${PN::1}/${PN}/${P}.tar.gz"
 LICENSE="CC0-1.0"
 SLOT="0"
 KEYWORDS="~amd64 ~ia64 ~ppc ~ppc64 ~x86 ~ppc-macos ~x64-macos ~x86-macos ~sparc-solaris ~sparc64-solaris ~x64-solaris ~x86-solaris"
-IUSE="cpu_flags_x86_ssse3 cpu_flags_x86_avx cpu_flags_x86_xop"
+
+blake2_impl() {
+	local code='
+#if defined(__XOP__)
+	HAVE_XOP
+#elif defined(__AVX__)
+	HAVE_AVX
+#elif defined(__SSSE3__)
+	HAVE_SSSE3
+#elif defined(__SSE2__)
+	HAVE_SSE2
+#endif
+'
+	local res=$($(tc-getCC) -E -P ${CFLAGS} - <<<"${code}")
+
+	case ${res} in
+		*HAVE_XOP*)    echo XOP;;
+		# this does not actually do anything but implicitly enabled SSE4.1...
+		*HAVE_AVX*)    echo AVX;;
+		*HAVE_SSSE3*)  echo SSSE3;;
+		# note: SSE2 is 2.5x slower than pure REGS, so we ignore it
+		#*HAVE_SSE2*)  echo SSE2;;
+		*)             echo REGS;;
+	esac
+}
 
 python_prepare_all() {
-	local impl=REGS
-	# note: SSE2 is 2.5x slower than pure REGS, so we ignore it
-	use cpu_flags_x86_ssse3 && impl=SSSE3
-	# this does not actually do anything but implicitly enabled SSE4.1...
-	use cpu_flags_x86_avx && impl=AVX
-	use cpu_flags_x86_xop && impl=XOP
-
 	# uncomment the implementation of choice
-	sed -i -e "/BLAKE2_COMPRESS_${impl}/s:^#::" setup.py || die
+	sed -i -e "/BLAKE2_COMPRESS_$(blake2_impl)/s:^#::" setup.py || die
 
 	# avoid segfault due to over(?) optimisation
 	if [[ ${CHOST} == *86*-darwin* ]] ; then