From e5f13a66567b1987e0aae42c6fdcd277bb5810ba Mon Sep 17 00:00:00 2001
From: Lasse Collin <lasse.collin@tukaani.org>
Date: Sat, 1 Jun 2019 18:46:54 +0300
Subject: [PATCH] tuklib_integer: Autodetect support for unaligned access on
 ARM.

The result is used as the default for --enable-unaligned-access.
The test should work with GCC and Clang.
---
 m4/tuklib_integer.m4 | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/m4/tuklib_integer.m4 b/m4/tuklib_integer.m4
index 2ab72a2f..c3c59fe3 100644
--- a/m4/tuklib_integer.m4
+++ b/m4/tuklib_integer.m4
@@ -58,6 +58,17 @@ if test "x$enable_unaligned_access" = xauto ; then
 		i?86|x86_64|powerpc|powerpc64)
 			enable_unaligned_access=yes
 			;;
+		arm*|aarch64*)
+			# On 32-bit and 64-bit ARM, GCC and Clang
+			# #define __ARM_FEATURE_UNALIGNED if
+			# unaligned access is supported.
+			AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+#ifndef __ARM_FEATURE_UNALIGNED
+compile error
+#endif
+int main(void) { return 0; }
+])], [enable_unaligned_access=yes], [enable_unaligned_access=no])
+			;;
 		*)
 			enable_unaligned_access=no
 			;;