From d37afa9ab0146e4d2d6a1b1af51632b6129a8966 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Fri, 6 May 2016 06:56:08 -0400
Subject: [PATCH] Improve include logic for <arm_acle.h> under GCC

---
 cpu.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/cpu.h b/cpu.h
index 90a499d0..56baf5ae 100644
--- a/cpu.h
+++ b/cpu.h
@@ -20,7 +20,7 @@
 # if CRYPTOPP_BOOL_NEON_INTRINSICS_AVAILABLE
 #  include <arm_neon.h>
 # endif
-# if (__ARM_ACLE >= 200)
+# if defined(__ARM_FEATURE_CRC32) || (__ARM_ACLE >= 200)
 #  include <arm_acle.h>
 # endif
 #endif  // ARM-32 or ARM-64
@@ -242,6 +242,7 @@ void CRYPTOPP_API DetectArmFeatures();
 
 //! \brief Determine if an ARM processor has Advanced SIMD available
 //! \returns true if the hardware is capable of Advanced SIMD at runtime, false otherwise.
+//! \details Runtime support requires compile time support.
 inline bool HasNEON()
 {
 	if (!g_ArmDetectionDone)
@@ -251,6 +252,8 @@ inline bool HasNEON()
 
 //! \brief Determine if an ARM processor has CRC32 available
 //! \returns true if the hardware is capable of CRC32 at runtime, false otherwise.
+//! \details Runtime support requires compile time support. When compiling with GCC, you may
+//!   need to compile with <tt>-march=armv8-a+crc</tt>.
 inline bool HasCRC32()
 {
 	if (!g_ArmDetectionDone)