From f86aca72586f76ecca754e9f984af1918dd5fb85 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Fri, 6 May 2016 05:20:56 -0400
Subject: [PATCH] Improved compile time checking to make runtime check
 consitent with lack of availability

---
 cpu.cpp | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/cpu.cpp b/cpu.cpp
index bd2f5183..3247e5e7 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -269,16 +269,23 @@ void __attribute__ ((constructor)) DetectArmFeatures()
 void DetectArmFeatures()
 #endif
 {
-#if defined(__linux__) && defined(__aarch64__)
+#if defined(__linux__) && defined(__aarch64__) // ARM-64
 	const unsigned long hwcaps = getauxval(AT_HWCAP);
 	g_hasNEON = !!(hwcaps & HWCAP_ASIMD);
+# if defined(__ARM_FEATURE_CRC32)
 	g_hasCRC32 = !!(hwcaps & HWCAP_CRC32);
-#elif defined(__linux__)
+# else
+	g_hasCRC32 = false;
+# endif
+#elif defined(__linux__) // ARM-32
 	const unsigned long hwcaps = getauxval(AT_HWCAP);
 	g_hasNEON = !!(hwcaps & HWCAP_ARM_NEON);
-	// g_hasCRC32 = !!(hwcaps & HWCAP_ARM_CRC32);
+# if defined(__ARM_FEATURE_CRC32)
+	g_hasCRC32 = !!(hwcaps & HWCAP_ARM_CRC32);
+# else
 	g_hasCRC32 = false;
-#elif defined(_WIN32) && defined(_M_ARM)
+# endif
+#elif defined(_WIN32) && defined(_M_ARM) // Microsoft ARM
 	g_hasNEON = true;
 	g_hasCRC32 = false;
 #endif