From 9d2455a69949356713cdbb8e34d20063e19cd457 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Sat, 20 May 2017 18:03:53 -0400
Subject: [PATCH] Add inline ASM for missing CRC intrinsics (Issue 428)

---
 crc.cpp | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/crc.cpp b/crc.cpp
index 1add0d84..18babbb7 100644
--- a/crc.cpp
+++ b/crc.cpp
@@ -13,6 +13,33 @@ NAMESPACE_BEGIN(CryptoPP)
 # undef CRYPTOPP_BOOL_SSE4_INTRINSICS_AVAILABLE
 #endif
 
+
+// Use inline ASM to provide the instructions when the user omits -march=native
+#if (CRYPTOPP_GCC_VERSION >= 40300 || CRYPTOPP_LLVM_CLANG_VERSION >= 30200 || CRYPTOPP_APPLE_CLANG_VERSION >= 30200) && !defined(__SSE4_2__)
+GCC_INLINE unsigned int GCC_INLINE_ATTRIB
+MM_CRC32_U8(unsigned int crc, unsigned char val)
+{
+	asm ("crc32 %1, %0" : "+r"(crc) : "r"(val));
+	return crc;
+}
+GCC_INLINE unsigned int GCC_INLINE_ATTRIB
+MM_CRC32_U16(unsigned int crc, unsigned short val)
+{
+	asm ("crc32 %1, %0" : "+r"(crc) : "r"(val));
+	return crc;
+}
+GCC_INLINE unsigned int GCC_INLINE_ATTRIB
+MM_CRC32_U32(unsigned int crc, unsigned int val)
+{
+	asm ("crc32 %1, %0" : "+r"(crc) : "r"(val));
+	return crc;
+}
+#else
+	#define MM_CRC32_U8(a,b)  _mm_crc32_u8(a,b)
+	#define MM_CRC32_U16(a,b) _mm_crc32_u16(a,b)
+	#define MM_CRC32_U32(a,b) _mm_crc32_u32(a,b)
+#endif
+
 /* Table of CRC-32's of all single byte values (made by makecrc.c) */
 const word32 CRC32::m_tab[] = {
 #ifdef IS_LITTLE_ENDIAN
@@ -303,13 +330,13 @@ void CRC32C::Update(const byte *s, size_t n)
 	if (HasSSE4())
 	{
 		for(; !IsAligned<word32>(s) && n > 0; s++, n--)
-			m_crc = _mm_crc32_u8(m_crc, *s);
+			m_crc = MM_CRC32_U8(m_crc, *s);
 
 		for(; n > 4; s+=4, n-=4)
-			m_crc = _mm_crc32_u32(m_crc, *(const word32 *)(void*)s);
+			m_crc = MM_CRC32_U32(m_crc, *(const word32 *)(void*)s);
 
 		for(; n > 0; s++, n--)
-			m_crc = _mm_crc32_u8(m_crc, *s);
+			m_crc = MM_CRC32_U8(m_crc, *s);
 
 		return;
 	}