Added SSE intrinsics to scanner.

The gain seems to be only measurable on rather long messages.

Makefile

@@ -17,7 +17,7 @@ CC = gcc -std=c11
 
 release release32 : CFLAGS = -O3 -Wall -Wextra -Iinclude -march=native -mtune=native \
 -fomit-frame-pointer -Wl,--as-needed -flto -ffunction-sections -fdata-sections -Wl,--gc-sections \
--DNDEBUG -DRELEASE
+-DNDEBUG -DRELEASE -DUSE_SSE
 
 debug : CFLAGS = -g -Wall -Wextra -Iinclude -DDEBUG
 

README.md

@@ -26,10 +26,10 @@ _OS:_ Linux Mint 17.2 64bit
 
 FIX message type                  | FIX specification                        | Validation | Average time to parse one message
 ----------------------------------|------------------------------------------|------------|--------------------------------------------------
-NewOrderSingle('D')               | Hand-coded spec. for this message only   | No         | 0.328 µs/msg
-NewOrderSingle('D')               | Hand-coded spec. for this message only   | Yes        | 0.561 µs/msg
-NewOrderSingle('D')               | Compiled full spec. for FIX.4.4          | Yes        | 0.734 µs/msg
-MarketDataIncrementalRefresh('X') | Hand-coded spec. for this message only   | Yes        | 1.280 µs/msg
-MarketDataIncrementalRefresh('X') | Compiled full spec. for FIX.4.4          | Yes        | 1.418 µs/msg
+NewOrderSingle('D')               | Hand-coded spec. for this message only   | No         | 0.338 µs/msg
+NewOrderSingle('D')               | Hand-coded spec. for this message only   | Yes        | 0.550 µs/msg
+NewOrderSingle('D')               | Compiled full spec. for FIX.4.4          | Yes        | 0.765 µs/msg
+MarketDataIncrementalRefresh('X') | Hand-coded spec. for this message only   | Yes        | 1.245 µs/msg
+MarketDataIncrementalRefresh('X') | Compiled full spec. for FIX.4.4          | Yes        | 1.392 µs/msg
 
 For more details see `doc/` directory of the project.

src/scanner.c

@@ -30,6 +30,10 @@ EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "fix_impl.h"
 
+#ifdef USE_SSE
+#include <xmmintrin.h>
+#endif
+
 // message buffer handling
 static
 char* make_space(fix_parser* const parser, char* dest, unsigned extra_len)
@@ -103,9 +107,36 @@ bool copy_chunk(scanner_state* const state)
 static
 unsigned char copy_cs(char* restrict dest, const char* restrict src, unsigned n)
 {
-	unsigned char cs = (*dest++ = *src++);
+	unsigned char cs = 0;
+
+#ifdef USE_SSE
+	if(n >= sizeof(__m128i))
+	{
+		__m128i cs128 = _mm_loadu_si128((const __m128i*)src);
+
+		src += sizeof(__m128i);
+		_mm_storeu_si128((__m128i*)dest, cs128);
+		dest += sizeof(__m128i);
+
+		while((n -= sizeof(__m128i)) >= sizeof(__m128i))
+		{
+			const __m128i tmp = _mm_loadu_si128((const __m128i*)src);
+
+			src += sizeof(__m128i);
+			_mm_storeu_si128((__m128i*)dest, tmp);
+			dest += sizeof(__m128i);
+			cs128 = _mm_add_epi8(cs128, tmp);
+		}
+
+		cs128 = _mm_add_epi8(cs128, _mm_srli_si128(cs128, 8));
+		cs128 = _mm_add_epi8(cs128, _mm_srli_si128(cs128, 4));
+		cs128 = _mm_add_epi8(cs128, _mm_srli_si128(cs128, 2));
+		cs128 = _mm_add_epi8(cs128, _mm_srli_si128(cs128, 1));
+		cs += _mm_extract_epi16(cs128, 0);	// SSE4: _mm_extract_epi8 ?
+	}
+#endif	// #ifdef USE_SSE
 
-	while(--n > 0)
+	while(n-- > 0)
 		cs += (*dest++ = *src++);
 
 	return cs;