Improve and modularize compile-time CPU detection.

Ideally, we should move this to autoconf.

cpu-miner.c

@@ -37,8 +37,8 @@ enum {
 };
 
 enum sha256_algos {
-	ALGO_C,
-	ALGO_4WAY
+	ALGO_C,			/* plain C */
+	ALGO_4WAY,		/* parallel SSE2 */
 };
 
 static bool opt_debug;
@@ -63,7 +63,7 @@ static struct option_help options_help[] = {
 	{ "algo XXX",
 	  "(-a XXX) Specify sha256 implementation:\n"
 	  "\tc\t\tLinux kernel sha256, implemented in C (default)"
-#ifdef __SSE2__
+#ifdef WANT_SSE2_4WAY
 	  "\n\t4way\t\ttcatm's 4-way SSE2 implementation (EXPERIMENTAL)"
 #endif
 	  },
@@ -301,18 +301,23 @@ static void *miner_thread(void *thr_id_int)
 		gettimeofday(&tv_start, NULL);
 
 		/* scan nonces for a proof-of-work hash */
-		if (opt_algo == ALGO_C)
+		switch (opt_algo) {
+		case ALGO_C:
 			rc = scanhash(work.midstate, work.data + 64,
 				      work.hash1, work.hash, &hashes_done);
-#ifdef __SSE2__
-		else {
+			break;
+
+#ifdef WANT_SSE2_4WAY
+		case ALGO_4WAY: {
 			unsigned int rc4 =
 				ScanHash_4WaySSE2(work.midstate, work.data + 64,
 						  work.hash1, work.hash,
 						  &hashes_done);
 			rc = (rc4 == -1) ? false : true;
-		}
+			}
+			break;
 #endif
+		}
 
 		hashmeter(thr_id, &tv_start, hashes_done);
 
@@ -347,7 +352,7 @@ static void parse_arg (int key, char *arg)
 	case 'a':
 		if (!strcmp(arg, "c"))
 			opt_algo = ALGO_C;
-#ifdef __SSE2__
+#ifdef WANT_SSE2_4WAY
 		else if (!strcmp(arg, "4way"))
 			opt_algo = ALGO_4WAY;
 #endif

miner.h

@@ -4,6 +4,10 @@
 #include <stdbool.h>
 #include <jansson.h>
 
+#ifdef __SSE2__
+#define WANT_SSE2_4WAY 1
+#endif
+
 #ifndef ARRAY_SIZE
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
 #endif

sha256_4way.c

@@ -4,14 +4,15 @@
 
 // tcatm's 4-way 128-bit SSE2 SHA-256
 
-#ifdef __SSE2__
-
 #include <string.h>
 #include <assert.h>
 
 #include <xmmintrin.h>
 #include <stdint.h>
 #include <stdio.h>
+#include "miner.h"
+
+#ifdef WANT_SSE2_4WAY
 
 #define NPAR 32
 
@@ -467,4 +468,4 @@ static void DoubleBlockSHA256(const void* pin, void* pad, const void *pre, unsig
 
 }
 
-#endif /* __SSE2__ */
+#endif /* WANT_SSE2_4WAY */