Don't load all of rm.sm[i]

For whatever reason, Go insisted on loading rm.sm[i] in several chunks,
even though it could be loaded in a single 64-bit block. Instead, let's
reorder our loads to minimize the amount of memory we're uselessly
moving around.

This gives us about a 15% perf boost in
github.com/julienschmidt/go-http-routing-benchmark's
BenchmarkGoji_StaticAll, and questionable benefits (i.e., not
distinguishable from noise but certainly no worse) on Goji's own
benchmarks.

web/fast_router.go

@@ -48,8 +48,8 @@ Unfortunately, the code implementing all of this is pretty bad (both inefficient
 and hard to read). Maybe someday I'll come and take a second pass at it.
 */
 type state struct {
-	bs   [3]byte
 	mode smMode
+	bs   [3]byte
 	i    int32
 }
 type stateMachine []state

web/router.go

@@ -170,29 +170,31 @@ func (rm routeMachine) route(c *C, w http.ResponseWriter, r *http.Request) (meth
 
 	var i int
 	for {
-		s := rm.sm[i]
-		if s.mode&smSetCursor != 0 {
-			p = r.URL.Path[s.i:]
+		sm := rm.sm[i].mode
+		if sm&smSetCursor != 0 {
+			si := rm.sm[i].i
+			p = r.URL.Path[si:]
 			i++
 			continue
 		}
 
-		length := int(s.mode & smLengthMask)
+		length := int(sm & smLengthMask)
 		match := false
 		if length <= len(p) {
+			bs := rm.sm[i].bs
 			switch length {
 			case 3:
-				if p[2] != s.bs[2] {
+				if p[2] != bs[2] {
 					break
 				}
 				fallthrough
 			case 2:
-				if p[1] != s.bs[1] {
+				if p[1] != bs[1] {
 					break
 				}
 				fallthrough
 			case 1:
-				if p[0] != s.bs[0] {
+				if p[0] != bs[0] {
 					break
 				}
 				fallthrough
@@ -202,20 +204,21 @@ func (rm routeMachine) route(c *C, w http.ResponseWriter, r *http.Request) (meth
 			}
 		}
 
-		if match && s.mode&smRoute != 0 {
-			if matchRoute(rm.routes[s.i], m, &methods, r, c) {
-				rm.routes[s.i].handler.ServeHTTPC(*c, w, r)
+		if match && sm&smRoute != 0 {
+			si := rm.sm[i].i
+			if matchRoute(rm.routes[si], m, &methods, r, c) {
+				rm.routes[si].handler.ServeHTTPC(*c, w, r)
 				return 0, true
 			} else {
 				i++
 			}
-		} else if (match && s.mode&smJumpOnMatch != 0) ||
-			(!match && s.mode&smJumpOnMatch == 0) {
+		} else if (match && sm&smJumpOnMatch != 0) ||
+			(!match && sm&smJumpOnMatch == 0) {
 
-			if s.mode&smFail != 0 {
+			if sm&smFail != 0 {
 				return methods, false
 			}
-			i = int(s.i)
+			i = int(rm.sm[i].i)
 		} else {
 			i++
 		}