Refactor decoding the SELECT enum, so that there may be fewer compares.

src/vmod_selector.c

@@ -547,21 +547,27 @@ select(VRT_CTX, const struct match_data * const restrict match,
 	if (match->n == 1)
 		return match->indices[0];
 
-	if (selects == VENUM(UNIQUE)) {
+	switch (selects[0]) {
+	case 'U':
+		assert(selects == VENUM(UNIQUE));
 		VERR(ctx, "%s.%s(select=UNIQUE): %d elements were matched",
 		     obj, method, match->n);
 		return (UINT_MAX);
-	}
-	if (selects == VENUM(FIRST))
+	case 'L':
+		if (selects == VENUM(LAST))
+			return match->max;
+		if (selects == VENUM(LONGEST))
+			return match->indices[match->n - 1];
+		WRONG("illegal select enum");
+	case 'F':
+		assert(selects == VENUM(FIRST));
 		return match->min;
-	if (selects == VENUM(LAST))
-		return match->max;
-	if (selects == VENUM(SHORTEST))
+	case 'S':
+		assert(selects == VENUM(SHORTEST));
 		return match->indices[0];
-	if (selects == VENUM(LONGEST))
-		return match->indices[match->n - 1];
-	WRONG("illegal select enum");
-	return (UINT_MAX);
+	default:
+		WRONG("illegal select enum");
+	}
 }
 
 VCL_INT