fix(asm): correct RISC-V operand order and complete RVC compression

Assisted-by: DeepSeek V4 Pro

verify/l64_groundtruth_test.go

@@ -7,6 +7,7 @@ import (
 	"bytes"
 	"fmt"
 	"os"
+	"strings"
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/asm"
@@ -81,11 +82,23 @@ func diffHex(a, b []byte) string {
 	}
 	for i := 0; i < n; i += 4 {
 		ab, bb := "??", "??"
-		if i < len(a) {
+		if i+4 <= len(a) {
 			ab = fmt.Sprintf("%02x%02x%02x%02x", a[i], a[i+1], a[i+2], a[i+3])
+		} else if i < len(a) {
+			var sb strings.Builder
+			for j := i; j < len(a); j++ {
+				fmt.Fprintf(&sb, "%02x", a[j])
+			}
+			ab = sb.String()
 		}
-		if i < len(b) {
+		if i+4 <= len(b) {
 			bb = fmt.Sprintf("%02x%02x%02x%02x", b[i], b[i+1], b[i+2], b[i+3])
+		} else if i < len(b) {
+			var sb strings.Builder
+			for j := i; j < len(b); j++ {
+				fmt.Fprintf(&sb, "%02x", b[j])
+			}
+			bb = sb.String()
 		}
 		mark := " "
 		if ab != bb {