internal/pkg: skip duplicate early

This significantly increases IR generation performance.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/ir.go

@@ -254,15 +254,16 @@ func (c *Cache) encodeAll(
 	a Artifact,
 	encoded map[Artifact]struct{},
 ) (err error) {
+	if _, ok := encoded[a]; ok {
+		return
+	}
+
 	for _, d := range a.Dependencies() {
 		if err = c.encodeAll(w, d, encoded); err != nil {
 			return
 		}
 	}
 
-	if _, ok := encoded[a]; ok {
-		return
-	}
 	encoded[a] = struct{}{}
 	return c.Encode(w, a)
 }