shader: Add TryInstRecursive utility to values

src/shader_recompiler/frontend/ir/value.h

@@ -57,6 +57,7 @@ public:
 
     [[nodiscard]] IR::Inst* Inst() const;
     [[nodiscard]] IR::Inst* InstRecursive() const;
+    [[nodiscard]] IR::Inst* TryInstRecursive() const;
     [[nodiscard]] IR::Value Resolve() const;
     [[nodiscard]] IR::Reg Reg() const;
     [[nodiscard]] IR::Pred Pred() const;
@@ -308,6 +309,13 @@ inline IR::Inst* Value::InstRecursive() const {
     return inst;
 }
 
+inline IR::Inst* Value::TryInstRecursive() const {
+    if (IsIdentity()) {
+        return inst->Arg(0).TryInstRecursive();
+    }
+    return type == Type::Opaque ? inst : nullptr;
+}
+
 inline IR::Value Value::Resolve() const {
     if (IsIdentity()) {
         return inst->Arg(0).Resolve();