shader: Add copy constructor to instructions

src/shader_recompiler/frontend/ir/basic_block.h

@@ -40,6 +40,9 @@ public:
     /// Appends a new instruction to the end of this basic block.
     void AppendNewInst(Opcode op, std::initializer_list<Value> args);
 
+    /// Prepends a copy of an instruction to this basic block before the insertion point.
+    iterator PrependNewInst(iterator insertion_point, const Inst& base_inst);
+
     /// Prepends a new instruction to this basic block before the insertion point.
     iterator PrependNewInst(iterator insertion_point, Opcode op,
                             std::initializer_list<Value> args = {}, u32 flags = 0);