adding get_expression

src/parser/utils_parser.py

@@ -145,3 +145,28 @@ def get_empty_spec():
     spec["rules"] = ""
 
     return spec
+
+#It returns the expression that a instruction takes as argument
+#It returns a expression of the form:
+# op -> opcode_name
+# exp -> [int_val] | [input_var] | [op, [exp]]
+
+def get_expression(var, instructions):
+    if var.startswith("0x"):
+        return [var]
+
+    candidates = list(filter(lambda x: var in x.get_out_args(), instructions))
+    if len(candidates) == 0:
+        return [var]
+
+    assert(len(candidates) == 1, "[ERROR]: A variable cannot be generated by more than one instruction")
+
+    new_instruction = candidates[0]
+
+    sub_expression = []
+    for v in new_instruction.get_in_args():
+        new_subexp = get_expression(v,instructions)
+        sub_expression.append(new_subexp)
+
+    return [new_instruction.get_op_name(),sub_expression]
+