optimize for constant int get

src/codegen/codegen.cpp

@@ -197,6 +197,15 @@ CodeGen::value2reg(Value *v, int i, string recommend) {
     if (dynamic_cast<Constant *>(v)) {
         if (v == CONST_0)
             return "$zero";
+        if (dynamic_cast<ConstantInt *>(v)) {
+            auto const_int_v = static_cast<ConstantInt *>(v)->get_value();
+            auto [l, h] = immRange(12, false);
+            if (l <= const_int_v and const_int_v <= h) {
+                output.push_back("addi.d " + reg_name + ", $zero, " +
+                                 to_string(const_int_v));
+                return reg_name;
+            }
+        }
         auto constant = static_cast<Constant *>(v);
         if (ROdata.find(constant) == ROdata.end())
             ROdata[constant] = ".LC" + to_string(ROdata.size());