Initial commit from sysy-main

testdata/functional/35_op_priority1.sy

@@ -0,0 +1,9 @@
+//test the priority of add and mul
+int main(){
+    int a, b, c, d;
+    a = 10;
+    b = 4;
+    c = 2;
+    d = 2;
+    return c + a * b - d; 
+}