Update model solution.

- Stop calculating operands for & operators.
- Evaluate the lhs of compound operators only once.
- Add `side-effect.c` example.

examples/ir2/typedef.ir

@@ -8,11 +8,10 @@ init:
 
 block b0:
   %b0:i0:unit = store 0:i32 %l0:i32*
-  %b0:i1:i32 = load %l0:i32*
+  %b0:i1:unit = nop
   %b0:i2:unit = nop
-  %b0:i3:unit = nop
-  %b0:i4:unit = store 1:i32 %l0:i32*
-  %b0:i5:unit = nop
-  %b0:i6:i32 = load %l0:i32*
-  ret %b0:i6:i32
+  %b0:i3:unit = store 1:i32 %l0:i32*
+  %b0:i4:unit = nop
+  %b0:i5:i32 = load %l0:i32*
+  ret %b0:i5:i32
 }