Code generation is probably missing somewhat trivial optimizations. Here's one example:

  int func(int x) {
      return x * 1;
  }

...still produces unnecessary stack manipulation:

   0000 C1            [10]   56 	pop	bc
   0001 E1            [10]   57 	pop	hl
   0002 E5            [11]   58 	push	hl
   0003 C5            [11]   59 	push	bc
   0004 C9            [10]   60 	ret

Plain "ret" would have been enough.