copyprop.dcf

来自「用Java实现的编译器。把源代码编译成SPARC汇编程序」· DCF 代码 · 共 45 行

class Program {
  
  void main() {
    int a,b,c,d,e,f;

    callout("printf","A? ");
    //a = callout("readint");

    callout("printf","B? ");
    //b = callout("readint");

    callout("printf","C? ");
    //c = callout("readint");
    a = 1;
    b = 2;
    c = 3;

    d = a + b;
    e = d;  // may be removed
    f = e;   // should be optimized to f = d
 
    callout("printf", "f: %d  ", f);
    
    e = c;  // may not remove
    f = e + 3; // may replace the e by c
    a = b;  // may be removed
    if (c < 5) { 
      e = e + c; // may replace the e by c
      b = a;     // should replace a by b, maybe eliminate entirely
    }

    a = e - 3;

    callout("printf", "a: %d  ", a);
    callout("printf", "b: %d  ", b);
    callout("printf", "c: %d  ", c);
    callout("printf", "d: %d  ", d);
    callout("printf", "e: %d  ", e);
    callout("printf", "f: %d\n\n", f);
  }
}