algebra.dcf

用Java实现的编译器。把源代码编译成SPARC汇编程序

// some tests for algebraic simplificationm

class Program {

  // has a side effect
  int foo() {
    callout("printf", "Hi, I am a side effect.\n");
    return 10;
  }
  
  void main() {
    int a,b,c;
    int x,y,z;

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

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

    callout("printf","C? ");
    c = callout("readint");

    x = a - a;  // should go to 0
    y = b * 1;  // should go to b
    z = c + 0;  // should go to c

    callout("printf", "x: %d  ", x);
    callout("printf", "y: %d  ", y);
    callout("printf", "z: %d\n", z);

    x = a + b + c - a; // ideally, should reduce to b + c.
    y = 3 * b + 4 * b; // relatively easily converted to 7 * b
    z = -2 * c + a * c + 2 * c + 3 * a * c; // convertable to (4 * a * c)

    callout("printf", "x: %d  ", x);
    callout("printf", "y: %d  ", y);
    callout("printf", "z: %d\n", z);

    x = a * 0 + 0 * (foo()); // convertable to 0, but foo() still needs
                             // to be called, since it has a side effect.
    y = b * foo() + c * foo(); // convertable to (b+c)*foo(), 
                               // but call foo twice.
    z = (a - a) * (b); // convertable to 0; make sure that multiple rounds 
                       // happen.

    callout("printf", "x: %d  ", x);
    callout("printf", "y: %d  ", y);
    callout("printf", "z: %d\n", z);

    x = (a + b) * (c + 1); // this is as efficent as it gets. 
                       // it's bad if it's canonicalized to something worse.
    
    callout("printf", "x: %d\n", x);
  }
}