Patch: don't generate dead bytecode

[Bryce McKinlay]

Per Bothner wrote:

> Folding a binary operator when both operand are constants is presumably
> safe - or are the some traps I'm not aware of? 


Here's a case which we get wrong with -O. Note that if x and y are not 
constant, it works correctly.

public class PR4822
{
  public static void main(String[] args)
  {
    int x = 99;
    int y = 0;

    if ((x = y) == (99 - (y = 99)))
      System.out.println ("OK");
    else
      System.out.println ("FAIL");
  }
}


regards

Bryce.