Hi Richard,

> Don't we still need this code (without the REG_DEAD handling) for the
> case in which…
> 
>> +      /* As we are transforming
>> +	 if (x > y)
>> +	   {
>> +	     a = b;
>> +	     c = d;
>> +	   }
>> +	 into
>> +	   a = (x > y) ...
>> +	   c = (x > y) ...
>> +
>> +	 we potentially check x > y before every set.
>> +	 Even though the check might be removed by subsequent passes, this means
>> +	 that we cannot transform
>> +	   if (x > y)
>> +	     {
>> +	       x = y;
>> +	       ...
>> +	     }
>> +	 into
>> +	   x = (x > y) ...
>> +	   ...
>> +	 since this would invalidate x and the following to-be-removed checks.
>> +	 Therefore we introduce a temporary every time we are about to
>> +	 overwrite a variable used in the check.  Costing of a sequence with
>> +	 these is going to be inaccurate so only use temporaries when
>> +	 needed.  */
>> +      if (reg_overlap_mentioned_p (target, cond))
>> +	temp = gen_reg_rtx (GET_MODE (target));
> 
> …this code triggers?  I don't see otherwise how later uses of x would
> pick up “temp” instead of the original target.  E.g. suppose we had:
> 
>      if (x > y)
>        {
>          x = …;
>          z = x; // x does not die here
>        }
> 
> Without the loop, it looks like z would pick up the old value of x
> (used in the comparison) instead of the new one.

getting back to this now.  I re-added handling of the situation you 
mentioned (even though I didn't manage to trigger it myself).

Regards
  Robin