[patch][4.7] Enhance XOR handling in simplify-rtx.c

[Chung-Lin Tang]

On 2011/3/18 12:18 AM, Richard Henderson wrote:
> On 03/16/2011 06:55 PM, Chung-Lin Tang wrote:
>> You have to use DeMorgan's Law to distribute the ~ operator:
> 
> Duh.  Not sure where my head was yesterday.
> 
> Let's enhance the comment for someone else having an off day.  Perhaps
> 
> 	/* Given (xor (and A B) C), using P^Q == ~P&Q | ~Q&P and DeMorgan's
> 	   we can transform
> 		A&B ^ C == ~(A&B)&C | ~C&(A&B)
> 			== (~A|~B)&C | A&B&~C
> 			== ~A&C | ~B&C | A&B&~C
> 	   Attempt a few simplifications when B and C are both constants.  */
> 
>> +      if (GET_CODE (op0) == AND
>> +	  && CONST_INT_P (op1) && CONST_INT_P (XEXP (op0, 1)))
> 
> Should have a newline before the second && here.
> 
> Ok with those changes.

Thanks, committed patch attached below. Hope the comments are now
descriptive enough.

C.L.
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