[llvm-commits] [llvm] r61401 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/2008-12-23-dagcombine-6.ll

[Dale Johannesen]

On Dec 23, 2008, at 3:30 PMPST, Chris Lattner wrote:

>
> On Dec 23, 2008, at 3:16 PM, Dale Johannesen wrote:
>
>>
>> On Dec 23, 2008, at 3:14 PMPST, Chris Lattner wrote:
>>
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=61401&view=rev
>>>> Log:
>>>> Add another permutation where we should get rid of a-a.
>>>
>>>> @@ -1177,13 +1177,20 @@
>>>>  return N0.getOperand(1);
>>>> // fold (A+B)-B -> A
>>>> if (N0.getOpcode() == ISD::ADD && N0.getOperand(1) == N1)
>>>> -    return N0.getOperand(0);
>>>> -  // fold ((A+(B-C))-B) -> A-C
>>>> +    return N0.getOperand(0);
>>>> +  // fold ((A+(B+-C))-B) -> A+-C
>>>
>>> I don't see why you'd ever way to match on A + (-B).  Shouldn't dag
>>> combine independently fold this into A-B?
>>
>> That should be read "plus or minus".
>
> Ah, please clarify the comment, thanks!

What would you prefer?  I've used this elsewhere without confusing  
anybody.