[llvm-commits] [llvm] r61401 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/2008-12-23-dagcombine-6.ll
clattner at apple.com
Tue Dec 23 15:30:45 PST 2008
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
>>> 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!
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