[llvm-commits] [PATCH] AndOrXor Chain Optimization
Chris Lattner
clattner at apple.com
Wed Aug 17 11:40:31 PDT 2011
On Aug 16, 2011, at 3:47 PM, Eli Friedman wrote:
> 2011/8/16 Daniel Nicácio <dnicacios at gmail.com>:
>> ping
>> Updated patch with revision 137728
>
> This is a lot of code for a rather obscure optimization; I don't see
> how it is worthwhile.
I agree. Does this actually speed up a known program, or is this just a theoretical exercise?
-Chris
> -Eli
>
>> 2011/8/5 Daniel Nicácio <dnicacios at gmail.com>
>>>
>>> New unified diff file attached.
>>> Daniel Nicacio
>>>
>>> 2011/8/4 Eli Friedman <eli.friedman at gmail.com>
>>>>
>>>> 2011/8/4 Daniel Nicácio <dnicacios at gmail.com>
>>>>>
>>>>> Hi, this patch increments the instcombiner pass.
>>>>> It adds a new XOR, OR, AND optimization, trying to find a chain of
>>>>> logical instructions (xor, and, or) operating on different bits of the same
>>>>> word. If this chain is found, it is collapsed into a single logical
>>>>> instruction.
>>>>> The figure below shows a generic example:
>>>>> Any comments and critics are welcome.
>>>>
>>>> Please attach a single diff containing all the changes, and please use
>>>> "svn diff" or some other tool that makes a unified diff.
>>>> -Eli
>>
>>
>
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