[PATCH][X86] __builtin_ctz/clz sometimed defined for zero input

[Sean Silva]

On Mon, Oct 27, 2014 at 7:40 PM, Richard Smith <richard at metafoo.co.uk>
wrote:

> On Mon, Oct 27, 2014 at 7:09 PM, Sean Silva <chisophugis at gmail.com> wrote:
>
>>
>>
>> On Mon, Oct 27, 2014 at 6:16 PM, Robinson, Paul <
>> Paul_Robinson at playstation.sony.com> wrote:
>>
>>>  I don't know about Mac, but on my Ubuntu, Intrin.h shows up in the
>>> expected place:
>>>
>>>
>>>
>>> ~/projects/upstream/writeable/obj$ find . -name Intrin.h
>>>
>>> ./Debug+Asserts/lib/clang/3.6.0/include/Intrin.h
>>>
>>> ./Debug+Asserts/lib/clang/3.5.0/include/Intrin.h
>>>
>>> ./Debug+Asserts/lib/clang/3.4/include/Intrin.h
>>>
>>> ./Debug+Asserts/lib/clang/3.5/include/Intrin.h
>>>
>>
>> I presume that isn't where existing software for those platforms looks
>> for them.
>>
>
> It is, but they do nothing but #include_next the next Intrin.h if you're
> not targeting win32, so they act as if they don't exist.
>

Why do they do that?

-- Sean Silva


>
>
>> -- Sean Silva
>>
>>
>>>
>>>
>>> *From:* Chandler Carruth [mailto:chandlerc at google.com]
>>> *Sent:* Monday, October 27, 2014 5:17 PM
>>> *To:* Robinson, Paul
>>> *Cc:* Sean Silva; cfe-commits at cs.uiuc.edu
>>> *Subject:* Re: [PATCH][X86] __builtin_ctz/clz sometimed defined for
>>> zero input
>>>
>>>
>>>
>>>
>>>
>>> On Mon, Oct 27, 2014 at 5:02 PM, Robinson, Paul <
>>> Paul_Robinson at playstation.sony.com> wrote:
>>>
>>> That makes lzcntintrin.h completely pointless.  They'd just be alternate
>>> names for the functions in Intrin.h.
>>>
>>>
>>> If those names need to be supported for compatibility and portability
>>> then it still seems to have a point.
>>>
>>>
>>>
>>> Note that Intrin.h doesn't exist on Linux or Mac.
>>>
>>
>>
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>>
>>
>
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