[llvm-dev] Question on target-features

[Dangeti Tharun kumar via llvm-dev]

Thanks for the clarification. :)

On Fri, Sep 27, 2019 at 9:33 PM Craig Topper <craig.topper at gmail.com> wrote:

> And -feature will remove all other features that depend on the feature. So
> for x86, -sse2 will disable sse2, sse3, sse4.1, sse4.2, avx, avx2, etc.
>
> On Fri, Sep 27, 2019 at 8:13 AM Krzysztof Parzyszek via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> This thread is getting from bad to worse…  Certain features are assumed
>> as default for a given processor, so -feature will actually have an effect
>> of removing it from the feature string that is parsed in the subtarget.
>> Back to “no”…
>>
>>
>>
>> --
>>
>> Krzysztof Parzyszek  kparzysz at quicinc.com   AI tools development
>>
>>
>>
>> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of *Krzysztof
>> Parzyszek via llvm-dev
>> *Sent:* Friday, September 27, 2019 10:07 AM
>> *To:* Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>;
>> llvm-dev at lists.llvm.org
>> *Subject:* [EXT] Re: [llvm-dev] Question on target-features
>>
>>
>>
>> Ugh, that would be a “yes” then…
>>
>>
>>
>> --
>>
>> Krzysztof Parzyszek  kparzysz at quicinc.com   AI tools development
>>
>>
>>
>> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of *Krzysztof
>> Parzyszek via llvm-dev
>> *Sent:* Friday, September 27, 2019 10:05 AM
>> *To:* Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>;
>> llvm-dev at lists.llvm.org
>> *Subject:* [EXT] Re: [llvm-dev] Question on target-features
>>
>>
>>
>> No.  The way +feature works is that it causes the assignment
>> Attribute=Value to happen, where Attribute and Value are strings defined in
>> a td file.  With -feature, this assignment does not happen, so whatever the
>> default value is of Attribute, it will remain unchanged.
>>
>>
>>
>> --
>>
>> Krzysztof Parzyszek  kparzysz at quicinc.com   AI tools development
>>
>>
>>
>> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of *Dangeti
>> Tharun kumar via llvm-dev
>> *Sent:* Friday, September 27, 2019 9:23 AM
>> *To:* llvm-dev <llvm-dev at lists.llvm.org>
>> *Subject:* [EXT] [llvm-dev] Question on target-features
>>
>>
>>
>> Hi,
>>
>>
>>
>> In "target-features" list in LLVM-IR, there are "+feature", "-feature".
>> My question is, does "-feature" is equivalent to not specifying a feature
>> at all?
>>
>> For example:
>>
>> *attributes #0 = {  "target-cpu"="znver2"  "target-features"="+avx
>> -avx2" }*
>>
>> Wheather it is equalent to omitting the avx2 from list?
>>
>> *attributes #0 = {  "target-cpu"="znver2"  "target-features"="+avx" }*
>>
>> --
>>
>> Regards,
>>
>> DTharun
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
> --
> ~Craig
>


-- 
Regards,
DTharun
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