[llvm-dev] Question on target-features

[Craig Topper via llvm-dev]

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
> _______________________________________________
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> llvm-dev at lists.llvm.org
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>
-- 
~Craig
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