[llvm-dev] Question on target-features

[Cranmer, Joshua via llvm-dev]

Since the target cpu is znver2, which has avx2, target-features of “+avx -avx2” is not equivalent to “+avx”. So the two attributes in the original question are not equivalent.

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Krzysztof Parzyszek via llvm-dev
Sent: Friday, September 27, 2019 11:07
To: Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>; llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] Question on target-features

Ugh, that would be a “yes” then…

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Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto: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<mailto:cs15mtech11002 at iith.ac.in>>; llvm-dev at lists.llvm.org<mailto: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.

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Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto: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<mailto: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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