[llvm-dev] Document to understand vectorized code

[Sudakshina Dutta via llvm-dev]

Dear Stefanos,

I want to understand how the generated code works. For example, the code
that I generated using -Rpass=loop-vectorize -Rpass-analysis=loop-vectorize
has many shufflevector and other instructions. I wanted to have a document
(if there exists any) where an example on loop-vectorization is done with
some explanation on the workflow of the code.

Thanks,
Sudakshina

On Mon, Jun 7, 2021 at 7:03 AM Stefanos Baziotis <
stefanos.baziotis at gmail.com> wrote:

> Hi Sudakshina,
>
> First, it helps if you can put your code in a godbolt snippet, like this
> [1]. It helps people in multiple ways (e.g., they don't have to download
> files, they can see exactly what cmd arguments you used, they can
> tweak the cmd arguments without having LLVM on their machine etc.).
>
> Is there any comprehensive tutorial/document to understand generated
>> instructions or the semantics of the vectorized code ?
>
>
> This is quite generic, what is more specifically that you want to
> understand? Do you want to understand what each individual instruction
> does? Do you maybe understand that but
> you don't know what is the general method to generate, let's say by hand,
> vectorized code (or more specifically, branching vectorized code). Or
> maybe, you want to understand
> how _LLVM_ generates this code, i.e., the inner workings of the
> vectorization passes.
>
> Best,
> Stefanos
>
> [1] https://godbolt.org/z/8eKqnrMPn
>
> Στις Κυρ, 6 Ιουν 2021 στις 6:17 π.μ., ο/η Sudakshina Dutta via llvm-dev <
> llvm-dev at lists.llvm.org> έγραψε:
>
>> Dear all,
>>
>> Greetings. I have generated a vectorized code from a C source file
>> (attached). Is there any comprehensive tutorial/document to understand
>> generated instructions or the semantics of the vectorized code ?
>>
>> Thanks,
>> Sudakshina
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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