[LLVMdev] aarch64 status for generating SIMD instructions

[Michael Zolotukhin]

Hi Ralph,

A bunch of useful options for vectorizers is listed in [1].

Also, what you see might be a target-independent issue, not an aarch64-specific. If you can share the code you tested I can try to explain why vectorizer fails to handle it, and hopefully we can fix it later:)

Thanks,
Michael

[1] http://llvm.org/docs/Vectorizers.html <http://llvm.org/docs/Vectorizers.html>


> On Feb 9, 2015, at 2:19 PM, Ralph Campbell <ralph.campbell at broadcom.com> wrote:
> 
> So far, all I have tried is –O3 and with & without “-mcpu=cortex-a57”.
> I’m new to LLVM so I’m not familiar with what optimization flags are available.
> I tried poking around in the LLVM documentation but haven’t found a definitive list.
> The clang man page is skimpy on details.
>  
> From: Arnaud A. de Grandmaison [mailto:arnaud.degrandmaison at arm.com] 
> Sent: Monday, February 09, 2015 2:11 PM
> To: Ralph Campbell
> Cc: llvmdev at cs.uiuc.edu
> Subject: RE: aarch64 status for generating SIMD instructions
>  
> Which compiler flags have you been using ?
>  
> There is definitely support for AArch64’s SIMD instructions, but their use depends on what the vectorizers can do with your code.
>  
> From: llvmdev-bounces at cs.uiuc.edu <mailto:llvmdev-bounces at cs.uiuc.edu> [mailto:llvmdev-bounces at cs.uiuc.edu <mailto:llvmdev-bounces at cs.uiuc.edu>] On Behalf Of Ralph Campbell
> Sent: 09 February 2015 22:30
> To: llvmdev at cs.uiuc.edu <mailto:llvmdev at cs.uiuc.edu>
> Subject: [LLVMdev] aarch64 status for generating SIMD instructions
>  
> I’m using Fedora 22 and gcc 4.9.2 to run llvm 3.5.1 on an ARM Juno reference box (cortex A53 & A57).
> I tried compiling some simple functions like dot product and axpy() into assembly to see if any of the SIMD instructions were generated (they weren’t).
> Perhaps I’m missing some compiler flag to enable it.
>  
> Does anyone know what the status is for aarch64 generating SIMD instructions?
> Anyone coordinating or leading this effort? (if there is one)
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