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LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU

github.com

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Re: LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU

#2

Post by willvarfar »

It bugs me that LLVM targets are not properly 'plug in'.

LLVM backends can be in a plugin, but you have to tell the frontend which target to use (so it can use the correct data-layout etc). Its the frontends that don't support plug-in targets. Clang, for example, hardcodes the supported targets.

A combination of using enums as a 'target triple' and lack of dynamic target registration conspire against easy-to-use out-of-tree targets :(

Re: LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU

#5

Post by pepijndevos »

cnvogel wrote: post #4
pepijndevos wrote: post #3

What can you do with this?

This has some additional info from the author: http://crna.cc/

I get that it's a compiler backend for the GPU of the Raspi, but what does that mean? I mean, can you compile arbitrary C code to run on the GPU? Is this for making a GPU firmware? Divers? games? Bitcoin miners?

Re: LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU

#6

Post by jdmoreira »

pepijndevos wrote: post #5
cnvogel wrote: post #4

Earlier quoted context omitted.

This has some additional info from the author: http://crna.cc/

I get that it's a compiler backend for the GPU of the Raspi, but what does that mean? I mean, can you compile arbitrary C code to run on the GPU? Is this for making a GPU firmware? Divers? games? Bitcoin miners?

Whatever you want. It runs on each GPU core. You can do a lot of DSP for example.

Re: LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU

#9

Post by krasin »

willvarfar wrote: post #2

It bugs me that LLVM targets are not properly 'plug in'. LLVM backends can be in a plugin, but you have to tell the frontend which target to use (so it can use the correct data-layout etc). Its the frontends that don't support plug-in targets. Clang, for example, hardcodes the supported targets. A combination of using enums as a 'target triple' and lack of dynamic target registration conspire against easy-to-use out-…

Out-of-tree targets for LLVM are generally a bad idea given how fast LLVM is changed. Every change could break the out-of-tree target, and being out-of-tree, there's no way the upstream developers could notice that.

Re: LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU

#10

Post by TD-Linux »

haberman wrote: post #7

You can run C code on GPUs? I don't know anything about GPUs, but I thought they had a completely different programming model that requires different programming languages and paradigms.

Yup. Check out the VideoCore ISA:

http://www.broadcom.com/docs/support/videocore/VideoCoreIV-A...

Note that in this case, the author is writing the bootloader firmware so performance isn't a major concern, though.

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