llvm dev - Aug 2016 - Annotating DAG with locations for specific machine instructions

I have a target-specific LoopPass which checks loops to see whether some
machine-specific instructions can be profitably used and needs to mark them
in a way that can easily be seen during machine instruction lowering. So
what I imagine could work is inserting pseudo-instructions, e.g. at the end
of the loop header - but I haven't seen how to do this through IRBuilder or
recognized an equivalent action being performed on other targets. Please
point me at an example of this approach (or educate me on why it's never
going to work...)
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if i understand well, Hexagon backend may have what you need. 
HexagonHardwareLoops.cpp  to begin.

On 29/08/2016 02:07 μμ, Tyro Software via llvm-dev
wrote:
> I have a target-specific LoopPass which checks loops to see whether 
> some machine-specific instructions can be profitably used and needs to 
> mark them in a way that can easily be seen during machine instruction 
> lowering. So what I imagine could work is inserting 
> pseudo-instructions, e.g. at the end of the loop header - but I 
> haven't seen how to do this through IRBuilder or recognized an 
> equivalent action being performed on other targets. Please point me at 
> an example of this approach (or educate me on why it's never going to 
> work...)
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

-- 

Nikos Stavropoulos
Compiler Engineer

Think-Silicon

http://www.think-silicon.com

Patras Science Park
26504, Patras, Greece
tel: +30 2610 911543

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Have you thought of inserting intrinsics into the IR and then picking them
up and removing them in the backend?

- Ryan

On Mon, Aug 29, 2016 at 7:07 AM, Tyro Software via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> I have a target-specific LoopPass which checks loops to see whether some
> machine-specific instructions can be profitably used and needs to mark them
> in a way that can easily be seen during machine instruction lowering. So
> what I imagine could work is inserting pseudo-instructions, e.g. at the end
> of the loop header - but I haven't seen how to do this through
IRBuilder or
> recognized an equivalent action being performed on other targets. Please
> point me at an example of this approach (or educate me on why it's
never
> going to work...)
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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