[LLVMdev] Use of llvm.prefetch intrinsic for basicblock prefetching

usha shau
Tue, 23 Sep 2014 03:09:31 -0000

Hi,

Thanks,
I am targetting x86 architecture.

-Usha

On Mon, Sep 22, 2014 at 10:39 PM, Hal Finkel <hfinkel at anl.gov> wrote:

> ----- Original Message -----
> > From: "usha shau" <ushashau1 at gmail.com>
> > To: llvmdev at cs.uiuc.edu
> > Sent: Monday, September 22, 2014 7:01:20 AM
> > Subject: [LLVMdev] Use of llvm.prefetch intrinsic for basicblock
> prefetching
> >
> > Hi,
> >
> >
> > I am new to LLVM and using it for my project where I want to perform
> > software prefetching of code blocks.
> > I am not able to use the llvm.prefetch instruction to fetch a block
> > of code in instruction cache. The LangRef manual mentions that
> > giving last argument as '0' performs prefetch on instruction
cache.
> > However, I get the following error when I do that.
> >
> > LLVM ERROR: Cannot select: 0x2a39348: ch = Prefetch 0x2a39030,
> > 0x2a39138, 0x2a38c10, 0x2a39240, 0x2a38c10<LD1[%x1]> [ORD=9]
[ID=15]
> > 0x2a39138: i64 = FrameIndex<1> [ID=4]
> > 0x2a38c10: i32 = Constant<0> [ID=1]
> > 0x2a39240: i32 = Constant<1> [ID=5]
> > 0x2a38c10: i32 = Constant<0> [ID=1]
> > In function: main
> >
> >
> > What does this error mean?
> > Can anyone please tell me if I can inform the processor to prefetch
> > code to instruction cache?
>
> It means that the target backend does not implement that prefetch variant
> and that it does not provide the appropriate fall-back behavior. What
> architecture are you targeting?
>
> Generally speaking, please file a bug report.
>
>  -Hal
>
> >
> > Thanks in advance.
> > Usha
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
>
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