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

[Hal Finkel]

----- Original Message -----
> From: "usha shau" <ushashau1 at gmail.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: llvmdev at cs.uiuc.edu
> Sent: Monday, September 22, 2014 10:09:31 PM
> Subject: Re: [LLVMdev] Use of llvm.prefetch intrinsic for basicblock prefetching
> 
> 
> 
> 
> Hi,
> 
> 
> Thanks,
> I am targetting x86 architecture.

Interesting; looks like something needs to be fixed. Please file a bug using http://llvm.org/bugs/ (select "libraries" as the product and "Backend: X86" as the component).

 -Hal

> 
> -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
> > 
> > _______________________________________________
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> > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
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> > 
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
> 
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory