llvm dev - Sep 2014 - [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
<http://llvm.org/docs/LangRef.html#llvm-prefetch-intrinsic>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?

Thanks in advance.
Usha
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----- 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

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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