[llvm-dev] sum elements in the vector

Fri May 27 15:50:37 PDT 2016

Hi Shahid.

Do you mind providing a concrete example of X86 code where an intrinsic was
added (preferrable with filenames and line numbers)? I'm having difficulty
tracking down the steps you provided.

Any help is appreciated.

On Mon, Apr 4, 2016 at 9:02 PM, Shahid, Asghar-ahmad <
Asghar-ahmad.Shahid at amd.com> wrote:

> Hi Rail,
>
>
>
> We had done this for generation of X86 PSAD (sum of absolute difference)
> instruction through
>
> Llvm intrinsic. Doing this requires following
>
> 1.       Define an intrinsic, xyz(),  for the required instruction and
> corresponding SDNode
>
> 2.       Generate the “call xyz() “ IR based the matched pattern
>
> 3.       Map “call xyz()” IR to corresponding SDNode in
> SelectionDagBuilder.cpp
>
> 4.       Provide default expansion of the xyz() intrinsic
>
> 5.       Legalize type and/or operation
>
> 6.       Provide Lowering of intrinsic/SDNode to generate your target
> instruction
>
>
>
> You can visit http://llvm.org/docs/ExtendingLLVM.html for details.
>
>
>
> Regards,
>
> Shahid
>
>
>
>
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *Rail
> Shafigulin via llvm-dev
> *Sent:* Monday, April 04, 2016 11:00 PM
> *To:* Das, Dibyendu
> *Cc:* llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] sum elements in the vector
>
>
>
> Thanks for the pointers. I looked at hadd instructions. They seem to do
> very similar to what I need. Unfortunately as I said before my LLVM
> experience is limited. My understanding is that when I create a new type of
> SDNode I need to specify a pattern for it, so that when LLVM is analyzing
> the code and is seeing a given pattern it would create this particular
> node. I'm really struggling to understand how it is done. So here are the
> problems that I'm having.
>
>
>
> 1. How do I identify that pattern that should be used?
>
> 2. How do I specify a given pattern?
>
>
>
> Do you (or someone else) mind helping me out?
>
>
>
> Any help is appreciated.
>
>
>
> On Mon, Apr 4, 2016 at 9:59 AM, Das, Dibyendu <Dibyendu.Das at amd.com>
> wrote:
>
> This is roughly along the lines of x86 hadd* instructions though the
> semantics of hadd* may not exactly match what you are looking for. This is
> probably more in line with x86/ARM SAD-like instructions but I don’t think
> llvm generates SAD without intrinsics.
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *Rail
> Shafigulin via llvm-dev
> *Sent:* Monday, April 04, 2016 9:34 AM
> *To:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* [llvm-dev] sum elements in the vector
>
>
>
> My target has an instruction that adds up all elements in the vector and
> stores the result in a register. I'm trying to implement it in my compiler
> but I'm not sure even where to start.
>
>
>
> I did look at other targets, but they don't seem to have anything like it
> ( I could be wrong. My experience with LLVM is limited, so if I missed it,
> I'd appreciate if someone could point it out ).
>
>
>
> My understanding is that if SDNode for such an instruction doesn't exist I
> have to define one. Unfortunately, I don't know how to do it. I don't even
> know where to start looking. Would someone care to point me in the right
> direction?
>
>
>
> Any help is appreciated.
>
>
>
> --
>
> Rail Shafigulin
>
> Software Engineer
> Esencia Technologies
>
>
>
>
>
> --
>
> Rail Shafigulin
>
> Software Engineer
> Esencia Technologies
>

-- 
Rail Shafigulin
Software Engineer
Esencia Technologies

On Mon, Apr 4, 2016 at 9:02 PM, Shahid, Asghar-ahmad <
Asghar-ahmad.Shahid at amd.com> wrote:

> Hi Rail,
>
>
>
> We had done this for generation of X86 PSAD (sum of absolute difference)
> instruction through
>
> Llvm intrinsic. Doing this requires following
>
> 1.       Define an intrinsic, xyz(),  for the required instruction and
> corresponding SDNode
>
> 2.       Generate the “call xyz() “ IR based the matched pattern
>
> 3.       Map “call xyz()” IR to corresponding SDNode in
> SelectionDagBuilder.cpp
>
> 4.       Provide default expansion of the xyz() intrinsic
>
> 5.       Legalize type and/or operation
>
> 6.       Provide Lowering of intrinsic/SDNode to generate your target
> instruction
>
>
>
> You can visit http://llvm.org/docs/ExtendingLLVM.html for details.
>
>
>
> Regards,
>
> Shahid
>
>
>
>
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *Rail
> Shafigulin via llvm-dev
> *Sent:* Monday, April 04, 2016 11:00 PM
> *To:* Das, Dibyendu
> *Cc:* llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] sum elements in the vector
>
>
>
> Thanks for the pointers. I looked at hadd instructions. They seem to do
> very similar to what I need. Unfortunately as I said before my LLVM
> experience is limited. My understanding is that when I create a new type of
> SDNode I need to specify a pattern for it, so that when LLVM is analyzing
> the code and is seeing a given pattern it would create this particular
> node. I'm really struggling to understand how it is done. So here are the
> problems that I'm having.
>
>
>
> 1. How do I identify that pattern that should be used?
>
> 2. How do I specify a given pattern?
>
>
>
> Do you (or someone else) mind helping me out?
>
>
>
> Any help is appreciated.
>
>
>
> On Mon, Apr 4, 2016 at 9:59 AM, Das, Dibyendu <Dibyendu.Das at amd.com>
> wrote:
>
> This is roughly along the lines of x86 hadd* instructions though the
> semantics of hadd* may not exactly match what you are looking for. This is
> probably more in line with x86/ARM SAD-like instructions but I don’t think
> llvm generates SAD without intrinsics.
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *Rail
> Shafigulin via llvm-dev
> *Sent:* Monday, April 04, 2016 9:34 AM
> *To:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* [llvm-dev] sum elements in the vector
>
>
>
> My target has an instruction that adds up all elements in the vector and
> stores the result in a register. I'm trying to implement it in my compiler
> but I'm not sure even where to start.
>
>
>
> I did look at other targets, but they don't seem to have anything like it
> ( I could be wrong. My experience with LLVM is limited, so if I missed it,
> I'd appreciate if someone could point it out ).
>
>
>
> My understanding is that if SDNode for such an instruction doesn't exist I
> have to define one. Unfortunately, I don't know how to do it. I don't even
> know where to start looking. Would someone care to point me in the right
> direction?
>
>
>
> Any help is appreciated.
>
>
>
> --
>
> Rail Shafigulin
>
> Software Engineer
> Esencia Technologies
>
>
>
>
>
> --
>
> Rail Shafigulin
>
> Software Engineer
> Esencia Technologies
>

-- 
Rail Shafigulin
Software Engineer
Esencia Technologies
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