llvm dev - Nov 2021 - Re-using a node in a DAG output pattern in TableGen

Hello, 

I currently have an instruction selection pattern that looks like this : 




def : Pat<myinputop type:$v0 type:$v1, 
(COMPNHQ 
(ADDHQrr 
(SLLHQSri $v0, 8), 
(SLLHQSri $v1, 8), 
), 
(SLLHQSri $v0, 8), 
comparison_ltu 
)>; 



This output pattern is supposed to be a DAG: the node (SLLHQSri $v0, 8) is used
two times.

Experimentally, TableGen seems to recognize it as such (the node `(SLLHQSri $v0,
8)` will not be duplicated).

I am wondering if there is a way to avoid having to repeat (SLLHQSri $v0, 8) in
the syntax of TableGen, something like:

BQ_BEGIN

def : Pat<inputpattern type:$v0 type:$v1, 
(COMPNHQ 
(ADDHQrr 
(SLLHQSri $v0, 8):$myvar, 
(SLLHQSri $v1, 8), 
), 
$myvar, 
comparison_ltu 
)>; 

BQ_END

If I try this, I get the error "Node 'myvar' in output pattern but
not input pattern".

Does anyone know if there is a way to name nodes from an output pattern to
produce a non-tree output DAG?

Do you know of any existing pattern featuring output DAG that are not trees? 

Thanks 

Cyril Six 
Compiler Engineer • Kalray 
Phone: 
csix at kalrayinc.com • [ https://www.kalrayinc.com/ | www.kalrayinc.com ] 

[ https://www.kalrayinc.com/ |   ] 
	
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You might give OutPatFrag a try:

// OutPatFrag is a pattern fragment that is used as part of an output pattern
// (not an input pattern). These do not have predicates or transforms, but are
// used to avoid repeated subexpressions in output patterns.
class OutPatFrag<dag ops, dag frag>
 : PatFrag<ops, frag, [{}], NOOP_SDNodeXForm>;

________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Cyril Six
via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Monday, November 8, 2021 6:37 AM
To: llvm-dev <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] Re-using a node in a DAG output pattern in TableGen

External email: Use caution opening links or attachments

Hello,

I currently have an instruction selection pattern that looks like this :

def : Pat<myinputop type:$v0 type:$v1,
          (COMPNHQ
            (ADDHQrr
              (SLLHQSri $v0, 8),
              (SLLHQSri $v1, 8),
            ),
            (SLLHQSri $v0, 8),
            comparison_ltu
          )>;
This output pattern is supposed to be a DAG: the node (SLLHQSri $v0, 8) is used
two times.

Experimentally, TableGen seems to recognize it as such (the node `(SLLHQSri $v0,
8)` will not be duplicated).

I am wondering if there is a way to avoid having to repeat (SLLHQSri $v0, 8) in
the syntax of TableGen, something like:
def : Pat<inputpattern type:$v0 type:$v1,
          (COMPNHQ
            (ADDHQrr
              (SLLHQSri $v0, 8):$myvar,
              (SLLHQSri $v1, 8),
            ),
            $myvar,
            comparison_ltu
          )>;
If I try this, I get the error "Node 'myvar' in output pattern but
not input pattern".

Does anyone know if there is a way to name nodes from an output pattern to
produce a non-tree output DAG?

Do you know of any existing pattern featuring output DAG that are not trees?

Thanks

Cyril Six
Compiler Engineer • Kalray
Phone:
csix at kalrayinc.com •
www.kalrayinc.com<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.kalrayinc.com%2F&data=04%7C01%7Cjeckhardt%40nvidia.com%7C1bf04ec61fbb4f4958a908d9a2b48d7d%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637719718619602934%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=RtINTAlB1bxfjgh9PqVW7J%2FZ6pXFOUPPlAWtyK70t2U%3D&reserved=0>

[Kalray
logo]<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.kalrayinc.com%2F&data=04%7C01%7Cjeckhardt%40nvidia.com%7C1bf04ec61fbb4f4958a908d9a2b48d7d%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637719718619612928%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=9kPWz9fpnv2ZIP%2Fg6CVNCevmc141CEV2ZdG9EtDsxcU%3D&reserved=0>
Intelligent Data Processing
>From Cloud to Edge
Please consider the environment before printing this e-mail.
This message contains information that may be privileged or confidential and is
the property of Kalray S.A. It is intended only for the person to whom it is
addressed. If you are not the intended recipient, you are not authorized to
print, retain, copy, disseminate, distribute, or use this message or any part
thereof. If you receive this message in error, please notify the sender
immediately and delete all copies of this message.

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