llvm dev - Aug 2020 - Understanding assert in SelectionDAGBuilder.cpp

Hi,
I am new to LLVM. I am experimenting with a toy backend. I don't understand
"LowerFormalArguments didn't return a valid chain" in
SelectionDAGBuilder.cpp file. What is the interface here? What does it mean
by returning a Chain?

Thanks
Jen.
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Have you read
http://llvm.org/docs/CodeGenerator.html#instruction-selection-section ?  That
covers the general DAG representation and the meaning of a “chain”.

In general, if you don’t understand how something in SelectionDAG is supposed to
work, I’d suggest looking at other targets, and using the dumping options
frequently.

-Eli

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of jeniffer
lesley via llvm-dev
Sent: Saturday, August 1, 2020 10:35 AM
To: llvm-dev at lists.llvm.org
Subject: [EXT] [llvm-dev] Understanding assert in SelectionDAGBuilder.cpp

Hi,
I am new to LLVM. I am experimenting with a toy backend. I don't understand
"LowerFormalArguments didn't return a valid chain" in
SelectionDAGBuilder.cpp file. What is the interface here? What does it mean by
returning a Chain?

Thanks
Jen.

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Thanks, I'll check it out. Is the interface that functions mutate DAG and
return Chain nodes and we can traverse DAG using Chain? How do I traverse
DAG in BFS order?

On Mon, Aug 3, 2020, 11:14 PM Eli Friedman <efriedma at quicinc.com>
wrote:
> Have you read
> http://llvm.org/docs/CodeGenerator.html#instruction-selection-section ?
> That covers the general DAG representation and the meaning of a “chain”.
>
>
>
> In general, if you don’t understand how something in SelectionDAG is
> supposed to work, I’d suggest looking at other targets, and using the
> dumping options frequently.
>
>
>
> -Eli
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of
*jeniffer
> lesley via llvm-dev
> *Sent:* Saturday, August 1, 2020 10:35 AM
> *To:* llvm-dev at lists.llvm.org
> *Subject:* [EXT] [llvm-dev] Understanding assert in
> SelectionDAGBuilder.cpp
>
>
>
> Hi,
>
> I am new to LLVM. I am experimenting with a toy backend. I don't
> understand
>
> "LowerFormalArguments didn't return a valid chain" in
> SelectionDAGBuilder.cpp file. What is the interface here? What does it mean
> by returning a Chain?
>
>
>
> Thanks
>
> Jen.
>
>
>
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