llvm dev - Jun 2012 - [LLVMdev] Back-end: how to test all lowering condition

Dear All,
I am working on a back-end implementation for a new architecture which is
provided with its own assembler.
I am currently capable of writing most of the lowering process to generate a
decent assembly code.
Under certain circumstances, i.e. depending on the C code, some IR instructions
generate a Selection DAG for which I am not implementing a proper lowering, thus
resulting in the well-known "cannot select" error.
I guess this is because I have not implemented all possible instructions defined
in the Selection DAG, those declared in include/llvm/CodeGen/ISDOpcodes.h, which
apparently are different from those declared in the IR.

Problem1: how can I know the complete list of ISD:: instruction (SelectionDAG) I
have to implement (either by promoting, customizing and expanding)?
A possible solution is to implement all of them, taking the list defined in the
file mentioned above or taking the list from an already existing target (e.g.
MSP430 Mips).

Problem2: even if I implement the complete list, how can I test it? I cannot
write a .ll file containing directly the ISD:: instruction, but rather IR one
that causes the former to appear in the SelectionDAG. In such case, what is the
relationship between IR instructions and ISD:: ones?

Note to problem2: test/CodeGen/MSP430/setcc.ll is an example of test the uses
the IR instruction "icmp" to generate the "setcc"
SelectionDAG instruction.

Thank you all in advance for any suggestion you may give.
Cheers,
Christian.


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On Wed, Jun 20, 2012 at 01:50:51PM +0000, Christian Nastasi
wrote:
> Dear All,
> I am working on a back-end implementation for a new architecture which is
provided with its own assembler.
> I am currently capable of writing most of the lowering process to generate
a decent assembly code.
> Under certain circumstances, i.e. depending on the C code, some IR
instructions generate a Selection DAG for which I am not implementing a proper
lowering, thus resulting in the well-known "cannot select" error.
> I guess this is because I have not implemented all possible instructions
defined in the Selection DAG, those declared in
include/llvm/CodeGen/ISDOpcodes.h, which apparently are different from those
declared in the IR.
> 
> Problem1: how can I know the complete list of ISD:: instruction
(SelectionDAG) I have to implement (either by promoting, customizing and
expanding)?
> A possible solution is to implement all of them, taking the list defined in
the file mentioned above or taking the list from an already existing target
(e.g. MSP430 Mips).
>
The complete list of ISD opcodes is located in
include/llvm/CodeGen/ISDOpcodes.h, as far as I know you need to handle
all of them, however some of these are handled for you in the TargetLowering
constructor in lib/CodeGen/SelectionDAG/TargetLowering.cpp.

-Tom
> Problem2: even if I implement the complete list, how can I test it? I
cannot write a .ll file containing directly the ISD:: instruction, but rather IR
one that causes the former to appear in the SelectionDAG. In such case, what is
the relationship between IR instructions and ISD:: ones?
> 
> Note to problem2: test/CodeGen/MSP430/setcc.ll is an example of test the
uses the IR instruction "icmp" to generate the "setcc"
SelectionDAG instruction.
> 
> Thank you all in advance for any suggestion you may give.
> Cheers,
> Christian.
> 
> 
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Dear Tom,
thank you for your reply. What you suggest is something I was considering doing,
however there still no solution to my Problem2. How do I test the ISD 
instructions if I can only write IR instructions?

-----Original Message-----
From: Tom Stellard [mailto:thomas.stellard at amd.com]
Sent: Wednesday, June 20, 2012 4:14 PM
To: Christian Nastasi
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Back-end: how to test all lowering condition

On Wed, Jun 20, 2012 at 01:50:51PM +0000, Christian Nastasi
wrote:
> Dear All,
> I am working on a back-end implementation for a new architecture which is
provided with its own assembler.
> I am currently capable of writing most of the lowering process to generate
a decent assembly code.
> Under certain circumstances, i.e. depending on the C code, some IR
instructions generate a Selection DAG for which I am not implementing a proper
lowering, thus resulting in the well-known "cannot select" error.
> I guess this is because I have not implemented all possible instructions
defined in the Selection DAG, those declared in
include/llvm/CodeGen/ISDOpcodes.h, which apparently are different from those
declared in the IR.
>
> Problem1: how can I know the complete list of ISD:: instruction
(SelectionDAG) I have to implement (either by promoting, customizing and
expanding)?
> A possible solution is to implement all of them, taking the list defined in
the file mentioned above or taking the list from an already existing target
(e.g. MSP430 Mips).
>
The complete list of ISD opcodes is located in
include/llvm/CodeGen/ISDOpcodes.h, as far as I know you need to handle all of
them, however some of these are handled for you in the TargetLowering
constructor in lib/CodeGen/SelectionDAG/TargetLowering.cpp.

-Tom
> Problem2: even if I implement the complete list, how can I test it? I
cannot write a .ll file containing directly the ISD:: instruction, but rather IR
one that causes the former to appear in the SelectionDAG. In such case, what is
the relationship between IR instructions and ISD:: ones?
>
> Note to problem2: test/CodeGen/MSP430/setcc.ll is an example of test the
uses the IR instruction "icmp" to generate the "setcc"
SelectionDAG instruction.
>
> Thank you all in advance for any suggestion you may give.
> Cheers,
> Christian.
>
>
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intended recipient of this e-mail, you are hereby notified that any copying,
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e-mail and any of its attachments is strictly prohibited and may be unlawful. If
you have received this e-mail in error, please notify the sender immediately and
permanently delete the original e-mail and destroy any copies or printouts of
this e-mail as well as any attachments.
>
> _______________________________________________
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> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>


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distribution, dissemination or action taken in relation to the contents of this
e-mail and any of its attachments is strictly prohibited and may be unlawful. If
you have received this e-mail in error, please notify the sender immediately and
permanently delete the original e-mail and destroy any copies or printouts of
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