llvm dev - Apr 2019 - Virtual register defs don't dominate all uses

Hi all,
I'm getting this error:  "Virtual register defs don't dominate all
uses". It comes from llvm/lib/CodeGen/MachineVerifier.cpp:2138
I don't understand what it means. Does anyone know?

Thanks.
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Hi Josh,

That means that at least one use of the reporter virtual register happens before
its definition.
E.g.,
… = V1 <—— V1 is not defined here
V1 = … <— V1 def does not dominate all its use

Cheers,
-Quentin
> On Apr 16, 2019, at 2:47 PM, Josh Sharp via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
>  Hi all,
> I'm getting this error:  "Virtual register defs don't dominate
all uses". It comes from llvm/lib/CodeGen/MachineVerifier.cpp:2138
> I don't understand what it means. Does anyone know?
> 
> Thanks.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
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Thank you for the response.
What's the difference between running clang with the -emit-llvm option vs
running it with the --target=<mytarget> option.
The error I described happens only if I run: clang --target=<mytarget>
<inputfile>.c
However if I do clang -emit-llvm <inputfile>.c -o <outputfile>.bc
and then llc -march=<mytarget> <outputfile>.bc, no error occurs

Thanks
________________________________
From: qcolombet at apple.com <qcolombet at apple.com> on behalf of Quentin
Colombet <qcolombet at apple.com>
Sent: Tuesday, April 16, 2019 3:05 PM
To: Josh Sharp
Cc: via llvm-dev
Subject: Re: [llvm-dev] Virtual register defs don't dominate all uses

Hi Josh,

That means that at least one use of the reporter virtual register happens before
its definition.
E.g.,
… = V1 <—— V1 is not defined here
V1 = … <— V1 def does not dominate all its use

Cheers,
-Quentin
On Apr 16, 2019, at 2:47 PM, Josh Sharp via llvm-dev <llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:

 Hi all,
I'm getting this error:  "Virtual register defs don't dominate all
uses". It comes from llvm/lib/CodeGen/MachineVerifier.cpp:2138
I don't understand what it means. Does anyone know?

Thanks.
_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

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