[llvm-dev] How to interpret Selection DAG error output

[Jonathan Roelofs via llvm-dev]

On 2/18/16 12:19 PM, Rail Shafigulin via llvm-dev wrote:
>
>
> On Thu, Feb 18, 2016 at 10:50 AM, Krzysztof Parzyszek via llvm-dev
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>
>     On 2/18/2016 12:43 PM, Rail Shafigulin via llvm-dev wrote:
>
>
>         LLVM ERROR: Cannot select: 0x3284268: glue = EsenciaISD::SET_FLAG
>         0x3283608, 0x3283710, 0x3283e48 [ORD=3] [ID=11]
>             0x3283608: i32,ch = CopyFromReg 0x3257980, 0x3283500 [ORD=1]
>         [ID=9]
>               0x3283500: i32 = Register %vreg5 [ID=1]
>             0x3283710: i32 = Constant<3> [ID=2]
>             0x3283e48: i32 = Constant<20> [ID=8]
>         In function: fib
>
>         As far as I can understand LLVM cannot select it because the
>         pattern is
>         not specified. Unfortunately for me, I can't understand how to
>         interpret
>         this output. Would anybody be able to help me out?
>
>
>
>     The DAG node that has failed selection is "SET_FLAG %vreg5, 3, 20",
>     the type of the node is "glue" and all 3 arguments are i32.
>
> I understand where SET_FLAG, 3 and 20 come from, but how did you arrive
> the conclusion that %vreg5 should be part of the pattern?

The hex numbers are pointers. You can see the Use of 0x3283500 in the 
CopyFromReg inst, and the def is here:

0x3283500: i32 = Register %vreg5 [ID=1]

It's /just/ a dag.


Jon

>
>
>     The top line shows the node that caused the failure.  The hex
>     numbers on that line are the addresses of the arguments.  These
>     arguments are then listed below.
>
>     Newer versions of LLVM show node ids instead of addresses, but AFAIK
>     it was dependent on some configuration option.
>
>     -Krzysztof
>
>
>     --
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>
>
>
> --
> Rail Shafigulin
> Software Engineer
> Esencia Technologies
>
>
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-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded