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

[Krzysztof Parzyszek via llvm-dev]

On 2/18/2016 1:40 PM, Rail Shafigulin wrote:
>
>            0x3283608: i32,ch = CopyFromReg 0x3257980, 0x3283500 [ORD=1]
>          [ID=9]
>                0x3283500: i32 = Register %vreg5 [ID=1]
>
> Based on the code above, CopyFromReg is a node at address 0x3283608,
> returns i32, is of type chain and takes two inputs, the second of which
> is a %vreg5. So what is the first parameter? In fact where can I find
> the definition of CopyFromReg method?

The first parameter is a chain.

Here are some comments from include/llvm/CodeGen/ISDOpcodes.h:

     /// CopyToReg - This node has three operands: a chain, a register 
number to
     /// set to this value, and a value.
     CopyToReg,

     /// CopyFromReg - This node indicates that the input value is a 
virtual or
     /// physical register that is defined outside of the scope of this
     /// SelectionDAG.  The register is available from the 
RegisterSDNode object.
     CopyFromReg,

I usually grep the sources if I want to find out about something.  I'm 
not sure if there is a better documentation about ISD nodes.

-Krzysztof


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