llvm dev - Apr 2019 - CCAction definition?

Simple TableGen question, where is the definition for *CCAction*? It's
given a forward declaration in *TargetCallingConv.td* alongside another
forward declaration for *CallingConv*.

*class CCAction;*
*class CallingConv;*


As I'd expect, *CallingConv* is defined later in the file:

*class CallingConv<list<CCAction> actions> { ... }*

But I can't find any definition for *CCAction* anywhere in the LLVM
sources. I thought this might be idiomatically referring to an underlying
C++ type but I couldn't find that either. Any explanation?

thanks,

C
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> On Apr 10, 2019, at 11:15, Chris Sears via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Simple TableGen question, where is the definition for CCAction? It's
given a forward declaration in TargetCallingConv.td alongside another forward
declaration for CallingConv.
> 
> class CCAction;
That's actually the whole declaration. It defines a tablegen class with no
fields and is only really there to allow tablegen to type check
CallingConv's argument.
> class CallingConv;
> 
> As I'd expect, CallingConv is defined later in the file:
> 
> class CallingConv<list<CCAction> actions> { ... }
> But I can't find any definition for CCAction anywhere in the LLVM
sources. I thought this might be idiomatically referring to an underlying C++
type but I couldn't find that either. Any explanation?
There's no correspondence with C++. Tablegen is essentially a database of
records that the llvm-tblgen command can use to generate other files (usually
C++). In this case, the code generator is in
utils/TableGen/CallingConvEmitter.cpp and you'll see checks like
'Action->isSubClassOf("CCAssignToReg")' for each of
CCAction's subclasses.

Hope that helps
> thanks,
> 
> C
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