[llvm-dev] CCAction definition?

Daniel Sanders via llvm-dev
Wed, 10 Apr 2019 19:48:57 -0000

> 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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