[LLVMdev] the definitions of internal functions and external functions

[Duncan Sands]

Hi WeiHu,

> I have a llvm pass in hand written by other people. There are following
> statements that I couldn't understand:
> -------------------------------program----------------------------------------------------
> ...
> // Calls to internal functions.
> if (!F->isDeclaration()) {
> DOUT << " internal call" << opcode << ": " << name << "\n";
> return ...;
> }
> // Calls to external functions
> ...
> -------------------------------------------------------------------------------------------
> My question is:
> What's the definitions of internal functions and external functions? In c,
> internal functions is functions that it is only called in the file where it
> defines using keyword "static", external functions is functions that can be
> called by other files, defining using keyword "external". Are these definitions
> identical with the definitions in llvm?

the comments in your pass are misleading.  In LLVM, as in C, external functions
are those not defined in the module.  If "F->isDeclaration()" is true, then F is
an external function.  If F is not an external function, then it is defined in
the module.  It may or may not have internal linkage (internal linkage -> static
in C).  To be honest there are several linkage types that mean that the function
is not externally visible, see the isLocalLinkage method in GlobalValue.h.

Ciao,

Duncan.