[llvm-commits] [llvm] r106227 - /llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

[Dale Johannesen]

On Jun 17, 2010, at 10:50 AM, Jim Grosbach wrote:

> Add entries for Expanding atomic intrinsics to libcalls. Just a  
> placeholder
> for the moment. The implementation of the libcall will follow.
>
> Currently, the llvm-gcc knows when the intrinsics can be correctly  
> handled by
> the back end and only generates them in those cases, issuing  
> libcalls directly
> otherwise. That's too much coupling. The intrinsics should always be
> generated and the back end decide how to handle them, be it with a  
> libcall,
> inline code, or whatever. This patch is a step in that direction.

I think this is overstated.  Which intrinsics are valid is dependent  
on dialect; for example, there are many library functions in C99 that  
are not in C89.  It is appropriate for FEs to determine which calls  
the BEs are allowed to treat specially according to language rules,  
and generate intrinsics only for these.  The actual special treatment,  
if any, I agree should be up to the BEs.