R600 intrinsics patch

[Matt Arsenault]

On 03/17/2015 08:11 AM, Tom Stellard wrote:
> The target prefix for all these has been changed from AMDGPU to amdgpu.
> I don't think this is necessary.  Matt may know more about this.
I don't remember all the details, but this is basically necessary for 
the automatic support from GCCBuiltin to work properly. The current set 
of builtins handled in clang need custom handling for things like 
conversion to/from i1, converting struct returns to out arguments, and 
handling overloads so they require custom code anyway. For simpler 
builtins, to not need custom code needs the target prefix to match.