[Triple] Add Facebook vendor

[smeenai]

Summary

Add a compiler vendor for Facebook, to enable future vendor-specific
behavior.

[davide]

The patch has no tests associated. Also, can you please state what's your long(er) term plan?
As it stands, this is pretty much dead code, unless there's something else coming soon in the pipeline.

[compnerd]

The patch implicitly has tests: the unit tests generically walks over the enumeration, so it is covered by existing tests.

This would allow Facebook to play around with changes that they need for local development, which may not necessarily be generic enough or generally correct for merging into the mainline.

I don't think that there is any real maintenance cost associated with adding the additional vendor triple, especially if it doesnt require altering the normal code paths.

[compnerd]

Spoke with @davide offline. He's fine with with this, was just curious what the intention here was.

[smeenai]

To address @dberlin's comments on the mailing list (I've lost the original mail so I can't reply directly):

So why not keep this patch local as well?
In particular, if this is for local development, keeping this patch local
also helps enforce this since any accidental use of the triple in public
code will break quite obviously.

The intent is to be able to upstream anything generic enough to be generally useful, even where the behavior is vendor-specific.

llvm/trunk/include/llvm/ADT/Triple.h

public:
   enum VendorType {
     UnknownVendor,
 
     Apple,
     PC,
     SCEI,
     BGP,
     BGQ,
+    Facebook,
     Freescale,
     IBM,
     ImaginationTechnologies,
     MipsTechnologies,
     NVIDIA,
     CSR,
     Myriad,
     AMD,

llvm/trunk/lib/Support/Triple.cpp

StringRef Triple::getVendorTypeName(VendorType Kind) {
   switch (Kind) {
   case UnknownVendor: return "unknown";
 
   case Apple: return "apple";
   case PC: return "pc";
   case SCEI: return "scei";
   case BGP: return "bgp";
   case BGQ: return "bgq";
+  case Facebook: return "facebook";
   case Freescale: return "fsl";
   case IBM: return "ibm";
   case ImaginationTechnologies: return "img";
   case MipsTechnologies: return "mti";
   case NVIDIA: return "nvidia";
   case CSR: return "csr";
   case Myriad: return "myriad";
   case AMD: return "amd";

 
 static Triple::VendorType parseVendor(StringRef VendorName) {
   return StringSwitch<Triple::VendorType>(VendorName)
     .Case("apple", Triple::Apple)
     .Case("pc", Triple::PC)
     .Case("scei", Triple::SCEI)
     .Case("bgp", Triple::BGP)
     .Case("bgq", Triple::BGQ)
+    .Case("facebook", Triple::Facebook)
     .Case("fsl", Triple::Freescale)
     .Case("ibm", Triple::IBM)
     .Case("img", Triple::ImaginationTechnologies)
     .Case("mti", Triple::MipsTechnologies)
     .Case("nvidia", Triple::NVIDIA)
     .Case("csr", Triple::CSR)
     .Case("myriad", Triple::Myriad)
     .Case("amd", Triple::AMD)