[OpenCL] Add LangAS::opencl_private to represent private address space in AST

Currently Clang uses default address space (0) to represent private address space for OpenCL
in AST. There are two issues with this:

Multiple address spaces including private address space cannot be diagnosed.
There is no mangling for default address space. For example, if private int* is emitted as
i32 addrspace(5)* in IR. It is supposed to be mangled as PUAS5i but it is mangled as
Pi instead.

This patch attempts to represent OpenCL private address space explicitly in AST. It adds
a new enum LangAS::opencl_private and adds it to the variable types which are implicitly
private:

automatic variables without address space qualifier

function parameter

pointee type without address space qualifier (OpenCL 1.2 and below)

Differential Revision: https://reviews.llvm.org/D35082

llvm-svn: 315668
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 9a94900..37f2ff3 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -340,7 +340,7 @@
 
   // First argument is an ndrange_t type.
   Expr *NDRangeArg = TheCall->getArg(0);
-  if (NDRangeArg->getType().getAsString() != "ndrange_t") {
+  if (NDRangeArg->getType().getUnqualifiedType().getAsString() != "ndrange_t") {
     S.Diag(NDRangeArg->getLocStart(),
            diag::err_opencl_builtin_expected_type)
         << TheCall->getDirectCallee() << "'ndrange_t'";
@@ -784,8 +784,11 @@
   case Builtin::BIto_local:
     Qual.setAddressSpace(LangAS::opencl_local);
     break;
+  case Builtin::BIto_private:
+    Qual.setAddressSpace(LangAS::opencl_private);
+    break;
   default:
-    Qual.removeAddressSpace();
+    llvm_unreachable("Invalid builtin function");
   }
   Call->setType(S.Context.getPointerType(S.Context.getQualifiedType(
       RT.getUnqualifiedType(), Qual)));