[AArch64] Add aarch64_vector_pcs function attribute to Clang

This is the Clang patch to complement the following LLVM patches:
  https://reviews.llvm.org/D51477
  https://reviews.llvm.org/D51479

More information describing the vector ABI and procedure call standard
can be found here:

https://developer.arm.com/products/software-development-tools/\
                          hpc/arm-compiler-for-hpc/vector-function-abi

Patch by Kerry McLaughlin.

Reviewed By: rjmccall

Differential Revision: https://reviews.llvm.org/D54425

llvm-svn: 347571
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 16d3324..dbceaa7 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1102,6 +1102,7 @@
   case CC_X86_64SysV:
     return llvm::dwarf::DW_CC_LLVM_X86_64SysV;
   case CC_AAPCS:
+  case CC_AArch64VectorCall:
     return llvm::dwarf::DW_CC_LLVM_AAPCS;
   case CC_AAPCS_VFP:
     return llvm::dwarf::DW_CC_LLVM_AAPCS_VFP;