[COFF, ARM64] Add ARM64 support for MS intrinsic _fastfail

The MSDN document was also updated to reflect this, but it probably will take a few days to show in below link.

https://docs.microsoft.com/en-us/cpp/intrinsics/fastfail

Differential Revision: https://reviews.llvm.org/D57631

llvm-svn: 353337
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 59af0f4..7df7be6 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -997,6 +997,9 @@
       Asm = "udf #251";
       Constraints = "{r0}";
       break;
+    case llvm::Triple::aarch64:
+      Asm = "brk #0xF003";
+      Constraints = "{w0}";
     }
     llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, {Int32Ty}, false);
     llvm::InlineAsm *IA =