diff --git a/contrib/llvm/tools/clang/lib/CodeGen/TargetInfo.cpp b/contrib/llvm/tools/clang/lib/CodeGen/TargetInfo.cpp
index 4b8006428f8f..abd633280b9d 100644
--- a/contrib/llvm/tools/clang/lib/CodeGen/TargetInfo.cpp
+++ b/contrib/llvm/tools/clang/lib/CodeGen/TargetInfo.cpp
@@ -3543,7 +3543,17 @@ ABIArgInfo X86_64ABIInfo::classifyRegCallStructType(QualType Ty,
 
 void X86_64ABIInfo::computeInfo(CGFunctionInfo &FI) const {
 
-  bool IsRegCall = FI.getCallingConvention() == llvm::CallingConv::X86_RegCall;
+  const unsigned CallingConv = FI.getCallingConvention();
+  // It is possible to force Win64 calling convention on any x86_64 target by
+  // using __attribute__((ms_abi)). In such case to correctly emit Win64
+  // compatible code delegate this call to WinX86_64ABIInfo::computeInfo.
+  if (CallingConv == llvm::CallingConv::Win64) {
+    WinX86_64ABIInfo Win64ABIInfo(CGT);
+    Win64ABIInfo.computeInfo(FI);
+    return;
+  }
+
+  bool IsRegCall = CallingConv == llvm::CallingConv::X86_RegCall;
 
   // Keep track of the number of assigned registers.
   unsigned FreeIntRegs = IsRegCall ? 11 : 6;
diff --git a/sys/sys/param.h b/sys/sys/param.h
index 4b4d49ed7266..d2d0a4d5243e 100644
--- a/sys/sys/param.h
+++ b/sys/sys/param.h
@@ -60,7 +60,7 @@
  *		in the range 5 to 9.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1200056	/* Master, propagated to newvers */
+#define __FreeBSD_version 1200057	/* Master, propagated to newvers */
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,