Index: lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- lib/CodeGen/CGDebugInfo.cpp
+++ lib/CodeGen/CGDebugInfo.cpp
@@ -831,6 +831,39 @@
       getDeclContextDescriptor(Ty->getDecl()));
 }
 
+static unsigned getDwarfCC(CallingConv CC) {
+  switch (CC) {
+  case CC_C:
+    // Avoid emitting DW_AT_calling_convention if the C convention was used.
+    return 0;
+
+  case CC_X86StdCall:
+    return llvm::dwarf::DW_CC_BORLAND_stdcall;
+  case CC_X86FastCall:
+    return llvm::dwarf::DW_CC_BORLAND_msfastcall;
+  case CC_X86ThisCall:
+    return llvm::dwarf::DW_CC_BORLAND_thiscall;
+  case CC_X86VectorCall:
+    return llvm::dwarf::DW_CC_LLVM_vectorcall;
+  case CC_X86Pascal:
+    return llvm::dwarf::DW_CC_BORLAND_pascal;
+
+  // FIXME: Create new DW_CC_ codes for these calling conventions.
+  case CC_X86_64Win64:
+  case CC_X86_64SysV:
+  case CC_AAPCS:
+  case CC_AAPCS_VFP:
+  case CC_IntelOclBicc:
+  case CC_SpirFunction:
+  case CC_SpirKernel:
+  case CC_Swift:
+  case CC_PreserveMost:
+  case CC_PreserveAll:
+    return 0;
+  }
+  return 0;
+}
+
 llvm::DIType *CGDebugInfo::CreateType(const FunctionType *Ty,
                                       llvm::DIFile *Unit) {
   SmallVector<llvm::Metadata *, 16> EltTys;
@@ -850,7 +883,8 @@
   }
 
   llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(EltTys);
-  return DBuilder.createSubroutineType(EltTypeArray);
+  return DBuilder.createSubroutineType(EltTypeArray, 0,
+                                       getDwarfCC(Ty->getCallConv()));
 }
 
 /// Convert an AccessSpecifier into the corresponding DINode flag.
@@ -1103,7 +1137,8 @@
   if (Func->getExtProtoInfo().RefQualifier == RQ_RValue)
     Flags |= llvm::DINode::FlagRValueReference;
 
-  return DBuilder.createSubroutineType(EltTypeArray, Flags);
+  return DBuilder.createSubroutineType(EltTypeArray, Flags,
+                                       getDwarfCC(Func->getCallConv()));
 }
 
 /// isFunctionLocalClass - Return true if CXXRecordDecl is defined
@@ -2562,9 +2597,9 @@
   SmallVector<QualType, 16> ArgTypes;
   for (const ParmVarDecl *Parm: FD->parameters())
     ArgTypes.push_back(Parm->getType());
-  QualType FnType =
-    CGM.getContext().getFunctionType(FD->getReturnType(), ArgTypes,
-                                     FunctionProtoType::ExtProtoInfo());
+  CallingConv CC = FD->getType()->castAs<FunctionType>()->getCallConv();
+  QualType FnType = CGM.getContext().getFunctionType(
+      FD->getReturnType(), ArgTypes, FunctionProtoType::ExtProtoInfo(CC));
   llvm::DISubprogram *SP = DBuilder.createTempFunctionFwdDecl(
       DContext, Name, LinkageName, Unit, Line,
       getOrCreateFunctionType(FD, FnType, Unit), !FD->isExternallyVisible(),
@@ -2668,6 +2703,10 @@
 
   if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(D))
     return getOrCreateMethodType(Method, F);
+
+  const auto *FTy = FnType->getAs<FunctionType>();
+  CallingConv CC = FTy ? FTy->getCallConv() : CallingConv::CC_C;
+
   if (const ObjCMethodDecl *OMethod = dyn_cast<ObjCMethodDecl>(D)) {
     // Add "self" and "_cmd"
     SmallVector<llvm::Metadata *, 16> Elts;
@@ -2701,7 +2740,7 @@
       Elts.push_back(DBuilder.createUnspecifiedParameter());
 
     llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(Elts);
-    return DBuilder.createSubroutineType(EltTypeArray);
+    return DBuilder.createSubroutineType(EltTypeArray, 0, getDwarfCC(CC));
   }
 
   // Handle variadic function types; they need an additional
@@ -2715,7 +2754,7 @@
           EltTys.push_back(getOrCreateType(FPT->getParamType(i), F));
       EltTys.push_back(DBuilder.createUnspecifiedParameter());
       llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(EltTys);
-      return DBuilder.createSubroutineType(EltTypeArray);
+      return DBuilder.createSubroutineType(EltTypeArray, 0, getDwarfCC(CC));
     }
 
   return cast<llvm::DISubroutineType>(getOrCreateType(FnType, F));
Index: lib/CodeGen/CodeGenFunction.cpp
===================================================================
--- lib/CodeGen/CodeGenFunction.cpp
+++ lib/CodeGen/CodeGenFunction.cpp
@@ -762,15 +762,18 @@
 
   // Emit subprogram debug descriptor.
   if (CGDebugInfo *DI = getDebugInfo()) {
+    // Reconstruct the type from the argument list so that implicit parameters,
+    // such as 'this' and 'vtt', show up in the debug info. Preserve the calling
+    // convention.
+    CallingConv CC = CallingConv::CC_C;
+    if (auto *FD = dyn_cast_or_null<FunctionDecl>(D))
+      if (const auto *SrcFnTy = FD->getType()->getAs<FunctionType>())
+        CC = SrcFnTy->getCallConv();
     SmallVector<QualType, 16> ArgTypes;
-    for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
-	 i != e; ++i) {
-      ArgTypes.push_back((*i)->getType());
-    }
-
-    QualType FnType =
-      getContext().getFunctionType(RetTy, ArgTypes,
-                                   FunctionProtoType::ExtProtoInfo());
+    for (const VarDecl *VD : Args)
+      ArgTypes.push_back(VD->getType());
+    QualType FnType = getContext().getFunctionType(
+        RetTy, ArgTypes, FunctionProtoType::ExtProtoInfo(CC));
     DI->EmitFunctionStart(GD, Loc, StartLoc, FnType, CurFn, Builder);
   }
 
Index: test/CodeGenCXX/debug-info-calling-conventions.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/debug-info-calling-conventions.cpp
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 %s -triple=i686-pc-windows-msvc -debug-info-kind=limited -emit-llvm -o - | FileCheck %s
+
+struct A {
+  void thiscallcc();
+};
+void A::thiscallcc() {}
+
+// CHECK: !DISubprogram(name: "thiscallcc", {{.*}} type: ![[thiscallty:[^,]*]], {{.*}})
+// CHECK: ![[thiscallty]] = !DISubroutineType(cc: DW_CC_BORLAND_thiscall, types: ![[thisargs:[^,)]*]])
+// CHECK: ![[thisargs]] = !{null, ![[thisptrty:[^,}]*]]}
+// CHECK: ![[thisptrty]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !{{.*}}, size: 32, align: 32, flags: DIFlagArtificial | DIFlagObjectPointer)
+
+void cdeclcc() {}
+void __fastcall fastcallcc() {}
+void __stdcall stdcallcc() {}
+void __vectorcall vectorcallcc() {}
+
+// CHECK: !DISubprogram(name: "cdeclcc", {{.*}} type: ![[cdeclty:[^,]*]], {{.*}})
+// CHECK: ![[cdeclty]] = !DISubroutineType(types: ![[noargs:[^,)]*]])
+// CHECK: ![[noargs]] = !{null}
+// CHECK: !DISubprogram(name: "fastcallcc", {{.*}} type: ![[fastcallty:[^,]*]], {{.*}})
+// CHECK: ![[fastcallty]] = !DISubroutineType(cc: DW_CC_BORLAND_msfastcall, types: ![[noargs]])
+// CHECK: !DISubprogram(name: "stdcallcc", {{.*}} type: ![[stdcallty:[^,]*]], {{.*}})
+// CHECK: ![[stdcallty]] = !DISubroutineType(cc: DW_CC_BORLAND_stdcall, types: ![[noargs]])
+// CHECK: !DISubprogram(name: "vectorcallcc", {{.*}} type: ![[vectorcallty:[^,]*]], {{.*}})
+// CHECK: ![[vectorcallty]] = !DISubroutineType(cc: DW_CC_LLVM_vectorcall, types: ![[noargs]])