diff --git a/lib/AsmParser/LLLexer.cpp b/lib/AsmParser/LLLexer.cpp
index 46f3cbc..9b4370f 100644
--- a/lib/AsmParser/LLLexer.cpp
+++ b/lib/AsmParser/LLLexer.cpp
@@ -537,6 +537,7 @@
   KEYWORD(coldcc);
   KEYWORD(x86_stdcallcc);
   KEYWORD(x86_fastcallcc);
+  KEYWORD(x86_thiscallcc);
   KEYWORD(arm_apcscc);
   KEYWORD(arm_aapcscc);
   KEYWORD(arm_aapcs_vfpcc);
diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 3b08ca1..226d8d3 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -1074,6 +1074,7 @@
 ///   ::= 'coldcc'
 ///   ::= 'x86_stdcallcc'
 ///   ::= 'x86_fastcallcc'
+///   ::= 'x86_thiscallcc'
 ///   ::= 'arm_apcscc'
 ///   ::= 'arm_aapcscc'
 ///   ::= 'arm_aapcs_vfpcc'
@@ -1088,6 +1089,7 @@
   case lltok::kw_coldcc:         CC = CallingConv::Cold; break;
   case lltok::kw_x86_stdcallcc:  CC = CallingConv::X86_StdCall; break;
   case lltok::kw_x86_fastcallcc: CC = CallingConv::X86_FastCall; break;
+  case lltok::kw_x86_thiscallcc: CC = CallingConv::X86_ThisCall; break;
   case lltok::kw_arm_apcscc:     CC = CallingConv::ARM_APCS; break;
   case lltok::kw_arm_aapcscc:    CC = CallingConv::ARM_AAPCS; break;
   case lltok::kw_arm_aapcs_vfpcc:CC = CallingConv::ARM_AAPCS_VFP; break;
diff --git a/lib/AsmParser/LLToken.h b/lib/AsmParser/LLToken.h
index 3ac9169..5eed170 100644
--- a/lib/AsmParser/LLToken.h
+++ b/lib/AsmParser/LLToken.h
@@ -68,7 +68,7 @@
     kw_c,
 
     kw_cc, kw_ccc, kw_fastcc, kw_coldcc,
-    kw_x86_stdcallcc, kw_x86_fastcallcc,
+    kw_x86_stdcallcc, kw_x86_fastcallcc, kw_x86_thiscallcc,
     kw_arm_apcscc, kw_arm_aapcscc, kw_arm_aapcs_vfpcc,
     kw_msp430_intrcc,
 
diff --git a/lib/Target/CBackend/CBackend.cpp b/lib/Target/CBackend/CBackend.cpp
index cc9e1d7..55b8aaa 100644
--- a/lib/Target/CBackend/CBackend.cpp
+++ b/lib/Target/CBackend/CBackend.cpp
@@ -2165,6 +2165,9 @@
    case CallingConv::X86_FastCall:
     Out << "__attribute__((fastcall)) ";
     break;
+   case CallingConv::X86_ThisCall:
+    Out << "__attribute__((thiscall)) ";
+    break;
    default:
     break;
   }
diff --git a/lib/Target/MSIL/MSILWriter.cpp b/lib/Target/MSIL/MSILWriter.cpp
index 332a150..3de173c 100644
--- a/lib/Target/MSIL/MSILWriter.cpp
+++ b/lib/Target/MSIL/MSILWriter.cpp
@@ -278,6 +278,8 @@
     return "modopt([mscorlib]System.Runtime.CompilerServices.CallConvFastcall) ";
   case CallingConv::X86_StdCall:
     return "modopt([mscorlib]System.Runtime.CompilerServices.CallConvStdcall) ";
+  case CallingConv::X86_ThisCall:
+    return "modopt([mscorlib]System.Runtime.CompilerServices.CallConvThiscall) ";
   default:
     errs() << "CallingConvID = " << CallingConvID << '\n';
     llvm_unreachable("Unsupported calling convention");
diff --git a/lib/Target/X86/X86CallingConv.td b/lib/Target/X86/X86CallingConv.td
index fd15efd..a5774e1 100644
--- a/lib/Target/X86/X86CallingConv.td
+++ b/lib/Target/X86/X86CallingConv.td
@@ -307,6 +307,20 @@
   CCDelegateTo<CC_X86_32_Common>
 ]>;
 
+def CC_X86_32_ThisCall : CallingConv<[
+  // Promote i8/i16 arguments to i32.
+  CCIfType<[i8, i16], CCPromoteToType<i32>>,
+
+  // The 'nest' parameter, if any, is passed in EAX.
+  CCIfNest<CCAssignToReg<[EAX]>>,
+
+  // The first integer argument is passed in ECX
+  CCIfType<[i32], CCAssignToReg<[ECX]>>,
+
+  // Otherwise, same as everything else.
+  CCDelegateTo<CC_X86_32_Common>
+]>;
+
 def CC_X86_32_FastCC : CallingConv<[
   // Handles byval parameters.  Note that we can't rely on the delegation
   // to CC_X86_32_Common for this because that happens after code that
diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index 953ba18..7f97b48 100644
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -180,6 +180,8 @@
 
   if (CC == CallingConv::X86_FastCall)
     return CC_X86_32_FastCall;
+  else if (CC == CallingConv::X86_ThisCall)
+    return CC_X86_32_ThisCall;
   else if (CC == CallingConv::Fast)
     return CC_X86_32_FastCC;
   else if (CC == CallingConv::GHC)
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 88ee52f..9fa7bb1 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1383,6 +1383,8 @@
     return !Subtarget->is64Bit();
   case CallingConv::X86_FastCall:
     return !Subtarget->is64Bit();
+  case CallingConv::X86_ThisCall:
+    return !Subtarget->is64Bit();
   case CallingConv::Fast:
     return GuaranteedTailCallOpt;
   case CallingConv::GHC:
@@ -1404,6 +1406,8 @@
 
   if (CC == CallingConv::X86_FastCall)
     return CC_X86_32_FastCall;
+  else if (CC == CallingConv::X86_ThisCall)
+    return CC_X86_32_ThisCall;
   else if (CC == CallingConv::Fast)
     return CC_X86_32_FastCC;
   else if (CC == CallingConv::GHC)
@@ -1595,7 +1599,8 @@
   // If the function takes variable number of arguments, make a frame index for
   // the start of the first vararg value... for expansion of llvm.va_start.
   if (isVarArg) {
-    if (Is64Bit || CallConv != CallingConv::X86_FastCall) {
+    if (Is64Bit || (CallConv != CallingConv::X86_FastCall &&
+                    CallConv != CallingConv::X86_ThisCall)) {
       FuncInfo->setVarArgsFrameIndex(MFI->CreateFixedObject(1, StackSize,
                                                             true, false));
     }
@@ -1715,7 +1720,8 @@
   if (!Is64Bit) {
     // RegSaveFrameIndex is X86-64 only.
     FuncInfo->setRegSaveFrameIndex(0xAAAAAAA);
-    if (CallConv == CallingConv::X86_FastCall)
+    if (CallConv == CallingConv::X86_FastCall ||
+        CallConv == CallingConv::X86_ThisCall)
       // fastcc functions can't have varargs.
       FuncInfo->setVarArgsFrameIndex(0xAAAAAAA);
   }
@@ -7119,6 +7125,7 @@
       break;
     }
     case CallingConv::X86_FastCall:
+    case CallingConv::X86_ThisCall:
     case CallingConv::Fast:
       // Pass 'nest' parameter in EAX.
       // Must be kept in sync with X86CallingConv.td
diff --git a/lib/VMCore/AsmWriter.cpp b/lib/VMCore/AsmWriter.cpp
index 4e8938f..e48c026 100644
--- a/lib/VMCore/AsmWriter.cpp
+++ b/lib/VMCore/AsmWriter.cpp
@@ -1573,6 +1573,7 @@
   case CallingConv::Cold:         Out << "coldcc "; break;
   case CallingConv::X86_StdCall:  Out << "x86_stdcallcc "; break;
   case CallingConv::X86_FastCall: Out << "x86_fastcallcc "; break;
+  case CallingConv::X86_ThisCall: Out << "x86_thiscallcc "; break;
   case CallingConv::ARM_APCS:     Out << "arm_apcscc "; break;
   case CallingConv::ARM_AAPCS:    Out << "arm_aapcscc "; break;
   case CallingConv::ARM_AAPCS_VFP:Out << "arm_aapcs_vfpcc "; break;
@@ -1845,6 +1846,7 @@
     case CallingConv::Cold:  Out << " coldcc"; break;
     case CallingConv::X86_StdCall:  Out << " x86_stdcallcc"; break;
     case CallingConv::X86_FastCall: Out << " x86_fastcallcc"; break;
+    case CallingConv::X86_ThisCall: Out << " x86_thiscallcc"; break;
     case CallingConv::ARM_APCS:     Out << " arm_apcscc "; break;
     case CallingConv::ARM_AAPCS:    Out << " arm_aapcscc "; break;
     case CallingConv::ARM_AAPCS_VFP:Out << " arm_aapcs_vfpcc "; break;
@@ -1897,6 +1899,7 @@
     case CallingConv::Cold:  Out << " coldcc"; break;
     case CallingConv::X86_StdCall:  Out << " x86_stdcallcc"; break;
     case CallingConv::X86_FastCall: Out << " x86_fastcallcc"; break;
+    case CallingConv::X86_ThisCall: Out << " x86_thiscallcc"; break;
     case CallingConv::ARM_APCS:     Out << " arm_apcscc "; break;
     case CallingConv::ARM_AAPCS:    Out << " arm_aapcscc "; break;
     case CallingConv::ARM_AAPCS_VFP:Out << " arm_aapcs_vfpcc "; break;
diff --git a/lib/VMCore/Verifier.cpp b/lib/VMCore/Verifier.cpp
index b785349..75988cc 100644
--- a/lib/VMCore/Verifier.cpp
+++ b/lib/VMCore/Verifier.cpp
@@ -688,6 +688,7 @@
   case CallingConv::Fast:
   case CallingConv::Cold:
   case CallingConv::X86_FastCall:
+  case CallingConv::X86_ThisCall:
     Assert1(!F.isVarArg(),
             "Varargs functions must have C calling conventions!", &F);
     break;