Index: include/llvm/IR/Function.h
===================================================================
--- include/llvm/IR/Function.h
+++ include/llvm/IR/Function.h
@@ -61,10 +61,12 @@
   /*
    * Value::SubclassData
    *
-   * bit 0  : HasLazyArguments
-   * bit 1  : HasPrefixData
-   * bit 2  : HasPrologueData
-   * bit 3-6: CallingConvention
+   * bit 0      : HasLazyArguments
+   * bit 1      : HasPrefixData
+   * bit 2      : HasPrologueData
+   * bit 3      : [reserved]
+   * bits 4-13  : CallingConvention
+   * bits 14-15 : [reserved]
    */
 
   /// Bits from GlobalObject::GlobalObjectSubclassData.
@@ -158,11 +160,12 @@
   /// calling convention of this function.  The enum values for the known
   /// calling conventions are defined in CallingConv.h.
   CallingConv::ID getCallingConv() const {
-    return static_cast<CallingConv::ID>(getSubclassDataFromValue() >> 3);
+    return static_cast<CallingConv::ID>((getSubclassDataFromValue() >> 4) &
+                                        0x3ff);
   }
   void setCallingConv(CallingConv::ID CC) {
-    setValueSubclassData((getSubclassDataFromValue() & 7) |
-                         (static_cast<unsigned>(CC) << 3));
+    setValueSubclassData((getSubclassDataFromValue() & 0xc00f) |
+                         ((static_cast<unsigned>(CC) & 0x3ff) << 4));
   }
 
   /// @brief Return the attribute list for this Function.
Index: test/Bitcode/compatibility-3.6.ll
===================================================================
--- test/Bitcode/compatibility-3.6.ll
+++ test/Bitcode/compatibility-3.6.ll
@@ -375,8 +375,8 @@
 ; CHECK: declare x86_vectorcallcc void @f.cc80()
 declare x86_vectorcallcc void @f.x86_vectorcallcc()
 ; CHECK: declare x86_vectorcallcc void @f.x86_vectorcallcc()
-declare cc8191 void @f.cc8191()
-; CHECK: declare cc8191 void @f.cc8191()
+declare cc1023 void @f.cc1023()
+; CHECK: declare cc1023 void @f.cc1023()
 
 ; Functions -- ret attrs (Return attributes)
 declare zeroext i64 @f.zeroext()
Index: test/Bitcode/compatibility-3.7.ll
===================================================================
--- test/Bitcode/compatibility-3.7.ll
+++ test/Bitcode/compatibility-3.7.ll
@@ -375,8 +375,8 @@
 ; CHECK: declare x86_vectorcallcc void @f.cc80()
 declare x86_vectorcallcc void @f.x86_vectorcallcc()
 ; CHECK: declare x86_vectorcallcc void @f.x86_vectorcallcc()
-declare cc8191 void @f.cc8191()
-; CHECK: declare cc8191 void @f.cc8191()
+declare cc1023 void @f.cc1023()
+; CHECK: declare cc1023 void @f.cc1023()
 
 ; Functions -- ret attrs (Return attributes)
 declare zeroext i64 @f.zeroext()
Index: test/Bitcode/compatibility.ll
===================================================================
--- test/Bitcode/compatibility.ll
+++ test/Bitcode/compatibility.ll
@@ -377,8 +377,8 @@
 ; CHECK: declare x86_vectorcallcc void @f.cc80()
 declare x86_vectorcallcc void @f.x86_vectorcallcc()
 ; CHECK: declare x86_vectorcallcc void @f.x86_vectorcallcc()
-declare cc8191 void @f.cc8191()
-; CHECK: declare cc8191 void @f.cc8191()
+declare cc1023 void @f.cc1023()
+; CHECK: declare cc1023 void @f.cc1023()
 
 ; Functions -- ret attrs (Return attributes)
 declare zeroext i64 @f.zeroext()
Index: test/Bitcode/tailcall.ll
===================================================================
--- test/Bitcode/tailcall.ll
+++ test/Bitcode/tailcall.ll
@@ -3,16 +3,16 @@
 
 ; Check that musttail and tail roundtrip.
 
-declare cc8191 void @t1_callee()
-define cc8191 void @t1() {
-; CHECK: tail call cc8191 void @t1_callee()
-  tail call cc8191 void @t1_callee()
+declare cc1023 void @t1_callee()
+define cc1023 void @t1() {
+; CHECK: tail call cc1023 void @t1_callee()
+  tail call cc1023 void @t1_callee()
   ret void
 }
 
-declare cc8191 void @t2_callee()
-define cc8191 void @t2() {
-; CHECK: musttail call cc8191 void @t2_callee()
-  musttail call cc8191 void @t2_callee()
+declare cc1023 void @t2_callee()
+define cc1023 void @t2() {
+; CHECK: musttail call cc1023 void @t2_callee()
+  musttail call cc1023 void @t2_callee()
   ret void
 }