clang: add support for asmjs arch and Emscripten OS

include/clang/Basic/TargetCXXABI.h

Index: include/clang/Basic/TargetCXXABI.h
diff --git a/include/clang/Basic/TargetCXXABI.h b/include/clang/Basic/TargetCXXABI.h
index 5669d2a55937da80fd50b351d0cdb2cde89228e6..caf3b0f5aaa5b796b45af590431ef0492f288e05 100644
--- a/include/clang/Basic/TargetCXXABI.h
+++ b/include/clang/Basic/TargetCXXABI.h
@@ -79,6 +79,12 @@ public:
     ///   - guard variables  are smaller.
     GenericAArch64,
 
+    // @LOCALMOD-START Emscripten
+    /// Emscripten uses the Itanium C++, with the exception that it uses
+    /// ARM-style pointers to member functions.
+    Emscripten,
+    // @LOCALMOD-END Emscripten
+
     /// The Microsoft ABI is the ABI used by Microsoft Visual Studio (and
     /// compatible compilers).
     ///
@@ -112,6 +118,7 @@ public:
     case GenericAArch64:
     case GenericItanium:
     case GenericARM:
+    case Emscripten: // @LOCALMOD Emscripten
     case iOS:
     case iOS64:
       return true;
@@ -128,6 +135,7 @@ public:
     case GenericAArch64:
     case GenericItanium:
     case GenericARM:
+    case Emscripten: // @LOCALMOD Emscripten
     case iOS:
     case iOS64:
       return false;
@@ -138,6 +146,29 @@ public:
     llvm_unreachable("bad ABI kind");
   }
 
+  // @LOCALMOD-START Emscripten
+  /// \brief Are pointers to member functions differently aligned?
+  bool arePointersToMemberFunctionsAligned() const {
+    switch (getKind()) {
+    case Emscripten:
+      // Emscripten uses table indices for function pointers and therefore
+      // doesn't require alignment.
+      return false;
+    case GenericARM:
+    case GenericAArch64:
+      // TODO: ARM-style pointers to member functions put the discriminator in
+      //       the this adjustment, so they don't require functions to have any
+      //       special alignment and could therefore also return false.
+    case GenericItanium:
+    case iOS:
+    case iOS64:
+    case Microsoft:
+      return true;
+    }
+    llvm_unreachable("bad ABI kind");
+  }
+  // @LOCALMOD-END Emscripten
+
   /// \brief Is the default C++ member function calling convention
   /// the same as the default calling convention?
   bool isMemberFunctionCCDefault() const {
@@ -210,6 +241,7 @@ public:
 
     case GenericAArch64:
     case GenericItanium:
+    case Emscripten: // @LOCALMOD Emscripten
     case iOS:   // old iOS compilers did not follow this rule
     case Microsoft:
       return true;
@@ -256,6 +288,7 @@ public:
     case GenericItanium:
     case GenericAArch64:
     case GenericARM:
+    case Emscripten: // @LOCALMOD Emscripten
     case iOS:
       return UseTailPaddingUnlessPOD03;