diff --git a/llvm/lib/MC/MCParser/MasmParser.cpp b/llvm/lib/MC/MCParser/MasmParser.cpp
--- a/llvm/lib/MC/MCParser/MasmParser.cpp
+++ b/llvm/lib/MC/MCParser/MasmParser.cpp
@@ -611,15 +611,15 @@
 
   /// Parse up to a token of kind \p EndTok and return the contents from the
   /// current token up to (but not including) this token; the current token on
-  /// exit will be either this kind or EOF.
-  StringRef parseStringTo(AsmToken::TokenKind EndTok);
+  /// exit will be either this kind or EOF. Reads through instantiated macro
+  /// functions and text macros.
+  SmallVector<StringRef, 1> parseStringRefsTo(AsmToken::TokenKind EndTok);
+  std::string parseStringTo(AsmToken::TokenKind EndTok);
 
   /// Parse up to the end of statement and return the contents from the current
   /// token until the end of the statement; the current token on exit will be
   /// either the EndOfStatement or EOF.
-  StringRef parseStringToEndOfStatement() override {
-    return parseStringTo(AsmToken::EndOfStatement);
-  }
+  StringRef parseStringToEndOfStatement() override;
 
   bool parseTextItem(std::string &Data);
 
@@ -1122,8 +1122,11 @@
   const AsmToken *tok = &Lexer.Lex();
 
   while (tok->is(AsmToken::Identifier)) {
-    auto it = Variables.find(tok->getIdentifier());
+    auto it = Variables.find(tok->getIdentifier().lower());
+    const llvm::MCAsmMacro *M =
+        getContext().lookupMacro(tok->getIdentifier().lower());
     if (it != Variables.end() && it->second.IsText) {
+      // This is a textmacro; expand it in place.
       std::unique_ptr<MemoryBuffer> Instantiation =
           MemoryBuffer::getMemBufferCopy(it->second.TextValue,
                                          "<instantiation>");
@@ -1135,6 +1138,15 @@
                       /*EndStatementAtEOF=*/false);
       EndStatementAtEOFStack.push_back(false);
       tok = &Lexer.Lex();
+    } else if (M && M->Function && Lexer.peekTok().is(AsmToken::LParen)) {
+      // This is a macro function invocation; expand it in place.
+      const AsmToken MacroTok = *tok;
+      tok = &Lexer.Lex();
+      if (handleMacroInvocation(M, MacroTok.getLoc())) {
+        Lexer.UnLex(AsmToken(AsmToken::Error, MacroTok.getIdentifier()));
+        tok = &Lexer.Lex();
+      }
+      continue;
     } else {
       break;
     }
@@ -1321,18 +1333,62 @@
 
 /// Throw away the rest of the line for testing purposes.
 void MasmParser::eatToEndOfStatement() {
-  while (Lexer.isNot(AsmToken::EndOfStatement) && Lexer.isNot(AsmToken::Eof))
+  while (Lexer.isNot(AsmToken::EndOfStatement)) {
+    if (Lexer.is(AsmToken::Eof)) {
+      SMLoc ParentIncludeLoc = SrcMgr.getParentIncludeLoc(CurBuffer);
+      if (ParentIncludeLoc == SMLoc()) {
+        break;
+      }
+
+      EndStatementAtEOFStack.pop_back();
+      jumpToLoc(ParentIncludeLoc, 0, EndStatementAtEOFStack.back());
+    }
+
     Lexer.Lex();
+  }
 
   // Eat EOL.
   if (Lexer.is(AsmToken::EndOfStatement))
     Lexer.Lex();
 }
 
-StringRef MasmParser::parseStringTo(AsmToken::TokenKind EndTok) {
+SmallVector<StringRef, 1>
+MasmParser::parseStringRefsTo(AsmToken::TokenKind EndTok) {
+  SmallVector<StringRef, 1> Refs;
   const char *Start = getTok().getLoc().getPointer();
+  while (Lexer.isNot(EndTok)) {
+    if (Lexer.is(AsmToken::Eof)) {
+      SMLoc ParentIncludeLoc = SrcMgr.getParentIncludeLoc(CurBuffer);
+      if (ParentIncludeLoc == SMLoc()) {
+        break;
+      }
+      Refs.emplace_back(Start, getTok().getLoc().getPointer() - Start);
 
-  while (Lexer.isNot(EndTok) && Lexer.isNot(AsmToken::Eof))
+      EndStatementAtEOFStack.pop_back();
+      jumpToLoc(ParentIncludeLoc, 0, EndStatementAtEOFStack.back());
+      Lexer.Lex();
+      Start = getTok().getLoc().getPointer();
+    } else {
+      Lexer.Lex();
+    }
+  }
+  Refs.emplace_back(Start, getTok().getLoc().getPointer() - Start);
+  return Refs;
+}
+
+std::string MasmParser::parseStringTo(AsmToken::TokenKind EndTok) {
+  SmallVector<StringRef, 1> Refs = parseStringRefsTo(EndTok);
+  std::string Str;
+  for (StringRef S : Refs) {
+    Str.append(S.str());
+  }
+  return Str;
+}
+
+StringRef MasmParser::parseStringToEndOfStatement() {
+  const char *Start = getTok().getLoc().getPointer();
+
+  while (Lexer.isNot(AsmToken::EndOfStatement) && Lexer.isNot(AsmToken::Eof))
     Lexer.Lex();
 
   const char *End = getTok().getLoc().getPointer();
@@ -1370,7 +1426,6 @@
 
 /// Parse a primary expression and return it.
 ///  primaryexpr ::= (parenexpr
-///  primaryexpr ::= macro_function "(" macro_arguments ")"
 ///  primaryexpr ::= symbol
 ///  primaryexpr ::= number
 ///  primaryexpr ::= '.'
@@ -1420,12 +1475,6 @@
       Res = MCUnaryExpr::createNot(Res, getContext(), FirstTokenLoc);
       return false;
     }
-    // Parse macro function invocation.
-    if (const MCAsmMacro *M = getContext().lookupMacro(Identifier)) {
-      if (handleMacroInvocation(M, FirstTokenLoc))
-        return true;
-      return parsePrimaryExpr(Res, EndLoc, nullptr);
-    }
     // Parse symbol variant.
     std::pair<StringRef, StringRef> Split;
     if (!MAI.useParensForSymbolVariant()) {
@@ -2090,7 +2139,7 @@
     // does not understand Labels. This may cause us to see a Hash
     // here instead of a preprocessor line comment.
     if (getTok().is(AsmToken::Hash)) {
-      StringRef CommentStr = parseStringToEndOfStatement();
+      std::string CommentStr = parseStringTo(AsmToken::EndOfStatement);
       Lexer.Lex();
       Lexer.UnLex(AsmToken(AsmToken::EndOfStatement, CommentStr));
     }
@@ -2123,12 +2172,8 @@
   }
 
   // If macros are enabled, check to see if this is a macro instantiation.
-  if (const MCAsmMacro *M = getContext().lookupMacro(IDVal)) {
-    if (M->Function) {
-      return handleMacroInvocation(M, IDLoc);
-    } else {
-      return handleMacroEntry(M, IDLoc);
-    }
+  if (const MCAsmMacro *M = getContext().lookupMacro(IDVal.lower())) {
+    return handleMacroEntry(M, IDLoc);
   }
 
   // Otherwise, we have a normal instruction or directive.
@@ -2728,7 +2773,7 @@
       ++I;
       ++Pos;
     }
-    while (isMacroParameterChar(Body[I]) && I + 1 != End)
+    while (I < End && isMacroParameterChar(Body[I]))
       ++I;
 
     const char *Begin = Body.data() + Pos;
@@ -2829,11 +2874,14 @@
                                     AsmToken::TokenKind EndTok) {
   if (MP && MP->Vararg) {
     if (Lexer.isNot(EndTok)) {
-      StringRef Str = parseStringTo(EndTok);
-      MA.emplace_back(AsmToken::String, Str);
+      SmallVector<StringRef, 1> Str = parseStringRefsTo(EndTok);
+      for (StringRef S : Str) {
+        MA.emplace_back(AsmToken::String, S);
+      }
     }
     return false;
   }
+
   SMLoc StrLoc = Lexer.getLoc(), EndLoc;
   if (Lexer.is(AsmToken::Less) && isAngleBracketString(StrLoc, EndLoc)) {
     const char *StrChar = StrLoc.getPointer() + 1;
@@ -2863,7 +2911,7 @@
 
       if (Lexer.is(AsmToken::Space)) {
         SpaceEaten = true;
-        Lexer.Lex(); // Eat spaces.
+        Lex(); // Eat spaces.
       }
 
       // Spaces can delimit parameters, but could also be part an expression.
@@ -2872,11 +2920,11 @@
       if (!IsDarwin) {
         if (isOperator(Lexer.getKind()) && Lexer.isNot(EndTok)) {
           MA.push_back(getTok());
-          Lexer.Lex();
+          Lex();
 
           // Whitespace after an operator can be ignored.
           if (Lexer.is(AsmToken::Space))
-            Lexer.Lex();
+            Lex();
 
           continue;
         }
@@ -2898,7 +2946,7 @@
 
     // Append the token to the current argument list.
     MA.push_back(getTok());
-    Lexer.Lex();
+    Lex();
   }
 
   if (ParenLevel != 0)
@@ -5548,7 +5596,7 @@
     eatToEndOfStatement();
   }
 
-  if (getContext().lookupMacro(Name)) {
+  if (getContext().lookupMacro(Name.lower())) {
     return Error(NameLoc, "macro '" + Name + "' is already defined");
   }
 
@@ -5620,9 +5668,9 @@
 
     DEBUG_WITH_TYPE("asm-macros", dbgs()
                                       << "Un-defining macro: " << Name << "\n");
-    if (!getContext().lookupMacro(Name))
+    if (!getContext().lookupMacro(Name.lower()))
       return Error(NameLoc, "macro '" + Name + "' is not defined");
-    getContext().undefineMacro(Name);
+    getContext().undefineMacro(Name.lower());
 
     if (!parseOptionalToken(AsmToken::Comma))
       break;
@@ -5736,16 +5784,17 @@
 ///              [[text]]
 ///              [[text]] delimiter [[text]]
 bool MasmParser::parseDirectiveComment(SMLoc DirectiveLoc) {
-  StringRef FirstLine = parseStringToEndOfStatement();
+  std::string FirstLine = parseStringTo(AsmToken::EndOfStatement);
   size_t DelimiterEnd = FirstLine.find_first_of("\b\t\v\f\r\x1A ");
-  StringRef Delimiter = FirstLine.take_front(DelimiterEnd);
+  StringRef Delimiter = StringRef(FirstLine).take_front(DelimiterEnd);
   if (Delimiter.empty())
     return Error(DirectiveLoc, "no delimiter in 'comment' directive");
   do {
     if (getTok().is(AsmToken::Eof))
       return Error(DirectiveLoc, "unmatched delimiter in 'comment' directive");
     Lex();  // eat end of statement
-  } while (!parseStringToEndOfStatement().contains(Delimiter));
+  } while (
+      !StringRef(parseStringTo(AsmToken::EndOfStatement)).contains(Delimiter));
   return parseToken(AsmToken::EndOfStatement,
                     "unexpected token in 'comment' directive");
 }
@@ -5759,7 +5808,7 @@
   SMLoc IncludeLoc = getTok().getLoc();
 
   if (!parseAngleBracketString(Filename))
-    Filename = parseStringToEndOfStatement().str();
+    Filename = parseStringTo(AsmToken::EndOfStatement);
   if (check(!Filename.empty(), "missing filename in 'include' directive") ||
       check(getTok().isNot(AsmToken::EndOfStatement),
             "unexpected token in 'include' directive") ||
@@ -6131,9 +6180,9 @@
     }
   }
 
-  StringRef Message = ".err directive invoked in source file";
+  std::string Message = ".err directive invoked in source file";
   if (Lexer.isNot(AsmToken::EndOfStatement))
-    Message = parseStringToEndOfStatement();
+    Message = parseStringTo(AsmToken::EndOfStatement);
   Lex();
 
   return Error(DirectiveLoc, Message);
@@ -6153,11 +6202,11 @@
   if (parseTextItem(Text))
     return Error(getTok().getLoc(), "missing text item in '.errb' directive");
 
-  StringRef Message = ".errb directive invoked in source file";
+  std::string Message = ".errb directive invoked in source file";
   if (Lexer.isNot(AsmToken::EndOfStatement)) {
     if (parseToken(AsmToken::Comma))
       return addErrorSuffix(" in '.errb' directive");
-    Message = parseStringToEndOfStatement();
+    Message = parseStringTo(AsmToken::EndOfStatement);
   }
   Lex();
 
@@ -6195,11 +6244,11 @@
     }
   }
 
-  StringRef Message = ".errdef directive invoked in source file";
+  std::string Message = ".errdef directive invoked in source file";
   if (Lexer.isNot(AsmToken::EndOfStatement)) {
     if (parseToken(AsmToken::Comma))
       return addErrorSuffix(" in '.errdef' directive");
-    Message = parseStringToEndOfStatement();
+    Message = parseStringTo(AsmToken::EndOfStatement);
   }
   Lex();
 
@@ -6245,7 +6294,7 @@
       return TokError("expected string parameter for '.errdif' directive");
   }
 
-  StringRef Message;
+  std::string Message;
   if (ExpectEqual)
     Message = ".erridn directive invoked in source file";
   else
@@ -6253,7 +6302,7 @@
   if (Lexer.isNot(AsmToken::EndOfStatement)) {
     if (parseToken(AsmToken::Comma))
       return addErrorSuffix(" in '.erridn' directive");
-    Message = parseStringToEndOfStatement();
+    Message = parseStringTo(AsmToken::EndOfStatement);
   }
   Lex();
 
@@ -6285,11 +6334,11 @@
   if (parseAbsoluteExpression(ExprValue))
     return addErrorSuffix(" in '.erre' directive");
 
-  StringRef Message = ".erre directive invoked in source file";
+  std::string Message = ".erre directive invoked in source file";
   if (Lexer.isNot(AsmToken::EndOfStatement)) {
     if (parseToken(AsmToken::Comma))
       return addErrorSuffix(" in '.erre' directive");
-    Message = parseStringToEndOfStatement();
+    Message = parseStringTo(AsmToken::EndOfStatement);
   }
   Lex();
 
@@ -6499,12 +6548,9 @@
 }
 
 bool MasmParser::expandStatement(SMLoc Loc) {
-  SMLoc StartLoc = getTok().getLoc();
-  eatToEndOfStatement();
+  std::string Body = parseStringTo(AsmToken::EndOfStatement);
   SMLoc EndLoc = getTok().getLoc();
 
-  StringRef Body = StringRef(StartLoc.getPointer(),
-                             EndLoc.getPointer() - StartLoc.getPointer());
   MCAsmMacroParameters Parameters;
   MCAsmMacroArguments Arguments;
   for (const auto &V : Variables) {
@@ -6735,7 +6781,7 @@
     // Match ml64.exe; treat all characters to end of statement as a string,
     // ignoring comment markers, then discard anything following a space (using
     // the C locale).
-    Argument = parseStringToEndOfStatement().str();
+    Argument = parseStringTo(AsmToken::EndOfStatement);
     if (getTok().is(AsmToken::EndOfStatement))
       Argument += getTok().getString();
     int End = 0;
@@ -6807,7 +6853,8 @@
 
 bool MasmParser::parseDirectiveRadix(SMLoc DirectiveLoc) {
   const SMLoc Loc = getLexer().getLoc();
-  StringRef RadixString = parseStringToEndOfStatement().trim();
+  std::string RadixStringRaw = parseStringTo(AsmToken::EndOfStatement);
+  StringRef RadixString = StringRef(RadixStringRaw).trim();
   unsigned Radix;
   if (RadixString.getAsInteger(10, Radix)) {
     return Error(Loc,
@@ -6831,13 +6878,9 @@
          getTok().getString().equals_lower("echo"));
   Lexer.Lex();
 
-  SMLoc StartLoc = getTok().getLoc();
-  eatToEndOfStatement();
-  SMLoc EndLoc = getTok().getLoc();
-  StringRef Message = StringRef(StartLoc.getPointer(),
-                                EndLoc.getPointer() - StartLoc.getPointer());
+  std::string Message = parseStringTo(AsmToken::EndOfStatement);
   llvm::outs() << Message;
-  if (Message.back() != '\n')
+  if (!StringRef(Message).endswith("\n"))
     llvm::outs() << '\n';
   return false;
 }
diff --git a/llvm/test/tools/llvm-ml/macro_function.test b/llvm/test/tools/llvm-ml/macro_function.test
--- a/llvm/test/tools/llvm-ml/macro_function.test
+++ b/llvm/test/tools/llvm-ml/macro_function.test
@@ -103,4 +103,14 @@
   ret
 expr_recursive_test ENDP
 
+custom_strcat MACRO arg1, arg2
+  EXITM <arg1&arg2>
+ENDM
+
+expand_as_directive_test custom_strcat(P, ROC)
+; CHECK-LABEL: expand_as_directive_test:
+
+  ret
+expand_as_directive_test ENDP
+
 end