diff --git a/llvm/include/llvm/MC/MCParser/MCAsmParser.h b/llvm/include/llvm/MC/MCParser/MCAsmParser.h
--- a/llvm/include/llvm/MC/MCParser/MCAsmParser.h
+++ b/llvm/include/llvm/MC/MCParser/MCAsmParser.h
@@ -90,6 +90,14 @@
   IdKind Kind;
 };
 
+struct AsmFieldInfo {
+  StringRef Type;
+  unsigned Offset = 0;
+  unsigned Size = 0;
+  unsigned ElementSize = 0;
+  unsigned Length = 0;
+};
+
 /// Generic Sema callback for assembly parser.
 class MCAsmParserSemaCallback {
 public:
@@ -170,15 +178,16 @@
 
   virtual bool isParsingMasm() const { return false; }
 
-  virtual bool lookUpField(StringRef Name, StringRef &Type,
-                           unsigned &Offset) const {
+  virtual bool lookUpField(StringRef Name, AsmFieldInfo &Info) const {
     return true;
   }
-  virtual bool lookUpField(StringRef Base, StringRef Member, StringRef &Type,
-                           unsigned &Offset) const {
+  virtual bool lookUpField(StringRef Base, StringRef Member,
+                           AsmFieldInfo &Info) const {
     return true;
   }
 
+  virtual bool lookUpType(StringRef Name, unsigned &Size) const { return true; }
+
   /// Parse MS-style inline assembly.
   virtual bool parseMSInlineAsm(
       void *AsmLoc, std::string &AsmString, unsigned &NumOutputs,
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
@@ -20,6 +20,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/DebugInfo/CodeView/SymbolRecord.h"
@@ -333,7 +334,7 @@
 FieldInfo &StructInfo::addField(StringRef FieldName, FieldType FT,
                                 size_t FieldSize) {
   if (!FieldName.empty())
-    FieldsByName[FieldName] = Fields.size();
+    FieldsByName[FieldName.lower()] = Fields.size();
   Fields.emplace_back(FT);
   FieldInfo &Field = Fields.back();
   if (IsUnion) {
@@ -491,10 +492,11 @@
 
   bool isParsingMasm() const override { return true; }
 
-  bool lookUpField(StringRef Name, StringRef &Type,
-                   unsigned &Offset) const override;
-  bool lookUpField(StringRef Base, StringRef Member, StringRef &Type,
-                   unsigned &Offset) const override;
+  bool lookUpField(StringRef Name, AsmFieldInfo &Info) const override;
+  bool lookUpField(StringRef Base, StringRef Member,
+                   AsmFieldInfo &Info) const override;
+
+  bool lookUpType(StringRef Name, unsigned &Size) const override;
 
   bool parseMSInlineAsm(void *AsmLoc, std::string &AsmString,
                         unsigned &NumOutputs, unsigned &NumInputs,
@@ -565,7 +567,7 @@
   static void DiagHandler(const SMDiagnostic &Diag, void *Context);
 
   bool lookUpField(const StructInfo &Structure, StringRef Member,
-                   StringRef &Type, unsigned &Offset) const;
+                   AsmFieldInfo &Info) const;
 
   /// Should we emit DWARF describing this assembler source?  (Returns false if
   /// the source has .file directives, which means we don't want to generate
@@ -1411,24 +1413,23 @@
     }
 
     // Find the field offset if used.
-    StringRef Type;
-    unsigned Offset = 0;
+    AsmFieldInfo Info;
     Split = SymbolName.split('.');
     if (!Split.second.empty()) {
       SymbolName = Split.first;
       if (Structs.count(SymbolName.lower()) &&
-          !lookUpField(SymbolName, Split.second, Type, Offset)) {
+          !lookUpField(SymbolName, Split.second, Info)) {
         // This is actually a reference to a field offset.
-        Res = MCConstantExpr::create(Offset, getContext());
+        Res = MCConstantExpr::create(Info.Offset, getContext());
         return false;
       }
 
       auto TypeIt = KnownType.find(SymbolName);
       if (TypeIt == KnownType.end() ||
-          lookUpField(*TypeIt->second, Split.second, Type, Offset)) {
+          lookUpField(*TypeIt->second, Split.second, Info)) {
         std::pair<StringRef, StringRef> BaseMember = Split.second.split('.');
         StringRef Base = BaseMember.first, Member = BaseMember.second;
-        lookUpField(Base, Member, Type, Offset);
+        lookUpField(Base, Member, Info);
       }
     }
 
@@ -1454,10 +1455,10 @@
     // Otherwise create a symbol ref.
     const MCExpr *SymRef =
         MCSymbolRefExpr::create(Sym, Variant, getContext(), FirstTokenLoc);
-    if (Offset) {
-      Res = MCBinaryExpr::create(MCBinaryExpr::Add, SymRef,
-                                 MCConstantExpr::create(Offset, getContext()),
-                                 getContext());
+    if (Info.Offset) {
+      Res = MCBinaryExpr::create(
+          MCBinaryExpr::Add, SymRef,
+          MCConstantExpr::create(Info.Offset, getContext()), getContext());
     } else {
       Res = SymRef;
     }
@@ -6550,37 +6551,39 @@
   llvm_unreachable("Unstable rewrite sort.");
 }
 
-bool MasmParser::lookUpField(StringRef Name, StringRef &Type,
-                             unsigned &Offset) const {
+bool MasmParser::lookUpField(StringRef Name, AsmFieldInfo &Info) const {
   const std::pair<StringRef, StringRef> BaseMember = Name.split('.');
   const StringRef Base = BaseMember.first, Member = BaseMember.second;
-  return lookUpField(Base, Member, Type, Offset);
+  return lookUpField(Base, Member, Info);
 }
 
-bool MasmParser::lookUpField(StringRef Base, StringRef Member, StringRef &Type,
-                             unsigned &Offset) const {
+bool MasmParser::lookUpField(StringRef Base, StringRef Member,
+                             AsmFieldInfo &Info) const {
   if (Base.empty())
     return true;
 
-  unsigned BaseOffset = 0;
-  if (Base.contains('.') && !lookUpField(Base, Type, BaseOffset))
-    Base = Type;
+  AsmFieldInfo BaseInfo;
+  if (Base.contains('.') && !lookUpField(Base, BaseInfo))
+    Base = BaseInfo.Type;
 
   auto TypeIt = KnownType.find(Base);
   if (TypeIt != KnownType.end())
-    return lookUpField(*TypeIt->second, Member, Type, Offset);
+    return lookUpField(*TypeIt->second, Member, Info);
 
   auto StructIt = Structs.find(Base.lower());
   if (StructIt != Structs.end())
-    return lookUpField(StructIt->second, Member, Type, Offset);
+    return lookUpField(StructIt->second, Member, Info);
 
   return true;
 }
 
 bool MasmParser::lookUpField(const StructInfo &Structure, StringRef Member,
-                             StringRef &Type, unsigned &Offset) const {
+                             AsmFieldInfo &Info) const {
   if (Member.empty()) {
-    Type = Structure.Name;
+    Info.Type = Structure.Name;
+    Info.Size = Structure.Size;
+    Info.ElementSize = Structure.Size;
+    Info.Length = 1;
     return false;
   }
 
@@ -6589,7 +6592,7 @@
 
   auto StructIt = Structs.find(FieldName.lower());
   if (StructIt != Structs.end())
-    return lookUpField(StructIt->second, FieldMember, Type, Offset);
+    return lookUpField(StructIt->second, FieldMember, Info);
 
   auto FieldIt = Structure.FieldsByName.find(FieldName.lower());
   if (FieldIt == Structure.FieldsByName.end())
@@ -6597,9 +6600,12 @@
 
   const FieldInfo &Field = Structure.Fields[FieldIt->second];
   if (FieldMember.empty()) {
-    Offset += Field.Offset;
+    Info.Offset += Field.Offset;
+    Info.Size = Field.SizeOf << 3;
+    Info.ElementSize = Field.Type << 3;
+    Info.Length = Field.LengthOf;
     if (Field.Contents.FT == FT_STRUCT)
-      Type = Field.Contents.StructInfo.Structure.Name;
+      Info.Type = Field.Contents.StructInfo.Structure.Name;
     return false;
   }
 
@@ -6607,14 +6613,35 @@
     return true;
   const StructFieldInfo &StructInfo = Field.Contents.StructInfo;
 
-  bool Result = lookUpField(StructInfo.Structure, FieldMember, Type, Offset);
-  if (Result)
+  if (lookUpField(StructInfo.Structure, FieldMember, Info))
     return true;
 
-  Offset += Field.Offset;
+  Info.Offset += Field.Offset;
   return false;
 }
 
+bool MasmParser::lookUpType(StringRef Name, unsigned &Size) const {
+  Size = StringSwitch<unsigned>(Name)
+             .CasesLower("byte", "db", "sbyte", 8)
+             .CasesLower("word", "dw", "sword", 16)
+             .CasesLower("dword", "dd", "sdword", 32)
+             .CasesLower("fword", "df", 48)
+             .CasesLower("qword", "dq", "sqword", 64)
+             .CaseLower("real4", 32)
+             .CaseLower("real8", 64)
+             .Default(0);
+  if (Size) {
+    return false;
+  }
+
+  auto TypeIt = Structs.find(Name.lower());
+  if (TypeIt != Structs.end()) {
+    Size = TypeIt->second.Size << 3;
+    return false;
+  }
+  return true;
+}
+
 bool MasmParser::parseMSInlineAsm(
     void *AsmLoc, std::string &AsmString, unsigned &NumOutputs,
     unsigned &NumInputs, SmallVectorImpl<std::pair<void *, bool>> &OpDecls,
diff --git a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
--- a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -32,6 +32,7 @@
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
@@ -150,6 +151,13 @@
     IOK_TYPE,
   };
 
+  enum MasmOperatorKind {
+    MOK_INVALID = 0,
+    MOK_LENGTHOF,
+    MOK_SIZEOF,
+    MOK_TYPE,
+  };
+
   class InfixCalculator {
     typedef std::pair< InfixCalculatorTok, int64_t > ICToken;
     SmallVector<InfixCalculatorTok, 4> InfixOperatorStack;
@@ -368,6 +376,9 @@
     bool OffsetOperator;
     SMLoc OffsetOperatorLoc;
     StringRef CurType;
+    unsigned CurSize = 0;
+    unsigned CurElementSize = 0;
+    unsigned CurLength = 1;
 
     bool setSymRef(const MCExpr *Val, StringRef ID, StringRef &ErrMsg) {
       if (Sym) {
@@ -396,6 +407,9 @@
     const MCExpr *getSym() { return Sym; }
     StringRef getSymName() { return SymName; }
     StringRef getType() { return CurType; }
+    unsigned getSize() { return CurSize; }
+    unsigned getElementSize() { return CurElementSize; }
+    unsigned getLength() { return CurLength; }
     int64_t getImm() { return Imm + IC.execute(); }
     bool isValidEndState() {
       return State == IES_RBRAC || State == IES_INTEGER;
@@ -752,6 +766,7 @@
       case IES_RPAREN:
         State = IES_PLUS;
         IC.pushOperator(IC_PLUS);
+        CurLength = 1;
         break;
       case IES_INIT:
       case IES_CAST:
@@ -835,8 +850,8 @@
       }
     }
     bool onOffset(const MCExpr *Val, SMLoc OffsetLoc, StringRef ID,
-                  const InlineAsmIdentifierInfo &IDInfo, bool ParsingMSInlineAsm,
-                  StringRef &ErrMsg) {
+                  const InlineAsmIdentifierInfo &IDInfo,
+                  bool ParsingMSInlineAsm, StringRef &ErrMsg) {
       PrevState = State;
       switch (State) {
       default:
@@ -860,19 +875,25 @@
       }
       return false;
     }
-    void onCast(StringRef Type) {
+    void onCast(StringRef Type, unsigned Size) {
       PrevState = State;
       switch (State) {
       default:
         State = IES_ERROR;
         break;
       case IES_LPAREN:
-        setType(Type);
+        setTypeInfo(Type, Size, Size, 1);
         State = IES_CAST;
         break;
       }
     }
-    void setType(StringRef Type) { CurType = Type; }
+    void setTypeInfo(StringRef Type, unsigned Size, unsigned ElementSize,
+                     unsigned Length) {
+      CurType = Type;
+      CurSize = Size;
+      CurElementSize = ElementSize;
+      CurLength = Length;
+    }
   };
 
   bool Error(SMLoc L, const Twine &Msg, SMRange Range = None,
@@ -909,6 +930,8 @@
   bool ParseIntelDotOperator(IntelExprStateMachine &SM, SMLoc &End);
   unsigned IdentifyIntelInlineAsmOperator(StringRef Name);
   unsigned ParseIntelInlineAsmOperator(unsigned OpKind);
+  unsigned IdentifyMasmOperator(StringRef Name);
+  bool ParseMasmOperator(unsigned OpKind, int64_t &Val);
   bool ParseRoundingModeOp(SMLoc Start, OperandVector &Operands);
   bool ParseIntelNamedOperator(StringRef Name, IntelExprStateMachine &SM,
                                bool &ParseError, SMLoc &End);
@@ -1653,6 +1676,13 @@
       if (ParseIntelDotOperator(SM, End))
         return true;
       break;
+    case AsmToken::Dollar:
+      if (!Parser.isParsingMasm()) {
+        if ((Done = SM.isValidEndState()))
+          break;
+        return Error(Tok.getLoc(), "unknown token in expression");
+      }
+      LLVM_FALLTHROUGH;
     case AsmToken::At:
     case AsmToken::String:
     case AsmToken::Identifier: {
@@ -1664,7 +1694,10 @@
         const AsmToken &NextTok = getLexer().peekTok();
         if (NextTok.is(AsmToken::Identifier) &&
             NextTok.getIdentifier().equals_lower("ptr")) {
-          SM.onCast(Identifier);
+          unsigned Size;
+          if (Parser.lookUpType(Identifier, Size))
+            return Error(Tok.getLoc(), "unknown type");
+          SM.onCast(Identifier, Size);
           // Eat type and PTR.
           consumeToken();
           End = consumeToken();
@@ -1689,16 +1722,15 @@
             if (SM.onRegister(Reg, ErrMsg))
               return Error(IdentLoc, ErrMsg);
 
-            StringRef Type;
-            unsigned Offset = 0;
+            AsmFieldInfo Info;
             SMLoc FieldStartLoc = SMLoc::getFromPointer(Field.data());
-            if (Parser.lookUpField(Field, Type, Offset))
+            if (Parser.lookUpField(Field, Info))
               return Error(FieldStartLoc, "unknown offset");
             else if (SM.onPlus(ErrMsg))
               return Error(getTok().getLoc(), ErrMsg);
-            else if (SM.onInteger(Offset, ErrMsg))
+            else if (SM.onInteger(Info.Offset, ErrMsg))
               return Error(IdentLoc, ErrMsg);
-            SM.setType(Type);
+            SM.setTypeInfo(Info.Type, Info.Size, Info.ElementSize, Info.Length);
 
             End = consumeToken();
             break;
@@ -1744,6 +1776,16 @@
           return Error(IdentLoc, ErrMsg);
         break;
       }
+      if (Parser.isParsingMasm()) {
+        if (unsigned OpKind = IdentifyMasmOperator(Identifier)) {
+          int64_t Val;
+          if (ParseMasmOperator(OpKind, Val))
+            return true;
+          if (SM.onInteger(Val, ErrMsg))
+            return Error(IdentLoc, ErrMsg);
+          break;
+        }
+      }
       if (getParser().parsePrimaryExpr(Val, End)) {
         return Error(Tok.getLoc(), "Unexpected identifier!");
       } else if (SM.onIdentifierExpr(Val, Identifier, Info, false, ErrMsg)) {
@@ -1957,8 +1999,7 @@
 bool X86AsmParser::ParseIntelDotOperator(IntelExprStateMachine &SM,
                                          SMLoc &End) {
   const AsmToken &Tok = getTok();
-  StringRef Type;
-  unsigned Offset = 0;
+  AsmFieldInfo Info;
 
   // Drop the optional '.'.
   StringRef DotDispStr = Tok.getString();
@@ -1969,27 +2010,28 @@
   if (Tok.is(AsmToken::Real)) {
     APInt DotDisp;
     DotDispStr.getAsInteger(10, DotDisp);
-    Offset = DotDisp.getZExtValue();
+    Info.Offset = DotDisp.getZExtValue();
   } else if ((isParsingMSInlineAsm() || getParser().isParsingMasm()) &&
              Tok.is(AsmToken::Identifier)) {
     const std::pair<StringRef, StringRef> BaseMember = DotDispStr.split('.');
     const StringRef Base = BaseMember.first, Member = BaseMember.second;
-    if (getParser().lookUpField(SM.getType(), DotDispStr, Type, Offset) &&
-        getParser().lookUpField(SM.getSymName(), DotDispStr, Type, Offset) &&
-        getParser().lookUpField(DotDispStr, Type, Offset) &&
+    if (getParser().lookUpField(SM.getType(), DotDispStr, Info) &&
+        getParser().lookUpField(SM.getSymName(), DotDispStr, Info) &&
+        getParser().lookUpField(DotDispStr, Info) &&
         (!SemaCallback ||
-         SemaCallback->LookupInlineAsmField(Base, Member, Offset)))
+         SemaCallback->LookupInlineAsmField(Base, Member, Info.Offset)))
       return Error(Tok.getLoc(), "Unable to lookup field reference!");
-  } else
+  } else {
     return Error(Tok.getLoc(), "Unexpected token type!");
+  }
 
   // Eat the DotExpression and update End
   End = SMLoc::getFromPointer(DotDispStr.data());
   const char *DotExprEndLoc = DotDispStr.data() + DotDispStr.size();
   while (Tok.getLoc().getPointer() < DotExprEndLoc)
     Lex();
-  SM.addImm(Offset);
-  SM.setType(Type);
+  SM.addImm(Info.Offset);
+  SM.setTypeInfo(Info.Type, Info.Size, Info.ElementSize, Info.Length);
   return false;
 }
 
@@ -2059,6 +2101,66 @@
   return CVal;
 }
 
+// Query a candidate string for being an Intel assembly operator
+// Report back its kind, or IOK_INVALID if does not evaluated as a known one
+unsigned X86AsmParser::IdentifyMasmOperator(StringRef Name) {
+  return StringSwitch<unsigned>(Name.lower())
+      .Case("type", MOK_TYPE)
+      .Cases("size", "sizeof", MOK_SIZEOF)
+      .Cases("length", "lengthof", MOK_LENGTHOF)
+      .Default(MOK_INVALID);
+}
+
+/// Parse the 'LENGTHOF', 'SIZEOF', and 'TYPE' operators.  The LENGTHOF operator
+/// returns the number of elements in an array.  It returns the value 1 for
+/// non-array variables.  The SIZEOF operator returns the size of a type or
+/// variable in bytes.  A variable's size is the product of its LENGTH and TYPE.
+/// The TYPE operator returns the size of a variable. If the variable is an
+/// array, TYPE returns the size of a single element.
+bool X86AsmParser::ParseMasmOperator(unsigned OpKind, int64_t &Val) {
+  MCAsmParser &Parser = getParser();
+  Parser.Lex(); // Eat operator.
+
+  bool InParens = parseOptionalToken(AsmToken::LParen);
+
+  Val = 0;
+  if (OpKind == MOK_SIZEOF) {
+    // Check for SIZEOF(<type>)
+    const AsmToken &NextTok = Parser.getTok();
+    unsigned Size = 0;
+    if (NextTok.is(AsmToken::Identifier) &&
+        !Parser.lookUpType(NextTok.getIdentifier(), Size)) {
+      Val = Size >> 3;
+      Parser.Lex(); // Eat type.
+    }
+  }
+
+  if (!Val) {
+    IntelExprStateMachine SM;
+    SMLoc End;
+    if (ParseIntelExpression(SM, End))
+      return true;
+
+    switch (OpKind) {
+    default:
+      llvm_unreachable("Unexpected operand kind!");
+    case MOK_SIZEOF:
+      Val = SM.getSize() >> 3;
+      break;
+    case MOK_LENGTHOF:
+      Val = SM.getLength();
+      break;
+    case MOK_TYPE:
+      Val = SM.getElementSize() >> 3;
+      break;
+    }
+  }
+
+  if (InParens)
+    parseToken(AsmToken::RParen);
+  return false;
+}
+
 bool X86AsmParser::ParseIntelMemoryOperandSize(unsigned &Size) {
   Size = StringSwitch<unsigned>(getTok().getString())
     .Cases("BYTE", "byte", 8)
@@ -2161,6 +2263,8 @@
   unsigned BaseReg = SM.getBaseReg();
   unsigned IndexReg = SM.getIndexReg();
   unsigned Scale = SM.getScale();
+  if (!PtrInOperand)
+    Size = SM.getSize();
 
   if (Scale == 0 && BaseReg != X86::ESP && BaseReg != X86::RSP &&
       (IndexReg == X86::ESP || IndexReg == X86::RSP))
diff --git a/llvm/test/tools/llvm-ml/sizeof.test b/llvm/test/tools/llvm-ml/sizeof.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/llvm-ml/sizeof.test
@@ -0,0 +1,19 @@
+# RUN: llvm-ml -filetype=asm %s | FileCheck %s
+
+.code
+
+FOO STRUCT
+  x BYTE 5 DUP (?)
+FOO ENDS
+
+t1:
+mov eax, sizeof(dword)
+; CHECK: t1:
+; CHECK-NEXT: mov eax, 4
+
+t2:
+mov eax, sizeof(FOO)
+; CHECK: t2:
+; CHECK-NEXT: mov eax, 5
+
+END