diff --git a/llvm/include/llvm/MC/MCParser/MCAsmLexer.h b/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
--- a/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
+++ b/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
@@ -49,6 +49,7 @@
   bool SkipSpace = true;
   bool AllowAtInIdentifier;
   bool IsAtStartOfStatement = true;
+  bool LexMasmHexFloats = false;
   bool LexMasmIntegers = false;
   bool UseMasmDefaultRadix = false;
   unsigned DefaultRadix = 10;
@@ -159,6 +160,9 @@
 
   unsigned getMasmDefaultRadix() const { return DefaultRadix; }
   void setMasmDefaultRadix(unsigned Radix) { DefaultRadix = Radix; }
+
+  /// Set whether to lex masm-style hex float literals, such as 3f800000r.
+  void setLexMasmHexFloats(bool V) { LexMasmHexFloats = V; }
 };
 
 } // end namespace llvm
diff --git a/llvm/lib/MC/MCParser/AsmLexer.cpp b/llvm/lib/MC/MCParser/AsmLexer.cpp
--- a/llvm/lib/MC/MCParser/AsmLexer.cpp
+++ b/llvm/lib/MC/MCParser/AsmLexer.cpp
@@ -350,6 +350,11 @@
       return LexFloatLiteral();
     }
 
+    if (LexMasmHexFloats && (*CurPtr == 'r' || *CurPtr == 'R')) {
+      ++CurPtr;
+      return AsmToken(AsmToken::Real, StringRef(TokStart, CurPtr - TokStart));
+    }
+
     unsigned Radix = 0;
     if (*CurPtr == 'h' || *CurPtr == 'H') {
       // hexadecimal number
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
@@ -3425,10 +3425,13 @@
   // We don't truly support arithmetic on floating point expressions, so we
   // have to manually parse unary prefixes.
   bool IsNeg = false;
+  SMLoc SignLoc;
   if (getLexer().is(AsmToken::Minus)) {
+    SignLoc = getLexer().getLoc();
     Lexer.Lex();
     IsNeg = true;
   } else if (getLexer().is(AsmToken::Plus)) {
+    SignLoc = getLexer().getLoc();
     Lexer.Lex();
   }
 
@@ -3450,6 +3453,20 @@
       Value = APFloat::getZero(Semantics);
     else
       return TokError("invalid floating point literal");
+  } else if (IDVal.consume_back("r") || IDVal.consume_back("R")) {
+    // MASM hexadecimal floating-point literal; no APFloat conversion needed.
+    // To match ML64.exe, ignore the initial sign.
+    unsigned Size = Value.getSizeInBits(Semantics);
+    if (Size != (IDVal.size() << 2))
+      return TokError("invalid floating point literal");
+
+    // Consume the numeric token.
+    Lex();
+
+    Res = APInt(Size, IDVal, 16);
+    if (SignLoc.isValid())
+      return Warning(SignLoc, "MASM-style hex floats ignore explicit sign");
+    return false;
   } else if (errorToBool(
                  Value.convertFromString(IDVal, APFloat::rmNearestTiesToEven)
                      .takeError())) {
diff --git a/llvm/test/tools/llvm-ml/builtin_types.test b/llvm/test/tools/llvm-ml/builtin_types.test
--- a/llvm/test/tools/llvm-ml/builtin_types.test
+++ b/llvm/test/tools/llvm-ml/builtin_types.test
@@ -72,6 +72,14 @@
 ; CHECK-LABEL: t6_double:
 ; CHECK-NEXT: .quad 4608533498688228557
 
+t7_single_hex REAL4 3f800000r
+t7_double_hex REAL8 3FF0000000000000R
+
+; CHECK-LABEL: t7_single_hex:
+; CHECK-NEXT: .long 1065353216
+; CHECK-LABEL: t7_double_hex:
+; CHECK-NEXT: .quad 4607182418800017408
+
 .code
 
 END
diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -169,6 +169,10 @@
     "masm-integers",
     cl::desc("Enable binary and hex masm integers (0b110 and 0ABCh)"));
 
+static cl::opt<bool> LexMasmHexFloats(
+    "masm-hexfloats",
+    cl::desc("Enable MASM-style hex float initializers (3F800000r)"));
+
 static cl::opt<bool> NoExecStack("no-exec-stack",
                                  cl::desc("File doesn't need an exec stack"));
 
@@ -300,6 +304,7 @@
   Parser->setShowParsedOperands(ShowInstOperands);
   Parser->setTargetParser(*TAP);
   Parser->getLexer().setLexMasmIntegers(LexMasmIntegers);
+  Parser->getLexer().setLexMasmHexFloats(LexMasmHexFloats);
 
   int Res = Parser->Run(NoInitialTextSection);
 
diff --git a/llvm/tools/llvm-ml/llvm-ml.cpp b/llvm/tools/llvm-ml/llvm-ml.cpp
--- a/llvm/tools/llvm-ml/llvm-ml.cpp
+++ b/llvm/tools/llvm-ml/llvm-ml.cpp
@@ -177,6 +177,7 @@
   Lexer.setBuffer(SrcMgr.getMemoryBuffer(SrcMgr.getMainFileID())->getBuffer());
   Lexer.setLexMasmIntegers(true);
   Lexer.useMasmDefaultRadix(true);
+  Lexer.setLexMasmHexFloats(true);
 
   bool Error = false;
   while (Lexer.Lex().isNot(AsmToken::Eof)) {
@@ -208,6 +209,7 @@
   Parser->setTargetParser(*TAP);
   Parser->getLexer().setLexMasmIntegers(true);
   Parser->getLexer().useMasmDefaultRadix(true);
+  Parser->getLexer().setLexMasmHexFloats(true);
 
   int Res = Parser->Run(/*NoInitialTextSection=*/true);