Index: llvm/trunk/lib/CodeGen/MIRParser/MILexer.h
===================================================================
--- llvm/trunk/lib/CodeGen/MIRParser/MILexer.h
+++ llvm/trunk/lib/CodeGen/MIRParser/MILexer.h
@@ -118,6 +118,7 @@
     // Other tokens
     IntegerLiteral,
     FloatingPointLiteral,
+    HexLiteral,
     VirtualRegister,
     ConstantPoolItem,
     JumpTableIndex,
Index: llvm/trunk/lib/CodeGen/MIRParser/MILexer.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MIRParser/MILexer.cpp
+++ llvm/trunk/lib/CodeGen/MIRParser/MILexer.cpp
@@ -424,19 +424,6 @@
   return C == 'H' || C == 'K' || C == 'L' || C == 'M';
 }
 
-static Cursor maybeLexHexFloatingPointLiteral(Cursor C, MIToken &Token) {
-  if (C.peek() != '0' || C.peek(1) != 'x')
-    return None;
-  Cursor Range = C;
-  C.advance(2); // Skip '0x'
-  if (isValidHexFloatingPointPrefix(C.peek()))
-    C.advance();
-  while (isxdigit(C.peek()))
-    C.advance();
-  Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
-  return C;
-}
-
 static Cursor lexFloatingPointLiteral(Cursor Range, Cursor C, MIToken &Token) {
   C.advance();
   // Skip over [0-9]*([eE][-+]?[0-9]+)?
@@ -453,6 +440,28 @@
   return C;
 }
 
+static Cursor maybeLexHexadecimalLiteral(Cursor C, MIToken &Token) {
+  if (C.peek() != '0' || (C.peek(1) != 'x' && C.peek(1) != 'X'))
+    return None;
+  Cursor Range = C;
+  C.advance(2);
+  unsigned PrefLen = 2;
+  if (isValidHexFloatingPointPrefix(C.peek())) {
+    C.advance();
+    PrefLen++;
+  }
+  while (isxdigit(C.peek()))
+    C.advance();
+  StringRef StrVal = Range.upto(C);
+  if (StrVal.size() <= PrefLen)
+    return None;
+  if (PrefLen == 2)
+    Token.reset(MIToken::HexLiteral, Range.upto(C));
+  else // It must be 3, which means that there was a floating-point prefix.
+    Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
+  return C;
+}
+
 static Cursor maybeLexNumericalLiteral(Cursor C, MIToken &Token) {
   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
     return None;
@@ -609,7 +618,7 @@
     return R.remaining();
   if (Cursor R = maybeLexExternalSymbol(C, Token, ErrorCallback))
     return R.remaining();
-  if (Cursor R = maybeLexHexFloatingPointLiteral(C, Token))
+  if (Cursor R = maybeLexHexadecimalLiteral(C, Token))
     return R.remaining();
   if (Cursor R = maybeLexNumericalLiteral(C, Token))
     return R.remaining();
Index: llvm/trunk/lib/CodeGen/MIRParser/MIParser.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MIRParser/MIParser.cpp
+++ llvm/trunk/lib/CodeGen/MIRParser/MIParser.cpp
@@ -36,6 +36,7 @@
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetIntrinsicInfo.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
+#include <cctype>
 
 using namespace llvm;
 
@@ -453,8 +454,19 @@
     unsigned Reg = 0;
     if (parseNamedRegister(Reg))
       return true;
-    MBB.addLiveIn(Reg);
     lex();
+    LaneBitmask Mask = ~LaneBitmask(0);
+    if (consumeIfPresent(MIToken::colon)) {
+      // Parse lane mask.
+      if (Token.isNot(MIToken::IntegerLiteral) &&
+          Token.isNot(MIToken::HexLiteral))
+        return error("expected a lane mask");
+      static_assert(sizeof(LaneBitmask) == sizeof(unsigned), "");
+      if (getUnsigned(Mask))
+        return error("invalid lane mask value");
+      lex();
+    }
+    MBB.addLiveIn(Reg, Mask);
   } while (consumeIfPresent(MIToken::comma));
   return false;
 }
@@ -1107,7 +1119,8 @@
 bool MIParser::parseFPImmediateOperand(MachineOperand &Dest) {
   auto Loc = Token.location();
   lex();
-  if (Token.isNot(MIToken::FloatingPointLiteral))
+  if (Token.isNot(MIToken::FloatingPointLiteral) &&
+      Token.isNot(MIToken::HexLiteral))
     return error("expected a floating point literal");
   const Constant *C = nullptr;
   if (parseIRConstant(Loc, C))
@@ -1117,13 +1130,30 @@
 }
 
 bool MIParser::getUnsigned(unsigned &Result) {
-  assert(Token.hasIntegerValue() && "Expected a token with an integer value");
-  const uint64_t Limit = uint64_t(std::numeric_limits<unsigned>::max()) + 1;
-  uint64_t Val64 = Token.integerValue().getLimitedValue(Limit);
-  if (Val64 == Limit)
-    return error("expected 32-bit integer (too large)");
-  Result = Val64;
-  return false;
+  if (Token.hasIntegerValue()) {
+    const uint64_t Limit = uint64_t(std::numeric_limits<unsigned>::max()) + 1;
+    uint64_t Val64 = Token.integerValue().getLimitedValue(Limit);
+    if (Val64 == Limit)
+      return error("expected 32-bit integer (too large)");
+    Result = Val64;
+    return false;
+  }
+  if (Token.is(MIToken::HexLiteral)) {
+    StringRef S = Token.range();
+    assert(S[0] == '0' && tolower(S[1]) == 'x');
+    // This could be a floating point literal with a special prefix.
+    if (!isxdigit(S[2]))
+      return true;
+    StringRef V = S.substr(2);
+    unsigned BW = std::min<unsigned>(V.size()*4, 32);
+    APInt A(BW, V, 16);
+    APInt Limit = APInt(BW, std::numeric_limits<unsigned>::max());
+    if (A.ugt(Limit))
+      return error("expected 32-bit integer (too large)");
+    Result = A.getZExtValue();
+    return false;
+  }
+  return true;
 }
 
 bool MIParser::parseMBBReference(MachineBasicBlock *&MBB) {
Index: llvm/trunk/lib/CodeGen/MIRPrinter.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MIRPrinter.cpp
+++ llvm/trunk/lib/CodeGen/MIRPrinter.cpp
@@ -499,7 +499,7 @@
       First = false;
       printReg(LI.PhysReg, OS, TRI);
       if (LI.LaneMask != ~0u)
-        OS << ':' << PrintLaneMask(LI.LaneMask);
+        OS << ":0x" << PrintLaneMask(LI.LaneMask);
     }
     OS << "\n";
     HasLineAttributes = true;
Index: llvm/trunk/test/CodeGen/MIR/Hexagon/parse-lane-masks.mir
===================================================================
--- llvm/trunk/test/CodeGen/MIR/Hexagon/parse-lane-masks.mir
+++ llvm/trunk/test/CodeGen/MIR/Hexagon/parse-lane-masks.mir
@@ -0,0 +1,23 @@
+# RUN: llc -march=hexagon -run-pass none -o - %s | FileCheck %s
+# Check that the MIR parser can parse lane masks in block liveins.
+
+# CHECK-LABEL: name: foo
+# CHECK: bb.0:
+# CHECK: liveins: %d0:0x00000002, %d1, %d2:0x00000010
+
+--- |
+  define void @foo() {
+    ret void
+  }
+...
+
+---
+name: foo
+tracksRegLiveness: true
+
+body: |
+  bb.0:
+    liveins: %d0:0x00002, %d1, %d2:16
+    A2_nop
+...
+