Index: include/llvm/AsmParser/MnemonicSpellCheck.h
===================================================================
--- /dev/null
+++ include/llvm/AsmParser/MnemonicSpellCheck.h
@@ -0,0 +1,42 @@
+
+// Simple implementation of Levenshtein Distance calculation.
+unsigned CalcLevenshteinDist(std::string S, std::string T) {
+  const unsigned N = S.size() + 1;
+  const unsigned M = T.size() + 1;
+
+  if (!S.size()) return M;
+  if (!T.size()) return N;
+
+  std::vector<std::vector<unsigned> >Mat(M, std::vector<unsigned>(N));
+
+  for (unsigned i = 0; i<M; i++)
+    Mat[i][0] = i;
+
+  for (unsigned i = 0; i<N; i++)
+    Mat[0][i] = i;
+
+  auto Min = [] (unsigned N, unsigned M) { return N < M ? N : M; };
+
+  for (unsigned i = 1; i<N; i++) {
+    for (unsigned j = 1; j<M; j++) {
+      const unsigned Cost = S[i-1] == T[j-1] ? 0 : 1;
+      Mat[j][i] = Min(Mat[j-1][i] + 1, Min(Mat[j][i-1] + 1, Mat[j-1][i-1] + Cost));
+    }
+  }
+  return Mat[M-1][N-1];
+}
+
+// For now this returns just one alternative, but perhaps it should all.
+std::string MnemonicSpellCheck(std::string S) {
+  unsigned MinDist = ~0;
+  std::string Match = "(no match)";
+  for (unsigned i = 1; i < MnemonicStringTableSize; i++) {
+    std::string T = MnemonicStringTable[i];
+    unsigned Dist = CalcLevenshteinDist(S, T);
+    if (Dist < MinDist) {
+      MinDist = Dist;
+      Match = T;
+    }
+  }
+  return "did you mean: " + Match + "?";
+}
Index: include/llvm/TableGen/StringToOffsetTable.h
===================================================================
--- include/llvm/TableGen/StringToOffsetTable.h
+++ include/llvm/TableGen/StringToOffsetTable.h
@@ -23,10 +23,11 @@
 /// It can then output this string blob and use indexes into the string to
 /// reference each piece.
 class StringToOffsetTable {
-  StringMap<unsigned> StringOffset;
   std::string AggregateString;
 
 public:
+  StringMap<unsigned> StringOffset;
+
   bool Empty() const { return StringOffset.empty(); }
 
   unsigned GetOrAddStringOffset(StringRef Str, bool appendZero = true) {
Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -8985,6 +8985,8 @@
   return PlainMatchResult;
 }
 
+std::string MnemonicSpellCheck(std::string S);
+
 static const char *getSubtargetFeatureName(uint64_t Val);
 bool ARMAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                            OperandVector &Operands,
@@ -9078,9 +9080,12 @@
 
     return Error(ErrorLoc, "invalid operand for instruction");
   }
-  case Match_MnemonicFail:
-    return Error(IDLoc, "invalid instruction",
+  case Match_MnemonicFail: {
+    std::string Suggestion = MnemonicSpellCheck(
+      std::string(((ARMOperand &)*Operands[0]).getToken()));
+    return Error(IDLoc, "invalid instruction, " + Suggestion,
                  ((ARMOperand &)*Operands[0]).getLocRange());
+  }
   case Match_RequiresNotITBlock:
     return Error(IDLoc, "flag setting instruction only valid outside IT block");
   case Match_RequiresITBlock:
@@ -10183,6 +10188,7 @@
 #define GET_SUBTARGET_FEATURE_NAME
 #define GET_MATCHER_IMPLEMENTATION
 #include "ARMGenAsmMatcher.inc"
+#include "llvm/AsmParser/MnemonicSpellCheck.h"
 
 // FIXME: This structure should be moved inside ARMTargetParser
 // when we start to table-generate them, and we can use the ARM
Index: utils/TableGen/AsmMatcherEmitter.cpp
===================================================================
--- utils/TableGen/AsmMatcherEmitter.cpp
+++ utils/TableGen/AsmMatcherEmitter.cpp
@@ -2880,6 +2880,16 @@
                         StringTable.GetOrAddStringOffset(LenMnemonic, false));
   }
 
+  OS << "static std::string MnemonicStringTable[] = {\n";
+  for (const auto &MI : StringTable.StringOffset) {
+    std::string first(MI.first());
+    OS << "\"" << first.erase(0, 1) << "\",\n";
+  }
+  OS << "};\n\n";
+
+  OS << "static unsigned MnemonicStringTableSize = " <<
+        StringTable.StringOffset.size() << ";\n\n";
+
   OS << "static const char *const MnemonicTable =\n";
   StringTable.EmitString(OS);
   OS << ";\n\n";