[AsmParser] Mnemonic Spell Corrector

This implements suggesting other mnemonics when an invalid one is specified,
for example:

$ echo "adXd r1,r2,#3" | llvm-mc -triple arm
<stdin>:1:1: error: invalid instruction, did you mean: add, qadd?
adXd r1,r2,#3
^

The implementation is target agnostic, but as a first step I have added it only
to the ARM backend; so the ARM backend is a good example if someone wants to
enable this too for another target.

Differential Revision: https://reviews.llvm.org/D33128

llvm-svn: 307148

1 files changed, 43 insertions, 0 deletions

diff --git a/llvm/utils/TableGen/AsmMatcherEmitter.cpp b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
index 0980e08f67f..b73a4f17527 100644
--- a/llvm/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
@@ -2711,6 +2711,47 @@ static void emitCustomOperandParsing(raw_ostream &OS, CodeGenTarget &Target,
   OS << "}\n\n";
 }
 
+static void emitMnemonicSpellChecker(raw_ostream &OS, CodeGenTarget &Target,
+                                     unsigned VariantCount) {
+  OS << "std::string " << Target.getName() << "MnemonicSpellCheck(StringRef S, uint64_t FBS) {\n";
+  if (!VariantCount)
+    OS <<  "  return \"\";";
+  else {
+    OS << "  const unsigned MaxEditDist = 2;\n";
+    OS << "  std::vector<StringRef> Candidates;\n";
+    OS << "  StringRef Prev = \"\";\n";
+    OS << "  auto End = std::end(MatchTable0);\n";
+    OS << "\n";
+    OS << "  for (auto I = std::begin(MatchTable0); I < End; I++) {\n";
+    OS << "    // Ignore unsupported instructions.\n";
+    OS << "    if ((FBS & I->RequiredFeatures) != I->RequiredFeatures)\n";
+    OS << "      continue;\n";
+    OS << "\n";
+    OS << "    StringRef T = I->getMnemonic();\n";
+    OS << "    // Avoid recomputing the edit distance for the same string.\n";
+    OS << "    if (T.equals(Prev))\n";
+    OS << "      continue;\n";
+    OS << "\n";
+    OS << "    Prev = T;\n";
+    OS << "    unsigned Dist = S.edit_distance(T, false, MaxEditDist);\n";
+    OS << "    if (Dist <= MaxEditDist)\n";
+    OS << "      Candidates.push_back(T);\n";
+    OS << "  }\n";
+    OS << "\n";
+    OS << "  if (Candidates.empty())\n";
+    OS << "    return \"\";\n";
+    OS << "\n";
+    OS << "  std::string Res = \", did you mean: \";\n";
+    OS << "  unsigned i = 0;\n";
+    OS << "  for( ; i < Candidates.size() - 1; i++)\n";
+    OS << "    Res += Candidates[i].str() + \", \";\n";
+    OS << "  return Res + Candidates[i].str() + \"?\";\n";
+  }
+  OS << "}\n";
+  OS << "\n";
+}
+
+
 void AsmMatcherEmitter::run(raw_ostream &OS) {
   CodeGenTarget Target(Records);
   Record *AsmParser = Target.getAsmParser();
@@ -2974,6 +3015,8 @@ void AsmMatcherEmitter::run(raw_ostream &OS) {
     OS << "};\n\n";
   }
 
+  emitMnemonicSpellChecker(OS, Target, VariantCount);
+
   // Finally, build the match function.
   OS << "unsigned " << Target.getName() << ClassName << "::\n"
      << "MatchInstructionImpl(const OperandVector &Operands,\n";