Allow targets to add custom asm operand matching logic.

For example, ARM has several instructions with a literal '#0' immediate in the syntax
that's not represented as an actual operand. The asm matcher is expected a token
operand, but the parser will have created an immediate operand. This is currently
handled by dedicated per-instruction C++ munging of the ParsedAsmOperand list, but
will be better handled by this hook.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174487 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCTargetAsmParser.h

@@ -142,6 +142,15 @@ class MCTargetAsmParser : public MCAsmParserExtension {
                           MCStreamer &Out, unsigned &ErrorInfo,
                           bool MatchingInlineAsm) = 0;
 
+  /// Allow a target to add special case operand matching for things that
+  /// tblgen doesn't/can't handle effectively. For example, literal
+  /// immediates on ARM. TableGen expects a token operand, but the parser
+  /// will recognize them as immediates.
+  virtual unsigned validateTargetOperandClass(MCParsedAsmOperand *Op,
+                                              unsigned Kind) {
+    return Match_InvalidOperand;
+  }
+
   /// checkTargetMatchPredicate - Validate the instruction match against
   /// any complex target predicates not expressible via match classes.
   virtual unsigned checkTargetMatchPredicate(MCInst &Inst) {

utils/TableGen/AsmMatcherEmitter.cpp

@@ -2878,6 +2878,15 @@ void AsmMatcherEmitter::run(raw_ostream &OS) {
   OS << "(MatchClassKind)it->Classes[i]);\n";
   OS << "      if (Diag == Match_Success)\n";
   OS << "        continue;\n";
+  OS << "      // If the generic handler indicates an invalid operand\n";
+  OS << "      // failure, check for a special case.\n";
+  OS << "      if (Diag == Match_InvalidOperand) {\n";
+  OS << "        Diag = validateTargetOperandClass(Operands[i+1],\n";
+  OS.indent(43);
+  OS << "(MatchClassKind)it->Classes[i]);\n";
+  OS << "        if (Diag == Match_Success)\n";
+  OS << "          continue;\n";
+  OS << "      }\n";
   OS << "      // If this operand is broken for all of the instances of this\n";
   OS << "      // mnemonic, keep track of it so we can report loc info.\n";
   OS << "      // If we already had a match that only failed due to a\n";