[TableGen] AsmMatcher: Skip optional operands in the midle of instruction if it is not present

[SamWot]

Summary

Previosy, if actual instruction have one of optional operands then other optional operands listed before this also should be presented.
For example instruction v_fract_f32 v0, v1, mul:2 have one optional operand - OMod and do not have optional operand clamp. Previously this was not allowed because clamp is listed before omod in AsmString:

string AsmString = "v_fract_f32$vdst, $src0_modifiers$clamp$omod";

Making this work required some hacks (both OMod and Clamp match classes have same PredicateMethod).

Now, if MatchInstructionImpl meets formal optional operand that is not presented in actual instruction it skips this formal operand and tries to match current actual operand with next formal.

[ab]

LGTM, but please wait for D17644.

utils/TableGen/AsmMatcherEmitter.cpp

3137–3139

An extra comment here would help, I think.

[SamWot]

Added comment

[nhaustov]

r262314

utils/TableGen/AsmMatcherEmitter.cpp

#endif // NDEBUG
 
   if (HasMnemonicFirst) {
     OS << "    // equal_range guarantees that instruction mnemonic matches.\n";
     OS << "    assert(Mnemonic == it->getMnemonic());\n";
   }
 
   // Emit check that the subclasses match.
   OS << "    bool OperandsValid = true;\n";
-  OS << "    for (unsigned i = " << (HasMnemonicFirst ? "0" : "SIndex")
-     << "; i != " << MaxNumOperands << "; ++i) {\n";
-  OS << "      auto Formal = static_cast<MatchClassKind>(it->Classes[i]);\n";
-  OS << "      if (i" << (HasMnemonicFirst ? "+1" : "")
-     << " >= Operands.size()) {\n";
+  OS << "    for (unsigned FormalIdx = " << (HasMnemonicFirst ? "0" : "SIndex")
+     << ", ActualIdx = " << (HasMnemonicFirst ? "1" : "SIndex")
+     << "; FormalIdx != " << MaxNumOperands << "; ++FormalIdx) {\n";
+  OS << "      auto Formal = "
+     << "static_cast<MatchClassKind>(it->Classes[FormalIdx]);\n";
+  OS << "      if (ActualIdx >= Operands.size()) {\n";
   OS << "        OperandsValid = (Formal == " <<"InvalidMatchClass) || "
                                  "isSubclass(Formal, OptionalMatchClass);\n";
-  OS << "        if (!OperandsValid) ErrorInfo = i"
-     << (HasMnemonicFirst ? "+1" : "") << ";\n";
+  OS << "        if (!OperandsValid) ErrorInfo = ActualIdx;\n";
   OS << "        break;\n";
   OS << "      }\n";
-  OS << "      MCParsedAsmOperand &Actual = *Operands[i"
-     << (HasMnemonicFirst ? "+1" : "") << "];\n";
+  OS << "      MCParsedAsmOperand &Actual = *Operands[ActualIdx];\n";
   OS << "      unsigned Diag = validateOperandClass(Actual, Formal);\n";
-  OS << "      if (Diag == Match_Success)\n";
+  OS << "      if (Diag == Match_Success) {\n";
+  OS << "        ++ActualIdx;\n";
   OS << "        continue;\n";
+  OS << "      }\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(Actual, Formal);\n";
-  OS << "        if (Diag == Match_Success)\n";
+  OS << "        if (Diag == Match_Success) {\n";
+  OS << "          ++ActualIdx;\n";
   OS << "          continue;\n";
-  OS << "      }\n";
+  OS << "        }\n";
+  OS << "      }\n";
+  OS << "      // If current formal operand wasn't matched and it is optional\n"
+     << "      // then try to match next formal operand\n";
+  OS << "      if (Diag == Match_InvalidOperand "
+     << "&& isSubclass(Formal, OptionalMatchClass))\n";
+  OS << "        continue;\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";
   OS << "      // target predicate, that diagnostic is preferred.\n";
   OS << "      if (!HadMatchOtherThanPredicate &&\n";
-  OS << "          (it == MnemonicRange.first || ErrorInfo <= i"
-     << (HasMnemonicFirst ? "+1" : "") << ")) {\n";
-  OS << "        ErrorInfo = i" << (HasMnemonicFirst ? "+1" : "") << ";\n";
+  OS << "          (it == MnemonicRange.first || ErrorInfo <= ActualIdx)) {\n";
+  OS << "        ErrorInfo = ActualIdx;\n";
   OS << "        // InvalidOperand is the default. Prefer specificity.\n";
   OS << "        if (Diag != Match_InvalidOperand)\n";
   OS << "          RetCode = Diag;\n";
   OS << "      }\n";
   OS << "      // Otherwise, just reject this instance of the mnemonic.\n";
   OS << "      OperandsValid = false;\n";
   OS << "      break;\n";
   OS << "    }\n\n";