[RISCV] Clean up parsing floating point rounding mode

[jrtc27]

Summary

Currently this is done rather hackily by letting it be parsed as an
MCSymbolRefExpr whose name we then validate. Instead, use a custom
parser so we look at the identifier token directly and construct
the immediate at the same time.

[luismarques]

LGTM. Nice clean-up!

[asb]

This is much better, thank you.

[jrtc27]

Obsoleted by 2a45aa8dc2b98815c2e270be3c5d1832c9eec10e

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

#include "RISCVGenAsmMatcher.inc"
 
   OperandMatchResultTy parseCSRSystemRegister(OperandVector &Operands);
   OperandMatchResultTy parseImmediate(OperandVector &Operands);
   OperandMatchResultTy parseRegister(OperandVector &Operands,
                                      bool AllowParens = false);
   OperandMatchResultTy parseMemOpBaseReg(OperandVector &Operands);
   OperandMatchResultTy parseAtomicMemOp(OperandVector &Operands);
   OperandMatchResultTy parseFenceArg(OperandVector &Operands);
+  OperandMatchResultTy parseFRMArg(OperandVector &Operands);
   OperandMatchResultTy parseOperandWithModifier(OperandVector &Operands);
   OperandMatchResultTy parseBareSymbol(OperandVector &Operands);
   OperandMatchResultTy parseCallSymbol(OperandVector &Operands);
   OperandMatchResultTy parsePseudoJumpSymbol(OperandVector &Operands);
   OperandMatchResultTy parseJALOffset(OperandVector &Operands);
   OperandMatchResultTy parseVTypeI(OperandVector &Operands);
   OperandMatchResultTy parseMaskReg(OperandVector &Operands);
 
if (!IsConstantImm)
       return false;
     int64_t Mask = RISCVFenceField::I | RISCVFenceField::O |
                    RISCVFenceField::R | RISCVFenceField::W;
     return (Imm & ~Mask) == 0;
   }
 
   /// Return true if the operand is a valid floating point rounding mode.
   bool isFRMArg() const {
+    int64_t Imm;
+    RISCVMCExpr::VariantKind VK = RISCVMCExpr::VK_RISCV_None;
     if (!isImm())
       return false;
-    const MCExpr *Val = getImm();
-    auto *SVal = dyn_cast<MCSymbolRefExpr>(Val);
-    if (!SVal || SVal->getKind() != MCSymbolRefExpr::VK_None)
+    bool IsConstantImm = evaluateConstantImm(getImm(), Imm, VK);
+    if (!IsConstantImm)
       return false;
-
-    StringRef Str = SVal->getSymbol().getName();
-
-    return RISCVFPRndMode::stringToRoundingMode(Str) != RISCVFPRndMode::Invalid;
+    return RISCVFPRndMode::isValidRoundingMode(Imm);
   }
 
   bool isImmXLenLI() const {
     int64_t Imm;
     RISCVMCExpr::VariantKind VK = RISCVMCExpr::VK_RISCV_None;
     if (!isImm())
       return false;
     bool IsConstantImm = evaluateConstantImm(getImm(), Imm, VK);
void addCSRSystemRegisterOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     Inst.addOperand(MCOperand::createImm(SysReg.Encoding));
   }
 
   void addVTypeIOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     Inst.addOperand(MCOperand::createImm(getVType()));
   }
-
-  // Returns the rounding mode represented by this RISCVOperand. Should only
-  // be called after checking isFRMArg.
-  RISCVFPRndMode::RoundingMode getRoundingMode() const {
-    // isFRMArg has validated the operand, meaning this cast is safe.
-    auto SE = cast<MCSymbolRefExpr>(getImm());
-    RISCVFPRndMode::RoundingMode FRM =
-        RISCVFPRndMode::stringToRoundingMode(SE->getSymbol().getName());
-    assert(FRM != RISCVFPRndMode::Invalid && "Invalid rounding mode");
-    return FRM;
-  }
-
-  void addFRMArgOperands(MCInst &Inst, unsigned N) const {
-    assert(N == 1 && "Invalid number of operands!");
-    Inst.addOperand(MCOperand::createImm(getRoundingMode()));
-  }
 };
 } // end anonymous namespace.
 
 #define GET_REGISTER_MATCHER
 #define GET_SUBTARGET_FEATURE_NAME
 #define GET_MATCHER_IMPLEMENTATION
 #define GET_MNEMONIC_SPELL_CHECKER
 #include "RISCVGenAsmMatcher.inc"
case Match_InvalidSImm21Lsb0JAL:
     return generateImmOutOfRangeError(
         Operands, ErrorInfo, -(1 << 20), (1 << 20) - 2,
         "immediate must be a multiple of 2 bytes in the range");
   case Match_InvalidCSRSystemRegister: {
     return generateImmOutOfRangeError(Operands, ErrorInfo, 0, (1 << 12) - 1,
                                       "operand must be a valid system register "
                                       "name or an integer in the range");
   }
-  case Match_InvalidFRMArg: {
-    SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
-    return Error(
-        ErrorLoc,
-        "operand must be a valid floating point rounding mode mnemonic");
-  }
   case Match_InvalidBareSymbol: {
     SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
     return Error(ErrorLoc, "operand must be a bare symbol name");
   }
   case Match_InvalidPseudoJumpSymbol: {
     SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
     return Error(ErrorLoc, "operand must be a valid jump target");
   }
for (char c : Identifier) {
     Prev = c;
   }
 
   Res = MCConstantExpr::create(Imm, getContext());
   Operands.push_back(RISCVOperand::createImm(Res, S, E, isRV64()));
   return MatchOperand_Success;
 }
 
+OperandMatchResultTy RISCVAsmParser::parseFRMArg(OperandVector &Operands) {
+  SMLoc S = getLoc();
+  SMLoc E = SMLoc::getFromPointer(S.getPointer() - 1);
+  const MCExpr *Res;
+
+  if (getLexer().getKind() != AsmToken::Identifier) {
+    Error(S, "operand must be a valid floating point rounding mode mnemonic");
+    return MatchOperand_ParseFail;
+  }
+
+  StringRef Identifier = getParser().getTok().getIdentifier();
+  getParser().Lex();
+
+  RISCVFPRndMode::RoundingMode FRM =
+      RISCVFPRndMode::stringToRoundingMode(Identifier);
+  if (FRM == RISCVFPRndMode::Invalid) {
+    Error(S, "operand must be a valid floating point rounding mode mnemonic");
+    return MatchOperand_ParseFail;
+  }
+
+  Res = MCConstantExpr::create(FRM, getContext());
+  Operands.push_back(RISCVOperand::createImm(Res, S, E, isRV64()));
+  return MatchOperand_Success;
+}
+
 /// Looks at a token type and creates the relevant operand from this
 /// information, adding to Operands. If operand was parsed, returns false, else
 /// true.
 bool RISCVAsmParser::parseOperand(OperandVector &Operands, StringRef Mnemonic) {
   // Check if the current operand has a custom associated parser, if so, try to
   // custom parse the operand, or fallback to the general approach.
   OperandMatchResultTy Result =
       MatchOperandParserImpl(Operands, Mnemonic, /*ParseForAllFeatures=*/true);

llvm/lib/Target/RISCV/RISCVInstrInfoF.td

 //===----------------------------------------------------------------------===//
 // Operand and SDNode transformation definitions.
 //===----------------------------------------------------------------------===//
 
 // Floating-point rounding mode
 
 def FRMArg : AsmOperandClass {
   let Name = "FRMArg";
-  let RenderMethod = "addFRMArgOperands";
-  let DiagnosticType = "InvalidFRMArg";
+  let RenderMethod = "addImmOperands";
+  let ParserMethod = "parseFRMArg";
 }
 
 def frmarg : Operand<XLenVT> {
   let ParserMatchClass = FRMArg;
   let PrintMethod = "printFRMArg";
   let DecoderMethod = "decodeFRMArg";
 }