+ARMAsmParser::OperandMatchResultTy
+ARMAsmParser::parseModImm(OperandVector &Operands) {
+ MCAsmParser &Parser = getParser();
+ MCAsmLexer &Lexer = getLexer();
+ int64_t Imm1, Imm2;
+
+ SMLoc S = Parser.getTok().getLoc();
+
+ // 1) A mod_imm operand can appear in the place of a register name:
+ // add r0, #mod_imm
+ // add r0, r0, #mod_imm
+ // to correctly handle the latter, we bail out as soon as we see an
+ // identifier.
+ //
+ // 2) Similarly, we do not want to parse into complex operands:
+ // mov r0, #mod_imm
+ // mov r0, :lower16:(_foo)
+ if (Parser.getTok().is(AsmToken::Identifier) ||
+ Parser.getTok().is(AsmToken::Colon))
+ return MatchOperand_NoMatch;
+
+ // Hash (dollar) is optional as per the ARMARM
+ if (Parser.getTok().is(AsmToken::Hash) ||
+ Parser.getTok().is(AsmToken::Dollar)) {
+ // Avoid parsing into complex operands (#:)
+ if (Lexer.peekTok().is(AsmToken::Colon))
+ return MatchOperand_NoMatch;
+
+ // Eat the hash (dollar)
+ Parser.Lex();
+ }
+
+ SMLoc Sx1, Ex1;
+ Sx1 = Parser.getTok().getLoc();
+ const MCExpr *Imm1Exp;
+ if (getParser().parseExpression(Imm1Exp, Ex1)) {
+ Error(Sx1, "malformed expression");
+ return MatchOperand_ParseFail;
+ }
+
+ const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(Imm1Exp);
+
+ if (CE) {
+ // Immediate must fit within 32-bits
+ Imm1 = CE->getValue();
+ int Enc = ARM_AM::getSOImmVal(Imm1);
+ if (Enc != -1 && Parser.getTok().is(AsmToken::EndOfStatement)) {
+ // We have a match!
+ Operands.push_back(ARMOperand::CreateModImm((Enc & 0xFF),
+ (Enc & 0xF00) >> 7,
+ Sx1, Ex1));
+ return MatchOperand_Success;
+ }
+
+ // We have parsed an immediate which is not for us, fallback to a plain
+ // immediate. This can happen for instruction aliases. For an example,
+ // ARMInstrInfo.td defines the alias [mov <-> mvn] which can transform
+ // a mov (mvn) with a mod_imm_neg/mod_imm_not operand into the opposite
+ // instruction with a mod_imm operand. The alias is defined such that the
+ // parser method is shared, that's why we have to do this here.
+ if (Parser.getTok().is(AsmToken::EndOfStatement)) {
+ Operands.push_back(ARMOperand::CreateImm(Imm1Exp, Sx1, Ex1));
+ return MatchOperand_Success;
+ }
+ } else {
+ // Operands like #(l1 - l2) can only be evaluated at a later stage (via an
+ // MCFixup). Fallback to a plain immediate.
+ Operands.push_back(ARMOperand::CreateImm(Imm1Exp, Sx1, Ex1));
+ return MatchOperand_Success;
+ }
+
+ // From this point onward, we expect the input to be a (#bits, #rot) pair
+ if (Parser.getTok().isNot(AsmToken::Comma)) {
+ Error(Sx1, "expected modified immediate operand: #[0, 255], #even[0-30]");
+ return MatchOperand_ParseFail;
+ }
+
+ if (Imm1 & ~0xFF) {
+ Error(Sx1, "immediate operand must a number in the range [0, 255]");
+ return MatchOperand_ParseFail;
+ }
+
+ // Eat the comma
+ Parser.Lex();
+
+ // Repeat for #rot
+ SMLoc Sx2, Ex2;
+ Sx2 = Parser.getTok().getLoc();
+
+ // Eat the optional hash (dollar)
+ if (Parser.getTok().is(AsmToken::Hash) ||
+ Parser.getTok().is(AsmToken::Dollar))
+ Parser.Lex();
+
+ const MCExpr *Imm2Exp;
+ if (getParser().parseExpression(Imm2Exp, Ex2)) {
+ Error(Sx2, "malformed expression");
+ return MatchOperand_ParseFail;
+ }
+
+ CE = dyn_cast<MCConstantExpr>(Imm2Exp);
+
+ if (CE) {
+ Imm2 = CE->getValue();
+ if (!(Imm2 & ~0x1E)) {
+ // We have a match!
+ Operands.push_back(ARMOperand::CreateModImm(Imm1, Imm2, S, Ex2));
+ return MatchOperand_Success;
+ }
+ Error(Sx2, "immediate operand must an even number in the range [0, 30]");
+ return MatchOperand_ParseFail;
+ } else {
+ Error(Sx2, "constant expression expected");
+ return MatchOperand_ParseFail;
+ }
+}
+