RISCVAsmParser: Reject call foo@invalid

... instead of silently parsing and ignoring it without leaving an error
message.

While here, remove an unreachable `@plt`.

Pull Request: #135509

Author: MaskRay

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

@@ -2079,9 +2079,6 @@ ParseStatus RISCVAsmParser::parseBareSymbol(OperandVector &Operands) {
 
   SMLoc E = SMLoc::getFromPointer(S.getPointer() + Identifier.size());
 
-  if (Identifier.consume_back("@plt"))
-    return Error(getLoc(), "'@plt' operand not valid for instruction");
-
   MCSymbol *Sym = getContext().getOrCreateSymbol(Identifier);
 
   if (Sym->isVariable()) {
@@ -2129,8 +2126,9 @@ ParseStatus RISCVAsmParser::parseCallSymbol(OperandVector &Operands) {
     Lex();
     Lex();
     StringRef PLT;
+    SMLoc Loc = getLoc();
     if (getParser().parseIdentifier(PLT) || PLT != "plt")
-      return ParseStatus::Failure;
+      return Error(Loc, "@ (except the deprecated/ignored @plt) is disallowed");
   } else if (!getLexer().peekTok().is(AsmToken::EndOfStatement)) {
     // Avoid parsing the register in `call rd, foo` as a call symbol.
     return ParseStatus::NoMatch;

llvm/test/MC/RISCV/function-call-invalid.s

@@ -10,3 +10,5 @@ call %lo(1234) # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
 call %hi(foo) # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
 call %lo(foo) # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
 call foo, bar # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
+call foo@pls # CHECK: :[[@LINE]]:10: error: @ (except the deprecated/ignored @plt) is disallowed
+call foo@3 # CHECK: :[[@LINE]]:10: error: @ (except the deprecated/ignored @plt) is disallowed

llvm/test/MC/RISCV/tail-call-invalid.s

@@ -10,3 +10,4 @@ tail %hi(1234) # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
 tail %lo(1234) # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
 tail %hi(foo) # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
 tail %lo(foo) # CHECK: :[[@LINE]]:6: error: operand must be a bare symbol name
+tail foo@pls # CHECK: :[[@LINE]]:10: error: @ (except the deprecated/ignored @plt) is disallowed