Revert "[MC][AsmParser] Diagnose improperly nested .cfi frames"

This reverts commit a405193.

It broke: lld/test/COFF/gc-dwarf-eh.s

Author: jroelofs

llvm/lib/MC/MCParser/AsmParser.cpp

@@ -125,7 +125,6 @@ class AsmParser : public MCAsmParser {
   void *SavedDiagContext;
   std::unique_ptr<MCAsmParserExtension> PlatformParser;
   SMLoc StartTokLoc;
-  std::optional<SMLoc> CFIStartProcLoc;
 
   /// This is the current buffer index we're lexing from as managed by the
   /// SourceMgr object.
@@ -1950,11 +1949,6 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
       Lex();
     }
 
-    if (CFIStartProcLoc && Sym->isExternal())
-      return Error(StartTokLoc, "non-private labels cannot appear between "
-                                ".cfi_startproc / .cfi_endproc pairs") &&
-             Error(*CFIStartProcLoc, "previous .cfi_startproc was here");
-
     if (discardLTOSymbol(IDVal))
       return false;
 
@@ -4199,8 +4193,6 @@ bool AsmParser::parseDirectiveCFISections() {
 /// parseDirectiveCFIStartProc
 /// ::= .cfi_startproc [simple]
 bool AsmParser::parseDirectiveCFIStartProc() {
-  CFIStartProcLoc = StartTokLoc;
-
   StringRef Simple;
   if (!parseOptionalToken(AsmToken::EndOfStatement)) {
     if (check(parseIdentifier(Simple) || Simple != "simple",
@@ -4221,11 +4213,8 @@ bool AsmParser::parseDirectiveCFIStartProc() {
 /// parseDirectiveCFIEndProc
 /// ::= .cfi_endproc
 bool AsmParser::parseDirectiveCFIEndProc() {
-  CFIStartProcLoc = std::nullopt;
-
   if (parseEOL())
     return true;
-
   getStreamer().emitCFIEndProc();
   return false;
 }