[MC] Make MCAsmInfo::isAcceptableChar reflect MCAsmInfo::doesAllowAtInName

[efriedma]

Summary

On targets which don't allow "@" in identifiers, make sure we don't emit them; otherwise, we can't parse our own output.

[mstorsjo]

LGTM, sounds sensible!

[rnk]

lgtm

llvm/lib/MC/MCAsmInfo.cpp

MCAsmInfo::getExprForFDESymbol(const MCSymbol *Sym,
   const MCExpr *Res = MCSymbolRefExpr::create(Sym, Context);
   MCSymbol *PCSym = Context.createTempSymbol();
   Streamer.emitLabel(PCSym);
   const MCExpr *PC = MCSymbolRefExpr::create(PCSym, Context);
   return MCBinaryExpr::createSub(Res, PC, Context);
 }
 
 bool MCAsmInfo::isAcceptableChar(char C) const {
-  return isAlnum(C) || C == '_' || C == '$' || C == '.' || C == '@';
+  if (C == '@')
+    return doesAllowAtInName();
+
+  return isAlnum(C) || C == '_' || C == '$' || C == '.';
 }
 
 bool MCAsmInfo::isValidUnquotedName(StringRef Name) const {
   if (Name.empty())
     return false;
 
   // If any of the characters in the string is an unacceptable character, force
   // quotes.

llvm/test/CodeGen/AArch64/ehcontguard.ll

 ; RUN: llc < %s -mtriple=aarch64-windows | FileCheck %s
 ; EHCont Guard is currently only available on Windows
 
-; CHECK: .set @feat.00, 16384
+; CHECK: .set "@feat.00", 16384
 
 ; CHECK: .section .gehcont$y
 
 define dso_local void @"?func1@@YAXXZ"() #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
 entry:
   invoke void @"?func2@@YAXXZ"()
           to label %invoke.cont unwind label %catch.dispatch
 catch.dispatch:                                   ; preds = %entry

llvm/test/CodeGen/AArch64/win_cst_pool.ll

 ; RUN: llc < %s -mtriple=aarch64-win32-msvc | FileCheck %s
 ; RUN: llc < %s -mtriple=aarch64-win32-gnu | FileCheck -check-prefix=MINGW %s
 
 define double @double() {
   ret double 0x2000000000800001
 }
-; CHECK:              .globl  __real@2000000000800001
-; CHECK-NEXT:         .section        .rdata,"dr",discard,__real@2000000000800001
+; CHECK:              .globl "__real@2000000000800001"
+; CHECK-NEXT:         .section        .rdata,"dr",discard,"__real@2000000000800001"
 ; CHECK-NEXT:         .p2align  3
-; CHECK-NEXT: __real@2000000000800001:
+; CHECK-NEXT: "__real@2000000000800001":
 ; CHECK-NEXT:         .xword   0x2000000000800001
 ; CHECK:      double:
-; CHECK:               adrp    x8, __real@2000000000800001
-; CHECK-NEXT:          ldr     d0, [x8, :lo12:__real@2000000000800001]
+; CHECK:               adrp    x8, "__real@2000000000800001"
+; CHECK-NEXT:          ldr     d0, [x8, :lo12:"__real@2000000000800001"]
 ; CHECK-NEXT:          ret
 
 ; MINGW:              .section        .rdata,"dr"
 ; MINGW-NEXT:         .p2align  3
 ; MINGW-NEXT: [[LABEL:\.LC.*]]:
 ; MINGW-NEXT:         .xword  0x2000000000800001
 ; MINGW:      double:
 ; MINGW:               adrp    x8, [[LABEL]]
 ; MINGW-NEXT:          ldr     d0, [x8, :lo12:[[LABEL]]]
 ; MINGW-NEXT:          ret

llvm/unittests/MC/SystemZ/SystemZAsmLexerTest.cpp

 TEST_F(SystemZAsmLexerZOS, CheckPrintAcceptableSymbol) {
   std::string AsmStr = "ab13_$.@";
   EXPECT_EQ(true, MAI->isValidUnquotedName(AsmStr));
   AsmStr += "#";
   EXPECT_EQ(true, MAI->isValidUnquotedName(AsmStr));
 }
 
 TEST_F(SystemZAsmLexerLinux, CheckPrintAcceptableSymbol) {
-  std::string AsmStr = "ab13_$.@";
+  std::string AsmStr = "ab13_$.";
   EXPECT_EQ(true, MAI->isValidUnquotedName(AsmStr));
-  AsmStr += "#";
+  AsmStr = "ab13_$.@";
+  EXPECT_EQ(false, MAI->isValidUnquotedName(AsmStr));
+  AsmStr = "ab13_$.#";
   EXPECT_EQ(false, MAI->isValidUnquotedName(AsmStr));
 }
 
 TEST_F(SystemZAsmLexerZOS, CheckLabelCaseUpperCase) {
   StringRef AsmStr = "label";
 
   // Setup.
   setupCallToAsmParser(AsmStr);