Revert "[MCExpr] Remove generic getVariantKindName and getVariantKindForName"

This reverts commit 04b49b1.

This patch breaks ThinLTO/X86/memprof-tailcall-nonunique.ll.

Builtbot failures:
https://lab.llvm.org/buildbot/#/builders/108/builds/9933
https://lab.llvm.org/buildbot/#/builders/25/builds/6868
https://lab.llvm.org/buildbot/#/builders/46/builds/12890

Author: kazutakahirata

llvm/include/llvm/MC/MCExpr.h

@@ -416,6 +416,14 @@ class MCSymbolRefExpr : public MCExpr {
     return (getSubclassData() & HasSubsectionsViaSymbolsBit) != 0;
   }
 
+  /// @}
+  /// \name Static Utility Functions
+  /// @{
+
+  static StringRef getVariantKindName(VariantKind Kind);
+
+  static VariantKind getVariantKindForName(StringRef Name);
+
   /// @}
 
   static bool classof(const MCExpr *E) {

llvm/lib/MC/MCAsmInfo.cpp

@@ -139,13 +139,15 @@ void MCAsmInfo::initializeVariantKinds(ArrayRef<VariantKindDesc> Descs) {
 }
 
 StringRef MCAsmInfo::getVariantKindName(uint32_t Kind) const {
-  auto It = VariantKindToName.find(Kind);
-  assert(It != VariantKindToName.end() &&
-         "ensure the VariantKind is set in initializeVariantKinds");
-  return It->second;
+  if (!VariantKindToName.empty())
+    return VariantKindToName.find(Kind)->second;
+  return MCSymbolRefExpr::getVariantKindName(
+      MCSymbolRefExpr::VariantKind(Kind));
 }
 
 uint32_t MCAsmInfo::getVariantKindForName(StringRef Name) const {
+  if (NameToVariantKind.empty())
+    return MCSymbolRefExpr::getVariantKindForName(Name);
   auto It = NameToVariantKind.find(Name.lower());
   if (It != NameToVariantKind.end())
     return It->second;

llvm/lib/MC/MCExpr.cpp

@@ -86,10 +86,12 @@ void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const {
 
     const MCSymbolRefExpr::VariantKind Kind = SRE.getKind();
     if (Kind != MCSymbolRefExpr::VK_None) {
-      if (MAI->useParensForSymbolVariant()) // ARM
+      if (MAI && MAI->useParensForSymbolVariant()) // ARM
         OS << '(' << MAI->getVariantKindName(Kind) << ')';
-      else
+      else if (MAI)
         OS << '@' << MAI->getVariantKindName(Kind);
+      else
+        OS << '@' << MCSymbolRefExpr::getVariantKindName(Kind);
     }
 
     return;
@@ -246,6 +248,84 @@ const MCSymbolRefExpr *MCSymbolRefExpr::create(StringRef Name, VariantKind Kind,
   return create(Ctx.getOrCreateSymbol(Name), Kind, Ctx);
 }
 
+// TODO: Move target-specific Kinds to lib/Target/*/MCTargetDesc/*AsmInfo.cpp.
+StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
+  switch (Kind) {
+    // clang-format off
+  case VK_Invalid: default: return "<<invalid>>";
+  case VK_None: return "<<none>>";
+
+  case VK_DTPOFF: return "DTPOFF";
+  case VK_DTPREL: return "DTPREL";
+  case VK_GOT: return "GOT";
+  case VK_GOTENT: return "GOTENT";
+  case VK_GOTOFF: return "GOTOFF";
+  case VK_GOTREL: return "GOTREL";
+  case VK_PCREL: return "PCREL";
+  case VK_GOTPCREL: return "GOTPCREL";
+  case VK_GOTTPOFF: return "GOTTPOFF";
+  case VK_INDNTPOFF: return "INDNTPOFF";
+  case VK_NTPOFF: return "NTPOFF";
+  case VK_GOTNTPOFF: return "GOTNTPOFF";
+  case VK_PLT: return "PLT";
+  case VK_TLSGD: return "TLSGD";
+  case VK_TLSLD: return "TLSLD";
+  case VK_TLSLDM: return "TLSLDM";
+  case VK_TPOFF: return "TPOFF";
+  case VK_TPREL: return "TPREL";
+  case VK_TLSCALL: return "tlscall";
+  case VK_TLSDESC: return "tlsdesc";
+  case VK_TLVP: return "TLVP";
+  case VK_TLVPPAGE: return "TLVPPAGE";
+  case VK_TLVPPAGEOFF: return "TLVPPAGEOFF";
+  case VK_PAGE: return "PAGE";
+  case VK_PAGEOFF: return "PAGEOFF";
+  case VK_GOTPAGE: return "GOTPAGE";
+  case VK_GOTPAGEOFF: return "GOTPAGEOFF";
+  case VK_SECREL: return "SECREL32";
+  case VK_WEAKREF: return "WEAKREF";
+  case VK_COFF_IMGREL32: return "IMGREL";
+    // clang-format on
+  }
+  llvm_unreachable("Invalid variant kind");
+}
+
+// FIXME: All variant kinds are target-specific. Move them to
+// *AsmParser::getVariantKindForName and remove this function.
+MCSymbolRefExpr::VariantKind
+MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
+  return StringSwitch<VariantKind>(Name.lower())
+      .Case("dtprel", VK_DTPREL)
+      .Case("dtpoff", VK_DTPOFF)
+      .Case("got", VK_GOT)
+      .Case("gotent", VK_GOTENT)
+      .Case("gotoff", VK_GOTOFF)
+      .Case("gotrel", VK_GOTREL)
+      .Case("pcrel", VK_PCREL)
+      .Case("gotpcrel", VK_GOTPCREL)
+      .Case("gottpoff", VK_GOTTPOFF)
+      .Case("indntpoff", VK_INDNTPOFF)
+      .Case("ntpoff", VK_NTPOFF)
+      .Case("plt", VK_PLT)
+      .Case("tlscall", VK_TLSCALL)
+      .Case("tlsdesc", VK_TLSDESC)
+      .Case("tlsgd", VK_TLSGD)
+      .Case("tlsld", VK_TLSLD)
+      .Case("tlsldm", VK_TLSLDM)
+      .Case("tpoff", VK_TPOFF)
+      .Case("tprel", VK_TPREL)
+      .Case("tlvp", VK_TLVP)
+      .Case("tlvppage", VK_TLVPPAGE)
+      .Case("tlvppageoff", VK_TLVPPAGEOFF)
+      .Case("page", VK_PAGE)
+      .Case("pageoff", VK_PAGEOFF)
+      .Case("gotpage", VK_GOTPAGE)
+      .Case("gotpageoff", VK_GOTPAGEOFF)
+      .Case("imgrel", VK_COFF_IMGREL32)
+      .Case("secrel32", VK_SECREL)
+      .Default(VK_Invalid);
+}
+
 /* *** */
 
 void MCTargetExpr::anchor() {}

llvm/lib/Target/ARM/MCTargetDesc/ARMMCAsmInfo.cpp

@@ -129,8 +129,6 @@ ARMCOFFMCAsmInfoMicrosoft::ARMCOFFMCAsmInfoMicrosoft() {
 
   // Conditional Thumb 4-byte instructions can have an implicit IT.
   MaxInstLength = 6;
-
-  initializeVariantKinds(variantKindDescs);
 }
 
 void ARMCOFFMCAsmInfoGNU::anchor() { }

llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmInfo.cpp

@@ -53,8 +53,6 @@ SystemZMCAsmInfoGOFF::SystemZMCAsmInfoGOFF(const Triple &TT) {
   IsLittleEndian = false;
   MaxInstLength = 6;
   SupportsDebugInformation = true;
-
-  initializeVariantKinds(variantKindDescs);
 }
 
 bool SystemZMCAsmInfoGOFF::isAcceptableChar(char C) const {