[NFC][AArch64] Make extension descriptions available in TargetParser

This introduces a new field to AArch64TargetParser's ExtensionInfo
struct that contains the extension description from the TableGen record.
This allows us to simplify the information flow for functionality such
as '--print-supported-extensions'.

Author: pratlucas

clang/tools/driver/cc1_main.cpp

@@ -148,7 +148,7 @@ static int PrintSupportedExtensions(std::string TargetStr) {
   if (MachineTriple.isRISCV())
     llvm::riscvExtensionsHelp(DescMap);
   else if (MachineTriple.isAArch64())
-    llvm::AArch64::PrintSupportedExtensions(DescMap);
+    llvm::AArch64::PrintSupportedExtensions();
   else if (MachineTriple.isARM())
     llvm::ARM::PrintSupportedExtensions(DescMap);
   else {

llvm/include/llvm/TargetParser/AArch64TargetParser.h

@@ -118,6 +118,7 @@ struct ExtensionInfo {
   std::optional<StringRef> Alias; // An alias for this extension, if one exists.
   ArchExtKind ID;                 // Corresponding to the ArchExtKind, this
                                   // extensions representation in the bitfield.
+  StringRef Description;          // The textual description of the extension
   StringRef TargetFeature;        // -target-feature/-mattr enable string, e.g. "+spe"
   StringRef NegTargetFeature;     // -target-feature/-mattr disable string, e.g. "-spe"
   CPUFeatures CPUFeature;      // Function Multi Versioning (FMV) bitfield value
@@ -325,7 +326,7 @@ bool isX18ReservedByDefault(const Triple &TT);
 // themselves, they are sequential (0, 1, 2, 3, ...).
 uint64_t getCpuSupportsMask(ArrayRef<StringRef> FeatureStrs);
 
-void PrintSupportedExtensions(StringMap<StringRef> DescMap);
+void PrintSupportedExtensions();
 
 } // namespace AArch64
 } // namespace llvm

llvm/lib/TargetParser/AArch64TargetParser.cpp

@@ -141,17 +141,17 @@ std::optional<AArch64::CpuInfo> AArch64::parseCpu(StringRef Name) {
   return {};
 }
 
-void AArch64::PrintSupportedExtensions(StringMap<StringRef> DescMap) {
+void AArch64::PrintSupportedExtensions() {
   outs() << "All available -march extensions for AArch64\n\n"
          << "    " << left_justify("Name", 20)
-         << (DescMap.empty() ? "\n" : "Description\n");
+         << "Description\n";
   for (const auto &Ext : Extensions) {
     // Extensions without a feature cannot be used with -march.
     if (!Ext.UserVisibleName.empty() && !Ext.TargetFeature.empty()) {
-      std::string Description = DescMap[Ext.UserVisibleName].str();
       outs() << "    "
-             << format(Description.empty() ? "%s\n" : "%-20s%s\n",
-                       Ext.UserVisibleName.str().c_str(), Description.c_str());
+             << format(Ext.Description.empty() ? "%s\n" : "%-20s%s\n",
+                       Ext.UserVisibleName.str().c_str(),
+                       Ext.Description.str().c_str());
     }
   }
 }

llvm/unittests/TargetParser/TargetParserTest.cpp

@@ -2353,17 +2353,11 @@ TEST(TargetParserTest, AArch64ArchExtFeature) {
 TEST(TargetParserTest, AArch64PrintSupportedExtensions) {
   std::string expected =
       "All available -march extensions for AArch64\n\n"
-      "    Name                Description\n"
-      "    aes                 This is a long dummy description\n"
-      "    b16b16\n"
-      "    bf16\n";
-
-  StringMap<StringRef> DummyMap;
-  DummyMap["aes"] = "This is a long dummy description";
+      "    Name                Description\n";
 
   outs().flush();
   testing::internal::CaptureStdout();
-  AArch64::PrintSupportedExtensions(DummyMap);
+  AArch64::PrintSupportedExtensions();
   outs().flush();
   std::string captured = testing::internal::GetCapturedStdout();
 

llvm/utils/TableGen/ARMTargetDefEmitter.cpp

@@ -101,6 +101,7 @@ static void EmitARMTargetDef(RecordKeeper &RK, raw_ostream &OS) {
     else
       OS << ", \"" << Alias << "\"";
     OS << ", AArch64::" << AEK;
+    OS << ", \"" << Rec->getValueAsString("Desc") << "\"";
     if (AEK == "AEK_NONE") {
       // HACK: don't emit posfeat/negfeat strings for FMVOnlyExtensions.
       OS << ", {}, {}";
@@ -113,7 +114,7 @@ static void EmitARMTargetDef(RecordKeeper &RK, raw_ostream &OS) {
     OS << ", " << (uint64_t)Rec->getValueAsInt("FMVPriority");
     OS << "},\n";
   };
-  OS << "  {\"none\", {}, AArch64::AEK_NONE, {}, {}, FEAT_INIT, \"\", "
+  OS << "  {\"none\", {}, AArch64::AEK_NONE, {}, {}, {}, FEAT_INIT, \"\", "
         "ExtensionInfo::MaxFMVPriority},\n";
   OS << "};\n"
      << "#undef EMIT_EXTENSIONS\n"