1 files changed, 29 insertions, 3 deletions
diff --git a/llvm/utils/TableGen/ARMTargetDefEmitter.cpp b/llvm/utils/TableGen/ARMTargetDefEmitter.cpp
index a4b25025b3c6..71ca331461c0 100644
--- a/llvm/utils/TableGen/ARMTargetDefEmitter.cpp
+++ b/llvm/utils/TableGen/ARMTargetDefEmitter.cpp
@@ -19,10 +19,38 @@
 #include "llvm/TableGen/Record.h"
 #include "llvm/TableGen/TableGenBackend.h"
 #include <cstdint>
+#include <set>
 #include <string>
 
 using namespace llvm;
 
+/// Collect the full set of implied features for a SubtargetFeature.
+static void CollectImpliedFeatures(std::set<Record *> &SeenFeats, Record *Rec) {
+  assert(Rec->isSubClassOf("SubtargetFeature") &&
+         "Rec is not a SubtargetFeature");
+
+  SeenFeats.insert(Rec);
+  for (Record *Implied : Rec->getValueAsListOfDefs("Implies"))
+    CollectImpliedFeatures(SeenFeats, Implied);
+}
+
+static void CheckFeatureTree(Record *Root) {
+  std::set<Record *> SeenFeats;
+  CollectImpliedFeatures(SeenFeats, Root);
+
+  // Check that each of the mandatory (implied) features which is an
+  // ExtensionWithMArch is also enabled by default.
+  auto DefaultExtsVec = Root->getValueAsListOfDefs("DefaultExts");
+  std::set<Record *> DefaultExts{DefaultExtsVec.begin(), DefaultExtsVec.end()};
+  for (auto *Feat : SeenFeats) {
+    if (Feat->isSubClassOf("ExtensionWithMArch") && !DefaultExts.count(Feat))
+      PrintFatalError(Root->getLoc(),
+                      "ExtensionWithMArch " + Feat->getName() +
+                          " is implied (mandatory) as a SubtargetFeature, but "
+                          "is not present in DefaultExts");
+  }
+}
+
 static void EmitARMTargetDef(RecordKeeper &RK, raw_ostream &OS) {
   OS << "// Autogenerated by ARMTargetDefEmitter.cpp\n\n";
 
@@ -283,9 +311,7 @@ static void EmitARMTargetDef(RecordKeeper &RK, raw_ostream &OS) {
     auto Profile = Arch->getValueAsString("Profile");
     auto ArchInfo = ArchInfoName(Major, Minor, Profile);
 
-    // The apple-latest alias is backend only, do not expose it to -mcpu.
-    if (Name == "apple-latest")
-      continue;
+    CheckFeatureTree(Arch);
 
     OS << "  {\n"
        << "    \"" << Name << "\",\n"