[llvm] Revert "Revert "[AArch64][AsmParser] Directives should clear transitively implied features (#106625)"" (PR #106814)

[Vitaly Buka via llvm-commits]

================
@@ -7075,30 +7075,22 @@ bool AArch64AsmParser::parseDirectiveCPU(SMLoc L) {
 
     bool EnableFeature = !Name.consume_front_insensitive("no");
 
-    bool FoundExtension = false;
-    for (const auto &Extension : ExtensionMap) {
-      if (Extension.Name != Name)
-        continue;
-
-      if (Extension.Features.none())
-        report_fatal_error("unsupported architectural extension: " + Name);
-
-      FeatureBitset Features = STI.getFeatureBits();
-      FeatureBitset ToggleFeatures =
-          EnableFeature
-              ? STI.SetFeatureBitsTransitively(~Features & Extension.Features)
-              : STI.ToggleFeature(Features & Extension.Features);
-      setAvailableFeatures(ComputeAvailableFeatures(ToggleFeatures));
-      FoundExtension = true;
+    auto It = llvm::find_if(ExtensionMap, [&Name](const auto &Extension) {
+      return Extension.Name == Name;
+    });
 
-      break;
-    }
+    if (It == std::end(ExtensionMap))
+      Error(CurLoc, "unsupported architectural extension: " + Name);
----------------
vitalybuka wrote:

We can't continue this loop if `It == std::end(ExtensionMap)`

https://github.com/llvm/llvm-project/pull/106814