================
@@ -1465,6 +1465,101 @@ bool 
DisassemblerLLVMC::MCDisasmInstance::IsAuthenticated(
   return InstrDesc.isAuthenticated() || IsBrkC47x;
 }
 
+static void
+UpdateSubtargetFeatures(const llvm::SubtargetFeatures &subtarget_features,
+                        std::string &user_feature_overrides) {
+
+  // Extract the default features string from the SubtargetFeatures object.
+  // We must store this in a std::string variable to ensure the memory exists
+  // for the StringRef to point to during the execution of this function.
+  std::string default_features_storage = subtarget_features.getString();
+  llvm::StringRef default_features = default_features_storage;
+
+  // If the user has not provided any overrides AND defaults exist,
+  // then simply use the default feature string.
+  if (user_feature_overrides.empty() && !default_features.empty()) {
+    user_feature_overrides = default_features.str();
+    return;
+  }
+
+  std::string warning_reason;
+  std::vector<std::string> valid_user_flags;
+  std::set<std::string> user_disabled_features;
+
+  for (llvm::StringRef flag : llvm::split(user_feature_overrides, ",")) {
+    bool is_valid = true;
+    flag = flag.trim();
+
+    // If we don't do this, flag.front() below will crash.
+    if (flag.empty())
+      continue;
+
+    // 1. Must be at least 2 chars (e.g., "+a").
+    // 2. Must start with '+' or '-' (Users can enable OR disable).
+    // 3. Name cannot start with a digit (e.g. "+123" is invalid)
+    // 4. All characters after the sign must be alphabets.
+    if (flag.front() != '+' && flag.front() != '-') {
+      is_valid = false;
+      warning_reason = "must start with '+' or '-'";
+    } else if (flag.size() < 2) {
+      is_valid = false;
+      warning_reason = "must have a name";
+    } else if (std::isdigit(static_cast<unsigned char>(flag[1]))) {
+      is_valid = false;
+      warning_reason = "name cannot start with a digit";
+    } else if (!std::all_of(flag.begin() + 1, flag.end(), [](unsigned char c) {
+                 return std::isalnum(c) || c == '_';
+               })) {
+      is_valid = false;
+      warning_reason = "contains invalid characters";
+    }
+    if (!is_valid) {
+      llvm::errs() << "Warning: Malformed feature '" << flag
+                   << "': " << warning_reason << ". Ignoring.\n";
----------------
santhoshe447 wrote:

I think adding a warning message would be helpful, so is it appropriate to use 
`Debugger::ReportWarning` in this case ?

https://github.com/llvm/llvm-project/pull/147990
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