[llvm] [llvm] Add format check for MCSubtargetFeatures (PR #180943)

[Georgiy Samoylov via llvm-commits]

https://github.com/sga-sc created https://github.com/llvm/llvm-project/pull/180943

This patch adds some format check for MCSubtargetInfo class to prevent creation of inconsistent objects

This patch is also needed to fix lldb argument parsing (https://github.com/llvm/llvm-project/pull/180901)

>From e02c44ea65a20caf5025edb5b42b9636bbc046ad Mon Sep 17 00:00:00 2001
From: Georgiy Samoylov <g.samoylov at syntacore.com>
Date: Wed, 11 Feb 2026 16:50:34 +0300
Subject: [PATCH] [llvm] Add format check for MCSubtargetFeatures

---
 llvm/include/llvm/MC/TargetRegistry.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/llvm/include/llvm/MC/TargetRegistry.h b/llvm/include/llvm/MC/TargetRegistry.h
index 4451dfa72a5f4..7cbbffcdac11c 100644
--- a/llvm/include/llvm/MC/TargetRegistry.h
+++ b/llvm/include/llvm/MC/TargetRegistry.h
@@ -351,6 +351,31 @@ class Target {
   /// InstrumentManager, if registered (default = nullptr).
   InstrumentManagerCtorTy InstrumentManagerCtorFn = nullptr;
 
+  bool isValidFeatureListFormat(StringRef FeaturesString) const {
+    if (FeaturesString.empty())
+      return true;
+
+    llvm::SmallVector<llvm::StringRef, 8> Features;
+    FeaturesString.split(Features, ',', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
+
+    if (Features.empty())
+      return false;
+
+    for (llvm::StringRef Feature : Features) {
+      if (Feature.empty())
+        return false;
+
+      char C = Feature.front();
+      if (C != '+' && C != '-')
+        return false;
+
+      if (Feature.size() == 1)
+        return false;
+    }
+
+    return true;
+  }
+
 public:
   Target() = default;
 
@@ -452,6 +477,8 @@ class Target {
                                          StringRef Features) const {
     if (!MCSubtargetInfoCtorFn)
       return nullptr;
+    if (!isValidFeatureListFormat(Features))
+      return nullptr;
     return MCSubtargetInfoCtorFn(TheTriple, CPU, Features);
   }