[IR] Don't verify module flags on every access

llvm/include/llvm/IR/Module.h

@@ -158,11 +158,6 @@ class LLVM_EXTERNAL_VISIBILITY Module {
   /// converted result in MFB.
   static bool isValidModFlagBehavior(Metadata *MD, ModFlagBehavior &MFB);
 
-  /// Check if the given module flag metadata represents a valid module flag,
-  /// and store the flag behavior, the key string and the value metadata.
-  static bool isValidModuleFlag(const MDNode &ModFlag, ModFlagBehavior &MFB,
-                                MDString *&Key, Metadata *&Val);
-
   struct ModuleFlagEntry {
     ModFlagBehavior Behavior;
     MDString *Key;
@@ -502,7 +497,7 @@ class LLVM_EXTERNAL_VISIBILITY Module {
 
   /// Return the first NamedMDNode in the module with the specified name. This
   /// method returns null if a NamedMDNode with the specified name is not found.
-  NamedMDNode *getNamedMetadata(const Twine &Name) const;
+  NamedMDNode *getNamedMetadata(StringRef Name) const;
 
   /// Return the named MDNode in the module with the specified name. This method
   /// returns a new NamedMDNode if a NamedMDNode with the specified name is not

llvm/lib/IR/AutoUpgrade.cpp

@@ -4886,7 +4886,25 @@ bool llvm::UpgradeDebugInfo(Module &M) {
   if (DisableAutoUpgradeDebugInfo)
     return false;
 
-  unsigned Version = getDebugMetadataVersionFromModule(M);
+  // We need to get metadata before the module is verified (i.e., getModuleFlag
+  // makes assumptions that we haven't verified yet). Carefully extract the flag
+  // from the metadata.
+  unsigned Version = 0;
+  if (NamedMDNode *ModFlags = M.getModuleFlagsMetadata()) {
+    auto OpIt = find_if(ModFlags->operands(), [](const MDNode *Flag) {
+      if (Flag->getNumOperands() < 3)
+        return false;
+      if (MDString *K = dyn_cast_or_null<MDString>(Flag->getOperand(1)))
+        return K->getString() == "Debug Info Version";
+      return false;
+    });
+    if (OpIt != ModFlags->op_end()) {
+      const MDOperand &ValOp = (*OpIt)->getOperand(2);
+      if (auto *CI = mdconst::dyn_extract_or_null<ConstantInt>(ValOp))
+        Version = CI->getZExtValue();
+    }
+  }
+
   if (Version == DEBUG_METADATA_VERSION) {
     bool BrokenDebugInfo = false;
     if (verifyModule(M, &llvm::errs(), &BrokenDebugInfo))

llvm/lib/IR/Module.cpp

@@ -259,10 +259,8 @@ GlobalIFunc *Module::getNamedIFunc(StringRef Name) const {
 /// getNamedMetadata - Return the first NamedMDNode in the module with the
 /// specified name. This method returns null if a NamedMDNode with the
 /// specified name is not found.
-NamedMDNode *Module::getNamedMetadata(const Twine &Name) const {
-  SmallString<256> NameData;
-  StringRef NameRef = Name.toStringRef(NameData);
-  return NamedMDSymTab.lookup(NameRef);
+NamedMDNode *Module::getNamedMetadata(StringRef Name) const {
+  return NamedMDSymTab.lookup(Name);
 }
 
 /// getOrInsertNamedMetadata - Return the first named MDNode in the module
@@ -296,46 +294,31 @@ bool Module::isValidModFlagBehavior(Metadata *MD, ModFlagBehavior &MFB) {
   return false;
 }
 
-bool Module::isValidModuleFlag(const MDNode &ModFlag, ModFlagBehavior &MFB,
-                               MDString *&Key, Metadata *&Val) {
-  if (ModFlag.getNumOperands() < 3)
-    return false;
-  if (!isValidModFlagBehavior(ModFlag.getOperand(0), MFB))
-    return false;
-  MDString *K = dyn_cast_or_null<MDString>(ModFlag.getOperand(1));
-  if (!K)
-    return false;
-  Key = K;
-  Val = ModFlag.getOperand(2);
-  return true;
-}
-
 /// getModuleFlagsMetadata - Returns the module flags in the provided vector.
 void Module::
 getModuleFlagsMetadata(SmallVectorImpl<ModuleFlagEntry> &Flags) const {
   const NamedMDNode *ModFlags = getModuleFlagsMetadata();
   if (!ModFlags) return;
 
   for (const MDNode *Flag : ModFlags->operands()) {
-    ModFlagBehavior MFB;
-    MDString *Key = nullptr;
-    Metadata *Val = nullptr;
-    if (isValidModuleFlag(*Flag, MFB, Key, Val)) {
-      // Check the operands of the MDNode before accessing the operands.
-      // The verifier will actually catch these failures.
-      Flags.push_back(ModuleFlagEntry(MFB, Key, Val));
-    }
+    // The verifier will catch errors, so no need to check them here.
+    auto *MFBConstant = mdconst::extract<ConstantInt>(Flag->getOperand(0));
+    auto MFB = static_cast<ModFlagBehavior>(MFBConstant->getLimitedValue());
+    MDString *Key = cast<MDString>(Flag->getOperand(1));
+    Metadata *Val = Flag->getOperand(2);
+    Flags.push_back(ModuleFlagEntry(MFB, Key, Val));
   }
 }
 
 /// Return the corresponding value if Key appears in module flags, otherwise
 /// return null.
 Metadata *Module::getModuleFlag(StringRef Key) const {
-  SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
-  getModuleFlagsMetadata(ModuleFlags);
-  for (const ModuleFlagEntry &MFE : ModuleFlags) {
-    if (Key == MFE.Key->getString())
-      return MFE.Val;
+  const NamedMDNode *ModFlags = getModuleFlagsMetadata();
+  if (!ModFlags)
+    return nullptr;
+  for (const MDNode *Flag : ModFlags->operands()) {
+    if (Key == cast<MDString>(Flag->getOperand(1))->getString())
+      return Flag->getOperand(2);
   }
   return nullptr;
 }
@@ -388,10 +371,7 @@ void Module::setModuleFlag(ModFlagBehavior Behavior, StringRef Key,
   NamedMDNode *ModFlags = getOrInsertModuleFlagsMetadata();
   // Replace the flag if it already exists.
   for (MDNode *Flag : ModFlags->operands()) {
-    ModFlagBehavior MFB;
-    MDString *K = nullptr;
-    Metadata *V = nullptr;
-    if (isValidModuleFlag(*Flag, MFB, K, V) && K->getString() == Key) {
+    if (cast<MDString>(Flag->getOperand(1))->getString() == Key) {
       Flag->replaceOperandWith(2, Val);
       return;
     }