diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -64,7 +64,7 @@
 CODEGENOPT(DisableO0ImplyOptNone , 1, 0) ///< Don't annonate function with optnone at O0
 CODEGENOPT(ExperimentalStrictFloatingPoint, 1, 0) ///< Enables the new, experimental
                                                   ///< strict floating point.
-CODEGENOPT(EnableNoundefAttrs, 1, 0) ///< Enable emitting `noundef` attributes on IR call arguments and return values
+CODEGENOPT(DisableNoundefAttrs, 1, 0) ///< Disable emitting `noundef` attributes on IR call arguments and return values
 CODEGENOPT(LegacyPassManager, 1, 0) ///< Use the legacy pass manager.
 CODEGENOPT(DebugPassManager, 1, 0) ///< Prints debug information for the new
                                    ///< pass manager.
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5314,9 +5314,9 @@
 def clear_ast_before_backend : Flag<["-"], "clear-ast-before-backend">,
   HelpText<"Clear the Clang AST before running backend code generation">,
   MarshallingInfoFlag<CodeGenOpts<"ClearASTBeforeBackend">>;
-def enable_noundef_analysis : Flag<["-"], "enable-noundef-analysis">, Group<f_Group>,
-  HelpText<"Enable analyzing function argument and return types for mandatory definedness">,
-  MarshallingInfoFlag<CodeGenOpts<"EnableNoundefAttrs">>;
+def disable_noundef_analysis : Flag<["-"], "disable-noundef-analysis">, Group<f_Group>,
+  HelpText<"Disable analyzing function argument and return types for mandatory definedness">,
+  MarshallingInfoFlag<CodeGenOpts<"DisableNoundefAttrs">>;
 def discard_value_names : Flag<["-"], "discard-value-names">,
   HelpText<"Discard value names in LLVM IR">,
   MarshallingInfoFlag<CodeGenOpts<"DiscardValueNames">>;
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2255,7 +2255,7 @@
                      getLangOpts().Sanitize.has(SanitizerKind::Return);
 
   // Determine if the return type could be partially undef
-  if (CodeGenOpts.EnableNoundefAttrs && HasStrictReturn) {
+  if (!CodeGenOpts.DisableNoundefAttrs && HasStrictReturn) {
     if (!RetTy->isVoidType() && RetAI.getKind() != ABIArgInfo::Indirect &&
         DetermineNoUndef(RetTy, getTypes(), DL, RetAI))
       RetAttrs.addAttribute(llvm::Attribute::NoUndef);
@@ -2390,7 +2390,7 @@
 
     // Decide whether the argument we're handling could be partially undef
     bool ArgNoUndef = DetermineNoUndef(ParamType, getTypes(), DL, AI);
-    if (CodeGenOpts.EnableNoundefAttrs && ArgNoUndef)
+    if (!CodeGenOpts.DisableNoundefAttrs && ArgNoUndef)
       Attrs.addAttribute(llvm::Attribute::NoUndef);
 
     // 'restrict' -> 'noalias' is done in EmitFunctionProlog when we