diff --git a/include/swift/AST/IRGenOptions.h b/include/swift/AST/IRGenOptions.h
index 3c38b98f7ba44..32f32734767a6 100644
--- a/include/swift/AST/IRGenOptions.h
+++ b/include/swift/AST/IRGenOptions.h
@@ -372,6 +372,8 @@ class IRGenOptions {
   /// Emit names of struct stored properties and enum cases.
   unsigned EnableReflectionNames : 1;
 
+  unsigned DisableLLVMMergeFunctions : 1;
+
   /// Emit mangled names of anonymous context descriptors.
   unsigned EnableAnonymousContextMangledNames : 1;
 
@@ -574,7 +576,8 @@ class IRGenOptions {
         SwiftAsyncFramePointer(SwiftAsyncFramePointerKind::Auto),
         HasValueNamesSetting(false), ValueNames(false),
         ReflectionMetadata(ReflectionMetadataMode::Runtime),
-        EnableReflectionNames(true), EnableAnonymousContextMangledNames(false),
+        EnableReflectionNames(true), DisableLLVMMergeFunctions(false),
+        EnableAnonymousContextMangledNames(false),
         ForcePublicLinkage(false), LazyInitializeClassMetadata(false),
         LazyInitializeProtocolConformances(false),
         IndirectAsyncFunctionPointer(false),
diff --git a/include/swift/Option/FrontendOptions.td b/include/swift/Option/FrontendOptions.td
index cc597a0c83955..ab2a7832d8d54 100644
--- a/include/swift/Option/FrontendOptions.td
+++ b/include/swift/Option/FrontendOptions.td
@@ -615,6 +615,9 @@ def disable_reflection_names : Flag<["-"], "disable-reflection-names">,
   HelpText<"Disable emission of names of stored properties and enum cases in"
            "reflection metadata">;
 
+def disable_llvm_merge_functions_pass : Flag<["-"], "disable-llvm-merge-functions-pass">,
+  HelpText<"Disable the MergeFunctionPass LLVM IR pass">;
+
 def function_sections: Flag<["-"], "function-sections">,
   Flags<[FrontendOption, NoInteractiveOption]>,
   HelpText<"Emit functions to separate sections.">;
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 59c54398e17ba..04c30fd64c755 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -3406,6 +3406,10 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
     Opts.EnableReflectionNames = false;
   }
 
+  if (Args.hasArg(OPT_disable_llvm_merge_functions_pass)) {
+    Opts.DisableLLVMMergeFunctions = true;
+  }
+
   if (Args.hasArg(OPT_force_public_linkage)) {
     Opts.ForcePublicLinkage = true;
   }
diff --git a/lib/IRGen/IRGen.cpp b/lib/IRGen/IRGen.cpp
index 882a5d79ed7a4..388328b950338 100644
--- a/lib/IRGen/IRGen.cpp
+++ b/lib/IRGen/IRGen.cpp
@@ -275,7 +275,7 @@ void swift::performLLVMOptimizations(const IRGenOptions &Opts,
     PTO.LoopInterleaving = true;
     PTO.LoopVectorization = true;
     PTO.SLPVectorization = true;
-    PTO.MergeFunctions = true;
+    PTO.MergeFunctions = !Opts.DisableLLVMMergeFunctions;
     // Splitting trades code size to enhance memory locality, avoid in -Osize.
     DoHotColdSplit = Opts.EnableHotColdSplit && !Opts.optimizeForSize();
     level = llvm::OptimizationLevel::Os;
@@ -388,7 +388,8 @@ void swift::performLLVMOptimizations(const IRGenOptions &Opts,
                                         allowlistFiles, ignorelistFiles));
     });
   }
-  if (RunSwiftSpecificLLVMOptzns) {
+
+  if (RunSwiftSpecificLLVMOptzns && !Opts.DisableLLVMMergeFunctions) {
     PB.registerOptimizerLastEPCallback(
         [&](ModulePassManager &MPM, OptimizationLevel Level) {
           if (Level != OptimizationLevel::O0) {