diff --git a/lldb/include/lldb/Symbol/SymbolFile.h b/lldb/include/lldb/Symbol/SymbolFile.h
index 9901c2c57557b..5501410aa49c1 100644
--- a/lldb/include/lldb/Symbol/SymbolFile.h
+++ b/lldb/include/lldb/Symbol/SymbolFile.h
@@ -131,6 +131,9 @@ class SymbolFile : public PluginInterface {
 
   Symtab *GetSymtab();
 
+  virtual llvm::VersionTuple GetProducerVersion(CompileUnit &comp_unit) {
+    return {};
+  }
   virtual lldb::LanguageType ParseLanguage(CompileUnit &comp_unit) = 0;
   /// Return the Xcode SDK comp_unit was compiled against.
   virtual XcodeSDK ParseXcodeSDK(CompileUnit &comp_unit) { return {}; }
diff --git a/lldb/include/lldb/Target/Process.h b/lldb/include/lldb/Target/Process.h
index fa346c5901e4d..01b54e3d17034 100644
--- a/lldb/include/lldb/Target/Process.h
+++ b/lldb/include/lldb/Target/Process.h
@@ -93,6 +93,9 @@ class ProcessProperties : public Properties {
   void SetDetachKeepsStopped(bool keep_stopped);
   bool GetWarningsOptimization() const;
   bool GetWarningsUnsupportedLanguage() const;
+#ifdef LLDB_ENABLE_SWIFT
+  bool GetWarningsToolchainMismatch() const;
+#endif
   bool GetStopOnExec() const;
   std::chrono::seconds GetUtilityExpressionTimeout() const;
   std::chrono::seconds GetInterruptTimeout() const;
@@ -371,7 +374,8 @@ class Process : public std::enable_shared_from_this<Process>,
   enum Warnings {
     eWarningsOptimization = 1,
     eWarningsUnsupportedLanguage = 2,
-    eWarningsSwiftImport
+    eWarningsSwiftImport,
+    eWarningsToolchainMismatch
   };
 
   typedef Range<lldb::addr_t, lldb::addr_t> LoadRange;
@@ -1329,6 +1333,7 @@ class Process : public std::enable_shared_from_this<Process>,
   ///     pre-computed.
   void PrintWarningOptimization(const SymbolContext &sc);
 
+#ifdef LLDB_ENABLE_SWIFT
   /// Prints a async warning message to the user one time per Process
   /// for a Module whose Swift AST sections couldn't be loaded because
   /// they aren't buildable on the current machine.
@@ -1338,6 +1343,11 @@ class Process : public std::enable_shared_from_this<Process>,
   void PrintWarningCantLoadSwiftModule(const Module &module,
                                        std::string details);
 
+  /// Print a user-visible warning about Swift CUs compiled with a
+  /// different Swift compiler than the one embedded in LLDB.
+  void PrintWarningToolchainMismatch(const SymbolContext &sc);
+#endif
+  
   /// Print a user-visible warning about a function written in a
   /// language that this version of LLDB doesn't support.
   ///
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index e5d9c6dcbe962..1f624d1d859a8 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -854,6 +854,16 @@ bool SymbolFileDWARF::FixupAddress(Address &addr) {
   // This is a normal DWARF file, no address fixups need to happen
   return true;
 }
+
+llvm::VersionTuple SymbolFileDWARF::GetProducerVersion(CompileUnit &comp_unit) {
+  std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
+  DWARFUnit *dwarf_cu = GetDWARFCompileUnit(&comp_unit);
+  if (dwarf_cu)
+    return dwarf_cu->GetProducerVersion();
+  else
+    return {};
+}
+
 lldb::LanguageType SymbolFileDWARF::ParseLanguage(CompileUnit &comp_unit) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
   DWARFUnit *dwarf_cu = GetDWARFCompileUnit(&comp_unit);
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
index 3f856f507c1b9..b8bbcbcf92dfb 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -108,6 +108,8 @@ class SymbolFileDWARF : public lldb_private::SymbolFile,
   void InitializeObject() override;
 
   // Compile Unit function calls
+  llvm::VersionTuple
+  GetProducerVersion(lldb_private::CompileUnit &comp_unit) override;
 
   lldb::LanguageType
   ParseLanguage(lldb_private::CompileUnit &comp_unit) override;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
index fec687dd6e737..fa598d2dd5a0b 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
@@ -621,6 +621,15 @@ size_t SymbolFileDWARFDebugMap::GetCompUnitInfosForModule(
   return cu_infos.size();
 }
 
+llvm::VersionTuple
+SymbolFileDWARFDebugMap::GetProducerVersion(CompileUnit &comp_unit) {
+  std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
+  SymbolFileDWARF *oso_dwarf = GetSymbolFile(comp_unit);
+  if (oso_dwarf)
+    return oso_dwarf->GetProducerVersion(comp_unit);
+  return {};
+}
+
 lldb::LanguageType
 SymbolFileDWARFDebugMap::ParseLanguage(CompileUnit &comp_unit) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h
index 766eab887774d..3870b06047480 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h
@@ -56,6 +56,8 @@ class SymbolFileDWARFDebugMap : public lldb_private::SymbolFile {
   void InitializeObject() override;
 
   // Compile Unit function calls
+  llvm::VersionTuple
+  GetProducerVersion(lldb_private::CompileUnit &comp_unit) override;
   lldb::LanguageType
   ParseLanguage(lldb_private::CompileUnit &comp_unit) override;
   lldb_private::XcodeSDK
diff --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
index 6f8c3e9d13943..fe02fe1728343 100644
--- a/lldb/source/Target/Process.cpp
+++ b/lldb/source/Target/Process.cpp
@@ -38,6 +38,7 @@
 #include "lldb/Interpreter/OptionValueProperties.h"
 #include "lldb/Symbol/Function.h"
 #include "lldb/Symbol/Symbol.h"
+#include "lldb/Symbol/SymbolFile.h"
 #include "lldb/Target/ABI.h"
 #include "lldb/Target/AssertFrameRecognizer.h"
 #include "lldb/Target/DynamicLoader.h"
@@ -71,6 +72,10 @@
 #include "lldb/Utility/State.h"
 #include "lldb/Utility/Timer.h"
 
+#ifdef LLDB_ENABLE_SWIFT
+#include "swift/Basic/Version.h"
+#endif
+
 using namespace lldb;
 using namespace lldb_private;
 using namespace std::chrono;
@@ -298,6 +303,14 @@ bool ProcessProperties::GetWarningsUnsupportedLanguage() const {
       nullptr, idx, g_process_properties[idx].default_uint_value != 0);
 }
 
+#ifdef LLDB_ENABLE_SWIFT
+bool ProcessProperties::GetWarningsToolchainMismatch() const {
+  const uint32_t idx = ePropertyWarningToolchainMismatch;
+  return m_collection_sp->GetPropertyAtIndexAsBoolean(
+      nullptr, idx, g_process_properties[idx].default_uint_value != 0);
+}
+#endif
+
 bool ProcessProperties::GetStopOnExec() const {
   const uint32_t idx = ePropertyStopOnExec;
   return m_collection_sp->GetPropertyAtIndexAsBoolean(
@@ -5907,6 +5920,7 @@ void Process::PrintWarningOptimization(const SymbolContext &sc) {
   }
 }
 
+#ifdef LLDB_ENABLE_SWIFT
 void Process::PrintWarningCantLoadSwiftModule(const Module &module,
                                               std::string details) {
   PrintWarning(Process::Warnings::eWarningsSwiftImport, (void *)&module,
@@ -5914,6 +5928,24 @@ void Process::PrintWarningCantLoadSwiftModule(const Module &module,
                module.GetFileSpec().GetCString(), details.c_str());
 }
 
+void Process::PrintWarningToolchainMismatch(const SymbolContext &sc) {
+  if (!GetWarningsToolchainMismatch())
+    return;
+  if (!sc.module_sp || !sc.comp_unit)
+    return;
+  if (sc.GetLanguage() != eLanguageTypeSwift)
+    return;
+  if (SymbolFile *sym_file = sc.module_sp->GetSymbolFile())
+    if (sym_file->GetProducerVersion(*sc.comp_unit) !=
+        swift::version::Version::getCurrentCompilerVersion())
+      PrintWarning(Process::Warnings::eWarningsToolchainMismatch,
+                   sc.module_sp.get(),
+                   "%s was compiled with a Swift compiler from a different "
+                   "toolchain. Swift expression evaluation may not work.\n",
+                   sc.module_sp->GetFileSpec().GetFilename().GetCString());
+}
+#endif
+
 void Process::PrintWarningUnsupportedLanguage(const SymbolContext &sc) {
   if (!GetWarningsUnsupportedLanguage())
     return;
diff --git a/lldb/source/Target/TargetProperties.td b/lldb/source/Target/TargetProperties.td
index 31a063a598cd3..7af1980dce83a 100644
--- a/lldb/source/Target/TargetProperties.td
+++ b/lldb/source/Target/TargetProperties.td
@@ -238,6 +238,9 @@ let Definition = "process" in {
   def WarningUnsupportedLanguage: Property<"unsupported-language-warnings", "Boolean">,
     DefaultTrue,
     Desc<"If true, warn when stopped in code that is written in a source language that LLDB does not support.">;
+  def WarningToolchainMismatch: Property<"toolchain-mismatch-warnings", "Boolean">,
+    DefaultTrue,
+    Desc<"If true, warn when stopped in code that was compiled by a Swift compiler different from the one embedded in LLDB.">;
   def StopOnExec: Property<"stop-on-exec", "Boolean">,
     Global,
     DefaultTrue,
diff --git a/lldb/source/Target/Thread.cpp b/lldb/source/Target/Thread.cpp
index 5c5001eed5273..5b6ebd6f0b499 100644
--- a/lldb/source/Target/Thread.cpp
+++ b/lldb/source/Target/Thread.cpp
@@ -321,11 +321,18 @@ void Thread::FrameSelectedCallback(StackFrame *frame) {
 
   if (frame->HasDebugInformation() &&
       (GetProcess()->GetWarningsOptimization() ||
-       GetProcess()->GetWarningsUnsupportedLanguage())) {
+       GetProcess()->GetWarningsUnsupportedLanguage()
+#ifdef LLDB_ENABLE_SWIFT
+       || GetProcess()->GetWarningsToolchainMismatch())
+#endif
+      ) {
     SymbolContext sc =
         frame->GetSymbolContext(eSymbolContextFunction | eSymbolContextModule);
     GetProcess()->PrintWarningOptimization(sc);
     GetProcess()->PrintWarningUnsupportedLanguage(sc);
+#ifdef LLDB_ENABLE_SWIFT
+    GetProcess()->PrintWarningToolchainMismatch(sc);
+#endif
   }
   SymbolContext msc = frame->GetSymbolContext(eSymbolContextModule);
   if (msc.module_sp)
diff --git a/lldb/test/Shell/Swift/ToolchainMismatch.test b/lldb/test/Shell/Swift/ToolchainMismatch.test
new file mode 100644
index 0000000000000..59d5b50d8f0a0
--- /dev/null
+++ b/lldb/test/Shell/Swift/ToolchainMismatch.test
@@ -0,0 +1,38 @@
+# REQUIRES: swift
+
+# Tests that a warning is printed when stopped in a Swift frame
+# compiled by a different Swift compiler than the one embedded in LLDB.
+
+# RUN: rm -rf %t && mkdir %t && cd %t
+# RUN: %target-swiftc -g \
+# RUN:          -module-cache-path %t/cache %S/Inputs/main.swift \
+# RUN:          -module-name main -o %t/a.ll -emit-ir
+# RUN: sed -i -e 's/producer: "[^"]*Swift [^"]*"/producer: "Future Swift (swiftlang-9999.8.7.6)"/g' %t/a.ll
+# RUN: %clang_host -c %t/a.ll -o %t/a.o
+# RUN: llvm-dwarfdump -r 0 %t/a.o | grep -q swiftlang-9999
+# RUN: %target-swiftc \
+# RUN:          -module-cache-path %t/cache \
+# RUN:          %t/a.o -o %t/a.out
+# RUN: %lldb %t/a.out -s %s 2>&1 | FileCheck %s
+
+# Sanity check: Swift
+# RUN: %target-swiftc -g \
+# RUN:          -module-cache-path %t/cache %S/Inputs/main.swift \
+# RUN:          -module-name main -o %t/good.out
+# RUN: %lldb %t/good.out -s %s 2>&1 | FileCheck %s --check-prefix=SANITY
+
+# Sanity check: Clang
+# RUN: %clang_host -g \
+# RUN:          %S/../Driver/Inputs/hello.cpp \
+# RUN:          -o %t/clang.out
+# RUN: %lldb %t/clang.out -s %s 2>&1 | FileCheck %s --check-prefix=SANITY
+
+b main
+run
+quit
+
+# The {{ }} avoids accidentally matching the input script!
+# CHECK: {{a\.out}} was compiled with a Swift compiler from a different toolchain.
+# CHECK: stop reason{{ = }}breakpoint
+# SANITY-NOT: {{a\.out}} was compiled with a Swift compiler from a different toolchain.
+# SANITY: stop reason{{ = }}breakpoint