Index: llvm/lib/Target/SystemZ/SystemZSubtarget.h
===================================================================
--- llvm/lib/Target/SystemZ/SystemZSubtarget.h
+++ llvm/lib/Target/SystemZ/SystemZSubtarget.h
@@ -84,12 +84,14 @@
   std::unique_ptr<const SystemZFrameLowering> FrameLowering;
 
   SystemZSubtarget &initializeSubtargetDependencies(StringRef CPU,
+                                                    StringRef TuneCPU,
                                                     StringRef FS);
   SystemZCallingConventionRegisters *initializeSpecialRegisters();
 
 public:
   SystemZSubtarget(const Triple &TT, const std::string &CPU,
-                   const std::string &FS, const TargetMachine &TM);
+                   const std::string &TuneCPU, const std::string &FS,
+                   const TargetMachine &TM);
 
   SystemZCallingConventionRegisters *getSpecialRegisters() const {
     assert(SpecialRegisters && "Unsupported SystemZ calling convention");
Index: llvm/lib/Target/SystemZ/SystemZSubtarget.cpp
===================================================================
--- llvm/lib/Target/SystemZ/SystemZSubtarget.cpp
+++ llvm/lib/Target/SystemZ/SystemZSubtarget.cpp
@@ -27,13 +27,14 @@
 // Pin the vtable to this file.
 void SystemZSubtarget::anchor() {}
 
-SystemZSubtarget &
-SystemZSubtarget::initializeSubtargetDependencies(StringRef CPU, StringRef FS) {
-  StringRef CPUName = CPU;
-  if (CPUName.empty())
-    CPUName = "generic";
+SystemZSubtarget &SystemZSubtarget::initializeSubtargetDependencies(
+    StringRef CPU, StringRef TuneCPU, StringRef FS) {
+  if (CPU.empty())
+    CPU = "generic";
+  if (TuneCPU.empty())
+    TuneCPU = CPU;
   // Parse features string.
-  ParseSubtargetFeatures(CPUName, /*TuneCPU*/ CPUName, FS);
+  ParseSubtargetFeatures(CPU, TuneCPU, FS);
 
   // -msoft-float implies -mno-vx.
   if (HasSoftFloat)
@@ -64,9 +65,10 @@
 }
 
 SystemZSubtarget::SystemZSubtarget(const Triple &TT, const std::string &CPU,
+                                   const std::string &TuneCPU,
                                    const std::string &FS,
                                    const TargetMachine &TM)
-    : SystemZGenSubtargetInfo(TT, CPU, /*TuneCPU*/ CPU, FS),
+    : SystemZGenSubtargetInfo(TT, CPU, TuneCPU, FS),
       HasDistinctOps(false), HasLoadStoreOnCond(false), HasHighWord(false),
       HasFPExtension(false), HasPopulationCount(false),
       HasMessageSecurityAssist3(false), HasMessageSecurityAssist4(false),
@@ -88,8 +90,8 @@
       HasResetDATProtection(false), HasProcessorActivityInstrumentation(false),
       HasSoftFloat(false), TargetTriple(TT),
       SpecialRegisters(initializeSpecialRegisters()),
-      InstrInfo(initializeSubtargetDependencies(CPU, FS)), TLInfo(TM, *this),
-      FrameLowering(SystemZFrameLowering::create(*this)) {}
+      InstrInfo(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
+      TLInfo(TM, *this), FrameLowering(SystemZFrameLowering::create(*this)) {}
 
 bool SystemZSubtarget::enableSubRegLiveness() const {
   return UseSubRegLiveness;
Index: llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
===================================================================
--- llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
+++ llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
@@ -187,10 +187,13 @@
 const SystemZSubtarget *
 SystemZTargetMachine::getSubtargetImpl(const Function &F) const {
   Attribute CPUAttr = F.getFnAttribute("target-cpu");
+  Attribute TuneAttr = F.getFnAttribute("tune-cpu");
   Attribute FSAttr = F.getFnAttribute("target-features");
 
   std::string CPU =
       CPUAttr.isValid() ? CPUAttr.getValueAsString().str() : TargetCPU;
+  std::string TuneCPU =
+      TuneAttr.isValid() ? TuneAttr.getValueAsString().str() : CPU;
   std::string FS =
       FSAttr.isValid() ? FSAttr.getValueAsString().str() : TargetFS;
 
@@ -202,13 +205,14 @@
   if (softFloat)
     FS += FS.empty() ? "+soft-float" : ",+soft-float";
 
-  auto &I = SubtargetMap[CPU + FS];
+  auto &I = SubtargetMap[CPU + TuneCPU + FS];
   if (!I) {
     // This needs to be done before we create a new subtarget since any
     // creation will depend on the TM and the code generation flags on the
     // function that reside in TargetOptions.
     resetTargetOptions(F);
-    I = std::make_unique<SystemZSubtarget>(TargetTriple, CPU, FS, *this);
+    I = std::make_unique<SystemZSubtarget>(TargetTriple, CPU, TuneCPU, FS,
+                                           *this);
   }
 
   return I.get();