Index: clang/lib/Basic/Targets/AArch64.h
===================================================================
--- clang/lib/Basic/Targets/AArch64.h
+++ clang/lib/Basic/Targets/AArch64.h
@@ -113,6 +113,8 @@
   getVScaleRange(const LangOptions &LangOpts) const override;
 
   bool hasFeature(StringRef Feature) const override;
+  void setFeatureEnabled(llvm::StringMap<bool> &Features, StringRef Name,
+                         bool Enabled) const override;
   bool handleTargetFeatures(std::vector<std::string> &Features,
                             DiagnosticsEngine &Diags) override;
 
Index: clang/lib/Basic/Targets/AArch64.cpp
===================================================================
--- clang/lib/Basic/Targets/AArch64.cpp
+++ clang/lib/Basic/Targets/AArch64.cpp
@@ -524,6 +524,25 @@
     .Default(false);
 }
 
+void AArch64TargetInfo::setFeatureEnabled(llvm::StringMap<bool> &Features,
+                                          StringRef Name, bool Enabled) const {
+  Features[Name] = Enabled;
+
+  llvm::AArch64::ArchKind AK = llvm::AArch64::getCPUArchKind(Name);
+  if ("9" == getArchVersionString(AK)) {
+    unsigned AK_v85 = static_cast<unsigned>(llvm::AArch64::ArchKind::ARMV8_5A);
+    AK_v85 += static_cast<unsigned>(AK) -
+              static_cast<unsigned>(llvm::AArch64::ArchKind::ARMV9A);
+    for (llvm::AArch64::ArchKind i =
+             static_cast<llvm::AArch64::ArchKind>(AK_v85);
+         i != llvm::AArch64::ArchKind::INVALID; --i)
+      Features[llvm::AArch64::getSubArch(i)] = Enabled;
+  }
+  for (llvm::AArch64::ArchKind i = --llvm::AArch64::getCPUArchKind(Name);
+       i != llvm::AArch64::ArchKind::INVALID; --i)
+    Features[llvm::AArch64::getSubArch(i)] = Enabled;
+}
+
 bool AArch64TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
                                              DiagnosticsEngine &Diags) {
   FPU = FPUMode;
@@ -612,31 +631,31 @@
       HasSM4 = true;
     if (Feature == "+strict-align")
       HasUnaligned = false;
-    if (Feature == "+v8a")
+    if (Feature == "+v8a" && ArchKind < llvm::AArch64::ArchKind::ARMV8A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8A;
-    if (Feature == "+v8.1a")
+    if (Feature == "+v8.1a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_1A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_1A;
-    if (Feature == "+v8.2a")
+    if (Feature == "+v8.2a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_2A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_2A;
-    if (Feature == "+v8.3a")
+    if (Feature == "+v8.3a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_3A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_3A;
-    if (Feature == "+v8.4a")
+    if (Feature == "+v8.4a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_4A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_4A;
-    if (Feature == "+v8.5a")
+    if (Feature == "+v8.5a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_5A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_5A;
-    if (Feature == "+v8.6a")
+    if (Feature == "+v8.6a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_6A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_6A;
-    if (Feature == "+v8.7a")
+    if (Feature == "+v8.7a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_7A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_7A;
-    if (Feature == "+v8.8a")
+    if (Feature == "+v8.8a" && ArchKind < llvm::AArch64::ArchKind::ARMV8_8A)
       ArchKind = llvm::AArch64::ArchKind::ARMV8_8A;
-    if (Feature == "+v9a")
+    if (Feature == "+v9a" && ArchKind < llvm::AArch64::ArchKind::ARMV9A)
       ArchKind = llvm::AArch64::ArchKind::ARMV9A;
-    if (Feature == "+v9.1a")
+    if (Feature == "+v9.1a" && ArchKind < llvm::AArch64::ArchKind::ARMV9_1A)
       ArchKind = llvm::AArch64::ArchKind::ARMV9_1A;
-    if (Feature == "+v9.2a")
+    if (Feature == "+v9.2a" && ArchKind < llvm::AArch64::ArchKind::ARMV9_2A)
       ArchKind = llvm::AArch64::ArchKind::ARMV9_2A;
-    if (Feature == "+v9.3a")
+    if (Feature == "+v9.3a" && ArchKind < llvm::AArch64::ArchKind::ARMV9_3A)
       ArchKind = llvm::AArch64::ArchKind::ARMV9_3A;
     if (Feature == "+v8r")
       ArchKind = llvm::AArch64::ArchKind::ARMV8R;
Index: clang/lib/Driver/ToolChains/Arch/AArch64.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Arch/AArch64.cpp
+++ clang/lib/Driver/ToolChains/Arch/AArch64.cpp
@@ -366,21 +366,36 @@
   int ArchFeatPos = -1;
 
   for (auto I = Features.begin(), E = Features.end(); I != E; I++) {
-    if (*I == "+v8a")   V8Version = 0;
-    else if (*I == "+v8.1a") V8Version = 1;
-    else if (*I == "+v8.2a") V8Version = 2;
-    else if (*I == "+v8.3a") V8Version = 3;
-    else if (*I == "+v8.4a") V8Version = 4;
-    else if (*I == "+v8.5a") V8Version = 5;
-    else if (*I == "+v8.6a") V8Version = 6;
-    else if (*I == "+v8.7a") V8Version = 7;
-    else if (*I == "+v8.8a") V8Version = 8;
-    else if (*I == "+v8.9a") V8Version = 9;
-    else if (*I == "+v9a")   V9Version = 0;
-    else if (*I == "+v9.1a") V9Version = 1;
-    else if (*I == "+v9.2a") V9Version = 2;
-    else if (*I == "+v9.3a") V9Version = 3;
-    else if (*I == "+v9.4a") V9Version = 4;
+    if (*I == "+v8a" && V8Version < 0)
+      V8Version = 0;
+    else if (*I == "+v8.1a" && V8Version < 1)
+      V8Version = 1;
+    else if (*I == "+v8.2a" && V8Version < 2)
+      V8Version = 2;
+    else if (*I == "+v8.3a" && V8Version < 3)
+      V8Version = 3;
+    else if (*I == "+v8.4a" && V8Version < 4)
+      V8Version = 4;
+    else if (*I == "+v8.5a" && V8Version < 5)
+      V8Version = 5;
+    else if (*I == "+v8.6a" && V8Version < 6)
+      V8Version = 6;
+    else if (*I == "+v8.7a" && V8Version < 7)
+      V8Version = 7;
+    else if (*I == "+v8.8a" && V8Version < 8)
+      V8Version = 8;
+    else if (*I == "+v8.9a" && V8Version < 9)
+      V8Version = 9;
+    else if (*I == "+v9a" && V9Version < 0)
+      V9Version = 0;
+    else if (*I == "+v9.1a" && V9Version < 1)
+      V9Version = 1;
+    else if (*I == "+v9.2a" && V9Version < 2)
+      V9Version = 2;
+    else if (*I == "+v9.3a" && V9Version < 3)
+      V9Version = 3;
+    else if (*I == "+v9.4a" && V9Version < 4)
+      V9Version = 4;
     else if (*I == "+sm4")  HasSM4 = true;
     else if (*I == "+sha3") HasSHA3 = true;
     else if (*I == "+sha2") HasSHA2 = true;
Index: llvm/include/llvm/Support/AArch64TargetParser.h
===================================================================
--- llvm/include/llvm/Support/AArch64TargetParser.h
+++ llvm/include/llvm/Support/AArch64TargetParser.h
@@ -113,6 +113,19 @@
 #include "AArch64TargetParser.def"
 };
 
+inline ArchKind operator--(ArchKind Kind) {
+  if (Kind == ArchKind::INVALID)
+    return ArchKind::INVALID;
+  if (Kind == ArchKind::ARMV8A)
+    return ArchKind::INVALID;
+  if (Kind == ArchKind::ARMV9A)
+    return ArchKind::INVALID;
+  if (Kind == ArchKind::ARMV8R)
+    return ArchKind::INVALID;
+  unsigned KindAsInteger = static_cast<unsigned>(Kind);
+  return static_cast<ArchKind>(--KindAsInteger);
+}
+
 // FIXME: These should be moved to TargetTuple once it exists
 bool getExtensionFeatures(uint64_t Extensions,
                           std::vector<StringRef> &Features);