[lldb] Remove nested switches from ARMGetSupportedArchitectureAtIndex (NFC)

[JDevlieghere]

Summary

Remove the nested switches from the ARMGetSupportedArchitectureAtIndex implementation. I considered a few alternatives, like changing the API (too intrusive) and trying to be clever by manipulating indexes (too hard to maintain). I'm not happy about the remaining amount of duplication, but it seemed like the best tradeoff.

[JDevlieghere]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

573

I could put this into a def file if desirable, but right now I'm still undecided whether that's overkill.

[jasonmolenda]

Nice cleanup of this table that's been growing over the years.

[labath]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

558

Is this any different from an ArrayRef<const char *>?

564–565

This wouldn't be needed with arrayref, as it has an appropriate C array constructor

[JDevlieghere]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

558

Totally forgot about that. Thanks for the suggestion.

[fixathon]

Added some follow up comments

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

561

This will default to the ArchSpec::eCore_arm_arm64 case if no matching ArchSpec is specified. Double-checking if this by intent.

640

Could we delete this unreachable return statement? It's tripping up static code checkers since all possible branches already have a return.

[JDevlieghere]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

561

I'm sure it was intentional when I wrote it, but I can't figure out for which core this would actually make sense. If the test suite passes with returning an empty array here, that works for me.

640

Yes, let's make it an llvm_unreachable (otherwise gcc will complain).

[fixathon]

Added comments

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

640

If we return {} in the default case, and delete this, gcc should not complain since all possible code paths will have a return, is that right?
Alternatively, we could break in the default case and leave this return alone. I prefer the first approach for consistency.

[JDevlieghere]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

640

Yes, you're right, it's only a problem for gcc when you explicitly handle every case (see all the instances of llvm_unreachable("Fully covered switch!"); in lldb/llvm).

[fixathon]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

640

I'll just add a break to the default case to avoid llvm_unreachable(). What's the best way to introduce this change? Can I link it to this diff somehow or a stand-alone new diff?

[fixathon]

Added a comment about a failing test.

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

561

When this is fixed, one test is failing, and I think that might be a problem with the test itself: test_ios in test/API/functionalities/gdb_remote_client/TestPlatformMacOSX.py running on MacOS.

File "lvm-project/lldb/test/API/functionalities/gdb_remote_client/TestPlatformMacOSX.py", line 48, in test_ios
  self.platform_test(host="ios",
File "llvm-project/lldb/test/API/functionalities/gdb_remote_client/TestPlatformMacOSX.py", line 44, in platform_test
  self.assertEqual(platform.GetName(), expected_platform)

AssertionError: 'host' != 'remote-ios'

• host+ remote-ios

[clayborg]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

561

Looks like it might be a problem with the test indeed. The "def qHostInfo(self):" from line 21 is returning a CPU type for the host of "cputype:16777223". This is 0x01000007 which is "x86_64" as the 'qHostInfo' packet uses a decimal encoding. Later when asked about the process with "def qProcessInfo(self):" it returns "cputype:100000c" which is hex encoded with no "0x" prefix and it means "arm64".

Not sure if this test is trying to test a remote ios debugging scenario from a desktop machine debugging to a ios device, but if this is the case, both qHostInfo and qProcessInfo should be agreeing on the architecture and using the same thing, which would be "arm64"? These are packets that are usually going to the "debugserver", which is run on a phone. So my guess would be to try and set qHostInfo to have "cputype:16777228" (which is decimal for 0x0100000c) and see if that works.

Jonas, does this make sense?

[JDevlieghere]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

561

No, this is intentional and pretty much the point of this test. There's more details in https://reviews.llvm.org/D121444 but the TL;DR is that this is testing running iPhone and iPad Apps on Apple Silicon Macs. That also explains the default then, which I was pretty sure I added for a reason :-)

[clayborg]

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

561

Gotcha, looks like Slava need to debug this and see why we are getting a invalid core type passed to the GetCompatibleArchs() function in the first place.

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.h

public:
   /// Return the toolchain directory the current LLDB instance is located in.
   static lldb_private::FileSpec GetCurrentToolchainDirectory();
 
   /// Return the command line tools directory the current LLDB instance is
   /// located in.
   static lldb_private::FileSpec GetCurrentCommandLineToolsDirectory();
 
 protected:
+  static const char *GetCompatibleArch(lldb_private::ArchSpec::Core core,
+                                       size_t idx);
+
   struct CrashInfoAnnotations {
     uint64_t version;          // unsigned long
     uint64_t message;          // char *
     uint64_t signature_string; // char *
     uint64_t backtrace;        // char *
     uint64_t message2;         // char *
     uint64_t thread;           // uint64_t
     uint64_t dialog_mode;      // unsigned int

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

if (idx == 0) {
         arch = HostInfo::GetArchitecture(HostInfo::eArchKind32);
         return arch.IsValid();
       }
     }
   }
   return false;
 }
 
-/// The architecture selection rules for arm processors These cpu subtypes have
-/// distinct names (e.g. armv7f) but armv7 binaries run fine on an armv7f
-/// processor.
-bool PlatformDarwin::ARMGetSupportedArchitectureAtIndex(uint32_t idx,
-                                                        ArchSpec &arch) {
-  ArchSpec system_arch(GetSystemArchitecture());
-
-#if defined(TARGET_OS_TV) && TARGET_OS_TV == 1
-#define OSNAME "tvos"
-#elif defined(TARGET_OS_WATCH) && TARGET_OS_WATCH == 1
-#define OSNAME "watchos"
-#elif defined(TARGET_OS_BRIDGE) && TARGET_OS_BRIDGE == 1
-#define OSNAME "bridgeos"
-#elif defined(TARGET_OS_OSX) && TARGET_OS_OSX == 1
-#define OSNAME "macosx"
-#else
-#define OSNAME "ios"
-#endif
+struct CompatibleArchs {
+  const char **archs = nullptr;
+  size_t size = 0;
+  operator bool() const { return archs != nullptr; }
+};
 
-#if TARGET_OS_OSX
-  if (IsHost()) {
-    if (idx == 0) {
-      arch.SetTriple("arm64e-apple-macosx");
-      return true;
-    } else if (idx == 1) {
-      arch.SetTriple("arm64-apple-macosx");
-      return true;
-    }
-    return false;
-  }
-#endif
+#define COMPATIBLE_ARCHS(archs)                                                \
+  { archs, (sizeof(archs) / sizeof(const char *)) }
 
-  const ArchSpec::Core system_core = system_arch.GetCore();
-  switch (system_core) {
+static CompatibleArchs GetCompatibleArchs(ArchSpec::Core core) {
+  switch (core) {
   default:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("arm64-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv7f-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv7k-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv7s-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("armv7m-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("armv7em-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 12:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 13:
-      arch.SetTriple("thumbv7f-apple-" OSNAME);
-      return true;
-    case 14:
-      arch.SetTriple("thumbv7k-apple-" OSNAME);
-      return true;
-    case 15:
-      arch.SetTriple("thumbv7s-apple-" OSNAME);
-      return true;
-    case 16:
-      arch.SetTriple("thumbv7m-apple-" OSNAME);
-      return true;
-    case 17:
-      arch.SetTriple("thumbv7em-apple-" OSNAME);
-      return true;
-    case 18:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 19:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 20:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 21:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 22:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
-
-  case ArchSpec::eCore_arm_arm64:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("arm64-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv7s-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv7f-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv7m-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv7em-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 12:
-      arch.SetTriple("thumbv7f-apple-" OSNAME);
-      return true;
-    case 13:
-      arch.SetTriple("thumbv7k-apple-" OSNAME);
-      return true;
-    case 14:
-      arch.SetTriple("thumbv7s-apple-" OSNAME);
-      return true;
-    case 15:
-      arch.SetTriple("thumbv7m-apple-" OSNAME);
-      return true;
-    case 16:
-      arch.SetTriple("thumbv7em-apple-" OSNAME);
-      return true;
-    case 17:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 18:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 19:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 20:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 21:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
-
-  case ArchSpec::eCore_arm_armv7f:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv7f-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("thumbv7f-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 12:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 13:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
-
+    LLVM_FALLTHROUGH;
+  case ArchSpec::eCore_arm_arm64: {
+    static const char *g_arm64_compatible_archs[] = {
+        "arm64",    "armv7",    "armv7f",   "armv7k",   "armv7s",   "armv7m",
+        "armv7em",  "armv6m",   "armv6",    "armv5",    "armv4",    "arm",
+        "thumbv7",  "thumbv7f", "thumbv7k", "thumbv7s", "thumbv7m", "thumbv7em",
+        "thumbv6m", "thumbv6",  "thumbv5",  "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_arm64_compatible_archs);
+  case ArchSpec::eCore_arm_armv7: {
+    static const char *g_armv7_compatible_archs[] = {
+        "armv7",   "armv6m",   "armv6",   "armv5",   "armv4",    "arm",
+        "thumbv7", "thumbv6m", "thumbv6", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv7_compatible_archs);
+  case ArchSpec::eCore_arm_armv7f: {
+    static const char *g_armv7f_compatible_archs[] = {
+        "armv7f",  "armv7",   "armv6m",   "armv6",   "armv5",
+        "armv4",   "arm",     "thumbv7f", "thumbv7", "thumbv6m",
+        "thumbv6", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv7f_compatible_archs);
   case ArchSpec::eCore_arm_armv7k:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv7k-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("thumbv7k-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 12:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 13:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
-
+    static const char *g_armv7k_compatible_archs[] = {
+        "armv7k",  "armv7",   "armv6m",   "armv6",   "armv5",
+        "armv4",   "arm",     "thumbv7k", "thumbv7", "thumbv6m",
+        "thumbv6", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv7k_compatible_archs);
   case ArchSpec::eCore_arm_armv7s:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv7s-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("thumbv7s-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 12:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 13:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
-
+    static const char *g_armv7s_compatible_archs[] = {
+        "armv7s",  "armv7",   "armv6m",   "armv6",   "armv5",
+        "armv4",   "arm",     "thumbv7s", "thumbv7", "thumbv6m",
+        "thumbv6", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv7s_compatible_archs);
   case ArchSpec::eCore_arm_armv7m:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv7m-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("thumbv7m-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 12:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 13:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
-
+    static const char *g_armv7m_compatible_archs[] = {
+        "armv7m",  "armv7",   "armv6m",   "armv6",   "armv5",
+        "armv4",   "arm",     "thumbv7m", "thumbv7", "thumbv6m",
+        "thumbv6", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv7m_compatible_archs);
   case ArchSpec::eCore_arm_armv7em:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv7em-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("thumbv7em-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 12:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 13:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
-
-  case ArchSpec::eCore_arm_armv7:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv7-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("thumbv7-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 10:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 11:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
+    static const char *g_armv7em_compatible_archs[] = {
+        "armv7em", "armv7",   "armv6m",    "armv6",   "armv5",
+        "armv4",   "arm",     "thumbv7em", "thumbv7", "thumbv6m",
+        "thumbv6", "thumbv5", "thumbv4t",  "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv7em_compatible_archs);
+  case ArchSpec::eCore_arm_armv6m:
+    static const char *g_armv6m_compatible_archs[] = {
+        "armv6m",   "armv6",   "armv5",   "armv4",    "arm",
+        "thumbv6m", "thumbv6", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv6m_compatible_archs);
+  case ArchSpec::eCore_arm_armv6:
+    static const char *g_armv6_compatible_archs[] = {
+        "armv6",   "armv5",   "armv4",    "arm",
+        "thumbv6", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv6_compatible_archs);
+  case ArchSpec::eCore_arm_armv5:
+    static const char *g_armv5_compatible_archs[] = {
+        "armv5", "armv4", "arm", "thumbv5", "thumbv4t", "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv5_compatible_archs);
+  case ArchSpec::eCore_arm_armv4:
+    static const char *g_armv4_compatible_archs[] = {
+        "armv4",
+        "arm",
+        "thumbv4t",
+        "thumb",
+    };
+    return COMPATIBLE_ARCHS(g_armv4_compatible_archs);
+  return {};
 
-  case ArchSpec::eCore_arm_armv6m:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv6m-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("thumbv6m-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 7:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 8:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 9:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
+const char *PlatformDarwin::GetCompatibleArch(ArchSpec::Core core, size_t idx) {
+  CompatibleArchs compatible_archs = GetCompatibleArchs(core);
+  if (!compatible_archs)
+    return nullptr;
+  if (idx < compatible_archs.size)
+    return compatible_archs.archs[idx];
+  return nullptr;
 
-  case ArchSpec::eCore_arm_armv6:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv6-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("thumbv6-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 6:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
+/// The architecture selection rules for arm processors These cpu subtypes have
+/// distinct names (e.g. armv7f) but armv7 binaries run fine on an armv7f
+/// processor.
+bool PlatformDarwin::ARMGetSupportedArchitectureAtIndex(uint32_t idx,
+                                                        ArchSpec &arch) {
+#if TARGET_OS_OSX
+  if (IsHost()) {
+    if (idx == 0) {
+      arch.SetTriple("arm64e-apple-macosx");
       return true;
-    case 7:
-      arch.SetTriple("thumb-apple-" OSNAME);
+    } else if (idx == 1) {
+      arch.SetTriple("arm64-apple-macosx");
       return true;
-    default:
-      break;
     }
-    break;
-
-  case ArchSpec::eCore_arm_armv5:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv5-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("thumbv5-apple-" OSNAME);
-      return true;
-    case 4:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 5:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
+    arch.Clear();
+    return false;
+#endif
 
-  case ArchSpec::eCore_arm_armv4:
-    switch (idx) {
-    case 0:
-      arch.SetTriple("armv4-apple-" OSNAME);
-      return true;
-    case 1:
-      arch.SetTriple("arm-apple-" OSNAME);
-      return true;
-    case 2:
-      arch.SetTriple("thumbv4t-apple-" OSNAME);
-      return true;
-    case 3:
-      arch.SetTriple("thumb-apple-" OSNAME);
-      return true;
-    default:
-      break;
-    }
-    break;
+#if defined(TARGET_OS_TV) && TARGET_OS_TV == 1
+#define OSNAME "tvos"
+#elif defined(TARGET_OS_WATCH) && TARGET_OS_WATCH == 1
+#define OSNAME "watchos"
+#elif defined(TARGET_OS_BRIDGE) && TARGET_OS_BRIDGE == 1
+#define OSNAME "bridgeos"
+#elif defined(TARGET_OS_OSX) && TARGET_OS_OSX == 1
+#define OSNAME "macosx"
+#else
+#define OSNAME "ios"
+#endif
+
+  const ArchSpec system_arch = GetSystemArchitecture();
+  const ArchSpec::Core system_core = system_arch.GetCore();
+  if (const char *compatible_arch = GetCompatibleArch(system_core, idx)) {
+    std::string triple =
+        llvm::formatv("{0}-apple-" OSNAME, compatible_arch).str();
+    arch.SetTriple(triple);
   }
+
   arch.Clear();
   return false;
 }
 
 static FileSpec GetXcodeSelectPath() {
   static FileSpec g_xcode_select_filespec;
 
   if (!g_xcode_select_filespec) {

lldb/unittests/Platform/PlatformDarwinTest.cpp

 #include <tuple>
 
 using namespace lldb;
 using namespace lldb_private;
 
 struct PlatformDarwinTester : public PlatformDarwin {
 public:
   using PlatformDarwin::FindComponentInPath;
+  using PlatformDarwin::GetCompatibleArch;
 };
 
 TEST(PlatformDarwinTest, TestParseVersionBuildDir) {
   llvm::VersionTuple V;
   llvm::StringRef D;
 
   std::tie(V, D) = PlatformDarwin::ParseVersionBuildDir("1.2.3 (test1)");
   EXPECT_EQ(llvm::VersionTuple(1, 2, 3), V);
EXPECT_EQ("/path/to/foobar", PlatformDarwinTester::FindComponentInPath(
                                    "/path/to/foobar", "foo"));
 
   EXPECT_EQ("/path/to/foobar", PlatformDarwinTester::FindComponentInPath(
                                    "/path/to/foobar", "bar"));
 
   EXPECT_EQ("",
             PlatformDarwinTester::FindComponentInPath("/path/to/foo", "bar"));
 }
+
+TEST(PlatformDarwinTest, GetCompatibleArchARM64) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_arm64;
+  EXPECT_STREQ("arm64", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv7", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("armv4", PlatformDarwinTester::GetCompatibleArch(core, 10));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 11));
+  EXPECT_STREQ("thumbv7", PlatformDarwinTester::GetCompatibleArch(core, 12));
+  EXPECT_STREQ("thumbv4t", PlatformDarwinTester::GetCompatibleArch(core, 21));
+  EXPECT_STREQ("thumb", PlatformDarwinTester::GetCompatibleArch(core, 22));
+  EXPECT_EQ(nullptr, PlatformDarwinTester::GetCompatibleArch(core, 23));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv7f) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv7f;
+  EXPECT_STREQ("armv7f", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv7", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 6));
+  EXPECT_STREQ("thumbv7f", PlatformDarwinTester::GetCompatibleArch(core, 7));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv7k) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv7k;
+  EXPECT_STREQ("armv7k", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv7", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 6));
+  EXPECT_STREQ("thumbv7k", PlatformDarwinTester::GetCompatibleArch(core, 7));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv7s) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv7s;
+  EXPECT_STREQ("armv7s", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv7", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 6));
+  EXPECT_STREQ("thumbv7s", PlatformDarwinTester::GetCompatibleArch(core, 7));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv7m) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv7m;
+  EXPECT_STREQ("armv7m", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv7", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 6));
+  EXPECT_STREQ("thumbv7m", PlatformDarwinTester::GetCompatibleArch(core, 7));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv7em) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv7em;
+  EXPECT_STREQ("armv7em", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv7", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 6));
+  EXPECT_STREQ("thumbv7em", PlatformDarwinTester::GetCompatibleArch(core, 7));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv7) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv7;
+  EXPECT_STREQ("armv7", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv6m", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 5));
+  EXPECT_STREQ("thumbv7", PlatformDarwinTester::GetCompatibleArch(core, 6));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv6m) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv6m;
+  EXPECT_STREQ("armv6m", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv6", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 4));
+  EXPECT_STREQ("thumbv6m", PlatformDarwinTester::GetCompatibleArch(core, 5));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv6) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv6;
+  EXPECT_STREQ("armv6", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv5", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 3));
+  EXPECT_STREQ("thumbv6", PlatformDarwinTester::GetCompatibleArch(core, 4));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv5) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv5;
+  EXPECT_STREQ("armv5", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("armv4", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 2));
+  EXPECT_STREQ("thumbv5", PlatformDarwinTester::GetCompatibleArch(core, 3));
+}
+
+TEST(PlatformDarwinTest, GetCompatibleArchARMv4) {
+  const ArchSpec::Core core = ArchSpec::eCore_arm_armv4;
+  EXPECT_STREQ("armv4", PlatformDarwinTester::GetCompatibleArch(core, 0));
+  EXPECT_STREQ("arm", PlatformDarwinTester::GetCompatibleArch(core, 1));
+  EXPECT_STREQ("thumbv4t", PlatformDarwinTester::GetCompatibleArch(core, 2));
+  EXPECT_STREQ("thumb", PlatformDarwinTester::GetCompatibleArch(core, 3));
+}