Index: lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
===================================================================
--- lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -5024,7 +5024,18 @@
 
       auto triple = base_triple;
       triple.setOSName(os.str());
-      os_name.clear();
+
+      // Disambiguate legacy simulator platforms.
+      if (base_triple.getArch() == llvm::Triple::x86_64 ||
+          base_triple.getArch() == llvm::Triple::x86) {
+        // The combination of legacy LC_VERSION_MIN load command and
+        // x86 architecture always indicates a simulator environment.
+        // The combination of LC_VERSION_MIN and arm architecture only
+        // appears for native binaries. Back-deploying simulator
+        // binaries on Apple Silicon Macs use the modern unambigous
+        // LC_BUILD_VERSION load commands; no special handling required.
+        triple.setEnvironment(llvm::Triple::Simulator);
+      }
       add_triple(triple);
       break;
     }
Index: lldb/source/Utility/ArchSpec.cpp
===================================================================
--- lldb/source/Utility/ArchSpec.cpp
+++ lldb/source/Utility/ArchSpec.cpp
@@ -1057,20 +1057,6 @@
       return true;
   }
 
-  if (lhs_triple_os != rhs_triple_os) {
-    const bool rhs_os_specified = rhs.TripleOSWasSpecified();
-    const bool lhs_os_specified = TripleOSWasSpecified();
-    // Both architectures had the OS specified, so if they aren't equal then
-    // we return false
-    if (rhs_os_specified && lhs_os_specified)
-      return false;
-
-    // Only fail if both os types are not unknown
-    if (lhs_triple_os != llvm::Triple::UnknownOS &&
-        rhs_triple_os != llvm::Triple::UnknownOS)
-      return false;
-  }
-
   // x86_64-apple-ios-macabi and x86_64-apple-ios are not compatible.
   if (lhs_triple_os == llvm::Triple::IOS &&
       rhs_triple_os == llvm::Triple::IOS &&
@@ -1079,6 +1065,19 @@
       lhs_triple_env != rhs_triple_env)
     return false;
 
+  if (lhs_triple_os != rhs_triple_os) {
+    const bool lhs_os_specified = TripleOSWasSpecified();
+    const bool rhs_os_specified = rhs.TripleOSWasSpecified();
+    // If both OS types are specified and different, fail.
+    if (lhs_os_specified && rhs_os_specified)
+      return false;
+
+    // If the pair of os+env is both unspecified, match any other os+env combo.
+    if (!exact_match && ((!lhs_os_specified && !lhs_triple.hasEnvironment()) ||
+                         (!rhs_os_specified && !rhs_triple.hasEnvironment())))
+      return true;
+  }
+
   return IsCompatibleEnvironment(lhs_triple_env, rhs_triple_env);
 }
 
Index: lldb/test/API/macosx/simulator/TestSimulatorPlatform.py
===================================================================
--- lldb/test/API/macosx/simulator/TestSimulatorPlatform.py
+++ lldb/test/API/macosx/simulator/TestSimulatorPlatform.py
@@ -6,7 +6,6 @@
 import unittest2
 
 
-@skipIfDarwin # rdar://problem/64552748
 class TestSimulatorPlatformLaunching(TestBase):
 
     mydir = TestBase.compute_mydir(__file__)
Index: lldb/unittests/Utility/ArchSpecTest.cpp
===================================================================
--- lldb/unittests/Utility/ArchSpecTest.cpp
+++ lldb/unittests/Utility/ArchSpecTest.cpp
@@ -305,6 +305,25 @@
     ArchSpec B("x86_64-apple-ios-simulator");
     ASSERT_FALSE(A.IsExactMatch(B));
     ASSERT_FALSE(A.IsCompatibleMatch(B));
+    ASSERT_FALSE(B.IsExactMatch(A));
+    ASSERT_FALSE(B.IsCompatibleMatch(A));
+  }
+  {
+    ArchSpec A("x86_64-apple-ios");
+    ArchSpec B("x86_64-apple-ios-simulator");
+    ASSERT_FALSE(A.IsExactMatch(B));
+    ASSERT_FALSE(A.IsCompatibleMatch(B));
+    ASSERT_FALSE(B.IsExactMatch(A));
+    ASSERT_FALSE(B.IsCompatibleMatch(A));
+  }
+  {
+    // FIXME: This is surprisingly not equivalent to "x86_64-*-*".
+    ArchSpec A("x86_64");
+    ArchSpec B("x86_64-apple-ios-simulator");
+    ASSERT_FALSE(A.IsExactMatch(B));
+    ASSERT_TRUE(A.IsCompatibleMatch(B));
+    ASSERT_FALSE(B.IsExactMatch(A));
+    ASSERT_TRUE(B.IsCompatibleMatch(A));
   }
   {
     ArchSpec A("arm64-apple-ios");