[pull] swift/release/5.4 from apple:swift/release/5.4

lldb/source/Host/macosx/objcxx/Host.mm

@@ -1108,6 +1108,40 @@ static Status LaunchProcessPosixSpawn(const char *exe_path,
     }
   }
 
+// posix_spawnattr_setbinpref_np appears to be an Apple extension per:
+// http://www.unix.com/man-page/OSX/3/posix_spawnattr_setbinpref_np/
+#if !defined(__arm__)
+  // Don't set the binpref if a shell was provided.  After all, that's only
+  // going to affect what version of the shell is launched, not what fork of
+  // the binary is launched.  We insert "arch --arch <ARCH> as part of the
+  // shell invocation to do that job on OSX.
+  if (launch_info.GetShell() == FileSpec()) {
+    // We don't need to do this for ARM, and we really shouldn't now that we
+    // have multiple CPU subtypes and no posix_spawnattr call that allows us to
+    // set which CPU subtype to launch...
+    const ArchSpec &arch_spec = launch_info.GetArchitecture();
+    cpu_type_t cpu = arch_spec.GetMachOCPUType();
+    cpu_type_t sub = arch_spec.GetMachOCPUSubType();
+    if (cpu != 0 && cpu != static_cast<cpu_type_t>(UINT32_MAX) &&
+        cpu != static_cast<cpu_type_t>(LLDB_INVALID_CPUTYPE) &&
+        !(cpu == 0x01000007 && sub == 8)) // If haswell is specified, don't try
+                                          // to set the CPU type or we will fail
+    {
+      size_t ocount = 0;
+      error.SetError(::posix_spawnattr_setbinpref_np(&attr, 1, &cpu, &ocount),
+                     eErrorTypePOSIX);
+      if (error.Fail())
+        LLDB_LOG(log,
+                 "error: {0}, ::posix_spawnattr_setbinpref_np ( &attr, 1, "
+                 "cpu_type = {1:x}, count => {2} )",
+                 error, cpu, ocount);
+
+      if (error.Fail() || ocount != 1)
+        return error;
+    }
+  }
+#endif
+
   const char *tmp_argv[2];
   char *const *argv = const_cast<char *const *>(
       launch_info.GetArguments().GetConstArgumentVector());