Revert "Handle step-in over a Darwin "branch island". (#138330)" (#138569)

This reverts commit 1ba89ad.

This was failing on the Green Dragon bot, which has an older OS than
have on hand, so I'll have to dig up one and see why it's failing there.

Author: jimingham

lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp

@@ -26,7 +26,6 @@
 #include "lldb/Target/Thread.h"
 #include "lldb/Target/ThreadPlanCallFunction.h"
 #include "lldb/Target/ThreadPlanRunToAddress.h"
-#include "lldb/Target/ThreadPlanStepInstruction.h"
 #include "lldb/Utility/DataBuffer.h"
 #include "lldb/Utility/DataBufferHeap.h"
 #include "lldb/Utility/LLDBLog.h"
@@ -924,15 +923,15 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread,
   if (current_symbol != nullptr) {
     std::vector<Address> addresses;
 
-    ConstString current_name =
-        current_symbol->GetMangled().GetName(Mangled::ePreferMangled);
     if (current_symbol->IsTrampoline()) {
+      ConstString trampoline_name =
+          current_symbol->GetMangled().GetName(Mangled::ePreferMangled);
 
-      if (current_name) {
+      if (trampoline_name) {
         const ModuleList &images = target_sp->GetImages();
 
         SymbolContextList code_symbols;
-        images.FindSymbolsWithNameAndType(current_name, eSymbolTypeCode,
+        images.FindSymbolsWithNameAndType(trampoline_name, eSymbolTypeCode,
                                           code_symbols);
         for (const SymbolContext &context : code_symbols) {
           Address addr = context.GetFunctionOrSymbolAddress();
@@ -946,8 +945,8 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread,
         }
 
         SymbolContextList reexported_symbols;
-        images.FindSymbolsWithNameAndType(current_name, eSymbolTypeReExported,
-                                          reexported_symbols);
+        images.FindSymbolsWithNameAndType(
+            trampoline_name, eSymbolTypeReExported, reexported_symbols);
         for (const SymbolContext &context : reexported_symbols) {
           if (context.symbol) {
             Symbol *actual_symbol =
@@ -969,7 +968,7 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread,
         }
 
         SymbolContextList indirect_symbols;
-        images.FindSymbolsWithNameAndType(current_name, eSymbolTypeResolver,
+        images.FindSymbolsWithNameAndType(trampoline_name, eSymbolTypeResolver,
                                           indirect_symbols);
 
         for (const SymbolContext &context : indirect_symbols) {
@@ -1029,18 +1028,6 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread,
       thread_plan_sp = std::make_shared<ThreadPlanRunToAddress>(
           thread, load_addrs, stop_others);
     }
-    // One more case we have to consider is "branch islands".  These are regular
-    // TEXT symbols but their names end in .island.  They are to allow arm64
-    // code to branch further than the size of the address slot allows.  We
-    // just need to single-instruction step in that case.
-    if (!thread_plan_sp && current_name.GetStringRef().ends_with(".island")) {
-      thread_plan_sp = std::make_shared<ThreadPlanStepInstruction>(
-          thread,
-          /* step_over= */ false, /* stop_others */ false, eVoteNoOpinion,
-          eVoteNoOpinion);
-      LLDB_LOG(log, "Stepping one instruction over branch island: '{0}'.",
-               current_name);
-    }
   } else {
     LLDB_LOGF(log, "Could not find symbol for step through.");
   }