[ORC] Switch to singleton pattern for UnwindInfoManager.

The find-dynamic-unwind-info callback registration APIs in libunwind limit the
number of callbacks that can be registered. If we use multiple
UnwindInfoManager instances, each with their own own callback function (as was
the case prior to this patch) we can quickly exceed this limit (see
#126611).

This patch updates the UnwindInfoManager class to use a singleton pattern,
with the single instance shared between all LLVM JITs in the process.

This change does _not_ apply to compact unwind info registered through the
ORC runtime (which currently installs its own callbacks).

As a bonus this change eliminates the need to load an IR "bouncer" module to
supply the unique callback for each instance, so support for compact-unwind can
be extended to the llvm-jitlink tools (which does not support adding IR).

Author: lhames

llvm/include/llvm/ExecutionEngine/Orc/Shared/OrcRTBridge.h

@@ -90,10 +90,6 @@ using SPSRunAsIntFunctionSignature = int32_t(shared::SPSExecutorAddr, int32_t);
 } // end namespace rt
 
 namespace rt_alt {
-extern const char *UnwindInfoManagerInstanceName;
-extern const char *UnwindInfoManagerFindSectionsHelperName;
-extern const char *UnwindInfoManagerEnableWrapperName;
-extern const char *UnwindInfoManagerDisableWrapperName;
 extern const char *UnwindInfoManagerRegisterActionName;
 extern const char *UnwindInfoManagerDeregisterActionName;
 } // end namespace rt_alt

llvm/include/llvm/ExecutionEngine/Orc/TargetProcess/UnwindInfoManager.h

@@ -15,14 +15,13 @@
 #define LLVM_EXECUTIONENGINE_ORC_TARGETPROCESS_UNWINDINFOMANAGER_H
 
 #include "llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h"
-#include "llvm/ExecutionEngine/Orc/TargetProcess/ExecutorBootstrapService.h"
 #include "llvm/Support/Error.h"
 #include <map>
 #include <mutex>
 
 namespace llvm::orc {
 
-class UnwindInfoManager : public ExecutorBootstrapService {
+class UnwindInfoManager {
 public:
   // This struct's layout should match the unw_dynamic_unwind_sections struct
   // from libunwind/src/libunwid_ext.h.
@@ -34,43 +33,40 @@ class UnwindInfoManager : public ExecutorBootstrapService {
     size_t compact_unwind_section_length;
   };
 
+  UnwindInfoManager(UnwindInfoManager &&) = delete;
+  UnwindInfoManager &operator=(UnwindInfoManager &&) = delete;
+  ~UnwindInfoManager();
+
   /// If the libunwind find-dynamic-unwind-info callback registration APIs are
-  /// available then this method will return an UnwindInfoManager instance,
-  /// otherwise it will return nullptr.
-  static std::unique_ptr<UnwindInfoManager> TryCreate();
+  /// available then this method will instantiate a global UnwindInfoManager
+  /// instance suitable for the process and return true. Otherwise it will
+  /// return false.
+  static bool TryEnable();
 
-  Error shutdown() override;
-  void addBootstrapSymbols(StringMap<ExecutorAddr> &M) override;
+  static void addBootstrapSymbols(StringMap<ExecutorAddr> &M);
 
-  Error enable(void *FindDynamicUnwindSections);
-  Error disable(void);
+  static Error registerSections(ArrayRef<orc::ExecutorAddrRange> CodeRanges,
+                                orc::ExecutorAddr DSOBase,
+                                orc::ExecutorAddrRange DWARFEHFrame,
+                                orc::ExecutorAddrRange CompactUnwind);
 
-  Error registerSections(ArrayRef<orc::ExecutorAddrRange> CodeRanges,
-                         orc::ExecutorAddr DSOBase,
-                         orc::ExecutorAddrRange DWARFEHFrame,
-                         orc::ExecutorAddrRange CompactUnwind);
+  static Error deregisterSections(ArrayRef<orc::ExecutorAddrRange> CodeRanges);
 
-  Error deregisterSections(ArrayRef<orc::ExecutorAddrRange> CodeRanges);
+private:
+  UnwindInfoManager() = default;
 
-  int findSections(uintptr_t Addr, UnwindSections *Info);
+  int findSectionsImpl(uintptr_t Addr, UnwindSections *Info);
+  static int findSections(uintptr_t Addr, UnwindSections *Info);
 
-private:
-  UnwindInfoManager(int (*AddFindDynamicUnwindSections)(void *),
-                    int (*RemoveFindDynamicUnwindSections)(void *))
-      : AddFindDynamicUnwindSections(AddFindDynamicUnwindSections),
-        RemoveFindDynamicUnwindSections(RemoveFindDynamicUnwindSections) {}
+  Error registerSectionsImpl(ArrayRef<orc::ExecutorAddrRange> CodeRanges,
+                             orc::ExecutorAddr DSOBase,
+                             orc::ExecutorAddrRange DWARFEHFrame,
+                             orc::ExecutorAddrRange CompactUnwind);
 
-  static int findSectionsHelper(UnwindInfoManager *Instance, uintptr_t Addr,
-                                UnwindSections *Info);
+  Error deregisterSectionsImpl(ArrayRef<orc::ExecutorAddrRange> CodeRanges);
 
   std::mutex M;
   std::map<uintptr_t, UnwindSections> UWSecs;
-
-  int (*AddFindDynamicUnwindSections)(void *) = nullptr;
-  int (*RemoveFindDynamicUnwindSections)(void *) = nullptr;
-  void *FindDynamicUnwindSections = nullptr;
-
-  static const char *AddFnName, *RemoveFnName;
 };
 
 } // namespace llvm::orc

llvm/include/llvm/ExecutionEngine/Orc/UnwindInfoRegistrationPlugin.h

@@ -19,15 +19,17 @@ namespace llvm::orc {
 
 class UnwindInfoRegistrationPlugin : public LinkGraphLinkingLayer::Plugin {
 public:
-  static Expected<std::shared_ptr<UnwindInfoRegistrationPlugin>>
-  Create(IRLayer &IRL, JITDylib &PlatformJD, ExecutorAddr Instance,
-         ExecutorAddr FindHelper, ExecutorAddr Enable, ExecutorAddr Disable,
-         ExecutorAddr Register, ExecutorAddr Deregister);
+  UnwindInfoRegistrationPlugin(ExecutionSession &ES, ExecutorAddr Register,
+                               ExecutorAddr Deregister)
+      : ES(ES), Register(Register), Deregister(Deregister) {
+    DSOBaseName = ES.intern("__jitlink$libunwind_dso_base");
+  }
 
   static Expected<std::shared_ptr<UnwindInfoRegistrationPlugin>>
-  Create(IRLayer &IRL, JITDylib &PlatformJD);
+  Create(ExecutionSession &ES, ExecutorAddr Register, ExecutorAddr Deregister);
 
-  ~UnwindInfoRegistrationPlugin();
+  static Expected<std::shared_ptr<UnwindInfoRegistrationPlugin>>
+  Create(ExecutionSession &ES);
 
   void modifyPassConfig(MaterializationResponsibility &MR,
                         jitlink::LinkGraph &G,
@@ -49,20 +51,11 @@ class UnwindInfoRegistrationPlugin : public LinkGraphLinkingLayer::Plugin {
                                    ResourceKey SrcKey) override {}
 
 private:
-  UnwindInfoRegistrationPlugin(ExecutionSession &ES, ExecutorAddr Instance,
-                               ExecutorAddr Disable, ExecutorAddr Register,
-                               ExecutorAddr Deregister)
-      : ES(ES), Instance(Instance), Disable(Disable), Register(Register),
-        Deregister(Deregister) {
-    DSOBaseName = ES.intern("__jitlink$libunwind_dso_base");
-  }
-
-  static Expected<ThreadSafeModule> makeBouncerModule(ExecutionSession &ES);
   Error addUnwindInfoRegistrationActions(jitlink::LinkGraph &G);
 
   ExecutionSession &ES;
   SymbolStringPtr DSOBaseName;
-  ExecutorAddr Instance, Disable, Register, Deregister;
+  ExecutorAddr Register, Deregister;
 };
 
 } // namespace llvm::orc

llvm/lib/ExecutionEngine/Orc/ExecutorProcessControl.cpp

@@ -54,9 +54,8 @@ SelfExecutorProcessControl::SelfExecutorProcessControl(
   // FIXME: Don't add an UnwindInfoManager by default -- it's redundant when
   //        the ORC runtime is loaded. We'll need a way to document this and
   //        allow clients to choose.
-  this->UnwindInfoMgr = UnwindInfoManager::TryCreate();
-  if (this->UnwindInfoMgr)
-    this->UnwindInfoMgr->addBootstrapSymbols(this->BootstrapSymbols);
+  if (UnwindInfoManager::TryEnable())
+    UnwindInfoManager::addBootstrapSymbols(this->BootstrapSymbols);
 #endif // __APPLE__
 }
 

llvm/lib/ExecutionEngine/Orc/LLJIT.cpp

@@ -1241,8 +1241,8 @@ Expected<JITDylibSP> setUpGenericLLVMIRPlatform(LLJIT &J) {
 
       // If UseEHFrames hasn't been set then we're good to use compact-unwind.
       if (!UseEHFrames) {
-        if (auto UIRP = UnwindInfoRegistrationPlugin::Create(
-                J.getIRCompileLayer(), PlatformJD)) {
+        if (auto UIRP =
+                UnwindInfoRegistrationPlugin::Create(J.getExecutionSession())) {
           OLL->addPlugin(std::move(*UIRP));
           LLVM_DEBUG(dbgs() << "Enabled compact-unwind support.\n");
         } else

llvm/lib/ExecutionEngine/Orc/Shared/OrcRTBridge.cpp

@@ -65,14 +65,6 @@ const char *RunAsIntFunctionWrapperName =
 
 } // end namespace rt
 namespace rt_alt {
-const char *UnwindInfoManagerInstanceName =
-    "orc_rt_alt_UnwindInfoManager_Instance";
-const char *UnwindInfoManagerFindSectionsHelperName =
-    "orc_rt_alt_UnwindInfoManager_findSectionsHelper";
-const char *UnwindInfoManagerEnableWrapperName =
-    "orc_rt_alt_UnwindInfoManager_enable";
-const char *UnwindInfoManagerDisableWrapperName =
-    "orc_rt_alt_UnwindInfoManager_disable";
 const char *UnwindInfoManagerRegisterActionName =
     "orc_rt_alt_UnwindInfoManager_register";
 const char *UnwindInfoManagerDeregisterActionName =