[ORC] Add a "lazy call-through" utility based on the same underlying trampoline

implementation as lazy compile callbacks, and a "lazy re-exports" utility that
builds lazy call-throughs.

Lazy call-throughs are similar to lazy compile callbacks (and are based on the
same underlying state saving/restoring trampolines) but resolve their targets
by performing a standard ORC lookup rather than invoking a user supplied
compiler callback. This allows them to inherit the thread-safety of ORC lookups
while blocking only the calling thread (whereas compile callbacks also block one
compile thread).

Lazy re-exports provide a simple way of building lazy call-throughs. Unlike a
regular re-export, a lazy re-export generates a new address (a stub entry point)
that will act like the re-exported symbol when called. The first call via a
lazy re-export will trigger compilation of the re-exported symbol before calling
through to it.

llvm-svn: 343061

Author: lhames

llvm/include/llvm/ExecutionEngine/Orc/LazyReexports.h

@@ -0,0 +1,191 @@
+//===------ LazyReexports.h -- Utilities for lazy reexports -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Lazy re-exports are similar to normal re-exports, except that for callable
+// symbols the definitions are replaced with trampolines that will look up and
+// call through to the re-exported symbol at runtime. This can be used to
+// enable lazy compilation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_ORC_LAZYREEXPORTS_H
+#define LLVM_EXECUTIONENGINE_ORC_LAZYREEXPORTS_H
+
+#include "llvm/ExecutionEngine/Orc/Core.h"
+#include "llvm/ExecutionEngine/Orc/IndirectionUtils.h"
+
+namespace llvm {
+
+class Triple;
+
+namespace orc {
+
+/// Manages a set of 'lazy call-through' trampolines. These are compiler
+/// re-entry trampolines that are pre-bound to look up a given symbol in a given
+/// JITDylib, then jump to that address. Since compilation of symbols is
+/// triggered on first lookup, these call-through trampolines can be used to
+/// implement lazy compilation.
+///
+/// The easiest way to construct these call-throughs is using the lazyReexport
+/// function.
+class LazyCallThroughManager {
+public:
+  /// Clients will want to take some action on first resolution, e.g. updating
+  /// a stub pointer. Instances of this class can be used to implement this.
+  class NotifyResolvedFunction {
+  public:
+    virtual ~NotifyResolvedFunction() {}
+
+    /// Called the first time a lazy call through is executed and the target
+    /// symbol resolved.
+    virtual Error operator()(JITDylib &SourceJD,
+                             const SymbolStringPtr &SymbolName,
+                             JITTargetAddress ResolvedAddr) = 0;
+
+  private:
+    virtual void anchor();
+  };
+
+  template <typename NotifyResolvedImpl>
+  class NotifyResolvedFunctionImpl : public NotifyResolvedFunction {
+  public:
+    NotifyResolvedFunctionImpl(NotifyResolvedImpl NotifyResolved)
+        : NotifyResolved(std::move(NotifyResolved)) {}
+    Error operator()(JITDylib &SourceJD, const SymbolStringPtr &SymbolName,
+                     JITTargetAddress ResolvedAddr) {
+      return NotifyResolved(SourceJD, SymbolName, ResolvedAddr);
+    }
+
+  private:
+    NotifyResolvedImpl NotifyResolved;
+  };
+
+  /// Create a shared NotifyResolvedFunction from a given type that is
+  /// callable with the correct signature.
+  template <typename NotifyResolvedImpl>
+  static std::unique_ptr<NotifyResolvedFunction>
+  createNotifyResolvedFunction(NotifyResolvedImpl NotifyResolved) {
+    return llvm::make_unique<NotifyResolvedFunctionImpl<NotifyResolvedImpl>>(
+        std::move(NotifyResolved));
+  };
+
+  // Return a free call-through trampoline and bind it to look up and call
+  // through to the given symbol.
+  Expected<JITTargetAddress> getCallThroughTrampoline(
+      JITDylib &SourceJD, SymbolStringPtr SymbolName,
+      std::shared_ptr<NotifyResolvedFunction> NotifyResolved);
+
+protected:
+  LazyCallThroughManager(ExecutionSession &ES,
+                         JITTargetAddress ErrorHandlerAddr,
+                         std::unique_ptr<TrampolinePool> TP);
+
+  JITTargetAddress callThroughToSymbol(JITTargetAddress TrampolineAddr);
+
+  void setTrampolinePool(std::unique_ptr<TrampolinePool> TP) {
+    this->TP = std::move(TP);
+  }
+
+private:
+  using ReexportsMap =
+      std::map<JITTargetAddress, std::pair<JITDylib *, SymbolStringPtr>>;
+
+  using NotifiersMap =
+      std::map<JITTargetAddress, std::shared_ptr<NotifyResolvedFunction>>;
+
+  std::mutex LCTMMutex;
+  ExecutionSession &ES;
+  JITTargetAddress ErrorHandlerAddr;
+  std::unique_ptr<TrampolinePool> TP;
+  ReexportsMap Reexports;
+  NotifiersMap Notifiers;
+};
+
+/// A lazy call-through manager that builds trampolines in the current process.
+class LocalLazyCallThroughManager : public LazyCallThroughManager {
+private:
+  LocalLazyCallThroughManager(ExecutionSession &ES,
+                              JITTargetAddress ErrorHandlerAddr)
+      : LazyCallThroughManager(ES, ErrorHandlerAddr, nullptr) {}
+
+  template <typename ORCABI> Error init() {
+    auto TP = LocalTrampolinePool<ORCABI>::Create(
+        [this](JITTargetAddress TrampolineAddr) {
+          return callThroughToSymbol(TrampolineAddr);
+        });
+
+    if (!TP)
+      return TP.takeError();
+
+    setTrampolinePool(std::move(*TP));
+    return Error::success();
+  }
+
+public:
+  /// Create a LocalLazyCallThroughManager using the given ABI. See
+  /// createLocalLazyCallThroughManager.
+  template <typename ORCABI>
+  static Expected<std::unique_ptr<LocalLazyCallThroughManager>>
+  Create(ExecutionSession &ES, JITTargetAddress ErrorHandlerAddr) {
+    auto LLCTM = std::unique_ptr<LocalLazyCallThroughManager>(
+        new LocalLazyCallThroughManager(ES, ErrorHandlerAddr));
+
+    if (auto Err = LLCTM->init<ORCABI>())
+      return std::move(Err);
+
+    return std::move(LLCTM);
+  }
+};
+
+/// Create a LocalLazyCallThroughManager from the given triple and execution
+/// session.
+Expected<std::unique_ptr<LazyCallThroughManager>>
+createLocalLazyCallThroughManager(const Triple &T, ExecutionSession &ES,
+                                  JITTargetAddress ErrorHandlerAddr);
+
+/// A materialization unit that builds lazy re-exports. These are callable
+/// entry points that call through to the given symbols.
+/// Unlike a 'true' re-export, the address of the lazy re-export will not
+/// match the address of the re-exported symbol, but calling it will behave
+/// the same as calling the re-exported symbol.
+class LazyReexportsMaterializationUnit : public MaterializationUnit {
+public:
+  LazyReexportsMaterializationUnit(LazyCallThroughManager &LCTManager,
+                                   IndirectStubsManager &ISManager,
+                                   JITDylib &SourceJD,
+                                   SymbolAliasMap CallableAliases);
+
+private:
+  void materialize(MaterializationResponsibility R) override;
+  void discard(const JITDylib &JD, SymbolStringPtr Name) override;
+  static SymbolFlagsMap extractFlags(const SymbolAliasMap &Aliases);
+
+  LazyCallThroughManager &LCTManager;
+  IndirectStubsManager &ISManager;
+  JITDylib &SourceJD;
+  SymbolAliasMap CallableAliases;
+  std::shared_ptr<LazyCallThroughManager::NotifyResolvedFunction>
+      NotifyResolved;
+};
+
+/// Define lazy-reexports based on the given SymbolAliasMap. Each lazy re-export
+/// is a callable symbol that will look up and dispatch to the given aliasee on
+/// first call. All subsequent calls will go directly to the aliasee.
+inline std::unique_ptr<LazyReexportsMaterializationUnit>
+lazyReexports(LazyCallThroughManager &LCTManager,
+              IndirectStubsManager &ISManager, JITDylib &SourceJD,
+              SymbolAliasMap CallableAliases) {
+  return llvm::make_unique<LazyReexportsMaterializationUnit>(
+      LCTManager, ISManager, SourceJD, std::move(CallableAliases));
+}
+
+} // End namespace orc
+} // End namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_ORC_LAZYREEXPORTS_H

llvm/lib/ExecutionEngine/Orc/CMakeLists.txt

@@ -5,6 +5,7 @@ add_llvm_library(LLVMOrcJIT
   IndirectionUtils.cpp
   IRCompileLayer.cpp
   IRTransformLayer.cpp
+  LazyReexports.cpp
   Legacy.cpp
   Layer.cpp
   LLJIT.cpp