From d958a5a9feea7239a73c2068f43f237db550f46e Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 22 Oct 2007 02:50:12 +0000
Subject: [PATCH] add a mechanism for the JIT to invoke a function to lazily
 create functions as they are referenced.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43210 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/ExecutionEngine/ExecutionEngine.h | 15 ++++++++++++++-
 lib/ExecutionEngine/ExecutionEngine.cpp        |  4 ++--
 lib/ExecutionEngine/JIT/Intercept.cpp          |  5 +++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/include/llvm/ExecutionEngine/ExecutionEngine.h b/include/llvm/ExecutionEngine/ExecutionEngine.h
index da034a7cc2f..3ec2641cada 100644
--- a/include/llvm/ExecutionEngine/ExecutionEngine.h
+++ b/include/llvm/ExecutionEngine/ExecutionEngine.h
@@ -64,6 +64,7 @@ class ExecutionEngine {
   const TargetData *TD;
   ExecutionEngineState state;
   bool LazyCompilationDisabled;
+
 protected:
   /// Modules - This is a list of ModuleProvider's that we are JIT'ing from.  We
   /// use a smallvector to optimize for the case where there is only one module.
@@ -78,7 +79,11 @@ protected:
   // at startup time if they are linked in.
   typedef ExecutionEngine *(*EECtorFn)(ModuleProvider*, std::string*);
   static EECtorFn JITCtor, InterpCtor;
-    
+
+  /// LazyFunctionCreator - If an unknown function is needed, this function
+  /// pointer is invoked to create it. If this returns null, the JIT will abort.
+  void* (*LazyFunctionCreator)(const std::string &);
+  
 public:
   /// lock - This lock is protects the ExecutionEngine, JIT, JITResolver and
   /// JITEmitter classes.  It must be held while changing the internal state of
@@ -218,6 +223,14 @@ public:
   bool isLazyCompilationDisabled() const {
     return LazyCompilationDisabled;
   }
+  
+  
+  /// InstallLazyFunctionCreator - If an unknown function is needed, the
+  /// specified function pointer is invoked to create it.  If it returns null,
+  /// the JIT will abort.
+  void InstallLazyFunctionCreator(void* (*P)(const std::string &)) {
+    LazyFunctionCreator = P;
+  }
 
 protected:
   void emitGlobals();
diff --git a/lib/ExecutionEngine/ExecutionEngine.cpp b/lib/ExecutionEngine/ExecutionEngine.cpp
index 2129dd5019d..d89a9bb4ac7 100644
--- a/lib/ExecutionEngine/ExecutionEngine.cpp
+++ b/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -33,13 +33,13 @@ STATISTIC(NumGlobals  , "Number of global vars initialized");
 ExecutionEngine::EECtorFn ExecutionEngine::JITCtor = 0;
 ExecutionEngine::EECtorFn ExecutionEngine::InterpCtor = 0;
 
-ExecutionEngine::ExecutionEngine(ModuleProvider *P) {
+ExecutionEngine::ExecutionEngine(ModuleProvider *P) : LazyFunctionCreator(0) {
   LazyCompilationDisabled = false;
   Modules.push_back(P);
   assert(P && "ModuleProvider is null?");
 }
 
-ExecutionEngine::ExecutionEngine(Module *M) {
+ExecutionEngine::ExecutionEngine(Module *M) : LazyFunctionCreator(0) {
   LazyCompilationDisabled = false;
   assert(M && "Module is null?");
   Modules.push_back(new ExistingModuleProvider(M));
diff --git a/lib/ExecutionEngine/JIT/Intercept.cpp b/lib/ExecutionEngine/JIT/Intercept.cpp
index 61035c25359..318d6067d6c 100644
--- a/lib/ExecutionEngine/JIT/Intercept.cpp
+++ b/lib/ExecutionEngine/JIT/Intercept.cpp
@@ -101,6 +101,11 @@ void *JIT::getPointerToNamedFunction(const std::string &Name) {
     Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
     if (Ptr) return Ptr;
   }
+  
+  /// If a LazyFunctionCreator is installed, use it to get/create the function. 
+  if (LazyFunctionCreator)
+    if (void *RP = LazyFunctionCreator(Name))
+      return RP;
 
   cerr << "ERROR: Program used external function '" << Name
        << "' which could not be resolved!\n";
-- 
2.34.1