Abstract the emission of global destructors into ABI-specific code

and only consider using __cxa_atexit in the Itanium logic.  The
default logic is to use atexit().

Emit "guarded" initializers in Microsoft mode unconditionally.
This is definitely not correct, but it's closer to correct than
just not emitting the initializer.

Based on a patch by Timur Iskhodzhanov!

llvm-svn: 155894

1 files changed, 54 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 1a36a085709..3188590d11e 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -119,6 +119,8 @@ public:
 
   void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
                        llvm::GlobalVariable *DeclPtr, bool PerformInit);
+  void registerGlobalDtor(CodeGenFunction &CGF, llvm::Constant *dtor,
+                          llvm::Constant *addr);
 };
 
 class ARMCXXABI : public ItaniumCXXABI {
@@ -1097,3 +1099,55 @@ void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
 
   CGF.EmitBlock(EndBlock);
 }
+
+/// Register a global destructor using __cxa_atexit.
+static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
+                                        llvm::Constant *dtor,
+                                        llvm::Constant *addr) {
+  // We're assuming that the destructor function is something we can
+  // reasonably call with the default CC.  Go ahead and cast it to the
+  // right prototype.
+  llvm::Type *dtorTy =
+    llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, false)->getPointerTo();
+
+  // extern "C" int __cxa_atexit(void (*f)(void *), void *p, void *d);
+  llvm::Type *paramTys[] = { dtorTy, CGF.Int8PtrTy, CGF.Int8PtrTy };
+  llvm::FunctionType *atexitTy =
+    llvm::FunctionType::get(CGF.IntTy, paramTys, false);
+
+  // Fetch the actual function.
+  llvm::Constant *atexit =
+    CGF.CGM.CreateRuntimeFunction(atexitTy, "__cxa_atexit");
+  if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit))
+    fn->setDoesNotThrow();
+
+  // Create a variable that binds the atexit to this shared object.
+  llvm::Constant *handle =
+    CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
+
+  llvm::Value *args[] = {
+    llvm::ConstantExpr::getBitCast(dtor, dtorTy),
+    llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
+    handle
+  };
+  CGF.Builder.CreateCall(atexit, args)->setDoesNotThrow();
+}
+
+/// Register a global destructor as best as we know how.
+void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
+                                       llvm::Constant *dtor,
+                                       llvm::Constant *addr) {
+  // Use __cxa_atexit if available.
+  if (CGM.getCodeGenOpts().CXAAtExit) {
+    return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr);
+  }
+
+  // In Apple kexts, we want to add a global destructor entry.
+  // FIXME: shouldn't this be guarded by some variable?
+  if (CGM.getContext().getLangOpts().AppleKext) {
+    // Generate a global destructor entry.
+    return CGM.AddCXXDtorEntry(dtor, addr);
+  }
+
+  CGF.registerGlobalDtorWithAtExit(dtor, addr);
+}