Add utility to append a function to the list of global constructors.

Patch by Kostya Serebryany.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143405 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 56 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/CMakeLists.txt b/lib/Transforms/Utils/CMakeLists.txt
index 7adc5f1ac2..6d5432d963 100644
--- a/lib/Transforms/Utils/CMakeLists.txt
+++ b/lib/Transforms/Utils/CMakeLists.txt
@@ -18,6 +18,7 @@ add_llvm_library(LLVMTransformUtils
   LowerInvoke.cpp
   LowerSwitch.cpp
   Mem2Reg.cpp
+  ModuleUtils.cpp
   PromoteMemoryToRegister.cpp
   SSAUpdater.cpp
   SimplifyCFG.cpp
diff --git a/lib/Transforms/Utils/ModuleUtils.cpp b/lib/Transforms/Utils/ModuleUtils.cpp
new file mode 100644
index 0000000000..db81de7b1d
--- /dev/null
+++ b/lib/Transforms/Utils/ModuleUtils.cpp
@@ -0,0 +1,55 @@
+//===-- ModuleUtils.cpp - Functions to manipulate Modules -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This family of functions perform manipulations on Modules.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Function.h"
+#include "llvm/Module.h"
+#include "llvm/Support/IRBuilder.h"
+using namespace llvm;
+
+void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority) {
+  IRBuilder<> IRB(M.getContext());
+  FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
+  StructType *Ty = StructType::get(
+      IRB.getInt32Ty(), PointerType::getUnqual(FnTy), NULL);
+
+  Constant *RuntimeCtorInit = ConstantStruct::get(
+      Ty, IRB.getInt32(Priority), F, NULL);
+
+  // Get the current set of static global constructors and add the new ctor
+  // to the list.
+  SmallVector<Constant *, 16> CurrentCtors;
+  if (GlobalVariable * GVCtor = M.getNamedGlobal("llvm.global_ctors")) {
+    if (Constant *Init = GVCtor->getInitializer()) {
+      unsigned n = Init->getNumOperands();
+      CurrentCtors.reserve(n + 1);
+      for (unsigned i = 0; i != n; ++i)
+        CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
+    }
+    GVCtor->eraseFromParent();
+  }
+
+  CurrentCtors.push_back(RuntimeCtorInit);
+
+  // Create a new initializer.
+  ArrayType *AT = ArrayType::get(RuntimeCtorInit->getType(),
+                                 CurrentCtors.size());
+  Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
+
+  // Create the new global variable and replace all uses of
+  // the old global variable with the new one.
+  (void)new GlobalVariable(M, NewInit->getType(), false,
+                           GlobalValue::AppendingLinkage, NewInit,
+                           "llvm.global_ctors");
+}