1 files changed, 84 insertions, 0 deletions
diff --git a/lib/Transforms/IPO/ElimAvailExtern.cpp b/lib/Transforms/IPO/ElimAvailExtern.cpp
new file mode 100644
index 000000000000..67ba72d6a360
--- /dev/null
+++ b/lib/Transforms/IPO/ElimAvailExtern.cpp
@@ -0,0 +1,84 @@
+//===-- ElimAvailExtern.cpp - DCE unreachable internal functions ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This transform is designed to eliminate available external global
+// definitions from the program, turning them into declarations.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Transforms/Utils/CtorUtils.h"
+#include "llvm/Transforms/Utils/GlobalStatus.h"
+#include "llvm/Pass.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "elim-avail-extern"
+
+STATISTIC(NumFunctions, "Number of functions removed");
+STATISTIC(NumVariables, "Number of global variables removed");
+
+namespace {
+  struct EliminateAvailableExternally : public ModulePass {
+    static char ID; // Pass identification, replacement for typeid
+    EliminateAvailableExternally() : ModulePass(ID) {
+      initializeEliminateAvailableExternallyPass(
+          *PassRegistry::getPassRegistry());
+    }
+
+    // run - Do the EliminateAvailableExternally pass on the specified module,
+    // optionally updating the specified callgraph to reflect the changes.
+    //
+    bool runOnModule(Module &M) override;
+  };
+}
+
+char EliminateAvailableExternally::ID = 0;
+INITIALIZE_PASS(EliminateAvailableExternally, "elim-avail-extern",
+                "Eliminate Available Externally Globals", false, false)
+
+ModulePass *llvm::createEliminateAvailableExternallyPass() {
+  return new EliminateAvailableExternally();
+}
+
+bool EliminateAvailableExternally::runOnModule(Module &M) {
+  bool Changed = false;
+
+  // Drop initializers of available externally global variables.
+  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
+       I != E; ++I) {
+    if (!I->hasAvailableExternallyLinkage())
+      continue;
+    if (I->hasInitializer()) {
+      Constant *Init = I->getInitializer();
+      I->setInitializer(nullptr);
+      if (isSafeToDestroyConstant(Init))
+        Init->destroyConstant();
+    }
+    I->removeDeadConstantUsers();
+    I->setLinkage(GlobalValue::ExternalLinkage);
+    NumVariables++;
+  }
+
+  // Drop the bodies of available externally functions.
+  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
+    if (!I->hasAvailableExternallyLinkage())
+      continue;
+    if (!I->isDeclaration())
+      // This will set the linkage to external
+      I->deleteBody();
+    I->removeDeadConstantUsers();
+    NumFunctions++;
+  }
+
+  return Changed;
+}