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diff --git a/contrib/llvm/lib/Transforms/IPO/GlobalDCE.cpp b/contrib/llvm/lib/Transforms/IPO/GlobalDCE.cpp
new file mode 100644
index 0000000..9b276ed
--- /dev/null
+++ b/contrib/llvm/lib/Transforms/IPO/GlobalDCE.cpp
@@ -0,0 +1,256 @@
+//===-- GlobalDCE.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 unreachable internal globals from the
+// program.  It uses an aggressive algorithm, searching out globals that are
+// known to be alive.  After it finds all of the globals which are needed, it
+// deletes whatever is left over.  This allows it to delete recursive chunks of
+// the program which are unreachable.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/SmallPtrSet.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"
+#include <unordered_map>
+using namespace llvm;
+
+#define DEBUG_TYPE "globaldce"
+
+STATISTIC(NumAliases  , "Number of global aliases removed");
+STATISTIC(NumFunctions, "Number of functions removed");
+STATISTIC(NumVariables, "Number of global variables removed");
+
+namespace {
+  struct GlobalDCE : public ModulePass {
+    static char ID; // Pass identification, replacement for typeid
+    GlobalDCE() : ModulePass(ID) {
+      initializeGlobalDCEPass(*PassRegistry::getPassRegistry());
+    }
+
+    // run - Do the GlobalDCE pass on the specified module, optionally updating
+    // the specified callgraph to reflect the changes.
+    //
+    bool runOnModule(Module &M) override;
+
+  private:
+    SmallPtrSet<GlobalValue*, 32> AliveGlobals;
+    SmallPtrSet<Constant *, 8> SeenConstants;
+    std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
+
+    /// GlobalIsNeeded - mark the specific global value as needed, and
+    /// recursively mark anything that it uses as also needed.
+    void GlobalIsNeeded(GlobalValue *GV);
+    void MarkUsedGlobalsAsNeeded(Constant *C);
+
+    bool RemoveUnusedGlobalValue(GlobalValue &GV);
+  };
+}
+
+/// Returns true if F contains only a single "ret" instruction.
+static bool isEmptyFunction(Function *F) {
+  BasicBlock &Entry = F->getEntryBlock();
+  if (Entry.size() != 1 || !isa<ReturnInst>(Entry.front()))
+    return false;
+  ReturnInst &RI = cast<ReturnInst>(Entry.front());
+  return RI.getReturnValue() == nullptr;
+}
+
+char GlobalDCE::ID = 0;
+INITIALIZE_PASS(GlobalDCE, "globaldce",
+                "Dead Global Elimination", false, false)
+
+ModulePass *llvm::createGlobalDCEPass() { return new GlobalDCE(); }
+
+bool GlobalDCE::runOnModule(Module &M) {
+  bool Changed = false;
+
+  // Remove empty functions from the global ctors list.
+  Changed |= optimizeGlobalCtorsList(M, isEmptyFunction);
+
+  // Collect the set of members for each comdat.
+  for (Function &F : M)
+    if (Comdat *C = F.getComdat())
+      ComdatMembers.insert(std::make_pair(C, &F));
+  for (GlobalVariable &GV : M.globals())
+    if (Comdat *C = GV.getComdat())
+      ComdatMembers.insert(std::make_pair(C, &GV));
+  for (GlobalAlias &GA : M.aliases())
+    if (Comdat *C = GA.getComdat())
+      ComdatMembers.insert(std::make_pair(C, &GA));
+
+  // Loop over the module, adding globals which are obviously necessary.
+  for (Function &F : M) {
+    Changed |= RemoveUnusedGlobalValue(F);
+    // Functions with external linkage are needed if they have a body
+    if (!F.isDeclaration() && !F.hasAvailableExternallyLinkage())
+      if (!F.isDiscardableIfUnused())
+        GlobalIsNeeded(&F);
+  }
+
+  for (GlobalVariable &GV : M.globals()) {
+    Changed |= RemoveUnusedGlobalValue(GV);
+    // Externally visible & appending globals are needed, if they have an
+    // initializer.
+    if (!GV.isDeclaration() && !GV.hasAvailableExternallyLinkage())
+      if (!GV.isDiscardableIfUnused())
+        GlobalIsNeeded(&GV);
+  }
+
+  for (GlobalAlias &GA : M.aliases()) {
+    Changed |= RemoveUnusedGlobalValue(GA);
+    // Externally visible aliases are needed.
+    if (!GA.isDiscardableIfUnused())
+      GlobalIsNeeded(&GA);
+  }
+
+  // Now that all globals which are needed are in the AliveGlobals set, we loop
+  // through the program, deleting those which are not alive.
+  //
+
+  // The first pass is to drop initializers of global variables which are dead.
+  std::vector<GlobalVariable *> DeadGlobalVars; // Keep track of dead globals
+  for (GlobalVariable &GV : M.globals())
+    if (!AliveGlobals.count(&GV)) {
+      DeadGlobalVars.push_back(&GV);         // Keep track of dead globals
+      if (GV.hasInitializer()) {
+        Constant *Init = GV.getInitializer();
+        GV.setInitializer(nullptr);
+        if (isSafeToDestroyConstant(Init))
+          Init->destroyConstant();
+      }
+    }
+
+  // The second pass drops the bodies of functions which are dead...
+  std::vector<Function *> DeadFunctions;
+  for (Function &F : M)
+    if (!AliveGlobals.count(&F)) {
+      DeadFunctions.push_back(&F);         // Keep track of dead globals
+      if (!F.isDeclaration())
+        F.deleteBody();
+    }
+
+  // The third pass drops targets of aliases which are dead...
+  std::vector<GlobalAlias*> DeadAliases;
+  for (GlobalAlias &GA : M.aliases())
+    if (!AliveGlobals.count(&GA)) {
+      DeadAliases.push_back(&GA);
+      GA.setAliasee(nullptr);
+    }
+
+  if (!DeadFunctions.empty()) {
+    // Now that all interferences have been dropped, delete the actual objects
+    // themselves.
+    for (Function *F : DeadFunctions) {
+      RemoveUnusedGlobalValue(*F);
+      M.getFunctionList().erase(F);
+    }
+    NumFunctions += DeadFunctions.size();
+    Changed = true;
+  }
+
+  if (!DeadGlobalVars.empty()) {
+    for (GlobalVariable *GV : DeadGlobalVars) {
+      RemoveUnusedGlobalValue(*GV);
+      M.getGlobalList().erase(GV);
+    }
+    NumVariables += DeadGlobalVars.size();
+    Changed = true;
+  }
+
+  // Now delete any dead aliases.
+  if (!DeadAliases.empty()) {
+    for (GlobalAlias *GA : DeadAliases) {
+      RemoveUnusedGlobalValue(*GA);
+      M.getAliasList().erase(GA);
+    }
+    NumAliases += DeadAliases.size();
+    Changed = true;
+  }
+
+  // Make sure that all memory is released
+  AliveGlobals.clear();
+  SeenConstants.clear();
+  ComdatMembers.clear();
+
+  return Changed;
+}
+
+/// GlobalIsNeeded - the specific global value as needed, and
+/// recursively mark anything that it uses as also needed.
+void GlobalDCE::GlobalIsNeeded(GlobalValue *G) {
+  // If the global is already in the set, no need to reprocess it.
+  if (!AliveGlobals.insert(G).second)
+    return;
+
+  if (Comdat *C = G->getComdat()) {
+    for (auto &&CM : make_range(ComdatMembers.equal_range(C)))
+      GlobalIsNeeded(CM.second);
+  }
+
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G)) {
+    // If this is a global variable, we must make sure to add any global values
+    // referenced by the initializer to the alive set.
+    if (GV->hasInitializer())
+      MarkUsedGlobalsAsNeeded(GV->getInitializer());
+  } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(G)) {
+    // The target of a global alias is needed.
+    MarkUsedGlobalsAsNeeded(GA->getAliasee());
+  } else {
+    // Otherwise this must be a function object.  We have to scan the body of
+    // the function looking for constants and global values which are used as
+    // operands.  Any operands of these types must be processed to ensure that
+    // any globals used will be marked as needed.
+    Function *F = cast<Function>(G);
+
+    for (Use &U : F->operands())
+      MarkUsedGlobalsAsNeeded(cast<Constant>(U.get()));
+
+    for (BasicBlock &BB : *F)
+      for (Instruction &I : BB)
+        for (Use &U : I.operands())
+          if (GlobalValue *GV = dyn_cast<GlobalValue>(U))
+            GlobalIsNeeded(GV);
+          else if (Constant *C = dyn_cast<Constant>(U))
+            MarkUsedGlobalsAsNeeded(C);
+  }
+}
+
+void GlobalDCE::MarkUsedGlobalsAsNeeded(Constant *C) {
+  if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
+    return GlobalIsNeeded(GV);
+
+  // Loop over all of the operands of the constant, adding any globals they
+  // use to the list of needed globals.
+  for (Use &U : C->operands()) {
+    // If we've already processed this constant there's no need to do it again.
+    Constant *Op = dyn_cast<Constant>(U);
+    if (Op && SeenConstants.insert(Op).second)
+      MarkUsedGlobalsAsNeeded(Op);
+  }
+}
+
+// RemoveUnusedGlobalValue - Loop over all of the uses of the specified
+// GlobalValue, looking for the constant pointer ref that may be pointing to it.
+// If found, check to see if the constant pointer ref is safe to destroy, and if
+// so, nuke it.  This will reduce the reference count on the global value, which
+// might make it deader.
+//
+bool GlobalDCE::RemoveUnusedGlobalValue(GlobalValue &GV) {
+  if (GV.use_empty())
+    return false;
+  GV.removeDeadConstantUsers();
+  return GV.use_empty();
+}