X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTransforms%2FIPO%2FStripSymbols.cpp;h=e459a634dcff19ebc8d0e254a6bb6b30e6ea09e0;hp=f2b561da80a6743b856f0c1261378d4c76edf560;hb=32e192aeb3884d41dca7fe0b0bb2169da6169208;hpb=460f656475738d1a95a6be95346908ce1597df25

diff --git a/lib/Transforms/IPO/StripSymbols.cpp b/lib/Transforms/IPO/StripSymbols.cpp
index f2b561da80a..e459a634dcf 100644
--- a/lib/Transforms/IPO/StripSymbols.cpp
+++ b/lib/Transforms/IPO/StripSymbols.cpp
@@ -9,7 +9,7 @@
 //
 // The StripSymbols transformation implements code stripping. Specifically, it
 // can delete:
-// 
+//
 //   * names for virtual registers
 //   * symbols for internal globals and functions
 //   * debug information
@@ -21,105 +21,132 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/IPO.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Instructions.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Module.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DebugInfo.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/TypeFinder.h"
+#include "llvm/IR/ValueSymbolTable.h"
 #include "llvm/Pass.h"
-#include "llvm/Analysis/DebugInfo.h"
-#include "llvm/ValueSymbolTable.h"
-#include "llvm/TypeSymbolTable.h"
 #include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/ADT/SmallPtrSet.h"
 using namespace llvm;
 
 namespace {
-  class VISIBILITY_HIDDEN StripSymbols : public ModulePass {
+  class StripSymbols : public ModulePass {
     bool OnlyDebugInfo;
   public:
     static char ID; // Pass identification, replacement for typeid
-    explicit StripSymbols(bool ODI = false) 
-      : ModulePass(&ID), OnlyDebugInfo(ODI) {}
+    explicit StripSymbols(bool ODI = false)
+      : ModulePass(ID), OnlyDebugInfo(ODI) {
+        initializeStripSymbolsPass(*PassRegistry::getPassRegistry());
+      }
 
-    virtual bool runOnModule(Module &M);
+    bool runOnModule(Module &M) override;
 
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
       AU.setPreservesAll();
     }
   };
 
-  class VISIBILITY_HIDDEN StripNonDebugSymbols : public ModulePass {
+  class StripNonDebugSymbols : public ModulePass {
   public:
     static char ID; // Pass identification, replacement for typeid
     explicit StripNonDebugSymbols()
-      : ModulePass(&ID) {}
+      : ModulePass(ID) {
+        initializeStripNonDebugSymbolsPass(*PassRegistry::getPassRegistry());
+      }
 
-    virtual bool runOnModule(Module &M);
+    bool runOnModule(Module &M) override;
 
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
       AU.setPreservesAll();
     }
   };
 
-  class VISIBILITY_HIDDEN StripDebugDeclare : public ModulePass {
+  class StripDebugDeclare : public ModulePass {
   public:
     static char ID; // Pass identification, replacement for typeid
     explicit StripDebugDeclare()
-      : ModulePass(&ID) {}
+      : ModulePass(ID) {
+        initializeStripDebugDeclarePass(*PassRegistry::getPassRegistry());
+      }
+
+    bool runOnModule(Module &M) override;
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.setPreservesAll();
+    }
+  };
+
+  class StripDeadDebugInfo : public ModulePass {
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    explicit StripDeadDebugInfo()
+      : ModulePass(ID) {
+        initializeStripDeadDebugInfoPass(*PassRegistry::getPassRegistry());
+      }
 
-    virtual bool runOnModule(Module &M);
+    bool runOnModule(Module &M) override;
 
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
       AU.setPreservesAll();
     }
   };
 }
 
 char StripSymbols::ID = 0;
-static RegisterPass<StripSymbols>
-X("strip", "Strip all symbols from a module");
+INITIALIZE_PASS(StripSymbols, "strip",
+                "Strip all symbols from a module", false, false)
 
 ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
   return new StripSymbols(OnlyDebugInfo);
 }
 
 char StripNonDebugSymbols::ID = 0;
-static RegisterPass<StripNonDebugSymbols>
-Y("strip-nondebug", "Strip all symbols, except dbg symbols, from a module");
+INITIALIZE_PASS(StripNonDebugSymbols, "strip-nondebug",
+                "Strip all symbols, except dbg symbols, from a module",
+                false, false)
 
 ModulePass *llvm::createStripNonDebugSymbolsPass() {
   return new StripNonDebugSymbols();
 }
 
 char StripDebugDeclare::ID = 0;
-static RegisterPass<StripDebugDeclare>
-Z("strip-debug-declare", "Strip all llvm.dbg.declare intrinsics");
+INITIALIZE_PASS(StripDebugDeclare, "strip-debug-declare",
+                "Strip all llvm.dbg.declare intrinsics", false, false)
 
 ModulePass *llvm::createStripDebugDeclarePass() {
   return new StripDebugDeclare();
 }
 
+char StripDeadDebugInfo::ID = 0;
+INITIALIZE_PASS(StripDeadDebugInfo, "strip-dead-debug-info",
+                "Strip debug info for unused symbols", false, false)
+
+ModulePass *llvm::createStripDeadDebugInfoPass() {
+  return new StripDeadDebugInfo();
+}
+
 /// OnlyUsedBy - Return true if V is only used by Usr.
 static bool OnlyUsedBy(Value *V, Value *Usr) {
-  for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
-    User *U = *I;
+  for (User *U : V->users())
     if (U != Usr)
       return false;
-  }
+
   return true;
 }
 
 static void RemoveDeadConstant(Constant *C) {
   assert(C->use_empty() && "Constant is not dead!");
-  SmallPtrSet<Constant *, 4> Operands;
+  SmallPtrSet<Constant*, 4> Operands;
   for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
-    if (isa<DerivedType>(C->getOperand(i)->getType()) &&
-        OnlyUsedBy(C->getOperand(i), C)) 
-      Operands.insert(C->getOperand(i));
+    if (OnlyUsedBy(C->getOperand(i), C))
+      Operands.insert(cast<Constant>(C->getOperand(i)));
   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
-    if (!GV->hasLocalLinkage()) return;   // Don't delete non static globals.
+    if (!GV->hasLocalLinkage()) return;   // Don't delete non-static globals.
     GV->eraseFromParent();
   }
   else if (!isa<Function>(C))
@@ -127,9 +154,8 @@ static void RemoveDeadConstant(Constant *C) {
       C->destroyConstant();
 
   // If the constant referenced anything, see if we can delete it as well.
-  for (SmallPtrSet<Constant *, 4>::iterator OI = Operands.begin(),
-         OE = Operands.end(); OI != OE; ++OI)
-    RemoveDeadConstant(*OI);
+  for (Constant *O : Operands)
+    RemoveDeadConstant(O);
 }
 
 // Strip the symbol table of its names.
@@ -146,33 +172,38 @@ static void StripSymtab(ValueSymbolTable &ST, bool PreserveDbgInfo) {
   }
 }
 
-// Strip the symbol table of its names.
-static void StripTypeSymtab(TypeSymbolTable &ST, bool PreserveDbgInfo) {
-  for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; ) {
-    if (PreserveDbgInfo && strncmp(TI->first.c_str(), "llvm.dbg", 8) == 0)
-      ++TI;
-    else
-      ST.remove(TI++);
+// Strip any named types of their names.
+static void StripTypeNames(Module &M, bool PreserveDbgInfo) {
+  TypeFinder StructTypes;
+  StructTypes.run(M, false);
+
+  for (unsigned i = 0, e = StructTypes.size(); i != e; ++i) {
+    StructType *STy = StructTypes[i];
+    if (STy->isLiteral() || STy->getName().empty()) continue;
+
+    if (PreserveDbgInfo && STy->getName().startswith("llvm.dbg"))
+      continue;
+
+    STy->setName("");
   }
 }
 
 /// Find values that are marked as llvm.used.
 static void findUsedValues(GlobalVariable *LLVMUsed,
-                           SmallPtrSet<const GlobalValue*, 8> &UsedValues) {
-  if (LLVMUsed == 0) return;
+                           SmallPtrSetImpl<const GlobalValue*> &UsedValues) {
+  if (!LLVMUsed) return;
   UsedValues.insert(LLVMUsed);
-  
-  ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
-  if (Inits == 0) return;
-  
+
+  ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
+
   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
-    if (GlobalValue *GV = 
+    if (GlobalValue *GV =
           dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
       UsedValues.insert(GV);
 }
 
 /// StripSymbolNames - Strip symbol names.
-bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {
+static bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {
 
   SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
   findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues);
@@ -184,187 +215,17 @@ bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {
       if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
         I->setName("");     // Internal symbols can't participate in linkage
   }
-  
+
   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
     if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
       if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
         I->setName("");     // Internal symbols can't participate in linkage
     StripSymtab(I->getValueSymbolTable(), PreserveDbgInfo);
   }
-  
-  // Remove all names from types.
-  StripTypeSymtab(M.getTypeSymbolTable(), PreserveDbgInfo);
 
-  return true;
-}
-
-// StripDebugInfo - Strip debug info in the module if it exists.  
-// To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and 
-// llvm.dbg.region.end calls, and any globals they point to if now dead.
-bool StripDebugInfo(Module &M) {
-
-  SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
-  findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues);
-  findUsedValues(M.getGlobalVariable("llvm.compiler.used"), llvmUsedValues);
-
-  SmallVector<GlobalVariable *, 2> CUs;
-  SmallVector<GlobalVariable *, 4> GVs;
-  SmallVector<GlobalVariable *, 4> SPs;
-  CollectDebugInfoAnchors(M, CUs, GVs, SPs);
-  // These anchors use LinkOnce linkage so that the optimizer does not
-  // remove them accidently. Set InternalLinkage for all these debug
-  // info anchors.
-  for (SmallVector<GlobalVariable *, 2>::iterator I = CUs.begin(),
-         E = CUs.end(); I != E; ++I)
-    (*I)->setLinkage(GlobalValue::InternalLinkage);
-  for (SmallVector<GlobalVariable *, 4>::iterator I = GVs.begin(),
-         E = GVs.end(); I != E; ++I)
-    (*I)->setLinkage(GlobalValue::InternalLinkage);
-  for (SmallVector<GlobalVariable *, 4>::iterator I = SPs.begin(),
-         E = SPs.end(); I != E; ++I)
-    (*I)->setLinkage(GlobalValue::InternalLinkage);
-
-
- // Delete all dbg variables.
-  for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 
-       I != E; ++I) {
-    GlobalVariable *GV = dyn_cast<GlobalVariable>(I);
-    if (!GV) continue;
-    if (!GV->use_empty() && llvmUsedValues.count(I) == 0) {
-      if (GV->getName().startswith("llvm.dbg")) {
-        GV->replaceAllUsesWith(M.getContext().getUndef(GV->getType()));
-      }
-    }
-  }
-
-  Function *FuncStart = M.getFunction("llvm.dbg.func.start");
-  Function *StopPoint = M.getFunction("llvm.dbg.stoppoint");
-  Function *RegionStart = M.getFunction("llvm.dbg.region.start");
-  Function *RegionEnd = M.getFunction("llvm.dbg.region.end");
-  Function *Declare = M.getFunction("llvm.dbg.declare");
-
-  std::vector<Constant*> DeadConstants;
-
-  // Remove all of the calls to the debugger intrinsics, and remove them from
-  // the module.
-  if (FuncStart) {
-    while (!FuncStart->use_empty()) {
-      CallInst *CI = cast<CallInst>(FuncStart->use_back());
-      Value *Arg = CI->getOperand(1);
-      assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
-      CI->eraseFromParent();
-      if (Arg->use_empty())
-        if (Constant *C = dyn_cast<Constant>(Arg)) 
-          DeadConstants.push_back(C);
-    }
-    FuncStart->eraseFromParent();
-  }
-  if (StopPoint) {
-    while (!StopPoint->use_empty()) {
-      CallInst *CI = cast<CallInst>(StopPoint->use_back());
-      Value *Arg = CI->getOperand(3);
-      assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
-      CI->eraseFromParent();
-      if (Arg->use_empty())
-        if (Constant *C = dyn_cast<Constant>(Arg)) 
-          DeadConstants.push_back(C);
-    }
-    StopPoint->eraseFromParent();
-  }
-  if (RegionStart) {
-    while (!RegionStart->use_empty()) {
-      CallInst *CI = cast<CallInst>(RegionStart->use_back());
-      Value *Arg = CI->getOperand(1);
-      assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
-      CI->eraseFromParent();
-      if (Arg->use_empty())
-        if (Constant *C = dyn_cast<Constant>(Arg)) 
-          DeadConstants.push_back(C);
-    }
-    RegionStart->eraseFromParent();
-  }
-  if (RegionEnd) {
-    while (!RegionEnd->use_empty()) {
-      CallInst *CI = cast<CallInst>(RegionEnd->use_back());
-      Value *Arg = CI->getOperand(1);
-      assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
-      CI->eraseFromParent();
-      if (Arg->use_empty())
-        if (Constant *C = dyn_cast<Constant>(Arg)) 
-          DeadConstants.push_back(C);
-    }
-    RegionEnd->eraseFromParent();
-  }
-  if (Declare) {
-    while (!Declare->use_empty()) {
-      CallInst *CI = cast<CallInst>(Declare->use_back());
-      Value *Arg1 = CI->getOperand(1);
-      Value *Arg2 = CI->getOperand(2);
-      assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
-      CI->eraseFromParent();
-      if (Arg1->use_empty()) {
-        if (Constant *C = dyn_cast<Constant>(Arg1)) 
-          DeadConstants.push_back(C);
-        else 
-          RecursivelyDeleteTriviallyDeadInstructions(Arg1);
-      }
-      if (Arg2->use_empty())
-        if (Constant *C = dyn_cast<Constant>(Arg2)) 
-          DeadConstants.push_back(C);
-    }
-    Declare->eraseFromParent();
-  }
-
-  // llvm.dbg.compile_units and llvm.dbg.subprograms are marked as linkonce
-  // but since we are removing all debug information, make them internal now.
-  // FIXME: Use private linkage maybe?
-  if (Constant *C = M.getNamedGlobal("llvm.dbg.compile_units"))
-    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
-      GV->setLinkage(GlobalValue::InternalLinkage);
-
-  if (Constant *C = M.getNamedGlobal("llvm.dbg.subprograms"))
-    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
-      GV->setLinkage(GlobalValue::InternalLinkage);
- 
-  if (Constant *C = M.getNamedGlobal("llvm.dbg.global_variables"))
-    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
-      GV->setLinkage(GlobalValue::InternalLinkage);
-
-  // Delete all dbg variables.
-  for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 
-       I != E; ++I) {
-    GlobalVariable *GV = dyn_cast<GlobalVariable>(I);
-    if (!GV) continue;
-    if (GV->use_empty() && llvmUsedValues.count(I) == 0
-        && (!GV->hasSection() 
-            || strcmp(GV->getSection().c_str(), "llvm.metadata") == 0))
-      DeadConstants.push_back(GV);
-  }
-
-  if (DeadConstants.empty())
-    return false;
-
-  // Delete any internal globals that were only used by the debugger intrinsics.
-  while (!DeadConstants.empty()) {
-    Constant *C = DeadConstants.back();
-    DeadConstants.pop_back();
-    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
-      if (GV->hasLocalLinkage())
-        RemoveDeadConstant(GV);
-    }
-    else
-      RemoveDeadConstant(C);
-  }
+  // Remove all names from types.
+  StripTypeNames(M, PreserveDbgInfo);
 
-  // Remove all llvm.dbg types.
-  TypeSymbolTable &ST = M.getTypeSymbolTable();
-  for (TypeSymbolTable::iterator TI = ST.begin(), TE = ST.end(); TI != TE; ) {
-    if (!strncmp(TI->first.c_str(), "llvm.dbg.", 9))
-      ST.remove(TI++);
-    else 
-      ++TI;
-  }
-  
   return true;
 }
 
@@ -387,43 +248,136 @@ bool StripDebugDeclare::runOnModule(Module &M) {
 
   if (Declare) {
     while (!Declare->use_empty()) {
-      CallInst *CI = cast<CallInst>(Declare->use_back());
-      Value *Arg1 = CI->getOperand(1);
-      Value *Arg2 = CI->getOperand(2);
+      CallInst *CI = cast<CallInst>(Declare->user_back());
+      Value *Arg1 = CI->getArgOperand(0);
+      Value *Arg2 = CI->getArgOperand(1);
       assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
       CI->eraseFromParent();
       if (Arg1->use_empty()) {
-        if (Constant *C = dyn_cast<Constant>(Arg1)) 
+        if (Constant *C = dyn_cast<Constant>(Arg1))
           DeadConstants.push_back(C);
-        else 
+        else
           RecursivelyDeleteTriviallyDeadInstructions(Arg1);
       }
       if (Arg2->use_empty())
-        if (Constant *C = dyn_cast<Constant>(Arg2)) 
+        if (Constant *C = dyn_cast<Constant>(Arg2))
           DeadConstants.push_back(C);
     }
     Declare->eraseFromParent();
   }
 
-  // Delete all llvm.dbg.global_variables.
-  for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 
-       I != E; ++I) {
-    GlobalVariable *GV = dyn_cast<GlobalVariable>(I);
-    if (!GV) continue;
-    if (GV->use_empty() && GV->getName().startswith("llvm.dbg.global_variable"))
-      DeadConstants.push_back(GV);
-  }
-
   while (!DeadConstants.empty()) {
     Constant *C = DeadConstants.back();
     DeadConstants.pop_back();
     if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
       if (GV->hasLocalLinkage())
         RemoveDeadConstant(GV);
-    }
-    else
+    } else
       RemoveDeadConstant(C);
   }
 
   return true;
 }
+
+/// Remove any debug info for global variables/functions in the given module for
+/// which said global variable/function no longer exists (i.e. is null).
+///
+/// Debugging information is encoded in llvm IR using metadata. This is designed
+/// such a way that debug info for symbols preserved even if symbols are
+/// optimized away by the optimizer. This special pass removes debug info for
+/// such symbols.
+bool StripDeadDebugInfo::runOnModule(Module &M) {
+  bool Changed = false;
+
+  LLVMContext &C = M.getContext();
+
+  // Find all debug info in F. This is actually overkill in terms of what we
+  // want to do, but we want to try and be as resilient as possible in the face
+  // of potential debug info changes by using the formal interfaces given to us
+  // as much as possible.
+  DebugInfoFinder F;
+  F.processModule(M);
+
+  // For each compile unit, find the live set of global variables/functions and
+  // replace the current list of potentially dead global variables/functions
+  // with the live list.
+  SmallVector<Value *, 64> LiveGlobalVariables;
+  SmallVector<Value *, 64> LiveSubprograms;
+  DenseSet<const MDNode *> VisitedSet;
+
+  for (DICompileUnit DIC : F.compile_units()) {
+    assert(DIC.Verify() && "DIC must verify as a DICompileUnit.");
+
+    // Create our live subprogram list.
+    DIArray SPs = DIC.getSubprograms();
+    bool SubprogramChange = false;
+    for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
+      DISubprogram DISP(SPs.getElement(i));
+      assert(DISP.Verify() && "DISP must verify as a DISubprogram.");
+
+      // Make sure we visit each subprogram only once.
+      if (!VisitedSet.insert(DISP).second)
+        continue;
+
+      // If the function referenced by DISP is not null, the function is live.
+      if (DISP.getFunction())
+        LiveSubprograms.push_back(DISP);
+      else
+        SubprogramChange = true;
+    }
+
+    // Create our live global variable list.
+    DIArray GVs = DIC.getGlobalVariables();
+    bool GlobalVariableChange = false;
+    for (unsigned i = 0, e = GVs.getNumElements(); i != e; ++i) {
+      DIGlobalVariable DIG(GVs.getElement(i));
+      assert(DIG.Verify() && "DIG must verify as DIGlobalVariable.");
+
+      // Make sure we only visit each global variable only once.
+      if (!VisitedSet.insert(DIG).second)
+        continue;
+
+      // If the global variable referenced by DIG is not null, the global
+      // variable is live.
+      if (DIG.getGlobal())
+        LiveGlobalVariables.push_back(DIG);
+      else
+        GlobalVariableChange = true;
+    }
+
+    // If we found dead subprograms or global variables, replace the current
+    // subprogram list/global variable list with our new live subprogram/global
+    // variable list.
+    if (SubprogramChange) {
+      // Make sure that 9 is still the index of the subprograms. This is to make
+      // sure that an assert is hit if the location of the subprogram array
+      // changes. This is just to make sure that this is updated if such an
+      // event occurs.
+      assert(DIC->getNumOperands() >= 10 &&
+             SPs == DIC->getOperand(9) &&
+             "DICompileUnits is expected to store Subprograms in operand "
+             "9.");
+      DIC->replaceOperandWith(9, MDNode::get(C, LiveSubprograms));
+      Changed = true;
+    }
+
+    if (GlobalVariableChange) {
+      // Make sure that 10 is still the index of global variables. This is to
+      // make sure that an assert is hit if the location of the subprogram array
+      // changes. This is just to make sure that this index is updated if such
+      // an event occurs.
+      assert(DIC->getNumOperands() >= 11 &&
+             GVs == DIC->getOperand(10) &&
+             "DICompileUnits is expected to store Global Variables in operand "
+             "10.");
+      DIC->replaceOperandWith(10, MDNode::get(C, LiveGlobalVariables));
+      Changed = true;
+    }
+
+    // Reset lists for the next iteration.
+    LiveSubprograms.clear();
+    LiveGlobalVariables.clear();
+  }
+
+  return Changed;
+}