[asan] Make ASan compatible with linker dead stripping on Linux.

[eugenis]

Summary

See this issue for more context:
https://github.com/google/sanitizers/issues/260

Instead of putting all global variable descriptions in one large
chunk, we emit one descriptor global for each original global. This
is more linker-gc friendly, as now individual globals can be
discarded along with their descriptors when unused.

The address of the descriptor section is obtained in the module
constructor and passed to the global registration function as an
argument. Similarly to MachO, we use a per-DSO registration flag. We
use the new SHT_ASSOCIATED section flag to link the global and its
descriptor together for linker GC.

[pcc]

The InstrumentGlobals function is now basically four functions in one at this point. I'm wondering whether this code could be made more readable if we split each target object format into its own function.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

1835

@rnk Can you remind me why this is not an issue for COFF?

test/Instrumentation/AddressSanitizer/global_metadata.ll

23

Don't you want to check the content of this global? And what about the global metadata for @.str?

[rnk]

In D28498#642272, @pcc wrote:

The InstrumentGlobals function is now basically four functions in one at this point. I'm wondering whether this code could be made more readable if we split each target object format into its own function.

I think I agree. We can extract any common code into helpers.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

1835

In COFF, comdats are not really groups with a string. It's more like, you have N separate comdat sections, one is the "leader", everyone points at the leader by referring to its symbol, and the leader may have static linkage. Basically, because the comdat key is a real symbol with linkage from an object file and not some globally unique string, this isn't a problem.

Also, I thought the point of the LLD change was so that we wouldn't have to do this? I thought the plan was to change our object emission to create a section group without a comdat key.

1841

!ELFUniqueModuleId.empty() maybe?

[eugenis]

Split implementation in one function per target binary format / global instrumentation kind.

[eugenis]

Since the fate of this change is yet unclear, I've moved the valuable refactoring to https://reviews.llvm.org/D28589.

[eugenis]

use SHT_ASSOCIATED

[pcc]

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

228

Should this be testing a new flag on GlobalObject, rather than the section name?

Also, do we need to teach globaldce about this?

[mehdi_amini]

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

228

MachO version is using llvm.compiler.used to avoid having to teach GlobalDCE and other part of LLVM about a special section semantics.

[eugenis]

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

228

Yeah, we could that, at a minimum.

But this code is definitely wrong: we don't want the new flag to be added on .S -> .o transform, unless explicitly given in the assembly.

[eugenis]

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

228

I'm not sure why I said that. This code has nothing to do with .S -> .o path.

llvm.compiler.used added.

I'm not convinced we need a whole IR thing (the global flag) for this tiny feature. Maybe e wait until there is more than one user?

[eugenis]

Added a new metadata, !associated, to mark asan globals.

[pcc]

test/Instrumentation/AddressSanitizer/global_metadata.ll

23

Looks like this hasn't been addressed.

[eugenis]

+ globaldce support for !associated

[eugenis]

Moved the new metadata implementation to https://reviews.llvm.org/D29104

[eugenis]

I've re-uploaded this as
https://reviews.llvm.org/D29104
https://reviews.llvm.org/D30120
https://reviews.llvm.org/D30121

docs/LangRef.rst

.. code-block:: llvm
    !0 = !{!"magic ptr"}
    !1 = !{!"other ptr"}
 
 '``type``' Metadata
 ^^^^^^^^^^^^^^^^^^^
 
 See :doc:`TypeMetadata`.
 
+'``associated``' Metadata
+^^^^^^^^^^^^^^^^^^^
+
+The ``associated`` metadata may be attached to a global variable
+declaration. It's only effect is adding SHT_ASSOCIATED flag on the
+corresponding section in the ELF targets.
 
 Module Flags Metadata
 =====================
 
 Information about the module as a whole is difficult to convey to LLVM's
 subsystems. The LLVM IR isn't sufficient to transmit this information.
 The ``llvm.module.flags`` named metadata exists in order to facilitate
 this. These flags are in the form of key / value pairs --- much like a

include/llvm/IR/LLVMContext.h

enum {
     MD_make_implicit = 14,            // "make.implicit"
     MD_unpredictable = 15,            // "unpredictable"
     MD_invariant_group = 16,          // "invariant.group"
     MD_align = 17,                    // "align"
     MD_loop = 18,                     // "llvm.loop"
     MD_type = 19,                     // "type"
     MD_section_prefix = 20,           // "section_prefix"
     MD_absolute_symbol = 21,          // "absolute_symbol"
+    MD_associated = 22,               // "associated"
   };
 
   /// Known operand bundle tag IDs, which always have the same value.  All
   /// operand bundle tags that LLVM has special knowledge of are listed here.
   /// Additionally, this scheme allows LLVM to efficiently check for specific
   /// operand bundle tags without comparing strings.
   enum {
     OB_deopt = 0,         // "deopt"

include/llvm/Transforms/IPO/GlobalDCE.h

 public:
   PreservedAnalyses run(Module &M, ModuleAnalysisManager &);
 
 private:
   SmallPtrSet<GlobalValue*, 32> AliveGlobals;
   SmallPtrSet<Constant *, 8> SeenConstants;
   std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
 
+  // Maps global to a set of !associated globals that depend on it.
+  std::unordered_multimap<GlobalValue *, GlobalValue *> AssociatedGlobals;
+
   /// 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);
+  void AddAssociatedGlobal(GlobalVariable *AG);
 };
 
 }
 
 #endif // LLVM_TRANSFORMS_IPO_GLOBALDCE_H

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
   Kind = getELFKindForNamedSection(SectionName, Kind);
 
   StringRef Group = "";
   unsigned Flags = getELFSectionFlags(Kind);
   if (const Comdat *C = getELFComdat(GO)) {
     Group = C->getName();
     Flags |= ELF::SHF_GROUP;
   }
+
+  if (GO->getMetadata(LLVMContext::MD_associated))
+    Flags |= ELF::SHF_ASSOCIATED;
+
   return getContext().getELFSection(SectionName,
                                     getELFSectionType(SectionName, Kind), Flags,
                                     /*EntrySize=*/0, Group);
 }
 
 /// Return the section prefix name used by options FunctionsSections and
 /// DataSections.
 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {

lib/IR/LLVMContext.cpp

std::pair<unsigned, StringRef> MDKinds[] = {
     {MD_make_implicit, "make.implicit"},
     {MD_unpredictable, "unpredictable"},
     {MD_invariant_group, "invariant.group"},
     {MD_align, "align"},
     {MD_loop, "llvm.loop"},
     {MD_type, "type"},
     {MD_section_prefix, "section_prefix"},
     {MD_absolute_symbol, "absolute_symbol"},
+    {MD_associated, "associated"},
   };
 
   for (auto &MDKind : MDKinds) {
     unsigned ID = getMDKindID(MDKind.second);
     assert(ID == MDKind.first && "metadata kind id drifted");
     (void)ID;
   }
 

lib/Transforms/IPO/GlobalDCE.cpp

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));
 
+  for (GlobalVariable &GV : M.globals())
+    if (GV.getMetadata(LLVMContext::MD_associated))
+      AddAssociatedGlobal(&GV);
+
   // Loop over the module, adding globals which are obviously necessary.
   for (GlobalObject &GO : M.global_objects()) {
     Changed |= RemoveUnusedGlobalValue(GO);
     // Functions with external linkage are needed if they have a body.
     // Externally visible & appending globals are needed, if they have an
     // initializer.
     if (!GO.isDeclaration() && !GO.hasAvailableExternallyLinkage())
       if (!GO.isDiscardableIfUnused())
PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &) {
   NumIFuncs += DeadIFuncs.size();
   for (GlobalIFunc *GIF : DeadIFuncs)
     EraseUnusedGlobalValue(GIF);
 
   // Make sure that all memory is released
   AliveGlobals.clear();
   SeenConstants.clear();
   ComdatMembers.clear();
+  AssociatedGlobals.clear();
 
   if (Changed)
     return PreservedAnalyses::none();
   return PreservedAnalyses::all();
 }
 
 /// GlobalIsNeeded - the specific global value as needed, and
 /// recursively mark anything that it uses as also needed.
 void GlobalDCEPass::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);
   }
 
+  for (auto &&AG : make_range(AssociatedGlobals.equal_range(G)))
+    GlobalIsNeeded(AG.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 (GlobalIndirectSymbol *GIS = dyn_cast<GlobalIndirectSymbol>(G)) {
     // The target of a global alias or ifunc is needed.
     MarkUsedGlobalsAsNeeded(GIS->getIndirectSymbol());
for (BasicBlock &BB : *F)
         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 GlobalDCEPass::AddAssociatedGlobal(GlobalVariable *AG) {
+  SmallPtrSet<Constant *, 8> Seen;
+  SmallVector<Constant *, 8> WorkList;
+  WorkList.push_back(AG->getInitializer());
+
+  while (!WorkList.empty()) {
+    Constant *C = WorkList.pop_back_val();
+    if (GlobalValue *GV = dyn_cast<GlobalValue>(C)) {
+      AssociatedGlobals.insert(std::make_pair(GV, AG));
+      continue;
+    }
+
+    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 && Seen.insert(Op).second)
+        WorkList.push_back(Op);
+    }
+  }
+}
+
 void GlobalDCEPass::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.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

 // Details of the algorithm:
 //  http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/None.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Analysis/MemoryBuiltins.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"

 static const char *const kAsanReportErrorTemplate = "__asan_report_";
 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
 static const char *const kAsanUnregisterGlobalsName =
     "__asan_unregister_globals";
 static const char *const kAsanRegisterImageGlobalsName =
   "__asan_register_image_globals";
 static const char *const kAsanUnregisterImageGlobalsName =
   "__asan_unregister_image_globals";
+static const char *const kAsanRegisterElfGlobalsName =
+  "__asan_register_elf_globals";
+static const char *const kAsanUnregisterElfGlobalsName =
+  "__asan_unregister_elf_globals";
 static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
 static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
 static const char *const kAsanInitName = "__asan_init";
 static const char *const kAsanVersionCheckName =
     "__asan_version_mismatch_check_v8";
 static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp";
 static const char *const kAsanPtrSub = "__sanitizer_ptr_sub";
 static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
 static const int kMaxAsanStackMallocSizeClass = 10;
 static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_";
 static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_";
 static const char *const kAsanGenPrefix = "__asan_gen_";
 static const char *const kODRGenPrefix = "__odr_asan_gen_";
 static const char *const kSanCovGenPrefix = "__sancov_gen_";
 static const char *const kAsanSetShadowPrefix = "__asan_set_shadow_";
 static const char *const kAsanPoisonStackMemoryName =
     "__asan_poison_stack_memory";
 static const char *const kAsanUnpoisonStackMemoryName =
     "__asan_unpoison_stack_memory";
+
+// ASan version script has __asan_* wildcard. Triple underscore prevents
+// exporting of this _local_ symbol.
 static const char *const kAsanGlobalsRegisteredFlagName =
-    "__asan_globals_registered";
+    "___asan_globals_registered";
 
 static const char *const kAsanOptionDetectUseAfterReturn =
     "__asan_option_detect_stack_use_after_return";
 
 static const char *const kAsanShadowMemoryDynamicAddress =
     "__asan_shadow_memory_dynamic_address";
 
 static const char *const kAsanAllocaPoison = "__asan_alloca_poison";

 
 private:
   void initializeCallbacks(Module &M);
 
   bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
   void InstrumentGlobalsCOFF(IRBuilder<> &IRB, Module &M,
                              ArrayRef<GlobalVariable *> ExtendedGlobals,
                              ArrayRef<Constant *> MetadataInitializers);
+  void InstrumentGlobalsELF(IRBuilder<> &IRB, Module &M,
+                            ArrayRef<GlobalVariable *> ExtendedGlobals,
+                            ArrayRef<Constant *> MetadataInitializers);
   void InstrumentGlobalsMachO(IRBuilder<> &IRB, Module &M,
                               ArrayRef<GlobalVariable *> ExtendedGlobals,
                               ArrayRef<Constant *> MetadataInitializers);
   void
   InstrumentGlobalsWithMetadataArray(IRBuilder<> &IRB, Module &M,
                                      ArrayRef<GlobalVariable *> ExtendedGlobals,
                                      ArrayRef<Constant *> MetadataInitializers);
 
private:
   Triple TargetTriple;
   ShadowMapping Mapping;
   Function *AsanPoisonGlobals;
   Function *AsanUnpoisonGlobals;
   Function *AsanRegisterGlobals;
   Function *AsanUnregisterGlobals;
   Function *AsanRegisterImageGlobals;
   Function *AsanUnregisterImageGlobals;
+  Function *AsanRegisterElfGlobals;
+  Function *AsanUnregisterElfGlobals;
 };
 
 // Stack poisoning does not play well with exception handling.
 // When an exception is thrown, we essentially bypass the code
 // that unpoisones the stack. This is why the run-time library has
 // to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
 // stack in the interceptor. This however does not work inside the
 // actual function which catches the exception. Most likely because the
AsanRegisterImageGlobals =
       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
           kAsanRegisterImageGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
   AsanRegisterImageGlobals->setLinkage(Function::ExternalLinkage);
 
   AsanUnregisterImageGlobals =
       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
           kAsanUnregisterImageGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
   AsanUnregisterImageGlobals->setLinkage(Function::ExternalLinkage);
+
+  AsanRegisterElfGlobals = checkSanitizerInterfaceFunction(
+      M.getOrInsertFunction(kAsanRegisterElfGlobalsName, IRB.getVoidTy(),
+                            IntptrTy, IntptrTy, IntptrTy, nullptr));
+  AsanRegisterElfGlobals->setLinkage(Function::ExternalLinkage);
+
+  AsanUnregisterElfGlobals = checkSanitizerInterfaceFunction(
+      M.getOrInsertFunction(kAsanUnregisterElfGlobalsName, IRB.getVoidTy(),
+                            IntptrTy, IntptrTy, IntptrTy, nullptr));
+  AsanUnregisterElfGlobals->setLinkage(Function::ExternalLinkage);
 }
 
 // Put the metadata and the instrumented global in the same group. This ensures
 // that the metadata is discarded if the instrumented global is discarded.
 void AddressSanitizerModule::SetComdatForGlobalMetadata(
     GlobalVariable *G, GlobalVariable *Metadata) {
   Module &M = *G->getParent();
   Comdat *C = G->getComdat();
for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
     assert(isPowerOf2_32(SizeOfGlobalStruct) &&
            "global metadata will not be padded appropriately");
     Metadata->setAlignment(SizeOfGlobalStruct);
 
     SetComdatForGlobalMetadata(G, Metadata);
   }
 }
 
+void AddressSanitizerModule::InstrumentGlobalsELF(
+    IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
+    ArrayRef<Constant *> MetadataInitializers) {
+  assert(ExtendedGlobals.size() == MetadataInitializers.size());
+
+  SmallVector<GlobalValue *, 16> MetadataGlobals(ExtendedGlobals.size());
+  for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
+    GlobalVariable *Metadata = CreateMetadataGlobal(
+        M, MetadataInitializers[i], ExtendedGlobals[i]->getName());
+    MDNode *MD = MDNode::get(M.getContext(), None);
+    Metadata->setMetadata(LLVMContext::MD_associated, MD);
+    MetadataGlobals[i] = Metadata;
+  }
+
+  // Update llvm.compiler.used, adding the new metadata globals. This is
+  // needed so that during LTO these variables stay alive.
+  if (!MetadataGlobals.empty())
+    appendToCompilerUsed(M, MetadataGlobals);
+
+  // RegisteredFlag serves two purposes. First, we can pass it to dladdr()
+  // to look up the loaded image that contains it. Second, we can store in it
+  // whether registration has already occurred, to prevent duplicate
+  // registration.
+  //
+  // common linkage ensures that there is only one global per shared library.
+  GlobalVariable *RegisteredFlag = new GlobalVariable(
+      M, IntptrTy, false, GlobalVariable::CommonLinkage,
+      ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
+  RegisteredFlag->setVisibility(GlobalVariable::HiddenVisibility);
+
+  // Create start and stop symbols.
+  GlobalVariable *StartELFMetadata = new GlobalVariable(
+      M, IntptrTy, false, GlobalVariable::ExternalWeakLinkage, nullptr,
+      "__start_" + getGlobalMetadataSection());
+  StartELFMetadata->setVisibility(GlobalVariable::HiddenVisibility);
+  GlobalVariable *StopELFMetadata = new GlobalVariable(
+      M, IntptrTy, false, GlobalVariable::ExternalWeakLinkage, nullptr,
+      "__stop_" + getGlobalMetadataSection());
+  StopELFMetadata->setVisibility(GlobalVariable::HiddenVisibility);
+
+  // Create a call to register the globals with the runtime.
+  IRB.CreateCall(AsanRegisterElfGlobals,
+                 {IRB.CreatePointerCast(RegisteredFlag, IntptrTy),
+                  IRB.CreatePointerCast(StartELFMetadata, IntptrTy),
+                  IRB.CreatePointerCast(StopELFMetadata, IntptrTy)});
+
+  // We also need to unregister globals at the end, e.g., when a shared library
+  // gets closed.
+  IRBuilder<> IRB_Dtor = CreateAsanModuleDtor(M);
+  IRB_Dtor.CreateCall(AsanUnregisterElfGlobals,
+                      {IRB.CreatePointerCast(RegisteredFlag, IntptrTy),
+                       IRB.CreatePointerCast(StartELFMetadata, IntptrTy),
+                       IRB.CreatePointerCast(StopELFMetadata, IntptrTy)});
+}
+
 void AddressSanitizerModule::InstrumentGlobalsMachO(
     IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
     ArrayRef<Constant *> MetadataInitializers) {
   assert(ExtendedGlobals.size() == MetadataInitializers.size());
 
   // On recent Mach-O platforms, use a structure which binds the liveness of
   // the global variable to the metadata struct. Keep the list of "Liveness" GV
   // created to be added to llvm.compiler.used
bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
   }
 
   size_t n = GlobalsToChange.size();
   if (n == 0) return false;
 
   auto &DL = M.getDataLayout();
 
   // A global is described by a structure
   //   size_t beg;
   //   size_t size;
   //   size_t size_with_redzone;
   //   const char *name;
   //   const char *module_name;
   //   size_t has_dynamic_init;
   //   void *source_location;
   //   size_t odr_indicator;
   // We initialize an array of such structures and pass it to a run-time call.
   StructType *GlobalStructTy =
       StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
                       IntptrTy, IntptrTy, IntptrTy, nullptr);
   SmallVector<GlobalVariable *, 16> NewGlobals(n);
   SmallVector<Constant *, 16> Initializers(n);
 
for (size_t i = 0; i < n; i++) {
 
     DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
 
     Initializers[i] = Initializer;
   }
 
   if (TargetTriple.isOSBinFormatCOFF()) {
     InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
+  } else if (TargetTriple.isOSBinFormatELF()) {
+    InstrumentGlobalsELF(IRB, M, NewGlobals, Initializers);
   } else if (ShouldUseMachOGlobalsSection()) {
     InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
   } else {
     InstrumentGlobalsWithMetadataArray(IRB, M, NewGlobals, Initializers);
   }
 
   // Create calls for poisoning before initializers run and unpoisoning after.
   if (HasDynamicallyInitializedGlobals)

test/Instrumentation/AddressSanitizer/global_metadata.ll

 ; RUN: opt < %s -asan -asan-module -S | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 ; Globals:
 @global = global i32 0, align 4
 @dyn_init_global = global i32 0, align 4
 @blacklisted_global = global i32 0, align 4
 @_ZZ4funcvE10static_var = internal global i32 0, align 4
 @.str = private unnamed_addr constant [14 x i8] c"Hello, world!\00", align 1
 @llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_asan_globals.cpp, i8* null }]
 
 ; Check that globals were instrumented:
+
 ; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, align 32
 ; CHECK: @.str = internal unnamed_addr constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, align 32
 
 ; Check emitted location descriptions:
 ; CHECK: [[VARNAME:@__asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
 ; CHECK: [[FILENAME:@__asan_gen_.[0-9]+]] = private unnamed_addr constant [22 x i8] c"/tmp/asan-globals.cpp\00", align 1
 ; CHECK: [[LOCDESCR:@__asan_gen_.[0-9]+]] = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* [[FILENAME]], i32 5, i32 5 }
+; CHECK: @__asan_global_global = {{.*}}i64 ptrtoint ({ i32, [60 x i8] }* @global to i64){{.*}} section "asan_globals"{{.*}}, !associated
+; CHECK: @__asan_global_.str = {{.*}}i64 ptrtoint ({ [14 x i8], [50 x i8] }* @.str to i64){{.*}} section "asan_globals"{{.*}}, !associated
+
+; The metadata has to be inserted to llvm.compiler.used to avoid being stripped
+; during LTO.
+; CHECK: @llvm.compiler.used {{.*}} @__asan_global_global {{.*}} section "llvm.metadata"
 
 ; Check that location descriptors and global names were passed into __asan_register_globals:
-; CHECK: i64 ptrtoint ([7 x i8]* [[VARNAME]] to i64)
-; CHECK: i64 ptrtoint ({ [22 x i8]*, i32, i32 }* [[LOCDESCR]] to i64)
+; CHECK: call void @__asan_register_elf_globals(i64 ptrtoint (i64* @___asan_globals_registered to i64), i64 ptrtoint (i64* @__start_asan_globals to i64), i64 ptrtoint (i64* @__stop_asan_globals to i64))
 
 ; Function Attrs: nounwind sanitize_address
 define internal void @__cxx_global_var_init() #0 section ".text.startup" {
 entry:
   %0 = load i32, i32* @global, align 4
   store i32 %0, i32* @dyn_init_global, align 4
   ret void
 }

test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll

 ; Find the liveness binder for @global and its metadata:
 ; CHECK: @__asan_binder_global = internal global {{.*}} @global {{.*}} [[METADATA]] {{.*}} section "__DATA,__asan_liveness,regular,live_support"
 
 ; The binder has to be inserted to llvm.compiler.used to avoid being stripped
 ; during LTO.
 ; CHECK: @llvm.compiler.used {{.*}} @__asan_binder_global {{.*}} section "llvm.metadata"
 
 ; Test that there is the flag global variable:
-; CHECK: @__asan_globals_registered = common hidden global i64 0
+; CHECK: @___asan_globals_registered = common hidden global i64 0
 
 ; Test that __asan_register_image_globals is invoked from the constructor:
 ; CHECK-LABEL: define internal void @asan.module_ctor
 ; CHECK-NOT: ret
-; CHECK: call void @__asan_register_image_globals(i64 ptrtoint (i64* @__asan_globals_registered to i64))
+; CHECK: call void @__asan_register_image_globals(i64 ptrtoint (i64* @___asan_globals_registered to i64))
 ; CHECK: ret
 
 ; Test that __asan_unregister_image_globals is invoked from the destructor:
 ; CHECK-LABEL: define internal void @asan.module_dtor
 ; CHECK-NOT: ret
-; CHECK: call void @__asan_unregister_image_globals(i64 ptrtoint (i64* @__asan_globals_registered to i64))
+; CHECK: call void @__asan_unregister_image_globals(i64 ptrtoint (i64* @___asan_globals_registered to i64))
 ; CHECK: ret

test/Instrumentation/AddressSanitizer/instrument_global.ll

 }
 
 
 !llvm.asan.globals = !{!0}
 !0 = !{[10 x i32]* @GlobDy, null, null, i1 true, i1 false}
 
 ; CHECK-LABEL: define internal void @asan.module_ctor
 ; CHECK-NOT: ret
-; CHECK: call void @__asan_register_globals
+; CHECK: call void @__asan_register_elf_globals
 ; CHECK: ret
 
 ; CHECK-LABEL: define internal void @asan.module_dtor
 ; CHECK-NOT: ret
-; CHECK: call void @__asan_unregister_globals
+; CHECK: call void @__asan_unregister_elf_globals
 ; CHECK: ret

test/ThinLTO/X86/lazyload_metadata.ll

 ; Do setup work for all below tests: generate bitcode and combined index
 ; RUN: opt -module-summary %s -o %t.bc -bitcode-mdindex-threshold=0
 ; RUN: opt -module-summary %p/Inputs/lazyload_metadata.ll -o %t2.bc -bitcode-mdindex-threshold=0
 ; RUN: llvm-lto -thinlto-action=thinlink -o %t3.bc %t.bc %t2.bc
 ; REQUIRES: asserts
 
 ; Check that importing @globalfunc1 does not trigger loading all the global
 ; metadata for @globalfunc2 and @globalfunc3
 
 ; RUN: llvm-lto -thinlto-action=import %t2.bc -thinlto-index=%t3.bc \
 ; RUN:          -o /dev/null -stats \
 ; RUN:  2>&1 | FileCheck %s -check-prefix=LAZY
-; LAZY: 49 bitcode-reader  - Number of Metadata records loaded
+; LAZY: 51 bitcode-reader  - Number of Metadata records loaded
 ; LAZY: 2 bitcode-reader  - Number of MDStrings loaded
 
 ; RUN: llvm-lto -thinlto-action=import %t2.bc -thinlto-index=%t3.bc \
 ; RUN:          -o /dev/null -disable-ondemand-mds-loading -stats \
 ; RUN:  2>&1 | FileCheck %s -check-prefix=NOTLAZY
-; NOTLAZY: 58 bitcode-reader  - Number of Metadata records loaded
+; NOTLAZY: 60 bitcode-reader  - Number of Metadata records loaded
 ; NOTLAZY: 7 bitcode-reader  - Number of MDStrings loaded
 
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.11.0"
 
 define void @globalfunc1(i32 %arg) {
   %x = call i1 @llvm.type.test(i8* undef, metadata !"typeid1")

 !1 = !{!2, !3, !4, !5, !6, !7, !8, !9}
 !2 = !{!"Hello World"}
 !3 = !{!"3"}
 !4 = !{!"4"}
 !5 = !{!"5"}
 !6 = !{!9}
 !7 = !{!"7"}
 !8 = !{!"8"}
-!9 = !{!6}
+!9 = !{!6}
 

test/Transforms/GlobalDCE/associated.ll

+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.A = type { i32, i32* }
+
+; CHECK: @x =
+@x = global i32 0, align 4
+
+; CHECK-NOT: @y0 =
+@y0 = internal global i32* @x, align 8
+; CHECK: @y1 =
+@y1 = internal global i32* @x, align 8, !associated !0
+
+; CHECK-NOT: @z0 =
+@z0 = internal global %struct.A { i32 5, i32* @x }, align 8
+; CHECK: @z1 =
+@z1 = internal global %struct.A { i32 5, i32* @x }, align 8, !associated !0
+
+; CHECK-NOT: @zz0 =
+@zz0 = internal global %struct.A* @z1, align 8
+; CHECK: @zz1 =
+@zz1 = internal global %struct.A* @z1, align 8, !associated !0
+
+!0 = !{}