Revert r298158.

Revert "[asan] Fix dead stripping of globals on Linux."

OOM in gold linker.

llvm-svn: 298288

3 files changed, 48 insertions, 136 deletions

diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
index c7e91cd07ca..ac62496e0fe 100644
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -28,11 +28,51 @@
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Transforms/IPO/FunctionAttrs.h"
 #include "llvm/Transforms/Utils/Cloning.h"
-#include "llvm/Transforms/Utils/ModuleUtils.h"
 using namespace llvm;
 
 namespace {
 
+// Produce a unique identifier for this module by taking the MD5 sum of the
+// names of the module's strong external symbols. This identifier is
+// normally guaranteed to be unique, or the program would fail to link due to
+// multiply defined symbols.
+//
+// If the module has no strong external symbols (such a module may still have a
+// semantic effect if it performs global initialization), we cannot produce a
+// unique identifier for this module, so we return the empty string, which
+// causes the entire module to be written as a regular LTO module.
+std::string getModuleId(Module *M) {
+  MD5 Md5;
+  bool ExportsSymbols = false;
+  auto AddGlobal = [&](GlobalValue &GV) {
+    if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
+        !GV.hasExternalLinkage())
+      return;
+    ExportsSymbols = true;
+    Md5.update(GV.getName());
+    Md5.update(ArrayRef<uint8_t>{0});
+  };
+
+  for (auto &F : *M)
+    AddGlobal(F);
+  for (auto &GV : M->globals())
+    AddGlobal(GV);
+  for (auto &GA : M->aliases())
+    AddGlobal(GA);
+  for (auto &IF : M->ifuncs())
+    AddGlobal(IF);
+
+  if (!ExportsSymbols)
+    return "";
+
+  MD5::MD5Result R;
+  Md5.final(R);
+
+  SmallString<32> Str;
+  MD5::stringifyResult(R, Str);
+  return ("$" + Str).str();
+}
+
 // Promote each local-linkage entity defined by ExportM and used by ImportM by
 // changing visibility and appending the given ModuleId.
 void promoteInternals(Module &ExportM, Module &ImportM, StringRef ModuleId) {
@@ -213,7 +253,7 @@ void forEachVirtualFunction(Constant *C, function_ref<void(Function *)> Fn) {
 void splitAndWriteThinLTOBitcode(
     raw_ostream &OS, function_ref<AAResults &(Function &)> AARGetter,
     Module &M) {
-  std::string ModuleId = getUniqueModuleId(&M);
+  std::string ModuleId = getModuleId(&M);
   if (ModuleId.empty()) {
     // We couldn't generate a module ID for this module, just write it out as a
     // regular LTO module.
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index c20ad6d5b94..afcf86547c7 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -101,10 +101,6 @@ 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";
@@ -124,11 +120,8 @@ 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 a
-// linker (gold) warning about attempting to export a 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";
@@ -619,10 +612,6 @@ private:
   void InstrumentGlobalsCOFF(IRBuilder<> &IRB, Module &M,
                              ArrayRef<GlobalVariable *> ExtendedGlobals,
                              ArrayRef<Constant *> MetadataInitializers);
-  void InstrumentGlobalsELF(IRBuilder<> &IRB, Module &M,
-                            ArrayRef<GlobalVariable *> ExtendedGlobals,
-                            ArrayRef<Constant *> MetadataInitializers,
-                            const std::string &UniqueModuleId);
   void InstrumentGlobalsMachO(IRBuilder<> &IRB, Module &M,
                               ArrayRef<GlobalVariable *> ExtendedGlobals,
                               ArrayRef<Constant *> MetadataInitializers);
@@ -633,8 +622,7 @@ private:
 
   GlobalVariable *CreateMetadataGlobal(Module &M, Constant *Initializer,
                                        StringRef OriginalName);
-  void SetComdatForGlobalMetadata(GlobalVariable *G, GlobalVariable *Metadata,
-                                  StringRef InternalSuffix);
+  void SetComdatForGlobalMetadata(GlobalVariable *G, GlobalVariable *Metadata);
   IRBuilder<> CreateAsanModuleDtor(Module &M);
 
   bool ShouldInstrumentGlobal(GlobalVariable *G);
@@ -659,8 +647,6 @@ private:
   Function *AsanUnregisterGlobals;
   Function *AsanRegisterImageGlobals;
   Function *AsanUnregisterImageGlobals;
-  Function *AsanRegisterElfGlobals;
-  Function *AsanUnregisterElfGlobals;
 };
 
 // Stack poisoning does not play well with exception handling.
@@ -1610,22 +1596,12 @@ void AddressSanitizerModule::initializeCallbacks(Module &M) {
       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, StringRef InternalSuffix) {
+    GlobalVariable *G, GlobalVariable *Metadata) {
   Module &M = *G->getParent();
   Comdat *C = G->getComdat();
   if (!C) {
@@ -1635,15 +1611,7 @@ void AddressSanitizerModule::SetComdatForGlobalMetadata(
       assert(G->hasLocalLinkage());
       G->setName(Twine(kAsanGenPrefix) + "_anon_global");
     }
-
-    if (!InternalSuffix.empty() && G->hasLocalLinkage()) {
-      std::string Name = G->getName();
-      Name += InternalSuffix;
-      C = M.getOrInsertComdat(Name);
-    } else {
-      C = M.getOrInsertComdat(G->getName());
-    }
-
+    C = M.getOrInsertComdat(G->getName());
     // Make this IMAGE_COMDAT_SELECT_NODUPLICATES on COFF.
     if (TargetTriple.isOSBinFormatCOFF())
       C->setSelectionKind(Comdat::NoDuplicates);
@@ -1698,67 +1666,8 @@ void AddressSanitizerModule::InstrumentGlobalsCOFF(
            "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,
-    const std::string &UniqueModuleId) {
-  assert(ExtendedGlobals.size() == MetadataInitializers.size());
-
-  SmallVector<GlobalValue *, 16> MetadataGlobals(ExtendedGlobals.size());
-  for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
-    GlobalVariable *G = ExtendedGlobals[i];
-    GlobalVariable *Metadata =
-        CreateMetadataGlobal(M, MetadataInitializers[i], G->getName());
-    MDNode *MD = MDNode::get(M.getContext(), ValueAsMetadata::get(G));
-    Metadata->setMetadata(LLVMContext::MD_associated, MD);
-    MetadataGlobals[i] = Metadata;
-
-    SetComdatForGlobalMetadata(G, Metadata, UniqueModuleId);
+    SetComdatForGlobalMetadata(G, 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(
@@ -2003,12 +1912,7 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
     Initializers[i] = Initializer;
   }
 
-  std::string ELFUniqueModuleId =
-      TargetTriple.isOSBinFormatELF() ? getUniqueModuleId(&M) : "";
-
-  if (!ELFUniqueModuleId.empty()) {
-    InstrumentGlobalsELF(IRB, M, NewGlobals, Initializers, ELFUniqueModuleId);
-  } else if (TargetTriple.isOSBinFormatCOFF()) {
+  if (TargetTriple.isOSBinFormatCOFF()) {
     InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
   } else if (ShouldUseMachOGlobalsSection()) {
     InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
diff --git a/llvm/lib/Transforms/Utils/ModuleUtils.cpp b/llvm/lib/Transforms/Utils/ModuleUtils.cpp
index 27b475392b6..a53da85f79f 100644
--- a/llvm/lib/Transforms/Utils/ModuleUtils.cpp
+++ b/llvm/lib/Transforms/Utils/ModuleUtils.cpp
@@ -229,35 +229,3 @@ void llvm::filterDeadComdatFunctions(
            ComdatEntriesCovered.end();
   });
 }
-
-std::string llvm::getUniqueModuleId(Module *M) {
-  MD5 Md5;
-  bool ExportsSymbols = false;
-  auto AddGlobal = [&](GlobalValue &GV) {
-    if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
-        !GV.hasExternalLinkage())
-      return;
-    ExportsSymbols = true;
-    Md5.update(GV.getName());
-    Md5.update(ArrayRef<uint8_t>{0});
-  };
-
-  for (auto &F : *M)
-    AddGlobal(F);
-  for (auto &GV : M->globals())
-    AddGlobal(GV);
-  for (auto &GA : M->aliases())
-    AddGlobal(GA);
-  for (auto &IF : M->ifuncs())
-    AddGlobal(IF);
-
-  if (!ExportsSymbols)
-    return "";
-
-  MD5::MD5Result R;
-  Md5.final(R);
-
-  SmallString<32> Str;
-  MD5::stringifyResult(R, Str);
-  return ("$" + Str).str();
-}