Revert #67745 "[asan] Ensure __asan_register_elf_globals is called in…

… COMDAT asan.module_ctor (#67745)"

This reverts commit 1a4b9b6.

When getUniqueModuleId(&M) is empty, we may add comdat to internal constants
like $.str, causing spurious `error: relocation refers to a symbol in a
discarded section` lld errors.

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -819,7 +819,7 @@ class ModuleAddressSanitizer {
 private:
   void initializeCallbacks(Module &M);
 
-  void InstrumentGlobals(IRBuilder<> &IRB, Module &M, bool *CtorComdat);
+  bool InstrumentGlobals(IRBuilder<> &IRB, Module &M, bool *CtorComdat);
   void InstrumentGlobalsCOFF(IRBuilder<> &IRB, Module &M,
                              ArrayRef<GlobalVariable *> ExtendedGlobals,
                              ArrayRef<Constant *> MetadataInitializers);
@@ -2237,7 +2237,7 @@ void ModuleAddressSanitizer::InstrumentGlobalsELF(
 
   // We also need to unregister globals at the end, e.g., when a shared library
   // gets closed.
-  if (DestructorKind != AsanDtorKind::None && !MetadataGlobals.empty()) {
+  if (DestructorKind != AsanDtorKind::None) {
     IRBuilder<> IrbDtor(CreateAsanModuleDtor(M));
     IrbDtor.CreateCall(AsanUnregisterElfGlobals,
                        {IRB.CreatePointerCast(RegisteredFlag, IntptrTy),
@@ -2343,8 +2343,10 @@ void ModuleAddressSanitizer::InstrumentGlobalsWithMetadataArray(
 // redzones and inserts this function into llvm.global_ctors.
 // Sets *CtorComdat to true if the global registration code emitted into the
 // asan constructor is comdat-compatible.
-void ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
+bool ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
                                                bool *CtorComdat) {
+  *CtorComdat = false;
+
   // Build set of globals that are aliased by some GA, where
   // getExcludedAliasedGlobal(GA) returns the relevant GlobalVariable.
   SmallPtrSet<const GlobalVariable *, 16> AliasedGlobalExclusions;
@@ -2362,6 +2364,11 @@ void ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
   }
 
   size_t n = GlobalsToChange.size();
+  if (n == 0) {
+    *CtorComdat = true;
+    return false;
+  }
+
   auto &DL = M.getDataLayout();
 
   // A global is described by a structure
@@ -2384,11 +2391,8 @@ void ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
 
   // We shouldn't merge same module names, as this string serves as unique
   // module ID in runtime.
-  GlobalVariable *ModuleName =
-      n != 0
-          ? createPrivateGlobalForString(M, M.getModuleIdentifier(),
-                                         /*AllowMerging*/ false, kAsanGenPrefix)
-          : nullptr;
+  GlobalVariable *ModuleName = createPrivateGlobalForString(
+      M, M.getModuleIdentifier(), /*AllowMerging*/ false, kAsanGenPrefix);
 
   for (size_t i = 0; i < n; i++) {
     GlobalVariable *G = GlobalsToChange[i];
@@ -2513,34 +2517,27 @@ void ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
   }
   appendToCompilerUsed(M, ArrayRef<GlobalValue *>(GlobalsToAddToUsedList));
 
-  if (UseGlobalsGC && TargetTriple.isOSBinFormatELF()) {
-    // Use COMDAT and register globals even if n == 0 to ensure that (a) the
-    // linkage unit will only have one module constructor, and (b) the register
-    // function will be called. The module destructor is not created when n ==
-    // 0.
+  std::string ELFUniqueModuleId =
+      (UseGlobalsGC && TargetTriple.isOSBinFormatELF()) ? getUniqueModuleId(&M)
+                                                        : "";
+
+  if (!ELFUniqueModuleId.empty()) {
+    InstrumentGlobalsELF(IRB, M, NewGlobals, Initializers, ELFUniqueModuleId);
     *CtorComdat = true;
-    InstrumentGlobalsELF(IRB, M, NewGlobals, Initializers,
-                         getUniqueModuleId(&M));
-  } else if (n == 0) {
-    // When UseGlobalsGC is false, COMDAT can still be used if n == 0, because
-    // all compile units will have identical module constructor/destructor.
-    *CtorComdat = TargetTriple.isOSBinFormatELF();
+  } else if (UseGlobalsGC && TargetTriple.isOSBinFormatCOFF()) {
+    InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
+  } else if (UseGlobalsGC && ShouldUseMachOGlobalsSection()) {
+    InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
   } else {
-    *CtorComdat = false;
-    if (UseGlobalsGC && TargetTriple.isOSBinFormatCOFF()) {
-      InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
-    } else if (UseGlobalsGC && ShouldUseMachOGlobalsSection()) {
-      InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
-    } else {
-      InstrumentGlobalsWithMetadataArray(IRB, M, NewGlobals, Initializers);
-    }
+    InstrumentGlobalsWithMetadataArray(IRB, M, NewGlobals, Initializers);
   }
 
   // Create calls for poisoning before initializers run and unpoisoning after.
   if (HasDynamicallyInitializedGlobals)
     createInitializerPoisonCalls(M, ModuleName);
 
   LLVM_DEBUG(dbgs() << M);
+  return true;
 }
 
 uint64_t

llvm/test/Instrumentation/AddressSanitizer/basic.ll

@@ -210,10 +210,8 @@ define void @test_swifterror_3() sanitize_address {
 
 ;; ctor/dtor have the nounwind attribute. See uwtable.ll, they additionally have
 ;; the uwtable attribute with the module flag "uwtable".
-; CHECK: define internal void @asan.module_ctor() #[[#ATTR:]] comdat {
+; CHECK: define internal void @asan.module_ctor() #[[#ATTR:]] {{(comdat )?}}{
 ; CHECK: call void @__asan_init()
-;; __asan_register_elf_globals is called even if this module does not contain global variables.
-; CHECK: call void @__asan_register_elf_globals(i64 ptrtoint (ptr @___asan_globals_registered to i64), i64 ptrtoint (ptr @__start_asan_globals to i64), i64 ptrtoint (ptr @__stop_asan_globals to i64))
 
 ; CHECK: attributes #[[#ATTR]] = { nounwind }
 

llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll

@@ -1,12 +1,8 @@
-; RUN: rm -rf %t && split-file %s %t && cd %t
-; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefix=CHECK %s
-; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-apple-macosx10.11.0 -S | FileCheck --check-prefix=CHECK %s
-; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-pc-windows-msvc19.0.24215 -S | FileCheck --check-prefix=CHECK %s
-; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -asan-mapping-scale=5 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefixes=CHECK,CHECK-S5 %s
+; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefix=CHECK %s
+; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-apple-macosx10.11.0 -S | FileCheck --check-prefix=CHECK %s
+; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-pc-windows-msvc19.0.24215 -S | FileCheck --check-prefix=CHECK %s
+; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -asan-mapping-scale=5 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefixes=CHECK,CHECK-S5 %s
 
-; RUN: opt < empty.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefix=ELF-NOGC %s
-
-;--- a.ll
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; Globals:
@@ -63,10 +59,3 @@ attributes #1 = { nounwind sanitize_address "less-precise-fpmad"="false" "frame-
 !7 = !{!"/tmp/asan-globals.cpp", i32 7, i32 5}
 !8 = !{!"/tmp/asan-globals.cpp", i32 12, i32 14}
 !9 = !{!"/tmp/asan-globals.cpp", i32 14, i32 25}
-
-;; In the presence of instrumented global variables, asan.module_ctor do not use comdat.
-; CHECK: define internal void @asan.module_ctor() #[[#ATTR:]] {
-
-; ELF-NOGC: define internal void @asan.module_ctor() #[[#ATTR:]] comdat {
-
-;--- empty.ll