[SanitizerCoverage] Create comdat for global arrays.

Summary:
Place global arrays in comdat sections with their associated functions.
This makes sure they are stripped along with the functions they
reference, even on the BFD linker.

Reviewers: eugenis

Reviewed By: eugenis

Subscribers: eraman, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D51902

llvm-svn: 341987

1 files changed, 26 insertions, 14 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
index 1f97e909851..5e7801f41a8 100644
--- a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -571,11 +571,34 @@ GlobalVariable *SanitizerCoverageModule::CreateFunctionLocalArrayInSection(
   auto Array = new GlobalVariable(
       *CurModule, ArrayTy, false, GlobalVariable::PrivateLinkage,
       Constant::getNullValue(ArrayTy), "__sancov_gen_");
-  if (auto Comdat = F.getComdat())
+  if (auto Comdat = F.getComdat()) {
     Array->setComdat(Comdat);
+  } else if (TargetTriple.isOSBinFormatELF()) {
+    // TODO: Refactor into a helper function and use it in ASan.
+    assert(F.hasName());
+    std::string Name = F.getName();
+    if (F.hasLocalLinkage()) {
+      std::string ModuleId = getUniqueModuleId(CurModule);
+      Name += ModuleId.empty() ? CurModule->getModuleIdentifier() : ModuleId;
+    }
+    Comdat = CurModule->getOrInsertComdat(Name);
+    // Make this IMAGE_COMDAT_SELECT_NODUPLICATES on COFF. Also upgrade private
+    // linkage to internal linkage so that a symbol table entry is emitted. This
+    // is necessary in order to create the comdat group.
+    if (TargetTriple.isOSBinFormatCOFF()) {
+      Comdat->setSelectionKind(Comdat::NoDuplicates);
+      if (F.hasPrivateLinkage())
+        F.setLinkage(GlobalValue::InternalLinkage);
+    }
+    F.setComdat(Comdat);
+    Array->setComdat(Comdat);
+  }
   Array->setSection(getSectionName(Section));
   Array->setAlignment(Ty->isPointerTy() ? DL->getPointerSize()
                                         : Ty->getPrimitiveSizeInBits() / 8);
+  GlobalsToAppendToCompilerUsed.push_back(Array);
+  MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
+  Array->addMetadata(LLVMContext::MD_associated, *MD);
   return Array;
 }
 
@@ -613,23 +636,12 @@ void SanitizerCoverageModule::CreateFunctionLocalArrays(
     FunctionGuardArray = CreateFunctionLocalArrayInSection(
         AllBlocks.size(), F, Int32Ty, SanCovGuardsSectionName);
     GlobalsToAppendToUsed.push_back(FunctionGuardArray);
-    GlobalsToAppendToCompilerUsed.push_back(FunctionGuardArray);
-    MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
-    FunctionGuardArray->addMetadata(LLVMContext::MD_associated, *MD);
   }
-  if (Options.Inline8bitCounters) {
+  if (Options.Inline8bitCounters)
     Function8bitCounterArray = CreateFunctionLocalArrayInSection(
         AllBlocks.size(), F, Int8Ty, SanCovCountersSectionName);
-    GlobalsToAppendToCompilerUsed.push_back(Function8bitCounterArray);
-    MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
-    Function8bitCounterArray->addMetadata(LLVMContext::MD_associated, *MD);
-  }
-  if (Options.PCTable) {
+  if (Options.PCTable)
     FunctionPCsArray = CreatePCArray(F, AllBlocks);
-    GlobalsToAppendToCompilerUsed.push_back(FunctionPCsArray);
-    MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
-    FunctionPCsArray->addMetadata(LLVMContext::MD_associated, *MD);
-  }
 }
 
 bool SanitizerCoverageModule::InjectCoverage(Function &F,