[PATCH] D51902: [SanitizerCoverage] Create comdat for global arrays.

[Matt Morehouse via Phabricator via llvm-commits]

morehouse updated this revision to Diff 164951.
morehouse added a comment.

- Rebase


https://reviews.llvm.org/D51902

Files:
  llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp


Index: llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -571,8 +571,28 @@
   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);


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