Index: llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -288,8 +288,10 @@
       M, SanCovModuleCtorName, InitFunctionName, {Ty, Ty},
       {SecStartPtr, IRB.CreatePointerCast(SecEnd, Ty)});
 
-  if (TargetTriple.supportsCOMDAT()) {
-    // Use comdat to dedup CtorFunc.
+  if (TargetTriple.supportsCOMDAT()&&
+      TargetTriple.getObjectFormat() != Triple::COFF) {
+    // Use comdat to dedup CtorFunc. Don't do it for COFF files since it breaks
+    // the linker flag: "/OPT:REF".
     CtorFunc->setComdat(M.getOrInsertComdat(SanCovModuleCtorName));
     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
   } else {