[sanitizer-coverage] make sure asan does not instrument coverage guards (reported in https://github.com/google/oss-fuzz/issues/84)

llvm-svn: 287030
diff --git a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
index 73881fa..031effb 100644
--- a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -514,7 +514,7 @@
   ArrayType *ArrayOfInt32Ty = ArrayType::get(Int32Ty, NumGuards);
   FunctionGuardArray = new GlobalVariable(
       *CurModule, ArrayOfInt32Ty, false, GlobalVariable::PrivateLinkage,
-      Constant::getNullValue(ArrayOfInt32Ty), "__sancov_guard");
+      Constant::getNullValue(ArrayOfInt32Ty), "__sancov_gen_");
   if (auto Comdat = F.getComdat())
     FunctionGuardArray->setComdat(Comdat);
   FunctionGuardArray->setSection(SanCovTracePCGuardSection);