[SanitizerCoverage] Add associated metadata to 8-bit counters.

Summary:
This allows counters associated with unused functions to be
dead-stripped along with their functions.  This approach is the same one
we used for PC tables.

Fixes an issue where LLD removes an unused PC table but leaves the 8-bit
counter.

Reviewers: eugenis

Reviewed By: eugenis

Subscribers: llvm-commits, hiraditya, kcc

Differential Revision: https://reviews.llvm.org/D49264

llvm-svn: 336941

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
index a9336381edd..a4dd48c8dd6 100644
--- a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -595,7 +595,9 @@ void SanitizerCoverageModule::CreateFunctionLocalArrays(
   if (Options.Inline8bitCounters) {
     Function8bitCounterArray = CreateFunctionLocalArrayInSection(
         AllBlocks.size(), F, Int8Ty, SanCovCountersSectionName);
-    GlobalsToAppendToUsed.push_back(Function8bitCounterArray);
+    GlobalsToAppendToCompilerUsed.push_back(Function8bitCounterArray);
+    MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
+    Function8bitCounterArray->addMetadata(LLVMContext::MD_associated, *MD);
   }
   if (Options.PCTable) {
     FunctionPCsArray = CreatePCArray(F, AllBlocks);