[PGO] Simplify coverage mapping lowering

Coverage mapping data may reference names of functions
that are skipped by FE (e.g, unused inline functions). Since
those functions are skipped, normal instr-prof function lowering
pass won't put those names in the right section, so special 
handling is needed to walk through coverage mapping structure
and recollect the references.

With this patch, only names that are skipped are processed. This
simplifies the lowering code and it no longer needs to make 
assumptions coverage mapping data layout. It should also be 
more efficient.

llvm-svn: 257092

1 files changed, 17 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index 1d4d709..03e22cd 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -910,11 +910,11 @@ static void dump(llvm::raw_ostream &OS, StringRef FunctionName,
 }
 
 void CoverageMappingModuleGen::addFunctionMappingRecord(
-    llvm::GlobalVariable *NamePtr, StringRef NameValue,
-    uint64_t FuncHash, const std::string &CoverageMapping) {
+    llvm::GlobalVariable *NamePtr, StringRef NameValue, uint64_t FuncHash,
+    const std::string &CoverageMapping, bool isUsed) {
   llvm::LLVMContext &Ctx = CGM.getLLVMContext();
   if (!FunctionRecordTy) {
-    #define COVMAP_FUNC_RECORD(Type, LLVMType, Name, Init) LLVMType,
+#define COVMAP_FUNC_RECORD(Type, LLVMType, Name, Init) LLVMType,
     llvm::Type *FunctionRecordTypes[] = {
       #include "llvm/ProfileData/InstrProfData.inc"
     };
@@ -929,6 +929,9 @@ void CoverageMappingModuleGen::addFunctionMappingRecord(
   };
   FunctionRecords.push_back(llvm::ConstantStruct::get(
       FunctionRecordTy, makeArrayRef(FunctionRecordVals)));
+  if (!isUsed)
+    FunctionNames.push_back(
+        llvm::ConstantExpr::getBitCast(NamePtr, llvm::Type::getInt8PtrTy(Ctx)));
   CoverageMappings += CoverageMapping;
 
   if (CGM.getCodeGenOpts().DumpCoverageMapping) {
@@ -1023,6 +1026,17 @@ void CoverageMappingModuleGen::emit() {
 
   // Make sure the data doesn't get deleted.
   CGM.addUsedGlobal(CovData);
+  // Create the deferred function records array
+  if (!FunctionNames.empty()) {
+    auto NamesArrTy = llvm::ArrayType::get(llvm::Type::getInt8PtrTy(Ctx),
+                                           FunctionNames.size());
+    auto NamesArrVal = llvm::ConstantArray::get(NamesArrTy, FunctionNames);
+    // This variable will *NOT* be emitted to the object file. It is used
+    // to pass the list of names referenced to codegen.
+    new llvm::GlobalVariable(CGM.getModule(), NamesArrTy, true,
+                             llvm::GlobalValue::InternalLinkage, NamesArrVal,
+                             llvm::getCoverageNamesVarName());
+  }
 }
 
 unsigned CoverageMappingModuleGen::getFileID(const FileEntry *File) {