[clang] [compiler-rt] [llvm] [InstrFDO][TypeProf] Implement binary instrumentation and profile read/write (PR #66825)

[Snehasish Kumar via cfe-commits]

================
@@ -1237,6 +1259,101 @@ void InstrLowerer::maybeSetComdat(GlobalVariable *GV, Function *Fn,
     GV->setLinkage(GlobalValue::InternalLinkage);
 }
 
+static inline bool shouldRecordVTableAddr(GlobalVariable *GV) {
+  if (!profDataReferencedByCode(*GV->getParent()))
+    return false;
+
+  if (!GV->hasLinkOnceLinkage() && !GV->hasLocalLinkage() &&
+      !GV->hasAvailableExternallyLinkage())
+    return true;
+
+  // This avoids the profile data from referencing internal symbols in
+  // COMDAT.
+  if (GV->hasLocalLinkage() && GV->hasComdat())
+    return false;
+
+  return true;
+}
+
+// FIXME: Introduce an internal alias like what's done for functions to reduce
+// the number of relocation entries.
+static inline Constant *getVTableAddrForProfData(GlobalVariable *GV) {
+  auto *Int8PtrTy = PointerType::getUnqual(GV->getContext());
+
+  // Store a nullptr in __profvt_ if a real address shouldn't be used.
+  if (!shouldRecordVTableAddr(GV))
+    return ConstantPointerNull::get(Int8PtrTy);
+
+  return ConstantExpr::getBitCast(GV, Int8PtrTy);
+}
+
+void InstrLowerer::getOrCreateVTableProfData(GlobalVariable *GV) {
+  assert(!DebugInfoCorrelate &&
+         "Value profiling is not supported with lightweight instrumentation");
+  if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
+    return;
+
+  if (GV->getName().starts_with("llvm.") ||
+      GV->getName().starts_with("__llvm") ||
+      GV->getName().starts_with("__prof"))
+    return;
+
+  // VTableProfData already created
+  auto It = VTableDataMap.find(GV);
+  if (It != VTableDataMap.end() && It->second)
+    return;
+
+  GlobalValue::LinkageTypes Linkage = GV->getLinkage();
+  GlobalValue::VisibilityTypes Visibility = GV->getVisibility();
+
+  // This is to keep consistent with per-function profile data
+  // for correctness.
+  if (TT.isOSBinFormatXCOFF()) {
+    Linkage = GlobalValue::InternalLinkage;
+    Visibility = GlobalValue::DefaultVisibility;
+  }
+
+  LLVMContext &Ctx = M.getContext();
+  Type *DataTypes[] = {
+#define INSTR_PROF_VTABLE_DATA(Type, LLVMType, Name, Init) LLVMType,
+#include "llvm/ProfileData/InstrProfData.inc"
+  };
+
+  auto *DataTy = StructType::get(Ctx, ArrayRef(DataTypes));
+
+  // Used by INSTR_PROF_VTABLE_DATA MACRO
+  Constant *VTableAddr = getVTableAddrForProfData(GV);
+  const std::string PGOVTableName = getPGOName(*GV);
+  // Record the length of the vtable. This is needed since vtable pointers
+  // loaded from C++ objects might be from the middle of a vtable definition.
+  uint32_t VTableSizeVal =
+      M.getDataLayout().getTypeAllocSize(GV->getValueType());
+
+  Constant *DataVals[] = {
+#define INSTR_PROF_VTABLE_DATA(Type, LLVMType, Name, Init) Init,
+#include "llvm/ProfileData/InstrProfData.inc"
+  };
+
+  std::string VarName = getInstrProfVTableVarPrefix().str() + PGOVTableName;
+  auto *Data =
+      new GlobalVariable(M, DataTy, false /* constant */, Linkage,
----------------
snehasish wrote:

nit: `/*constant=*/`

https://github.com/llvm/llvm-project/pull/66825