Add helper functions and comment

Author: ellishg

clang/lib/Driver/ToolChains/Darwin.cpp

@@ -21,6 +21,7 @@
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/ProfileData/InstrProf.h"
+#include "llvm/ProfileData/MemProf.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/Threading.h"
@@ -1619,7 +1620,9 @@ void DarwinClang::AddLinkRuntimeLibArgs(const ArgList &Args,
 
   if (Sanitize.needsMemProfRt())
     if (hasExportSymbolDirective(Args))
-      addExportedSymbol(CmdArgs, "___memprof_default_options_str");
+      addExportedSymbol(
+          CmdArgs,
+          llvm::memprof::getMemprofOptionsSymbolDarwinLinkageName().data());
 
   const XRayArgs &XRay = getXRayArgs();
   if (XRay.needsXRayRt()) {

llvm/include/llvm/ProfileData/MemProf.h

@@ -6,6 +6,7 @@
 #include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/STLFunctionalExtras.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/ProfileData/MemProfData.inc"
 #include "llvm/Support/BLAKE3.h"
@@ -42,6 +43,16 @@ constexpr uint64_t MaximumSupportedVersion = Version3;
 // Verify that the minimum and maximum satisfy the obvious constraint.
 static_assert(MinimumSupportedVersion <= MaximumSupportedVersion);
 
+inline llvm::StringRef getMemprofOptionsSymbolDarwinLinkageName() {
+  return "___memprof_default_options_str";
+}
+
+inline llvm::StringRef getMemprofOptionsSymbolName() {
+  // Darwin linkage names are prefixed with an extra "_". See
+  // DataLayout::getGlobalPrefix().
+  return getMemprofOptionsSymbolDarwinLinkageName().drop_front();
+}
+
 enum class Meta : uint64_t {
   Start = 0,
 #define MIBEntryDef(NameTag, Name, Type) NameTag,

llvm/lib/Transforms/Instrumentation/MemProfiler.cpp

@@ -568,10 +568,9 @@ void createMemprofHistogramFlagVar(Module &M) {
 void createMemprofDefaultOptionsVar(Module &M) {
   Constant *OptionsConst = ConstantDataArray::getString(
       M.getContext(), MemprofRuntimeDefaultOptions, /*AddNull=*/true);
-  GlobalVariable *OptionsVar =
-      new GlobalVariable(M, OptionsConst->getType(), /*isConstant=*/true,
-                         GlobalValue::WeakAnyLinkage, OptionsConst,
-                         "__memprof_default_options_str");
+  GlobalVariable *OptionsVar = new GlobalVariable(
+      M, OptionsConst->getType(), /*isConstant=*/true,
+      GlobalValue::WeakAnyLinkage, OptionsConst, getMemprofOptionsSymbolName());
   Triple TT(M.getTargetTriple());
   if (TT.supportsCOMDAT()) {
     OptionsVar->setLinkage(GlobalValue::ExternalLinkage);