[llvm-branch-commits] [llvm] [llvm][AsmPrinter] Emit call graph section (PR #87576)

[Paul Kirth via llvm-branch-commits]

================
@@ -1642,6 +1642,94 @@ void AsmPrinter::emitStackUsage(const MachineFunction &MF) {
     *StackUsageStream << "static\n";
 }
 
+/// Extracts a generalized numeric type identifier of a Function's type from
+/// type metadata. Returns null if metadata cannot be found.
+static ConstantInt *extractNumericCGTypeId(const Function &F) {
+  SmallVector<MDNode *, 2> Types;
+  F.getMetadata(LLVMContext::MD_type, Types);
+  for (const auto &Type : Types) {
+    if (Type->hasGeneralizedMDString()) {
+      MDString *MDGeneralizedTypeId = cast<MDString>(Type->getOperand(1));
+      uint64_t TypeIdVal = llvm::MD5Hash(MDGeneralizedTypeId->getString());
+      IntegerType *Int64Ty = Type::getInt64Ty(F.getContext());
+      return ConstantInt::get(Int64Ty, TypeIdVal);
+    }
+  }
+
+  return nullptr;
+}
+
+/// Emits .callgraph section.
+void AsmPrinter::emitCallGraphSection(const MachineFunction &MF,
+                                      FunctionInfo &FuncInfo) {
+  if (!MF.getTarget().Options.EmitCallGraphSection)
+    return;
+
+  // Switch to the call graph section for the function
+  MCSection *FuncCGSection =
+      getObjFileLowering().getCallGraphSection(*getCurrentSection());
+  assert(FuncCGSection && "null callgraph section");
+  OutStreamer->pushSection();
+  OutStreamer->switchSection(FuncCGSection);
+
+  // Emit format version number.
+  OutStreamer->emitInt64(0);
----------------
ilovepi wrote:

Lets use a constant defined somewhere for the version number, so its easy to update. Probably looking at PGO profile versioning is a reasonable place to take inspiration.

https://github.com/llvm/llvm-project/pull/87576