[llvm] [llvm-readobj] Dump callgraph section info for ELF (PR #157499)

[Paul Kirth via llvm-commits]

================
@@ -5263,6 +5299,181 @@ template <class ELFT> void GNUELFDumper<ELFT>::printCGProfile() {
   OS << "GNUStyle::printCGProfile not implemented\n";
 }
 
+namespace callgraph {
+LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
+enum Flags : uint8_t {
+  None = 0,
+  IsIndirectTarget = 1u << 0,
+  HasDirectCallees = 1u << 1,
+  HasIndirectCallees = 1u << 2,
+  LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue*/ HasIndirectCallees)
+};
+} // namespace callgraph
+
+template <class ELFT> bool ELFDumper<ELFT>::processCallGraphSection() {
+  const Elf_Shdr *CGSection = findSectionByName(".llvm.callgraph");
+  if (!CGSection) {
+    reportWarning(createError("No .llvm.callgraph section found."),
+                  "missing section");
+    return false;
+  }
+
+  Expected<ArrayRef<uint8_t>> SectionBytesOrErr =
+      Obj.getSectionContents(*CGSection);
+  if (!SectionBytesOrErr) {
+    reportError(SectionBytesOrErr.takeError(),
+                "unable to read the .llvm.callgraph section");
+  }
+
+  auto PrintMalformedError = [&](Error &E, Twine FuncPC, StringRef Component) {
+    reportError(std::move(E),
+                Twine("while reading call graph info's [" + Component +
+                      "] for function at [0x" + FuncPC + "]")
+                    .str());
+  };
+
+  DataExtractor Data(SectionBytesOrErr.get(), Obj.isLE(),
+                     ObjF.getBytesInAddress());
+
+  uint64_t UnknownCount = 0;
+  uint64_t Offset = 0;
+  while (Offset < CGSection->sh_size) {
+    Error CGSectionErr = Error::success();
+    uint8_t FormatVersionNumber = Data.getU8(&Offset, &CGSectionErr);
+    if (CGSectionErr) {
+      reportWarning(std::move(CGSectionErr),
+                    "while reading call graph info FormatVersionNumber");
+      return false;
+    }
+    if (FormatVersionNumber != 0) {
+      reportError(createError("Unknown format version value [" +
+                              std::to_string(FormatVersionNumber) +
+                              "] in .llvm.callgraph section."),
+                  "unknown value");
----------------
ilovepi wrote:

```suggestion
                  FileStr);
```

https://github.com/llvm/llvm-project/pull/157499