[llvm-objdump][CallGraphInfo][NFC] Introduce FunctionKind enum

[necipfazil]

Summary

Add FunctionKind enumeration for mapping function kinds to values from
.callgraph section.

This will be used in the upcoming patches where the .callgraph section is
parsed.

Patch 5/6: Extract call graph information from binary

Original RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-June/151044.html
Updated RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-July/151739.html

[morehouse]

llvm/tools/llvm-objdump/llvm-objdump.cpp

226

[necipfazil]

Fix docs

llvm/tools/llvm-objdump/llvm-objdump.cpp

 std::string objdump::TripleName;
 bool objdump::UnwindInfo;
 static bool Wide;
 std::string objdump::Prefix;
 uint32_t objdump::PrefixStrip;
 
 static bool QuietDisasm = false;
 
+// Enumeration of function kinds, and their mapping to function kind values
+// from call graph section (.callgraph).
+// Must stay in sync with enum from llvm/include/llvm/CodeGen/AsmPrinter.h.
+enum FunctionKind {
+  // Function cannot be target to indirect calls.
+  NOT_INDIRECT_TARGET = 0,
+  // Function may be target to indirect calls but its type id is unknown.
+  INDIRECT_TARGET_UNKNOWN_TID = 1,
+  // Function may be target to indirect calls and its type id is known.
+  INDIRECT_TARGET_KNOWN_TID = 2,
+
+  // Available in the binary but not listed in the call graph section.
+  NOT_LISTED = -1,
+};
+
 struct FunctionInfo {
   std::string Name;
+  FunctionKind Kind;
 
   struct DirectCallSite {
     uint64_t CallSite;
     uint64_t Callee;
     DirectCallSite(uint64_t CallSite, uint64_t Callee)
         : CallSite(CallSite), Callee(Callee) {}
   };
   SmallVector<DirectCallSite> DirectCallSites;
for (unsigned SI = 0, SE = Symbols.size(); SI != SE; ++SI) {
       if (SymbolizeOperands)
         collectLocalBranchTargets(Bytes, MIA, DisAsm, IP, PrimarySTI,
                                   SectionAddr, Index, End, AllLabels);
 
       if (CallGraphInfo && Symbols[SI].Type == ELF::STT_FUNC) {
         auto FuncPc = Symbols[SI].Addr;
         auto FuncName = Symbols[SI].Name.str();
         FuncInfo[FuncPc].Name = FuncName;
+        // Initalize to be later updated while parsing the call graph section.
+        FuncInfo[FuncPc].Kind = NOT_LISTED;
       }
       while (Index < End) {
         // ARM and AArch64 ELF binaries can interleave data and text in the
         // same section. We rely on the markers introduced to understand what
         // we need to dump. If the data marker is within a function, it is
         // denoted as a word/short etc.
         if (CheckARMELFData) {
           char Kind = getMappingSymbolKind(MappingSymbols, Index);