[llvm][AsmPrinter] Add direct calls to callgraph section

Extend CallGraphSection to include metadata about direct calls. This
simplifies the design of tools that must parse .callgraph section to not
require dependency on MC layer.

Author: Prabhuk

llvm/include/llvm/CodeGen/AsmPrinter.h

@@ -214,6 +214,7 @@ class LLVM_ABI AsmPrinter : public MachineFunctionPass {
     /// Map type identifiers to callsite labels. Labels are generated for each
     /// indirect callsite in the function.
     SmallVector<std::pair<CGTypeId, MCSymbol *>> CallSiteLabels;
+    SmallVector<std::pair<MCSymbol *, MCSymbol *>> DirectCallSiteLabels;
   };
 
   enum CallGraphSectionFormatVersion : uint64_t {

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -78,6 +78,7 @@
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
@@ -1733,6 +1734,14 @@ void AsmPrinter::emitCallGraphSection(const MachineFunction &MF,
   }
   FuncInfo.CallSiteLabels.clear();
 
+  const auto &DirectCallSiteLabels = FuncInfo.DirectCallSiteLabels;
+  OutStreamer->emitInt64(DirectCallSiteLabels.size());
+  for (const auto &[CallSiteAddrLabel, CalleeSymbol] : DirectCallSiteLabels) {
+    OutStreamer->emitSymbolValue(CallSiteAddrLabel, TM.getProgramPointerSize());
+    OutStreamer->emitSymbolValue(CalleeSymbol, TM.getProgramPointerSize());
+  }
+  FuncInfo.DirectCallSiteLabels.clear();
+
   OutStreamer->popSection();
 }
 
@@ -1872,9 +1881,28 @@ void AsmPrinter::emitIndirectCalleeLabels(
     const MachineInstr &MI) {
   // Only indirect calls have type identifiers set.
   const auto &CallSiteInfo = CallSitesInfoMap.find(&MI);
-  if (CallSiteInfo == CallSitesInfoMap.end())
+
+  // Handle direct callsite info
+  if (CallSiteInfo == CallSitesInfoMap.end()) {
+    const MachineOperand &CalleeOperand = MI.getOperand(0);
+    MCSymbol *CalleeSymbol = nullptr;
+    switch (CalleeOperand.getType()) {
+    case llvm::MachineOperand::MO_GlobalAddress:
+      CalleeSymbol = getSymbol(CalleeOperand.getGlobal());
+      break;
+    case llvm::MachineOperand::MO_ExternalSymbol:
+      CalleeSymbol = GetExternalSymbolSymbol(CalleeOperand.getSymbolName());
+      break;
+    default:
+      llvm_unreachable("Expect only direct call instructions to be handled.");
+    }
+    MCSymbol *S = MF->getContext().createTempSymbol();
+    OutStreamer->emitLabel(S);
+    FuncInfo.DirectCallSiteLabels.emplace_back(S, CalleeSymbol);
     return;
+  }
 
+  // Handle indirect callsite info.
   for (ConstantInt *CalleeTypeId : CallSiteInfo->second.CalleeTypeIds) {
     MCSymbol *S = MF->getContext().createTempSymbol();
     OutStreamer->emitLabel(S);
@@ -2064,8 +2092,13 @@ void AsmPrinter::emitFunctionBody() {
         break;
       }
 
-      if (TM.Options.EmitCallGraphSection && MI.isCall())
+      if (TM.Options.EmitCallGraphSection && MI.isCall()) {
+        llvm::outs() << "Dump MI for calls \n";
+        MI.dump();
+        llvm::outs() << "CallSitesInfoMap.size() " << CallSitesInfoMap.size()
+                     << "\n";
         emitIndirectCalleeLabels(FuncInfo, CallSitesInfoMap, MI);
+      }
 
       // If there is a post-instruction symbol, emit a label for it here.
       if (MCSymbol *S = MI.getPostInstrSymbol())