[llvm] [llvm][AsmPrinter] Call graph section format. (PR #159866)

[Paul Kirth via llvm-commits]

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@@ -1683,63 +1683,64 @@ void AsmPrinter::emitCallGraphSection(const MachineFunction &MF,
   OutStreamer->pushSection();
   OutStreamer->switchSection(FuncCGSection);
 
-  // Emit format version number.
-  OutStreamer->emitInt64(CallGraphSectionFormatVersion::V_0);
-
-  // Emit function's self information, which is composed of:
-  //  1) FunctionEntryPc
-  //  2) FunctionKind: Whether the function is indirect target, and if so,
-  //     whether its type id is known.
-  //  3) FunctionTypeId: Emit only when the function is an indirect target
-  //     and its type id is known.
-
-  // Emit function entry pc.
   const MCSymbol *FunctionSymbol = getFunctionBegin();
-  OutStreamer->emitSymbolValue(FunctionSymbol, TM.getProgramPointerSize());
-
+  const Function &F = MF.getFunction();
   // If this function has external linkage or has its address taken and
   // it is not a callback, then anything could call it.
-  const Function &F = MF.getFunction();
   bool IsIndirectTarget =
       !F.hasLocalLinkage() || F.hasAddressTaken(nullptr,
                                                 /*IgnoreCallbackUses=*/true,
                                                 /*IgnoreAssumeLikeCalls=*/true,
                                                 /*IgnoreLLVMUsed=*/false);
 
-  // FIXME: FunctionKind takes a few values but emitted as a 64-bit value.
-  // Can be optimized to occupy 2 bits instead.
-  // Emit function kind, and type id if available.
-  if (!IsIndirectTarget) {
-    OutStreamer->emitInt64(
-        static_cast<uint64_t>(FunctionKind::NOT_INDIRECT_TARGET));
-  } else {
-    if (const auto *TypeId = extractNumericCGTypeId(F)) {
-      OutStreamer->emitInt64(
-          static_cast<uint64_t>(FunctionKind::INDIRECT_TARGET_KNOWN_TID));
-      OutStreamer->emitInt64(TypeId->getZExtValue());
-    } else {
-      OutStreamer->emitInt64(
-          static_cast<uint64_t>(FunctionKind::INDIRECT_TARGET_UNKNOWN_TID));
-    }
-  }
+  const auto &DirectCallees = FuncCGInfo.DirectCallees;
+  const auto &IndirectCalleeTypeIDs = FuncCGInfo.IndirectCalleeTypeIDs;
+
+  uint8_t Flags = 0;
+  if (IsIndirectTarget)
+    Flags |= 1u << 0; // Set the first LSB bit to 1.
+  if (DirectCallees.size() > 0)
+    Flags |= 1u << 1; // Set the second LSB bit to 1.
+  if (IndirectCalleeTypeIDs.size() > 0)
+    Flags |= 1u << 2; // Set the third LSB bit to 1.
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ilovepi wrote:

i'd define an enum for these. 

https://github.com/llvm/llvm-project/pull/159866