[SystemZ][z/OS] Add entry point marker to PPA

Differential Revision: https://reviews.llvm.org/D115269

llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp

@@ -786,6 +786,50 @@ void SystemZAsmPrinter::emitEndOfAsmFile(Module &M) {
   emitStackMaps(SM);
 }
 
+void SystemZAsmPrinter::emitFunctionEntryLabel() {
+  const SystemZSubtarget &Subtarget =
+      static_cast<const SystemZSubtarget &>(MF->getSubtarget());
+
+  if (Subtarget.getTargetTriple().isOSzOS()) {
+    MCContext &OutContext = OutStreamer->getContext();
+    MCSymbol *EPMarkerSym = OutContext.createTempSymbol("CM_", true);
+
+    // EntryPoint Marker
+    const MachineFrameInfo &MFFrame = MF->getFrameInfo();
+    bool IsUsingAlloca = MFFrame.hasVarSizedObjects();
+
+    // Set Flags
+    uint8_t Flags = 0;
+    if (IsUsingAlloca)
+      Flags |= 0x04;
+
+    uint32_t DSASize = MFFrame.getStackSize();
+
+    // Combine into top 27 bits of DSASize and bottom 5 bits of Flags.
+    uint32_t DSAAndFlags = DSASize & 0xFFFFFFE0; // (x/32) << 5
+    DSAAndFlags |= Flags;
+
+    // Emit entry point marker section.
+    OutStreamer->AddComment("XPLINK Routine Layout Entry");
+    OutStreamer->emitLabel(EPMarkerSym);
+    OutStreamer->AddComment("Eyecatcher 0x00C300C500C500");
+    OutStreamer->emitIntValueInHex(0x00C300C500C500, 7); // Eyecatcher.
+    OutStreamer->AddComment("Mark Type C'1'");
+    OutStreamer->emitInt8(0xF1); // Mark Type.
+    if (OutStreamer->isVerboseAsm()) {
+      OutStreamer->AddComment("DSA Size 0x" + Twine::utohexstr(DSASize));
+      OutStreamer->AddComment("Entry Flags");
+      if (Flags & 0x04)
+        OutStreamer->AddComment("  Bit 2: 1 = Uses alloca");
+      else
+        OutStreamer->AddComment("  Bit 2: 0 = Does not use alloca");
+    }
+    OutStreamer->emitInt32(DSAAndFlags);
+  }
+
+  AsmPrinter::emitFunctionEntryLabel();
+}
+
 // Force static initialization.
 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeSystemZAsmPrinter() {
   RegisterAsmPrinter<SystemZAsmPrinter> X(getTheSystemZTarget());

llvm/lib/Target/SystemZ/SystemZAsmPrinter.h

@@ -51,6 +51,7 @@ public:
     SM.reset();
     return AsmPrinter::doInitialization(M);
   }
+  void emitFunctionEntryLabel() override;
 
 private:
   void LowerFENTRY_CALL(const MachineInstr &MI, SystemZMCInstLower &MCIL);

llvm/test/MC/GOFF/ppa1.ll

@@ -0,0 +1,15 @@
+; RUN: llc -mtriple s390x-ibm-zos < %s | FileCheck %s
+
+; CHECK: @@CM_0: * @void_test
+; CHECK: * XPLINK Routine Layout Entry
+; CHECK: .long   12779717 * Eyecatcher 0x00C300C500C500
+; CHECK: .short  197
+; CHECK: .byte   0
+; CHECK: .byte   241 * Mark Type C'1'
+; CHECK: .long   128 * DSA Size 0x80
+; CHECK: * Entry Flags
+; CHECK: *   Bit 2: 0 = Does not use alloca
+define void @void_test() {
+entry:
+  ret void
+}