[SystemZ][z/OS] Fix the entry point marker for leaf functions

The function emitFunctionEntryLabel does not look at whether or not a function is a leaf when setting the entry flags,
and instead blindly marks all functions as non-leaf routines. Change it to check if a function is a leaf function and
mark it accordingly.

llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp

@@ -1315,14 +1315,16 @@ void SystemZAsmPrinter::emitFunctionEntryLabel() {
     // EntryPoint Marker
     const MachineFrameInfo &MFFrame = MF->getFrameInfo();
     bool IsUsingAlloca = MFFrame.hasVarSizedObjects();
+    uint32_t DSASize = MFFrame.getStackSize();
+    bool IsLeaf = DSASize == 0 && MFFrame.getCalleeSavedInfo().empty();
 
     // Set Flags
     uint8_t Flags = 0;
+    if (IsLeaf)
+      Flags |= 0x08;
     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;
@@ -1340,6 +1342,10 @@ void SystemZAsmPrinter::emitFunctionEntryLabel() {
     if (OutStreamer->isVerboseAsm()) {
       OutStreamer->AddComment("DSA Size 0x" + Twine::utohexstr(DSASize));
       OutStreamer->AddComment("Entry Flags");
+      if (Flags & 0x08)
+        OutStreamer->AddComment("  Bit 1: 1 = Leaf function");
+      else
+        OutStreamer->AddComment("  Bit 1: 0 = Non-leaf function");
       if (Flags & 0x04)
         OutStreamer->AddComment("  Bit 2: 1 = Uses alloca");
       else

llvm/test/CodeGen/SystemZ/zos-prologue-epilog.ll

@@ -380,6 +380,10 @@ define void @large_stack2(i64 %n1, i64 %n2, i64 %n3) {
 }
 
 ; CHECK-LABEL: leaf_func
+; CHECK: .long	8 * DSA Size 0x0
+; CHECK-NEXT:     * Entry Flags
+; CHECK-NEXT:     *   Bit 1: 1 = Leaf function
+; CHECK-NEXT:     *   Bit 2: 0 = Does not use alloca
 ; CHECK-NOT: aghi  4,
 ; CHECK-NOT: stmg
 ; CHECK: agr	1, 2