omit empty frames for leaf functions

src/mir/FrameLowering.cpp

@@ -33,6 +33,21 @@ void RunFrameLowering(MachineFunction& function) {
   auto& blocks = function.GetBlocks();
   if (blocks.empty()) return;
 
+  bool has_call = false;
+  for (const auto& block : blocks) {
+    for (const auto& inst : block.GetInstructions()) {
+      if (inst.GetOpcode() == Opcode::Call) {
+        has_call = true;
+        break;
+      }
+    }
+    if (has_call) break;
+  }
+
+  if (function.GetFrameSize() == 0 && !has_call) {
+    return;
+  }
+
   // Insert Prologue at the start of the first block
   auto& entry_insts = blocks.front().GetInstructions();
   entry_insts.insert(entry_insts.begin(), MachineInstr(Opcode::Prologue));