perf(mir): leaf 函数省略帧指针——无调用+无栈帧时跳过 stp/ldp x29,x30

crypto 1482→1458（-24 指令），crc 306→303。

src/mir/AsmPrinter.cpp

@@ -422,6 +422,18 @@ namespace mir
             case Opcode::Prologue:
             {
                 const auto &cs_regs = function.GetCalleeSavedRegs();
+                // 若函数无需帧（leaf + 无栈槽 + 无被调用者保存寄存器），跳过帧设置
+                bool has_frame = function.GetFrameSize() > 0 || !cs_regs.empty();
+                if (!has_frame) {
+                    // 检查是否有 Call 指令，若有则需要保存 LR
+                    for (const auto &blk : function.GetBlocks()) {
+                        for (const auto &i : blk->GetInstructions()) {
+                            if (i.GetOpcode() == Opcode::Call) { has_frame = true; break; }
+                        }
+                        if (has_frame) break;
+                    }
+                }
+                if (!has_frame) return;  // leaf 函数，无需帧
                 os << "    stp x29, x30, [sp, #-16]!\n";
                 os << "    mov x29, sp\n";
                 if (function.GetFrameSize() > 0)
@@ -448,6 +460,16 @@ namespace mir
             case Opcode::Epilogue:
             {
                 const auto &cs_regs = function.GetCalleeSavedRegs();
+                bool has_frame = function.GetFrameSize() > 0 || !cs_regs.empty();
+                if (!has_frame) {
+                    for (const auto &blk : function.GetBlocks()) {
+                        for (const auto &i : blk->GetInstructions()) {
+                            if (i.GetOpcode() == Opcode::Call) { has_frame = true; break; }
+                        }
+                        if (has_frame) break;
+                    }
+                }
+                if (!has_frame) { os << "    ret\n"; return; }
                 int cs_offset = 0;
                 for (auto r : cs_regs)
                 {