RV architected registers:RV64RV32.2-14 Preserved Name Register Usage number on call？ x0 0 The constant value 0 n.a. x1 (ra) 1 Return address(link register) yes x2 (sp) 2 Stack pointer yes x3 (gp) 3 Global pointer yes x4 (tp) 4 Thread pointer yes x5-x7 5-7 Temporaries no x8-x9 8-9 Saved yes ×10-×17 10-17 Arguments/results no x18-×27 18-27 Saved yes ×28-×31 28-31 Temporaries no ·Preserved:在函数调用中保持不变RV architected registers：RV64/RV32，图2-14 • Preserved：在函数调用中保持不变