计算机系统基础：C语言视角（RISC-V版）.pptVIP

在内存中实现栈由一组存储单元和被称为“栈指针”的机制组成栈指针寄存器x2指向栈的栈顶最后压入的元素的存储单元地址PUSHpush: addi x2,x2,-4 sw x9,0(x2)将保存在x9中的数值压入栈POPpop: lw x9,0(x2) addi x2,x2,4注意：数值-3仍然保存在0xBFFFFFE4到0xBFFFFFE7这一段存储单元之中栈协议“栈协议”，控制访问规则“栈”要求：通过执行PUSH指令序列实现压栈通过执行POP指令序列实现出栈后进先出push: addi x2,x2,-4 sw x9,0(x2)pop: lw x9,0(x2) addi x2,x2,4采用栈机制的Sn01 luix2,0xc000002 addix2,x2,-16 #x2=0xBFFFFFF003 addix10,x0,3 #n=304 jalx1,Sn #callSn05 jend06# 07Sn: addi x2,x2,-4 #pushx108 sw x1,0(x2) 09 addi x6,x0,10A beq x10,x6,exit1 #n==1?0B addi x10,x10,-1 #n-10C jal x1,Sn #S(n-1)0D addi x10,x10,1 #n0E add x11,x11,x10#S(n-1)+n，S(n)的返回值0F j exit210exit1: addi x11,x0,1 #x11，S(1)的返回值11exit2: lw x1,0(x2) #popx112 addi x2,x2,413 ret跟踪指令序列执行过程01 luix2,0xc000002 addix2,x2,-16 #x2=0xBFFFFFF003 addix10,x0,3 #n=304 jalx1,Sn #callSn05 jend06# 07Sn: addi x2,x2,-4 #pushx108 sw x1,0(x2) 09 addi x6,x0,10A beq x10,x6,exit1 #n==1?0B addi x10,x10,-1 #n-10C jal x1,Sn #S(n-1)......07Sn: addi x2,x2,-4 #pushx108 sw x1,0(x2) 09 addi x6,x0,10A beq x10,x6,exit1 #n==1?0B addi x10,x10,-1 #n-10C jal x1,Sn #S(n-1)......07Sn: addi x2,x2,-4 #pushx108 sw x1,0(x2) 09 addi x6,x0,10A beq x10,x6,exit1 #n==1?0B addi x10,x10,-1 #n-10C jal x1,Sn #S(n-1)0D addi x10,x10,1 #n0E add x11,x11,x10 #S(n-1)+n，S(n)的返回值0F j exit210exit1: addi x11,x0,1 #x11，S(1)的返回值......0C jal x1,Sn #S(n-1)0D addi x10,x10,1 #n0E add x11,x11,x10 #S(n-1)+n，S(n)的返回值0F j exit210exit1: addi x11,x0,1 #x11，S(1)的返回值11exit2: lw x1,0(x2) #popx112 addi x2,x2,413 ret0C jal x1,Sn #S(n-1)0D addi x10,x10,1 #n0E add x11,x11,x10 #S(n-1)+n，S(n)的返回值0F j exit210exit1: addi x11,x0,1 #x11，S(1)的返回值11exit2: lw x1,0(x2) #popx112