计算机硬件RISC-V汇编指令笔记

[计算机硬件]RISC-V汇编指令笔记RISC-V汇编指令笔记本⽂主要作为RISC-VInstruction的⼀个梳理。RISC-VInstruction的格式通常为Operationcode+Destinationregister+Firstoperandregister+Secondoprandregister如，addx1,x2,x0对应的opcode=add;rd=x1;rs1=x2;rs2=x0.对于RISC-V，有32个寄存器，分别是：RISC-V寄存器表寄存器调⽤名字zero⽤途存储者N.A.x0常数0x1ra返回地址栈指针CallerCallee/x2spx3gp全局指针线程指针临时存储x4tp/x5-x7x8t0-t2CallerCalleeCalleeCallerCallerCalleeCallerCallerCalleeCallerCallerCalleeCallers0/fps1保存⽤寄存器/帧指针（配合栈指针界定⼀个函数的栈）x9保存⽤寄存器函数参数/返回值函数参数x10-x11x12-x17x18-x27x28-x31f0-f7a0-a1a2-a7s2-s11t3-t6保存⽤寄存器临时存储ft0-ft7fs0-fs1fa0-fa1fa2-fa7fs2-fs11ft8-ft11浮点临时存储浮点保存⽤寄存器浮点函数参数/返回值浮点函数参数浮点保存⽤寄存器浮点临时存储f8-f9f10-f11f12-f17f18-f27f28-f31tips:callee:是⼀个指针，指向拥有这个arguement对象的函数；caller:保留着调⽤当前函数的函数的引⽤。⽽RISC-VRV32标准指令集有以下⼏种框架：R-formatforregister-registerarithmetic/logicaloperationsI-formatforregister-immediatearith/logicaloperationsandloadsS-formatforstoresB-formatforbranchesU-formatfor20-bitupperimmediateinstructionsJ-formatforjumpsOthers:UsedforOS&SyncronizationR即Reg相关；I即⽴即数相关；S存储相关；B分⽀相关；U⾼位数相关（因为⼀条32位指令中⽆法表⽰⾼达32位的数据）；J跳转相关。tips:aboutarithmetic&logicaloperations.逻辑右移(LSR)是将各位依次右移指定位数，然后在左侧补0，算术右移(ASR)是将各位依次右移指定位数，然后在左侧⽤原符号位补齐。逻辑左移与算术左移操作相同。RISC-V采⽤⼩端格式（Little-Endian），即低位字节排放在内存的低地址端，⾼位字节排放在内存的⾼地址端。R-Format通常是xxxrd,rs1,rs2。310Funct77rs25rs15Funct33rd5opcode7Opcode=0110011Funct7+Funct3+opcodedefineswhatoperationtoperform.Funct7Funct3000opcode⽤途加法减法左移ADDSUBSLL000000001000000000000011001101100110110011000001SetLessThanSLT00000000100110011:=rs1<rs2?1:0SLTUXORSRLSRAOR000000000000000000000010000000000000000000011100101101110111011001101100110110011011001101100110110011SLTUnsigned异或逻辑右移算术右移或AND与相关伪指令：mvrd,rs=addird,rs,x0nop=addir0,r0,x0notrd,rs=xorird,rs,111111111111Note:因为某事突然发现RISC-V好像没有循环移位的指令（未查证），要实现循环移位估计要三条指令以上。I-FormatOpcode0010011Immediate12rs15Funct33rd5opcode7Shift-by-immediate5rs1Funct33rd5opcode70x000005第⼀部分包括ADDI,SLTI,SLTIU,XORI,ORI,ANDI（⽴即数有12位）和SLLI,SRLI,SRAI（⽴即数仅有5位）。第⼆部分包括loadinstruction，格式同ADDI（12位的⽴即数）LoadOpcode0000011有LB(loadbyte)，LH(loadhalfword=2bytes)，LW，LBU(loadunsignedbyte)，LHU(loadunsignedhalfword)S-FormatOpcode0100011imm[11:5]7rs25rs15Funct33imm[4:0]5opcode7包括SB，SW，SHB-FormatOpcode1100011imm[12]imm[10:5]rs25rs1Funct33imm[4:1]4imm[11]opcode16517可以表⽰-4096~4094的范围Note：The12immediatebitsencodeeven13-bitsignedbyteoffsets(lowestbitofoffsetisalwayszero,sononeedtostoreit).包括BEQ，BNE，BLT(branchlessthan:if[rs1]<[rs2],thenbranch)，BGE(branchgreaterthanorequal:if[rs1]>=[rs2],thenbranch)，BLTU，BGEU。相关伪指令：beqzx1,label=beqx1,x0,labelbnezx1,label=bnex1,x0,labelU-Formatimm[31:12]20rd5opcode7LUI–LoadUpperImmediateluird,upperim(20-bit)e.x.luix10,0x87654#x10=originalvalue→0x87654000AUIPC–AddUpperImmediatetoPCe.x.auipct0,1#t0=originalvalue→PC+0x00001000auipct0,0#t0=originalvalue→PC相关伪指令：加载⽴即数lird,imm(32-bit)=luird,imm(20-bit)addird,rd,imm(12-bit)加载地址lard,label=auipcrd,imm(20-bit)addird,rd,imm(12-bit)J-Formatimm[20]1imm[10:1]10imm[11]1imm[19:12]8rd5opcode7jalx0,labelDiscardreturnaddressjalra,function_nameCallFunctionwithin218(1instruction=22bytes).jrra#Callfunctionatany32-bitabsoluteaddressluix1,<high20-bit>jalrra,x1,<low12-bit>CallFunctionat32-bitabsoluteaddress#JumpPC-relativewith32-bitoffsetauipcx1,<high20-bit>jalrx0,x1,<low12