E203 译码模块(2)
常用的alu算术运算指令(包括ecall和 ebreak)在regular alu单元处理。regular alu单元为alu单元的一个子单元。regular单元的信息总线共21位，格式如下图所示，其中grp为000：
下面的代码产生regular alu单元的信息总线。
// ALU Instructions wire rv32_addi = rv32_op_imm & rv32_func3_000; wire rv32_slti = rv32_op_imm & rv32_func3_010; wire rv32_sltiu = rv32_op_imm & rv32_func3_011; wire rv32_xori = rv32_op_imm & rv32_func3_100; wire rv32_ori = rv32_op_imm & rv32_func3_110; wire rv32_andi = rv32_op_imm & rv32_func3_111; wire rv32_slli = rv32_op_imm & rv32_func3_001 & (rv32_instr[31:26] == 6'b000000); wire rv32_srli = rv32_op_imm & rv32_func3_101 & (rv32_instr[31:26] == 6'b000000); wire rv32_srai = rv32_op_imm & rv32_func3_101 & (rv32_instr[31:26] == 6'b010000); //对一些移位指令，shamt[5] must be zero for RV32I，在RV64I中才可以不为0 wire rv32_sxxi_shamt_legl = (rv32_instr[25] == 1'b0); wire rv32_sxxi_shamt_ilgl = (rv32_slli | rv32_srli | rv32_srai) & (~rv32_sxxi_shamt_legl); wire rv32_add = rv32_op & rv32_func3_000 & rv32_func7_0000000; wire rv32_sub = rv32_op & rv32_func3_000 & rv32_func7_0100000; wire rv32_sll = rv32_op & rv32_func3_001 & rv32_func7_0000000; wire rv32_slt = rv32_op & rv32_func3_010 & rv32_func7_0000000; wire rv32_sltu = rv32_op & rv32_func3_011 & rv32_func7_0000000; wire rv32_xor = rv32_op & rv32_func3_100 & rv32_func7_0000000; wire rv32_srl = rv32_op & rv32_func3_101 & rv32_func7_0000000; wire rv32_sra = rv32_op & rv32_func3_101 & rv32_func7_0100000; wire rv32_or = rv32_op & rv32_func3_110 & rv32_func7_0000000; wire rv32_and = rv32_op & rv32_func3_111 & rv32_func7_0000000; //对rv32 nop指令，31-20位为0 wire rv32_nop = rv32_addi & rv32_rs1_x0 & rv32_rd_x0 & (~(|rv32_instr[31:20])); // The ALU group of instructions will be handled by 1cycle ALU-datapath wire ecall_ebreak = rv32_ecall | rv32_ebreak | rv16_ebreak; //当前指令是alu_op指令 wire alu_op = (~rv32_sxxi_shamt_ilgl) & (~rv16_sxxi_shamt_ilgl) & (~rv16_li_lui_ilgl) & (~rv16_addi4spn_ilgl) & (~rv16_addi16sp_ilgl) & ( rv32_op_imm | rv32_op & (~rv32_func7_0000001) // Exclude the MULDIV | rv32_auipc | rv32_lui | rv16_addi4spn | rv16_addi | rv16_lui_addi16sp | rv16_li | rv16_mv | rv16_slli | rv16_miscalu | rv16_add | rv16_nop | rv32_nop | rv32_wfi // We just put WFI into ALU and do nothing in ALU | ecall_ebreak) ; wire need_imm; wire [`E203_DECINFO_ALU_WIDTH-1:0] alu_info_bus; assign alu_info_bus[`E203_DECINFO_GRP ] = `E203_DECINFO_GRP_ALU; assign alu_info_bus[`E203_DECINFO_RV32 ] = rv32; assign alu_info_bus[`E203_DECINFO_ALU_ADD] = rv32_add | rv32_addi | rv32_auipc | rv16_addi4spn | rv16_addi | rv16_addi16sp | rv16_add | // We also decode LI and MV as the add instruction, becuase // they all add x0 with a RS2 or Immeidate, and then write into RD rv16_li | rv16_mv; assign alu_info_bus[`E203_DECINFO_ALU_SUB] = rv32_sub | rv16_sub; assign alu_info_bus[`E203_DECINFO_ALU_SLT] = rv32_slt | rv32_slti; assign alu_info_bus[`E203_DECINFO_ALU_SLTU] = rv32_sltu | rv32_sltiu; assign alu_info_bus[`E203_DECINFO_ALU_XOR] = rv32_xor | rv32_xori | rv16_xor; assign alu_info_bus[`E203_DECINFO_ALU_SLL] = rv32_sll | rv32_slli | rv16_slli; assign alu_info_bus[`E203_DECINFO_ALU_SRL] = rv32_srl | rv32_srli | rv16_srli; assign alu_info_bus[`E203_DECINFO_ALU_SRA] = rv32_sra | rv32_srai | rv16_srai; assign alu_info_bus[`E203_DECINFO_ALU_OR ] = rv32_or | rv32_ori | rv16_or; assign alu_info_bus[`E203_DECINFO_ALU_AND] = rv32_and | rv32_andi | rv16_andi | rv16_and; assign alu_info_bus[`E203_DECINFO_ALU_LUI] = rv32_lui | rv16_lui; assign alu_info_bus[`E203_DECINFO_ALU_OP2IMM] = need_imm; assign alu_info_bus[`E203_DECINFO_ALU_OP1PC ] = rv32_auipc; assign alu_info_bus[`E203_DECINFO_ALU_NOP ] = rv16_nop | rv32_nop; assign alu_info_bus[`E203_DECINFO_ALU_ECAL ] = rv32_ecall; assign alu_info_bus[`E203_DECINFO_ALU_EBRK ] = rv32_ebreak | rv16_ebreak; assign alu_info_bus[`E203_DECINFO_ALU_WFI ] = rv32_wfi;
alu中包含一个csr读写控制子单元，所有csr指令都在这个子单元中执行。下面csr读写控制单元的信息总线，其中grp为011
wire csr_op = rv32_csr; wire [`E203_DECINFO_CSR_WIDTH-1:0] csr_info_bus; assign csr_info_bus[`E203_DECINFO_GRP ] = `E203_DECINFO_GRP_CSR; assign csr_info_bus[`E203_DECINFO_RV32 ] = rv32; assign csr_info_bus[`E203_DECINFO_CSR_CSRRW ] = rv32_csrrw | rv32_csrrwi; assign csr_info_bus[`E203_DECINFO_CSR_CSRRS ] = rv32_csrrs | rv32_csrrsi; assign csr_info_bus[`E203_DECINFO_CSR_CSRRC ] = rv32_csrrc | rv32_csrrci; assign csr_info_bus[`E203_DECINFO_CSR_RS1IMM] = rv32_csrrwi | rv32_csrrsi | rv32_csrrci; assign csr_info_bus[`E203_DECINFO_CSR_ZIMMM ] = rv32_rs1; assign csr_info_bus[`E203_DECINFO_CSR_RS1IS0] = rv32_rs1_x0; assign csr_info_bus[`E203_DECINFO_CSR_CSRIDX] = rv32_instr[31:20];
alu中乘法除法子单元进行乘法，除法运算，该单元的信息总线格式为：
// MUL/DIV Instructions wire rv32_mul = rv32_op & rv32_func3_000 & rv32_func7_0000001; wire rv32_mulh = rv32_op & rv32_func3_001 & rv32_func7_0000001; wire rv32_mulhsu = rv32_op & rv32_func3_010 & rv32_func7_0000001; wire rv32_mulhu = rv32_op & rv32_func3_011 & rv32_func7_0000001; wire rv32_div = rv32_op & rv32_func3_100 & rv32_func7_0000001; wire rv32_divu = rv32_op & rv32_func3_101 & rv32_func7_0000001; wire rv32_rem = rv32_op & rv32_func3_110 & rv32_func7_0000001; wire rv32_remu = rv32_op & rv32_func3_111 & rv32_func7_0000001; // The MULDIV group of instructions will be handled by MUL-DIV-datapath `ifdef E203_SUPPORT_MULDIV//{ wire muldiv_op = rv32_op & rv32_func7_0000001; `endif//} `ifndef E203_SUPPORT_MULDIV//{ wire muldiv_op = 1'b0; `endif//} wire [`E203_DECINFO_MULDIV_WIDTH-1:0] muldiv_info_bus; assign muldiv_info_bus[`E203_DECINFO_GRP ] = `E203_DECINFO_GRP_MULDIV; assign muldiv_info_bus[`E203_DECINFO_RV32 ] = rv32 ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_MUL ] = rv32_mul ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_MULH ] = rv32_mulh ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_MULHSU] = rv32_mulhsu ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_MULHU ] = rv32_mulhu ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_DIV ] = rv32_div ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_DIVU ] = rv32_divu ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_REM ] = rv32_rem ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_REMU ] = rv32_remu ; assign muldiv_info_bus[`E203_DECINFO_MULDIV_B2B ] = i_muldiv_b2b; assign dec_mulhsu = rv32_mulh | rv32_mulhsu | rv32_mulhu; assign dec_mul = rv32_mul; assign dec_div = rv32_div ; assign dec_divu = rv32_divu; assign dec_rem = rv32_rem; assign dec_remu = rv32_remu;
alu中的AGU子单元，主要负责Load，store指令和A扩展指令的地址生成，以及A扩展指令的微操作拆分和执行。
传输到AGU模块的信息总线格式为：
// =========================================================================== // Load/Store Instructions wire rv32_lb = rv32_load & rv32_func3_000; wire rv32_lh = rv32_load & rv32_func3_001; wire rv32_lw = rv32_load & rv32_func3_010; wire rv32_lbu = rv32_load & rv32_func3_100; wire rv32_lhu = rv32_load & rv32_func3_101; wire rv32_sb = rv32_store & rv32_func3_000; wire rv32_sh = rv32_store & rv32_func3_001; wire rv32_sw = rv32_store & rv32_func3_010; // =========================================================================== // Atomic Instructions `ifdef E203_SUPPORT_AMO//{ wire rv32_lr_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b00010); wire rv32_sc_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b00011); wire rv32_amoswap_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b00001); wire rv32_amoadd_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b00000); wire rv32_amoxor_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b00100); wire rv32_amoand_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b01100); wire rv32_amoor_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b01000); wire rv32_amomin_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b10000); wire rv32_amomax_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b10100); wire rv32_amominu_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b11000); wire rv32_amomaxu_w = rv32_amo & rv32_func3_010 & (rv32_func7[6:2] == 5'b11100); `endif//E203_SUPPORT_AMO} `ifndef E203_SUPPORT_AMO//{ wire rv32_lr_w = 1'b0; wire rv32_sc_w = 1'b0; wire rv32_amoswap_w = 1'b0; wire rv32_amoadd_w = 1'b0; wire rv32_amoxor_w = 1'b0; wire rv32_amoand_w = 1'b0; wire rv32_amoor_w = 1'b0; wire rv32_amomin_w = 1'b0; wire rv32_amomax_w = 1'b0; wire rv32_amominu_w = 1'b0; wire rv32_amomaxu_w = 1'b0; `endif//} wire amoldst_op = rv32_amo | rv32_load | rv32_store | rv16_lw | rv16_sw | (rv16_lwsp & (~rv16_lwsp_ilgl)) | rv16_swsp; // The RV16 always is word wire [1:0] lsu_info_size = rv32 ? rv32_func3[1:0] : 2'b10; // The RV16 always is signed wire lsu_info_usign = rv32? rv32_func3[2] : 1'b0; wire [`E203_DECINFO_AGU_WIDTH-1:0] agu_info_bus; assign agu_info_bus[`E203_DECINFO_GRP ] = `E203_DECINFO_GRP_AGU; assign agu_info_bus[`E203_DECINFO_RV32 ] = rv32; assign agu_info_bus[`E203_DECINFO_AGU_LOAD ] = rv32_load | rv32_lr_w | rv16_lw | rv16_lwsp; assign agu_info_bus[`E203_DECINFO_AGU_STORE ] = rv32_store | rv32_sc_w | rv16_sw | rv16_swsp; assign agu_info_bus[`E203_DECINFO_AGU_SIZE ] = lsu_info_size; assign agu_info_bus[`E203_DECINFO_AGU_USIGN ] = lsu_info_usign; assign agu_info_bus[`E203_DECINFO_AGU_EXCL ] = rv32_lr_w | rv32_sc_w; assign agu_info_bus[`E203_DECINFO_AGU_AMO ] = rv32_amo & (~(rv32_lr_w | rv32_sc_w));// We seperated the EXCL out of AMO in LSU handling assign agu_info_bus[`E203_DECINFO_AGU_AMOSWAP] = rv32_amoswap_w; assign agu_info_bus[`E203_DECINFO_AGU_AMOADD ] = rv32_amoadd_w ; assign agu_info_bus[`E203_DECINFO_AGU_AMOAND ] = rv32_amoand_w ; assign agu_info_bus[`E203_DECINFO_AGU_AMOOR ] = rv32_amoor_w ; assign agu_info_bus[`E203_DECINFO_AGU_AMOXOR ] = rv32_amoxor_w ; assign agu_info_bus[`E203_DECINFO_AGU_AMOMAX ] = rv32_amomax_w ; assign agu_info_bus[`E203_DECINFO_AGU_AMOMIN ] = rv32_amomin_w ; assign agu_info_bus[`E203_DECINFO_AGU_AMOMAXU] = rv32_amomaxu_w; assign agu_info_bus[`E203_DECINFO_AGU_AMOMINU] = rv32_amominu_w; assign agu_info_bus[`E203_DECINFO_AGU_OP2IMM ] = need_imm;
指令全为0和全为1是非法的指令，下面的代码判定指令是否为全0和全1。
// Reuse the common signals as much as possible to save gatecounts wire rv32_all0s_ilgl = rv32_func7_0000000 & rv32_rs2_x0 & rv32_rs1_x0 & rv32_func3_000 & rv32_rd_x0 & opcode_6_5_00 & opcode_4_2_000 & (opcode[1:0] == 2'b00); wire rv32_all1s_ilgl = rv32_func7_1111111 & rv32_rs2_x31 & rv32_rs1_x31 & rv32_func3_111 & rv32_rd_x31 & opcode_6_5_11 & opcode_4_2_111 & (opcode[1:0] == 2'b11); wire rv16_all0s_ilgl = rv16_func3_000 //rv16_func3 = rv32_instr[15:13]; & rv32_func3_000 //rv32_func3 = rv32_instr[14:12]; & rv32_rd_x0 //rv32_rd = rv32_instr[11:7]; & opcode_6_5_00 & opcode_4_2_000 & (opcode[1:0] == 2'b00); wire rv16_all1s_ilgl = rv16_func3_111 & rv32_func3_111 & rv32_rd_x31 & opcode_6_5_11 & opcode_4_2_111 & (opcode[1:0] == 2'b11); wire rv_all0s1s_ilgl = rv32 ? (rv32_all0s_ilgl | rv32_all1s_ilgl) : (rv16_all0s_ilgl | rv16_all1s_ilgl);
以下的代码判断指令是否需要寄存器操作数1，寄存器操作数2,是否需要写目的寄存器。
// All the RV32IMA need RD register except the // * Branch, Store, // * fence, fence_i // * ecall, ebreak wire rv32_need_rd = (~rv32_rd_x0) & ( ( (~rv32_branch) & (~rv32_store) & (~rv32_fence_fencei) & (~rv32_ecall_ebreak_ret_wfi) ) ); // All the RV32IMA need RS1 register except the // * lui // * auipc // * jal // * fence, fence_i // * ecall, ebreak // * csrrwi // * csrrsi // * csrrci wire rv32_need_rs1 = (~rv32_rs1_x0) & ( ( (~rv32_lui) & (~rv32_auipc) & (~rv32_jal) & (~rv32_fence_fencei) & (~rv32_ecall_ebreak_ret_wfi) & (~rv32_csrrwi) & (~rv32_csrrsi) & (~rv32_csrrci) ) ); // Following RV32IMA instructions need RS2 register // * branch // * store // * rv32_op // * rv32_amo except the rv32_lr_w wire rv32_need_rs2 = (~rv32_rs2_x0) & ( ( (rv32_branch) | (rv32_store) | (rv32_op) | (rv32_amo & (~rv32_lr_w)) ) );
