99 lines
2.7 KiB
C
99 lines
2.7 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <inttypes.h>
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#include <assert.h>
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inline uint32_t sign_extend(uint32_t word, uint32_t size)
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{
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const uint32_t mask = 1U << (size - 1);
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return (word ^ mask) - mask;
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}
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struct Instruction
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{
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uint8_t opcode;
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uint8_t rs1;
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uint8_t rs2;
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uint8_t rd;
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uint8_t funct3;
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uint8_t funct7;
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uint32_t imm;
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};
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struct Instruction decode_r_type(uint32_t word)
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{
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struct Instruction instruction = {0};
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instruction.opcode = word & 0x7F;
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instruction.rd = (word >> 7) & 0x1F;
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instruction.funct3 = (word >> 12) & 0x07;
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instruction.rs1 = (word >> 15) & 0x1F;
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instruction.rs2 = (word >> 20) & 0x1F;
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instruction.funct7 = word >> 25;
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return instruction;
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};
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struct Instruction decode_i_type(uint32_t word)
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{
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struct Instruction instruction = {0};
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instruction.opcode = word & 0x7F;
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instruction.rd = (word >> 7) & 0x1F;
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instruction.funct3 = (word >> 12) & 0x07;
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instruction.rs1 = (word >> 15) & 0x1F;
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instruction.imm = sign_extend(word >> 20, 12);
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return instruction;
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};
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struct Instruction decode_s_type(uint32_t word)
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{
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struct Instruction instruction = {0};
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instruction.opcode = word & 0x7F;
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instruction.funct3 = (word >> 12) & 0x07;
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instruction.rs1 = (word >> 15) & 0x1F;
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instruction.rs2 = (word >> 20) & 0x1F;
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instruction.imm = sign_extend(((word >> 7) & 0x1F) | (word >> 25), 12);
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return instruction;
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};
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struct Instruction decode_b_type(uint32_t word)
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{
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struct Instruction instruction = decode_s_type(word);
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instruction.imm = ((instruction.imm << 11) & 0x800) | (instruction.imm & 0xfffff7ff);
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return instruction;
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};
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struct Instruction decode_u_type(uint32_t word)
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{
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struct Instruction instruction = {0};
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instruction.opcode = word & 0x7F;
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instruction.rd = (word >> 7) & 0x1F;
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instruction.imm = word & 0xFFFFF000;
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return instruction;
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};
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struct Instruction decode_j_type(uint32_t word)
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{
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struct Instruction instruction = {0};
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instruction.opcode = word & 0x7F;
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instruction.rd = (word >> 7) & 0x1F;
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instruction.imm = sign_extend(
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((word & 0x80000000) >> 11) |
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((word & 0x000FF000) >> 0) |
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((word & 0x00100000) >> 9) |
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((word & 0x7FE00000) >> 20), 21);
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return instruction;
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}
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struct Hart
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{
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uint32_t pc;
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uint32_t regs[32];
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};
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int main(int argc, char* argv[])
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{
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uint32_t instruction = 0xfa728213;
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struct Instruction instr = decode_i_type(instruction);
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printf("%u %u %u\n", instr.rd, instr.rs1, instr.imm);
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return EXIT_SUCCESS;
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}
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