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