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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];
};
void execute_op_imm(struct Hart* hart, uint32_t instruction)
{
struct Instruction inst = decode_i_type(instruction);
switch (inst.funct3)
{
case 0: // ADDI
hart->regs[inst.rd] = hart->regs[inst.rs1] + inst.imm;
break;
case 1: // SLLI
hart->regs[inst.rd] = hart->regs[inst.rs1] << (inst.imm & 0x1F);
break;
case 2: // SLTI
hart->regs[inst.rd] = (int32_t)hart->regs[inst.rs1] < (int32_t)inst.imm ? 1 : 0;
break;
case 3: // SLTIU
hart->regs[inst.rd] = hart->regs[inst.rs1] < inst.imm ? 1 : 0;
break;
case 4: // XORI
hart->regs[inst.rd] = hart->regs[inst.rs1] ^ inst.imm;
break;
case 5: // SRLI, SRAI
{
const uint32_t shamt = inst.imm & 0x1F;
uint32_t res = hart->regs[inst.rs1] >> shamt;
if ((inst.imm & 0x400) && shamt > 0) { res = sign_extend(res, 32 - shamt); }
hart->regs[inst.rd] = res;
break;
}
case 6: // ORI
hart->regs[inst.rd] = hart->regs[inst.rs1] | inst.imm;
break;
case 7: // ANDI
hart->regs[inst.rd] = hart->regs[inst.rs1] & inst.imm;
break;
default:
assert(!"Unhandled OP-IMM");
}
}
void execute_op(struct Hart* hart, uint32_t instruction)
{
struct Instruction inst = decode_r_type(instruction);
switch (inst.funct3)
{
case 0: // ADD, SUB
if (instruction & 0x40000000)
{
hart->regs[inst.rd] = hart->regs[inst.rs1] - hart->regs[inst.rs2];
}
else
{
hart->regs[inst.rd] = hart->regs[inst.rs1] + hart->regs[inst.rs2];
}
break;
case 1: // SLL
hart->regs[inst.rd] = hart->regs[inst.rs1] << (hart->regs[inst.rs2] & 0x1F);
break;
case 2: // SLT
hart->regs[inst.rd] = (int32_t)hart->regs[inst.rs1] < (int32_t)hart->regs[inst.rs2] ? 1 : 0;
break;
case 3: // SLTU
hart->regs[inst.rd] = hart->regs[inst.rs1] < hart->regs[inst.rs2] ? 1 : 0;
break;
case 4: // XOR
hart->regs[inst.rd] = hart->regs[inst.rs1] ^ hart->regs[inst.rs2];
break;
case 5: // SRL, SRA
{
const uint32_t shamt = hart->regs[inst.rs2] & 0x1F;
uint32_t res = hart->regs[inst.rs1] >> shamt;
if ((instruction & 0x40000000) && shamt > 0) { res = sign_extend(res, 32 - shamt); }
hart->regs[inst.rd] = res;
break;
}
case 6: // OR
hart->regs[inst.rd] = hart->regs[inst.rs1] | hart->regs[inst.rs2];
break;
case 7: // AND
hart->regs[inst.rd] = hart->regs[inst.rs1] & hart->regs[inst.rs2];
break;
default:
assert(!"Unhandled OP-IMM");
}
}
void execute(struct Hart* hart, uint32_t instruction)
{
switch (instruction & 0x7f)
{
case 0x13:
execute_op_imm(hart, instruction);
break;
case 0x17: // AUIPC
{
struct Instruction inst = decode_u_type(instruction);
hart->regs[inst.rd] = inst.imm + hart->pc;
break;
}
case 0x33:
execute_op(hart, instruction);
break;
case 0x37: // LUI
{
struct Instruction inst = decode_u_type(instruction);
hart->regs[inst.rd] = inst.imm;
break;
}
default:
assert(!"Unhandled opcode");
}
}
void test_addi()
{
struct Hart hart = {0};
execute(&hart, 0x00500093); // addi x1, x0, 5
assert(hart.regs[1] == 5);
execute(&hart, 0xffe00093); // addi, x1, x0, -2
assert(hart.regs[1] == 0xfffffffe);
}
void test_slti_sltiu()
{
struct Hart hart = {0};
hart.regs[1] = 5;
execute(&hart, 0x00f0b113); // sltiu x2, x1, 15
assert(hart.regs[2] == 1);
execute(&hart, 0x0050b113); // sltiu x2, x1, 15
assert(hart.regs[2] == 0);
execute(&hart, 0x0010b113); // sltiu x2, x1, 15
assert(hart.regs[2] == 0);
execute(&hart, 0x00f0a113); // slti x2, x1, 15
assert(hart.regs[2] == 1);
execute(&hart, 0x0050a113); // slti x2, x1, 15
assert(hart.regs[2] == 0);
execute(&hart, 0x0010a113); // slti x2, x1, 15
assert(hart.regs[2] == 0);
execute(&hart, 0xffb0a113); // slti x2, x1, -5
assert(hart.regs[2] == 0);
hart.regs[1] = (uint32_t)-20;
execute(&hart, 0xffb0a113); // slti x2, x1, -5
assert(hart.regs[2] == 1);
}
void test_andi_ori_xori()
{
struct Hart hart = {0};
hart.regs[1] = 6;
execute(&hart, 0x00c0c113); // xori x2, x1, 12
assert(hart.regs[2] == 10);
execute(&hart, 0x00c0e113); // ori x2, x1, 12
assert(hart.regs[2] == 14);
execute(&hart, 0x00c0f113); // andi x2, x1, 12
assert(hart.regs[2] == 4);
}
void test_slli_srli_srai()
{
struct Hart hart = {0};
hart.regs[1] = 6;
execute(&hart, 0x00209113); // slli x2, x1, 2
assert(hart.regs[2] == 24);
execute(&hart, 0x0020d113); // srli x2, x1, 2
assert(hart.regs[2] == 1);
execute(&hart, 0x4020d113); // srai x2, x1, 2
assert(hart.regs[2] == 1);
hart.regs[1] = (uint32_t)-6;
execute(&hart, 0x0020d113); // srli x2, x1, 2
assert(hart.regs[2] == 0x3FFFFFFE);
execute(&hart, 0x4020d113); // srai x2, x1, 2
assert(hart.regs[2] == 0xFFFFFFFE);
}
void test_lui_auipc()
{
struct Hart hart = {0};
execute(&hart, 0x0007b0b7); // lui x1, 503808
assert(hart.regs[1] == 503808);
execute(&hart, 0x0007b097); // auipc x1, 503808
assert(hart.regs[1] == 503808);
hart.pc = 12;
execute(&hart, 0x0007b097); // auipc x1, 503808
assert(hart.regs[1] == 503820);
}
void test_op()
{
struct Hart hart = {0};
hart.regs[1] = 3;
hart.regs[2] = 4;
hart.regs[4] = (uint32_t)-1;
execute(&hart, 0x002081b3); // add, x3, x1, x2
assert(hart.regs[3] == 7);
execute(&hart, 0x402081b3); // sub x3, x1, x2
assert(hart.regs[3] == 0xFFFFFFFF);
execute(&hart, 0x0020a1b3); // slt x3, x1, x2
assert(hart.regs[3] == 1);
execute(&hart, 0x001121b3); // slt x3, x2, 1
assert(hart.regs[3] == 0);
execute(&hart, 0x001131b3); // sltu x3, x2, x1
assert(hart.regs[3] == 0);
execute(&hart, 0x0020b1b3); // sltu x3, x1, x2
assert(hart.regs[3] == 1);
execute(&hart, 0x0040a1b3); // slt x3, x1, x4
assert(hart.regs[3] == 0);
hart.regs[1] = 6;
hart.regs[2] = 12;
execute(&hart, 0x0020e1b3); // or x3, x1, x2
assert(hart.regs[3] == 14);
execute(&hart, 0x0020c1b3); // xor x3, x1, x2
assert(hart.regs[3] == 10);
execute(&hart, 0x0020f1b3); // and x3, x1, x2
assert(hart.regs[3] == 4);
hart.regs[1] = 6;
hart.regs[2] = 2;
execute(&hart, 0x002091b3); // sll x3, x1, x2
assert(hart.regs[3] == 24);
execute(&hart, 0x0020d1b3); // srl x3, x1, x2
assert(hart.regs[3] == 1);
execute(&hart, 0x4020d1b3); // sra x3, x1, x2
assert(hart.regs[3] == 1);
hart.regs[1] = (uint32_t)-6;
hart.regs[2] = 2;
execute(&hart, 0x4020d1b3); // sra x3, x1, x2
assert(hart.regs[3] == 0xFFFFFFFE);
}
void test()
{
test_addi();
test_slti_sltiu();
test_andi_ori_xori();
test_slli_srli_srai();
test_lui_auipc();
test_op();
}
int main(int argc, char* argv[])
{
test();
return EXIT_SUCCESS;
}
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