447 lines
12 KiB
C
447 lines
12 KiB
C
#include "emulator/hart.h"
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#include <stdio.h>
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#include <inttypes.h>
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#include <assert.h>
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#include <stdbool.h>
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#include <string.h>
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static 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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typedef struct Instruction Instruction;
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static Instruction decode_r_type(uint32_t word)
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{
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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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static Instruction decode_i_type(uint32_t word)
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{
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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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static Instruction decode_s_type(uint32_t word)
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{
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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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static Instruction decode_b_type(uint32_t word)
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{
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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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static Instruction decode_u_type(uint32_t word)
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{
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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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static Instruction decode_j_type(uint32_t word)
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{
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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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static void execute_op_imm(Hart* hart, uint32_t instruction)
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{
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const Instruction inst = decode_i_type(instruction);
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if (inst.rd == 0) return;
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switch (inst.funct3)
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{
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case 0: // ADDI
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hart->regs[inst.rd] = hart->regs[inst.rs1] + inst.imm;
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break;
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case 1: // SLLI
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hart->regs[inst.rd] = hart->regs[inst.rs1] << (inst.imm & 0x1F);
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break;
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case 2: // SLTI
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hart->regs[inst.rd] = (int32_t)hart->regs[inst.rs1] < (int32_t)inst.imm ? 1 : 0;
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break;
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case 3: // SLTIU
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hart->regs[inst.rd] = hart->regs[inst.rs1] < inst.imm ? 1 : 0;
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break;
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case 4: // XORI
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hart->regs[inst.rd] = hart->regs[inst.rs1] ^ inst.imm;
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break;
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case 5: // SRLI, SRAI
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{
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const uint32_t shamt = inst.imm & 0x1F;
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uint32_t res = hart->regs[inst.rs1] >> shamt;
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if ((inst.imm & 0x400) && shamt > 0) { res = sign_extend(res, 32 - shamt); }
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hart->regs[inst.rd] = res;
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break;
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}
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case 6: // ORI
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hart->regs[inst.rd] = hart->regs[inst.rs1] | inst.imm;
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break;
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case 7: // ANDI
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hart->regs[inst.rd] = hart->regs[inst.rs1] & inst.imm;
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break;
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default:
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assert(!"Unhandled OP-IMM");
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}
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}
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static void execute_op(Hart* hart, uint32_t instruction)
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{
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const Instruction inst = decode_r_type(instruction);
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if (inst.rd == 0) return;
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switch (inst.funct3)
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{
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case 0: // ADD, SUB
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if (instruction & 0x40000000)
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{
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hart->regs[inst.rd] = hart->regs[inst.rs1] - hart->regs[inst.rs2];
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}
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else
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{
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hart->regs[inst.rd] = hart->regs[inst.rs1] + hart->regs[inst.rs2];
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}
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break;
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case 1: // SLL
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hart->regs[inst.rd] = hart->regs[inst.rs1] << (hart->regs[inst.rs2] & 0x1F);
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break;
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case 2: // SLT
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hart->regs[inst.rd] = (int32_t)hart->regs[inst.rs1] < (int32_t)hart->regs[inst.rs2] ? 1 : 0;
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break;
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case 3: // SLTU
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hart->regs[inst.rd] = hart->regs[inst.rs1] < hart->regs[inst.rs2] ? 1 : 0;
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break;
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case 4: // XOR
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hart->regs[inst.rd] = hart->regs[inst.rs1] ^ hart->regs[inst.rs2];
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break;
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case 5: // SRL, SRA
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{
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const uint32_t shamt = hart->regs[inst.rs2] & 0x1F;
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uint32_t res = hart->regs[inst.rs1] >> shamt;
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if ((instruction & 0x40000000) && shamt > 0) { res = sign_extend(res, 32 - shamt); }
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hart->regs[inst.rd] = res;
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break;
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}
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case 6: // OR
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hart->regs[inst.rd] = hart->regs[inst.rs1] | hart->regs[inst.rs2];
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break;
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case 7: // AND
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hart->regs[inst.rd] = hart->regs[inst.rs1] & hart->regs[inst.rs2];
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break;
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default:
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assert(!"Unhandled OP-IMM");
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}
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}
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static void execute_branch(Hart* hart, uint32_t instruction)
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{
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const Instruction inst = decode_b_type(instruction);
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const uint32_t r1 = hart->regs[inst.rs1];
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const uint32_t r2 = hart->regs[inst.rs2];
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bool take_branch = false;
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switch (inst.funct3)
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{
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case 0: take_branch = (r1 == r2); break;
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case 1: take_branch = (r1 != r2); break;
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case 4: take_branch = (r1 < r2); break;
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case 5: take_branch = (r1 >= r2); break;
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case 6: take_branch = ((int32_t)r1 < (int32_t)r2); break;
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case 7: take_branch = ((int32_t)r1 >= (int32_t)r2); break;
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}
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if (take_branch)
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{
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hart->pc += inst.imm;
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}
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else
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{
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hart->pc += 4;
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}
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}
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static inline uint32_t load_size(Hart* hart, uint32_t address, uint32_t size)
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{
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if ((address & 0x80000000) == 0)
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{
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assert(address + size < hart->mem_size);
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uint32_t value = 0;
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memcpy(&value, hart->mem + address, size);
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return value;
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}
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return 0;
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}
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static uint32_t load_byte(Hart* hart, uint32_t address)
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{
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return load_size(hart, address, 1);
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}
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static uint32_t load_half(Hart* hart, uint32_t address)
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{
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return load_size(hart, address, 2);
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}
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static uint32_t load_word(Hart* hart, uint32_t address)
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{
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return load_size(hart, address, 4);
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}
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static inline void store_size(Hart* hart, uint32_t address, uint32_t value, uint32_t size)
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{
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if ((address & 0x80000000) == 0)
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{
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assert(address + size < hart->mem_size);
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memcpy(hart->mem + address, &value, size);
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}
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else if (address == 0x80000000)
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{
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fwrite(&value, 1, size, stdout);
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}
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}
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static void store_byte(Hart* hart, uint32_t address, uint8_t value)
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{
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store_size(hart, address, value, 1);
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}
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static void store_half(Hart* hart, uint32_t address, uint16_t value)
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{
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store_size(hart, address, value, 2);
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}
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static void store_word(Hart* hart, uint32_t address, uint32_t value)
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{
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store_size(hart, address, value, 4);
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}
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static void execute_op_load(Hart* hart, uint32_t instruction)
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{
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const Instruction inst = decode_i_type(instruction);
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const uint32_t address = hart->regs[inst.rs1] + inst.imm;
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uint32_t value = 0;
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switch (inst.funct3 & 0x03)
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{
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case 0:
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value = load_byte(hart, address);
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if ((inst.funct3 & 0x40) == 0)
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{
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value = sign_extend(value, 8);
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}
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break;
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case 1:
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value = load_half(hart, address);
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if ((inst.funct3 & 0x40) == 0)
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{
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value = sign_extend(value, 16);
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}
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break;
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case 2:
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value = load_byte(hart, address);
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break;
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default:
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assert(!"Unhandled load size");
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break;
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}
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if (inst.rd != 0)
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{
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hart->regs[inst.rd] = value;
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}
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}
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static void execute_op_store(Hart* hart, uint32_t instruction)
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{
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const Instruction inst = decode_s_type(instruction);
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const uint32_t address = hart->regs[inst.rs1] + inst.imm;
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const uint32_t value = hart->regs[inst.rs2];
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switch (inst.funct3 & 0x03)
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{
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case 0: store_byte(hart, address, value & 0xFF); break;
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case 1: store_half(hart, address, value & 0xFFFF); break;
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case 2: store_word(hart, address, value); break;
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default:
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assert(!"Unhandled store size");
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break;
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}
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}
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static void execute_misc_mem(Hart* hart, uint32_t instruction)
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{
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const Instruction inst = decode_i_type(instruction);
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if (inst.funct3 == 0)
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{
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// FENCE
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}
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else
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{
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assert(!"Unhandled MISC-MEM instruction");
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}
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}
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static void execute_system(Hart* hart, uint32_t instruction)
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{
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const Instruction inst = decode_i_type(instruction);
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if (inst.funct3 == 0 && inst.rs1 == 0 && inst.rd == 0)
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{
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if (inst.imm == 0)
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{
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// ECALL
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}
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else if (inst.imm == 1)
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{
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// EBREAK
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}
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else
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{
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assert(!"Unhandled SYSTEM/PRIV instruction");
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}
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}
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else
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{
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assert(!"Unhandled SYSTEM instruction");
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}
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}
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void execute(Hart* hart, uint32_t instruction)
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{
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switch (instruction & 0x7f)
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{
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case 0x03:
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execute_op_load(hart, instruction);
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hart->pc += 4;
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break;
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case 0x0F:
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execute_misc_mem(hart, instruction);
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hart->pc += 4;
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break;
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case 0x13:
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execute_op_imm(hart, instruction);
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hart->pc += 4;
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break;
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case 0x17: // AUIPC
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{
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Instruction inst = decode_u_type(instruction);
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if (inst.rd != 0)
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{
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hart->regs[inst.rd] = inst.imm + hart->pc;
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}
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hart->pc += 4;
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break;
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}
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case 0x23:
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execute_op_store(hart, instruction);
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hart->pc += 4;
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break;
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case 0x33:
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execute_op(hart, instruction);
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hart->pc += 4;
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break;
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case 0x37: // LUI
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{
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Instruction inst = decode_u_type(instruction);
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if (inst.rd != 0)
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{
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hart->regs[inst.rd] = inst.imm;
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}
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hart->pc += 4;
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break;
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}
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case 0x63:
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execute_branch(hart, instruction);
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break;
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case 0x67: // JALR
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{
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Instruction inst = decode_i_type(instruction);
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assert(inst.funct3 == 0);
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if (inst.rd != 0)
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{
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hart->regs[inst.rd] = hart->pc + 4;
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}
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hart->pc = (hart->regs[inst.rs1] + inst.imm) & 0xFFFFFFFE;
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break;
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}
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case 0x6F: // JAL
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{
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Instruction inst = decode_j_type(instruction);
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if (inst.rd != 0)
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{
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hart->regs[inst.rd] = hart->pc + 4;
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}
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hart->pc += inst.imm;
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break;
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}
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case 0x73:
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{
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execute_system(hart, instruction);
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hart->pc += 4;
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break;
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}
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default:
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assert(!"Unhandled opcode");
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}
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assert(hart->regs[0] == 0);
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}
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void execute_from(Hart* hart, uint32_t start_address)
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{
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hart->pc = start_address;
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while (true)
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{
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uint32_t instruction = load_word(hart, hart->pc);
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execute(hart, instruction);
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}
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}
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