lib/rv32/tests/asm.viv

# The assembler against encodings worked out by hand from the RISC-V
# unprivileged manual (version 20191213, figure 2.3 and chapter 24), and
# small programs assembled and run on the simulator.

from rv32.asm import assemble
from rv32.sim import machine, run
from rv32.bits import pow2

#| The 32-bit words of an assembled program's code.
def words(text: Str) -> [Int] {
    p = assemble(text)
    out: [Int] = []
    for k to p.text_bytes // 4 {
        w = sum([p.image[4 * k + j] * pow2(8 * int(j)) for j to 4])
        out = append(out, int(w))
    }
    return out
}

#| Assemble, run and give the exit code.
def exit_code(text: Str) -> Int {
    p = assemble(text)
    return run(machine(p.image, 0), 100000).exit_code
}

test "one instruction of each format" {
    assert_true(words("add a0, a0, a1")[0] == 0x00b50533)       # R
    assert_true(words("sub t0, t1, t2")[0] == 0x407302b3)       # R, funct7 0x20
    assert_true(words("addi a0, zero, -1")[0] == 0xfff00513)    # I
    assert_true(words("srai x5, x6, 3")[0] == 0x40335293)       # I, shift with funct7
    assert_true(words("lw ra, 12(sp)")[0] == 0x00c12083)        # load
    assert_true(words("sw ra, -4(sp)")[0] == 0xfe112e23)        # S
    assert_true(words("lui a0, 0x12345")[0] == 0x12345537)      # U
    assert_true(words("mul a0, a0, a1")[0] == 0x02b50533)       # R, funct7 1
    assert_true(words("remu t0, t1, t2")[0] == 0x027372b3)
    assert_true(words("ecall")[0] == 0x00000073)
    assert_true(words("ebreak")[0] == 0x00100073)
}

test "branches and jumps to labels, back and forward" {
    w = words("top: beq x0, x0, top\njal x0, top\nj 1f\nnop\n1: ret")
    assert_true(w[0] == 0x00000063)     # beq x0, x0, 0
    assert_true(w[1] == 0xffdff06f)     # jal x0, -4
    assert_true(w[2] == 0x0080006f)     # jal x0, +8
    assert_true(w[3] == 0x00000013)     # nop = addi x0, x0, 0
    assert_true(w[4] == 0x00008067)     # ret = jalr x0, 0(ra)
}

test "li picks one or two instructions" {
    assert_true(len(words("li a0, 2047")) == 1)
    w = words("li a0, 0x12345fff")
    #: the low part 0xfff reads as -1, so lui loads 0x12346 to make up for it
    assert_true(w[0] == 0x12346537)
    assert_true(w[1] == 0xfff50513)
}

test "programs run: a loop, a call, data" {
    assert_true(exit_code("li a0, 0\nli t0, 10\n1: add a0, a0, t0\naddi t0, t0, -1\nbnez t0, 1b\nli a7, 93\necall") == 55)
    assert_true(exit_code("call f\nli a7, 93\necall\nf: li a0, 7\nret") == 7)
    assert_true(exit_code("la t0, x\nlw a0, 0(t0)\nli a7, 93\necall\n.data\nx: .word 42") == 42)
}

# SPDX-License-Identifier: MIT OR Apache-2.0
# SPDX-FileCopyrightText: 2026 The Viv authors