mirror of
https://github.com/ratspeak/C6-Reticulum-ASM
synced 2026-08-12 18:07:18 -04:00
dac9e13b46
Loop forwards each byte to uart_tx_byte. ra/s0/s1 saved in a 16-byte frame; s0 holds the buffer cursor and s1 the remaining count, both across the inner call. Empty-buffer case exits at the loop head with one branch. Static checks: aligned prologue, sw of ra+s0+s1, lbu a0,0(s0) + addi s0,1 + addi s1,-1 in the loop, beqz s1 head exit, restored epilogue + ret.
70 lines
2.9 KiB
Python
70 lines
2.9 KiB
Python
"""Tests for src/uart/uart_tx_bytes.S.
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Static disassembly checks: prologue saves ra/s0/s1, loop forwards each
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byte to uart_tx_byte, epilogue restores and returns. Integration cover
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(actual byte-stream observed on qemu UART) lands when _main wires the
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boot chain.
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"""
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from __future__ import annotations
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import re
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import pytest
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from harness import build
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@pytest.fixture(scope="module")
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def artifacts() -> build.BuildArtifacts:
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return build.build("qemu-virt")
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def test_function_exists(artifacts: build.BuildArtifacts) -> None:
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assert build.symbol_address(artifacts.elf, "uart_tx_bytes") > 0
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def test_prologue_reserves_aligned_frame(artifacts: build.BuildArtifacts) -> None:
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"""16-byte stack frame, ra/s0/s1 saved before any other work."""
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body = build.objdump_disassemble(artifacts.elf, symbol="uart_tx_bytes")
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instrs = [line for line in body.splitlines() if re.match(r"^\s*[0-9a-f]{8}:", line)]
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# First instruction adjusts sp by -16 (compressed `c.addi16sp` is OK too).
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assert "sp" in instrs[0] and ("-16" in instrs[0] or "addi" in instrs[0]), instrs[0]
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# ra, s0, s1 stored in the frame somewhere in the prologue.
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head = "\n".join(instrs[:6])
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assert re.search(r"\bsw\b\s+ra,", head), head
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assert re.search(r"\bsw\b\s+s0,", head) or re.search(r"\bc\.swsp\b\s+s0,", head), head
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assert re.search(r"\bsw\b\s+s1,", head) or re.search(r"\bc\.swsp\b\s+s1,", head), head
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def test_calls_uart_tx_byte(artifacts: build.BuildArtifacts) -> None:
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body = build.objdump_disassemble(artifacts.elf, symbol="uart_tx_bytes")
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assert "uart_tx_byte" in body, body
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def test_loop_loads_byte_and_advances_cursor(artifacts: build.BuildArtifacts) -> None:
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body = build.objdump_disassemble(artifacts.elf, symbol="uart_tx_bytes")
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# `lbu a0, 0(s0)` (byte from cursor) and `addi s0, s0, 1` (advance).
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assert re.search(r"\blbu\b\s+a0,\s*0\(s0\)", body), body
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assert re.search(r"\baddi\b\s+s0,\s*s0,\s*1", body), body
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# Counter decrement: `addi s1, s1, -1`.
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assert re.search(r"\baddi\b\s+s1,\s*s1,\s*-1", body), body
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def test_epilogue_restores_and_returns(artifacts: build.BuildArtifacts) -> None:
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body = build.objdump_disassemble(artifacts.elf, symbol="uart_tx_bytes")
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instrs = [line for line in body.splitlines() if re.match(r"^\s*[0-9a-f]{8}:", line)]
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tail = "\n".join(instrs[-6:])
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assert re.search(r"\blw\b\s+ra,", tail) or "c.lw" in tail, tail
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assert "ret" in tail or "jalr\tzero" in tail, tail
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# sp restored upward by 16 (matching the prologue).
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assert "16" in tail, tail
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def test_count_zero_short_circuits(artifacts: build.BuildArtifacts) -> None:
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"""The empty-buffer case: a beqz at the loop head exits before any
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byte is read."""
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body = build.objdump_disassemble(artifacts.elf, symbol="uart_tx_bytes")
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# Find the first beqz that targets an address inside the function — that
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# is the loop-head exit.
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assert re.search(r"\bbeqz\b\s+s1", body), body
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