diff --git a/esphome/components/esp32/core.cpp b/esphome/components/esp32/core.cpp index 59b791da403..7ebbba609e8 100644 --- a/esphome/components/esp32/core.cpp +++ b/esphome/components/esp32/core.cpp @@ -22,8 +22,8 @@ extern "C" __attribute__((weak)) void initArduino() {} namespace esphome { void HOT yield() { vPortYield(); } -uint32_t IRAM_ATTR HOT millis() { return (uint32_t) (esp_timer_get_time() / 1000ULL); } -uint64_t HOT millis_64() { return static_cast(esp_timer_get_time()) / 1000ULL; } +uint32_t IRAM_ATTR HOT millis() { return micros_to_millis(static_cast(esp_timer_get_time())); } +uint64_t HOT millis_64() { return micros_to_millis(static_cast(esp_timer_get_time())); } void HOT delay(uint32_t ms) { vTaskDelay(ms / portTICK_PERIOD_MS); } uint32_t IRAM_ATTR HOT micros() { return (uint32_t) esp_timer_get_time(); } void IRAM_ATTR HOT delayMicroseconds(uint32_t us) { delay_microseconds_safe(us); } diff --git a/esphome/components/rp2040/core.cpp b/esphome/components/rp2040/core.cpp index 6386d53292f..a15ee7e2635 100644 --- a/esphome/components/rp2040/core.cpp +++ b/esphome/components/rp2040/core.cpp @@ -11,8 +11,8 @@ namespace esphome { void HOT yield() { ::yield(); } -uint64_t millis_64() { return time_us_64() / 1000ULL; } -uint32_t HOT millis() { return static_cast(millis_64()); } +uint64_t millis_64() { return micros_to_millis(time_us_64()); } +uint32_t HOT millis() { return micros_to_millis(time_us_64()); } void HOT delay(uint32_t ms) { ::delay(ms); } uint32_t HOT micros() { return ::micros(); } void HOT delayMicroseconds(uint32_t us) { delay_microseconds_safe(us); } diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h index c68cb549bb4..ae505a2d8a0 100644 --- a/esphome/core/helpers.h +++ b/esphome/core/helpers.h @@ -599,6 +599,44 @@ template constexpr uint32_t fnv1a_hash_extend(uint32_t hash, T constexpr uint32_t fnv1a_hash(const char *str) { return fnv1a_hash_extend(FNV1_OFFSET_BASIS, str); } inline uint32_t fnv1a_hash(const std::string &str) { return fnv1a_hash(str.c_str()); } +/// Convert a 64-bit microsecond count to milliseconds without calling +/// __udivdi3 (software 64-bit divide, ~1200 ns on Xtensa @ 240 MHz). +/// +/// Returns uint32_t by default (for millis()), or uint64_t when requested +/// (for millis_64()). The only difference is whether hi * Q is truncated +/// to 32 bits or widened to 64. +/// +/// On 32-bit targets, GCC does not optimize 64-bit constant division into a +/// multiply-by-reciprocal. Since 1000 = 8 * 125, we first right-shift by 3 +/// (free divide-by-8), then use the Euclidean division identity to decompose +/// the remaining 64-bit divide-by-125 into a single 32-bit division: +/// +/// floor(us / 1000) = floor(floor(us / 8) / 125) [exact for integers] +/// 2^32 = Q * 125 + R (34359738 * 125 + 46) +/// (hi * 2^32 + lo) / 125 = hi * Q + (hi * R + lo) / 125 +/// +/// GCC optimizes the remaining 32-bit "/ 125U" into a multiply-by-reciprocal +/// (mulhu + shift), so no division instruction is emitted. +/// +/// Safe for us up to ~3.2e18 (~101,700 years of microseconds). +/// +/// See: https://en.wikipedia.org/wiki/Euclidean_division +/// See: https://ridiculousfish.com/blog/posts/labor-of-division-episode-iii.html +template inline constexpr ESPHOME_ALWAYS_INLINE ReturnT micros_to_millis(uint64_t us) { + constexpr uint32_t d = 125U; + constexpr uint32_t q = static_cast((1ULL << 32) / d); // 34359738 + constexpr uint32_t r = static_cast((1ULL << 32) % d); // 46 + // 1000 = 8 * 125; divide-by-8 is a free shift + uint64_t x = us >> 3; + uint32_t lo = static_cast(x); + uint32_t hi = static_cast(x >> 32); + // Combine remainder term: hi * (2^32 % 125) + lo + uint32_t adj = hi * r + lo; + // If adj overflowed, the true value is 2^32 + adj; apply the identity again + // static_cast(hi) widens to 64-bit when ReturnT=uint64_t, preserving upper bits of hi*q + return static_cast(hi) * q + (adj < lo ? (adj + r) / d + q : adj / d); +} + /// Return a random 32-bit unsigned integer. uint32_t random_uint32(); /// Return a random float between 0 and 1. diff --git a/tests/integration/fixtures/micros_to_millis.yaml b/tests/integration/fixtures/micros_to_millis.yaml new file mode 100644 index 00000000000..d11808c43a2 --- /dev/null +++ b/tests/integration/fixtures/micros_to_millis.yaml @@ -0,0 +1,61 @@ +esphome: + name: micros-to-millis-test + platformio_options: + build_flags: + - "-DDEBUG" + on_boot: + - lambda: |- + using esphome::micros_to_millis; + const char *TAG = "MTM"; + int pass = 0, fail = 0; + + auto check = [&](const char *name, uint64_t us) { + uint32_t got = micros_to_millis(us); + uint32_t want = (uint32_t)(us / 1000ULL); + if (got == want) { pass++; } + else { ESP_LOGE(TAG, "%s FAILED: got=%u want=%u", name, got, want); fail++; } + }; + + // Basic values + check("zero", 0); + check("below_1ms", 999); + check("exactly_1ms", 1000); + check("above_1ms", 1001); + + // Shift boundary (1000 = 8 * 125, exercises the >>3 shift) + check("shift_7999", 7999); + check("shift_8000", 8000); + check("shift_8001", 8001); + + // 32-bit boundary + check("u32max_minus1", 0xFFFFFFFEULL); + check("u32max", 0xFFFFFFFFULL); + check("u32max_plus1", 0x100000000ULL); + + // Realistic uptimes + check("30_days", 2592000000000ULL); + check("1_year", 31536000000000ULL); + + // Carry path: construct x = us>>3 with specific hi/lo that trigger adj overflow + { uint64_t x = (603ULL << 32) | 0xFFFFFFFFU; check("carry_603", x << 3); } + { uint64_t x = (5000ULL << 32) | 0xFFFFFFFFU; check("carry_5000", x << 3); } + + // Carry boundary: exact transition where adj overflows (hi=1000, R=46) + { + uint32_t hi = 1000; + uint32_t thr = 0xFFFFFFFFU - hi * 46U; + uint64_t h = (uint64_t)hi << 32; + check("carry_before", (h | (thr - 1)) << 3); + check("carry_at", (h | thr) << 3); + check("carry_after", (h | (thr + 1)) << 3); + } + + // Mod-8 variations (exercises the >>3 truncation) + for (int i = 0; i < 8; i++) { check("mod8", 2592000000000ULL + i); } + + if (fail == 0) { ESP_LOGI(TAG, "ALL_PASSED %d tests", pass); } + else { ESP_LOGE(TAG, "%d FAILED out of %d", fail, pass + fail); } + +host: +api: +logger: diff --git a/tests/integration/test_micros_to_millis.py b/tests/integration/test_micros_to_millis.py new file mode 100644 index 00000000000..9960d6b017f --- /dev/null +++ b/tests/integration/test_micros_to_millis.py @@ -0,0 +1,46 @@ +"""Integration test for micros_to_millis Euclidean decomposition.""" + +from __future__ import annotations + +import asyncio +import re + +import pytest + +from .types import APIClientConnectedFactory, RunCompiledFunction + + +@pytest.mark.asyncio +async def test_micros_to_millis( + yaml_config: str, + run_compiled: RunCompiledFunction, + api_client_connected: APIClientConnectedFactory, +) -> None: + """Test that micros_to_millis matches reference uint64 division.""" + + all_passed = asyncio.Event() + failures: list[str] = [] + + def on_log_line(line: str) -> None: + clean_line = re.sub(r"\x1b\[[0-9;]*m", "", line) + if "ALL_PASSED" in clean_line: + all_passed.set() + elif "FAILED" in clean_line and "[MTM" in clean_line: + failures.append(clean_line) + + async with ( + run_compiled(yaml_config, line_callback=on_log_line), + api_client_connected() as client, + ): + device_info = await client.device_info() + assert device_info is not None + assert device_info.name == "micros-to-millis-test" + + try: + await asyncio.wait_for(all_passed.wait(), timeout=2.0) + except TimeoutError: + if failures: + pytest.fail(f"micros_to_millis failures: {failures}") + pytest.fail("micros_to_millis test timed out") + + assert not failures, f"micros_to_millis failures: {failures}"