NRF52 LTO flags (#10655)
* Add LTO support for nrf52840 while preserving interrupt handlers * nrf52840: enable whole-image LTO on all targets via nrf52_base Moves -flto + the nrf52_lto.py exclusion middleware from the rak4631 env (771018ca8) up to [nrf52_base], so every nrf52840 target inherits it. nrf52_lto.py keeps the interrupt handlers out of LTO (framework core + TinyUSB USBD_IRQHandler) -- they're referenced only from the asm vector table, so whole-program LTO would otherwise drop them and the chip hangs. HW-validated: RAK4631 (SX1262, -60KB) and muzi-base (LR1121) both boot and init their radios. Build-verified on canaryone (fresh board, base-inherited). Caveat: the RAK "1-Watt" variant's radio does not tolerate global-LTO (SX126x init fails); it shares the rak4631 binary, so keep that hardware on src-only or split it into a separate target. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> * nrf52840: move -fmerge-all-constants to nrf52_base (all targets) It had been trialed on rak4631 only; it's a general image-wide flag (the same one stm32 uses globally, ~0.7KB), so move it up to [nrf52_base] next to -flto so every nrf52840 target gets it instead of just rak4631. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> * nrf52_lto.py: normalize path separators for Windows (Copilot review) get_abspath() returns backslash-separated paths on Windows, so the "/FrameworkArduino/" / "/cores/nRF5/" substring matches would miss and the ISR-owning objects would still be LTO'd -> hang on first IRQ. Replace backslashes with forward slashes before matching. No-op on macOS/Linux. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> * Fix directory handling for LTO * Add post-link guard to check for dropped ISR handlers in nrf52 LTO --------- Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Co-authored-by: Jason P <applewiz@mac.com>
This commit is contained in:
Ben Meadors
co-authored by
GitHub
Claude Opus 4.8
Jason P
GitHub
Claude Opus 4.8
Jason P
parent
a9b98f47e9
commit
bf68b9e597
@@ -0,0 +1,138 @@
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#!/usr/bin/env python3
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# trunk-ignore-all(ruff/F821)
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# trunk-ignore-all(flake8/F821)
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#
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# Whole-image LTO for nrf52840 (~-60KB; ~-23KB beyond src-only LTO), EXCEPT the objects
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# that own interrupt/exception handlers.
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#
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# Every ISR is referenced only from the assembly vector table (gcc_startup_nrf52840.S),
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# which LTO cannot see -> whole-program LTO judges the handlers dead, removes them, and
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# the weak `b .` Default_Handler stubs prevail -> the IRQ lands in an infinite loop and the
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# chip hangs (or the peripheral silently stalls). Compiling the handler-bearing objects
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# WITHOUT LTO lets ordinary linking keep the strong handlers; everything else stays LTO'd:
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# - framework core (/FrameworkArduino/, /cores/nRF5/): every nrfx ISR + the FreeRTOS
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# SVC/PendSV port.
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# - TinyUSB nrf port (Adafruit_TinyUSB_nrf.cpp): USBD_IRQHandler (USB data path).
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# - library .cpp files that own a vector ISR (would otherwise be silently dropped):
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# bluefruit.cpp -> SD_EVT/SWI2_EGU2 (SoftDevice BLE-event delivery -- advertising
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# hangs without it)
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# Wire_nRF52.cpp -> SPIM0/TWIM0 + SPIM1/TWIM1 (interrupt-driven I2C/SPI)
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# PDM.cpp -> PDM_IRQHandler (PDM microphone)
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# RotaryEncoder.cpp -> QDEC_IRQHandler (hardware quadrature/rotary encoder)
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#
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# A post-link guard (bottom of this file) fails the build if a critical handler was dropped
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# anyway -- so a future deps bump or a new ISR-owning library becomes a red build, not a field
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# hang. To hunt a dropped ISR by hand: nm the .elf for `_IRQHandler$` symbols marked `W`, then
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# grep the libs/framework for who defines them.
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#
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# HW-validated: RAK4631 (SX1262) + muzi-base (LR1121).
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import glob
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import os
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Import("env")
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env.Append(LINKFLAGS=["-flto", "-flto-partition=1to1"])
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# The -fno-lto re-compiles below run with the global env, which lacks the framework's
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# bundled-library include dirs -- and those libs cross-include each other (Wire pulls in
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# Adafruit_TinyUSB.h, which pulls in SPI.h, ...). Add every bundled-lib dir (+ its src/) so
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# the re-compiles resolve without chasing headers one at a time.
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_fw = env.PioPlatform().get_package_dir("framework-arduinoadafruitnrf52") or ""
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_extra_inc = []
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for _d in sorted(glob.glob(os.path.join(_fw, "libraries", "*"))):
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if os.path.isdir(_d):
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_extra_inc.append(_d)
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if os.path.isdir(os.path.join(_d, "src")):
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_extra_inc.append(os.path.join(_d, "src"))
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FRAMEWORK = ("/FrameworkArduino/", "/cores/nRF5/")
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USB_ISR = "Adafruit_TinyUSB_nrf" # USBD_IRQHandler
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# Library .cpp files that define vector-table ISRs (the rest of their lib stays LTO'd):
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LIB_ISR = ("/bluefruit.cpp", "/Wire_nRF52.cpp", "/PDM.cpp", "/RotaryEncoder.cpp")
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def _no_lto(node):
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try:
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path = node.get_abspath()
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except Exception:
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path = str(node)
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path = path.replace(
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"\\", "/"
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) # normalize Windows backslashes so matches work cross-platform
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if (
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USB_ISR in path
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or any(s in path for s in FRAMEWORK)
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or any(s in path for s in LIB_ISR)
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):
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return env.Object(
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node,
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CCFLAGS=env["CCFLAGS"] + ["-fno-lto"],
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CPPPATH=env["CPPPATH"] + _extra_inc,
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)
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return node
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env.AddBuildMiddleware(_no_lto)
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# --- post-link guard: catch a dropped ISR handler at build time (CI footgun protection) ----
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# After every link, fail the build if one of these critical vector-table handlers resolved to
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# the weak `b .` Default_Handler stub -- i.e. LTO (or a deps bump, or a new ISR-owning library
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# that nobody added to LIB_ISR) silently dropped it. A dropped handler hangs the chip the
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# instant that IRQ fires; this turns a field hang into a red build. CI builds every nrf52840
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# target, so this runs on every PR automatically. All five are used by every nrf52840
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# Meshtastic build; if a board deliberately stops using one, edit this tuple on purpose.
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_REQUIRED_STRONG = (
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"SWI2_EGU2_IRQHandler", # SoftDevice BLE event (SD_EVT) -- advertising & connections
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"GPIOTE_IRQHandler", # GPIO interrupts: radio DIO + buttons
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"RTC1_IRQHandler", # FreeRTOS scheduler tick
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"USBD_IRQHandler", # USB CDC (serial console + 1200bps DFU trigger)
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"POWER_CLOCK_IRQHandler", # HF/LF clock + power (HFCLK start for radio & SoftDevice)
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)
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_tc = env.PioPlatform().get_package_dir("toolchain-gccarmnoneeabi") or ""
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_NM = os.path.join(_tc, "bin", "arm-none-eabi-nm")
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if not os.path.isfile(_NM):
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_NM = "arm-none-eabi-nm" # fall back to PATH
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def _assert_isr_handlers_survived(source, target, env):
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import subprocess
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import sys
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try:
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# Resolve the ELF at build time; target[0] is the buildprog alias, not the file.
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elf = env.subst("$BUILD_DIR/${PROGNAME}.elf")
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out = subprocess.check_output([_NM, elf], universal_newlines=True)
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except Exception as exc: # tooling hiccup: warn loudly, don't wedge the build
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print("nrf52_lto: WARNING - ISR-handler guard skipped (nm failed: %s)" % exc)
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return
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# nm line: "<addr> <type> <symbol>". type 'T'/'t' = strong (good); 'W'/'w' = weak stub.
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kind = {}
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for line in out.split("\n"):
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f = line.split()
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if len(f) >= 3 and f[-1].endswith("_IRQHandler"):
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kind[f[-1]] = f[-2]
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dropped = [h for h in _REQUIRED_STRONG if kind.get(h, "W").upper() != "T"]
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if dropped:
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sys.stderr.write(
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"\n*** nrf52 LTO guard: interrupt handler(s) DROPPED: %s ***\n"
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"Each resolved to the weak Default_Handler stub, so the chip hangs when that IRQ\n"
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"fires. Compile the .cpp that defines the handler with -fno-lto by adding it to\n"
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"LIB_ISR in extra_scripts/nrf52_lto.py. Find the owner of FOO_IRQHandler with:\n"
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" grep -rl FOO_IRQHandler <framework-arduinoadafruitnrf52>/{libraries,cores}\n\n"
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% ", ".join(dropped)
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)
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from SCons.Script import Exit
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Exit(1) # canonical SCons build-abort -> red build
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print(
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"nrf52_lto: ISR-handler guard OK -- %d critical handlers strong"
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% len(_REQUIRED_STRONG)
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)
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# Attach to the phony "buildprog" alias, NOT the .elf file node: SCons can skip a post-action
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# on a file target during an incremental relink (observed), but the buildprog alias runs every
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# build -- so the guard fires on local incremental rebuilds and clean CI builds alike.
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env.AddPostAction("buildprog", _assert_isr_handlers_survived)
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@@ -14,6 +14,7 @@ platform_packages =
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extra_scripts =
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${env.extra_scripts}
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extra_scripts/nrf52_extra.py
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pre:extra_scripts/nrf52_lto.py
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build_type = release
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build_flags =
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@@ -26,6 +27,8 @@ build_flags =
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-DMESHTASTIC_EXCLUDE_PAXCOUNTER=1
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-Os
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-std=gnu++17
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-flto ; whole-image LTO (~-60KB) on every nrf52840 target; nrf52_lto.py (pre: extra_script) keeps the interrupt handlers out of LTO so they survive
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-fmerge-all-constants ; fold identical constants image-wide (~0.7KB; same flag stm32 uses)
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build_unflags =
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-Ofast
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-Og
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