machine: make sure DMA buffers do not escape unnecessarily #4930
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Writing the pointer of a buffer to memory-mapped I/O will normally cause it to escape, which forces the compiler to heap-allocate the buffer. But we do know how long the value stays alive, so we can tell the compiler to keep it alive exactly until it is not needed anymore - and tell it to not treat the pointer-to-uintptr cast as escaping.
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Size difference with the dev branch: Binary size differencenot the same command!
tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/adafruit4650
go: downloading tinygo.org/x/tinyfont v0.3.0
not the same command!
tinygo build -size short -o ./build/test.hex -target=pico ./examples/tmc5160/main.go
go: downloading golang.org/x/exp v0.0.0-20241204233417-43b7b7cde48d
not the same command!
tinygo build -size short -o ./build/test.hex -target=nano-rp2040 -stack-size 8kb ./examples/net/websocket/dial/
go: downloading golang.org/x/net v0.33.0
not the same command!
tinygo build -size short -o ./build/test.hex -target=nano-rp2040 -stack-size 8kb ./examples/net/mqttclient/natiu/
go: downloading github.com/soypat/natiu-mqtt v0.5.1
not the same command!
tinygo build -size short -o ./build/test.hex -target=wioterminal -stack-size 8kb ./examples/net/mqttclient/paho/
go: downloading github.com/eclipse/paho.mqtt.golang v1.2.0
flash ram
before after diff before after diff
14700 14656 -44 -0.30% 6580 6580 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/hts221/main.go
11816 11792 -24 -0.20% 6580 6580 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/apds9960/proximity/main.go
14056 14044 -12 -0.09% 6580 6580 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/lps22hb/main.go
18428 18428 0 0.00% 6236 6236 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/adafruit4650
61844 61844 0 0.00% 6180 6180 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/adt7410/main.go
8840 8840 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/adxl345/main.go
13572 13572 0 0.00% 6796 6796 0 0.00% tinygo build -size short -o ./build/test.hex -target=pybadge ./examples/amg88xx
9000 9000 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/apa102/main.go
9264 9264 0 0.00% 4752 4752 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/apa102/itsybitsy-m0/main.go
7576 7576 0 0.00% 2320 2320 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/at24cx/main.go
8084 8084 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bh1750/main.go
7452 7452 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/blinkm/main.go
71124 71124 0 0.00% 3656 3656 0 0.00% tinygo build -size short -o ./build/test.hex -target=pinetime ./examples/bma42x/main.go
64556 64556 0 0.00% 6196 6196 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmi160/main.go
27620 27620 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmp180/main.go
64384 64384 0 0.00% 6220 6220 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmp280/main.go
11944 11944 0 0.00% 4812 4812 0 0.00% tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/bmp388/main.go
7868 7868 0 0.00% 3352 3352 0 0.00% tinygo build -size short -o ./build/test.hex -target=bluepill ./examples/ds1307/sram/main.go
22184 22184 0 0.00% 3556 3556 0 0.00% tinygo build -size short -o ./build/test.hex -target=bluepill ./examples/ds1307/time/main.go
70136 70136 0 0.00% 6368 6368 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/ds3231/main.go
4628 4628 0 0.00% 2280 2280 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/easystepper/main.go
70328 70328 0 0.00% 6980 6980 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/flash/console/spi
67088 67088 0 0.00% 9020 9020 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/flash/console/qspi
7300 7300 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/gc9a01/main.go
67496 67496 0 0.00% 6360 6360 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/i2c/main.go
67912 67912 0 0.00% 6504 6504 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/uart/main.go
7864 7864 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/hcsr04/main.go
5756 5756 0 0.00% 2280 2280 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hd44780/customchar/main.go
5796 5796 0 0.00% 2280 2280 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hd44780/text/main.go
10420 10420 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/hd44780i2c/main.go
16176 16176 0 0.00% 2364 2364 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hub75/main.go
10272 10272 0 0.00% 6916 6916 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/basic
11060 11060 0 0.00% 4876 4876 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/ili9341/basic
29636 29636 0 0.00% 38076 38076 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/pyportal_boing
10300 10300 0 0.00% 6916 6916 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/scroll
11140 11140 0 0.00% 4876 4876 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/ili9341/scroll
263720 263720 0 0.00% 46744 46744 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/slideshow
11044 11044 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/lis3dh/main.go
26348 26348 0 0.00% 2328 2328 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/lsm303agr/main.go
12368 12368 0 0.00% 4788 4788 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/lsm6ds3/main.go
10080 10080 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mag3110/main.go
9240 9240 0 0.00% 4772 4772 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp23017/main.go
9644 9644 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp23017-multiple/main.go
9488 9488 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp3008/main.go
69220 69220 0 0.00% 6196 6196 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp2515/main.go
27148 27148 0 0.00% 3640 3640 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/microbitmatrix/main.go
26964 26964 0 0.00% 5620 5620 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit-v2 ./examples/microbitmatrix/main.go
7540 7540 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mma8653/main.go
7448 7448 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mpu6050/main.go
75832 75832 0 0.00% 7452 7452 0 0.00% tinygo build -size short -o ./build/test.hex -target=p1am-100 ./examples/p1am/main.go
14024 14024 0 0.00% 5416 5416 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/pca9685/main.go
6268 6268 0 0.00% 3292 3292 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/pcd8544/setbuffer/main.go
4652 4652 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/pcd8544/setpixel/main.go
12412 12412 0 0.00% 5392 5392 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/seesaw
2841 2841 0 0.00% 558 558 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino ./examples/servo
15700 15700 0 0.00% 5464 5464 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/sgp30
8216 8216 0 0.00% 6788 6788 0 0.00% tinygo build -size short -o ./build/test.hex -target=pybadge ./examples/shifter/main.go
58008 58008 0 0.00% 3688 3688 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/sht3x/main.go
58000 58000 0 0.00% 3696 3696 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/sht4x/main.go
58008 58008 0 0.00% 3688 3688 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/shtc3/main.go
6044 6044 0 0.00% 2288 2288 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1306/i2c_128x32/main.go
5556 5556 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1306/spi_128x64/main.go
5900 5900 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1331/main.go
6808 6808 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/st7735/main.go
6704 6704 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/st7789/main.go
16784 16784 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/thermistor/main.go
10124 10124 0 0.00% 4532 4532 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-bluefruit ./examples/tone
10180 10180 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/tm1637/main.go
12540 12540 0 0.00% 5404 5404 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/touch/capacitive
9164 9164 0 0.00% 6780 6780 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/touch/resistive/fourwire/main.go
12576 12576 0 0.00% 6976 6976 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/touch/resistive/pyportal_touchpaint/main.go
15140 15140 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/vl53l1x/main.go
13660 13660 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/vl6180x/main.go
24780 24780 0 0.00% 13720 13720 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-nrf52840-sense ./examples/waveshare-epd/epd1in54/main.go
6532 6532 0 0.00% 2324 2324 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd2in13/main.go
6168 6168 0 0.00% 2316 2316 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd2in13x/main.go
6452 6452 0 0.00% 2324 2324 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd4in2/main.go
27908 27908 0 0.00% 18476 18476 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/waveshare-epd/epd2in66b/main.go
6960 6960 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/ws2812
5584 5584 0 0.00% 9538 9538 0 0.00% '-xesppie' is not a recognized feature for this target (ignoring feature)
63216 63216 0 0.00% 5948 5948 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-nrf52840 ./examples/is31fl3731/main.go
1581 1581 0 0.00% 598 598 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino ./examples/ws2812
1056 1056 0 0.00% 180 180 0 0.00% tinygo build -size short -o ./build/test.hex -target=digispark ./examples/ws2812
32096 32096 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/bme280/main.go
16368 16368 0 0.00% 4724 4724 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/microphone/main.go
11532 11532 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/buzzer/main.go
12300 12300 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/veml6070/main.go
6860 6860 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l293x/simple/main.go
8776 8776 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l293x/speed/main.go
6836 6836 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l9110x/simple/main.go
9180 9180 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l9110x/speed/main.go
7416 7416 0 0.00% 3324 3324 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-f103rb ./examples/shiftregister/main.go
6732 6732 0 0.00% 2272 2272 0 0.00% '-xesppie' is not a recognized feature for this target (ignoring feature)
13276 13276 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/lis2mdl/main.go
9884 9884 0 0.00% 4764 4764 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/max72xx/main.go
76656 76656 0 0.00% 6336 6336 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/dht/main.go
38040 38040 0 0.00% 6048 6048 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/pcf8523/
71748 71748 0 0.00% 6344 6344 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/alarm/
7256 7256 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/clkout/
71292 71292 0 0.00% 6340 6340 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/time/
71644 71644 0 0.00% 6344 6344 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/timer/
14048 14048 0 0.00% 5368 5368 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/qmi8658c/main.go
12584 12584 0 0.00% 5352 5352 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/pcf8591/
8756 8756 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/ina260/main.go
12344 12344 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/ina219/main.go
9408 9408 0 0.00% 5248 5248 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-l432kc ./examples/aht20/main.go
74080 74080 0 0.00% 10756 10756 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m4 ./examples/sdcard/console/
62264 62264 0 0.00% 8228 8228 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m4 ./examples/i2csoft/adt7410/
10388 10388 0 0.00% 6788 6788 0 0.00% tinygo build -size short -o ./build/test.elf -target=wioterminal ./examples/axp192/m5stack-core2-blinky/
10752 10752 0 0.00% 5340 5340 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/xpt2046/main.go
13220 13220 0 0.00% 4936 4936 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-wl55jc ./examples/sx126x/lora_rxtx/
32984 32984 0 0.00% 6604 6604 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/ssd1289/main.go
12988 12988 0 0.00% 6308 6308 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/irremote/main.go
12264 12264 0 0.00% 5412 5412 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/scd4x/main.go
8028 8028 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=circuitplay-express ./examples/makeybutton/main.go
9572 9572 0 0.00% 4764 4764 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/ds18b20/main.go
82956 82956 0 0.00% 6592 6592 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-wl55jc ./examples/lora/lorawan/atcmd/
17808 17808 0 0.00% 7012 7012 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/as560x/main.go
11632 11632 0 0.00% 5360 5360 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/mpu6886/main.go
7840 7840 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/ttp229/main.go
69196 69196 0 0.00% 6888 6888 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/ndir/main_ndir.go
62588 62588 0 0.00% 3784 3784 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ndir/main_ndir.go
65592 65592 0 0.00% 6252 6252 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/ndir/main_ndir.go
11080 11080 0 0.00% 5352 5352 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/mpu9150/main.go
10104 10104 0 0.00% 5824 5824 0 0.00% tinygo build -size short -o ./build/test.hex -target=macropad-rp2040 ./examples/encoders/quadrature-interrupt
68648 68648 0 0.00% 6860 6860 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/mcp9808/main.go
44228 44228 0 0.00% 6952 6952 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/tmc2209/main.go
15044 15044 0 0.00% 5348 5348 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/tmc5160/main.go
12456 12456 0 0.00% 4544 4544 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=nicenano ./examples/sharpmem/main.go
60768 60768 0 0.00% 5968 5968 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-nrf52840 ./examples/max6675/main.go
88776 88776 0 0.00% 7260 7260 0 0.00% tinygo build -size short -o ./build/test.hex -target=challenger-rp2040 ./examples/net/ntpclient/
298544 298544 0 0.00% 15908 15908 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal -stack-size 8kb ./examples/net/http-get/
119064 119064 0 0.00% 7828 7828 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 -stack-size 8kb ./examples/net/tcpclient/
102536 102536 0 0.00% 9808 9808 0 0.00% tinygo build -size short -o ./build/test.hex -target=metro-m4-airlift -stack-size 8kb ./examples/net/socket/
339988 339988 0 0.00% 16520 16520 0 0.00% tinygo build -size short -o ./build/test.hex -target=matrixportal-m4 -stack-size 8kb ./examples/net/webstatic/
111288 111288 0 0.00% 7784 7784 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-mkrwifi1010 -stack-size 8kb ./examples/net/tlsclient/
155964 155964 0 0.00% 8620 8620 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-rp2040 -stack-size 8kb ./examples/net/mqttclient/natiu/
116284 116284 0 0.00% 13104 13104 0 0.00% tinygo build -size short -o ./build/test.hex -target=wioterminal -stack-size 8kb ./examples/net/webclient/
290240 290240 0 0.00% 19564 19564 0 0.00% tinygo build -size short -o ./build/test.hex -target=wioterminal -stack-size 8kb ./examples/net/webserver/
290544 290544 0 0.00% 20864 20864 0 0.00% tinygo build -size short -o ./build/test.hex -target=wioterminal -stack-size 8kb ./examples/net/mqttclient/paho/
120528 120528 0 0.00% 11632 11632 0 0.00% tinygo build -size short -o ./build/test.hex -target=elecrow-rp2040 -stack-size 8kb ./examples/net/tlsclient/
118012 118012 0 0.00% 9544 9544 0 0.00% tinygo build -size short -o ./build/test.hex -target=elecrow-rp2350 -stack-size 8kb ./examples/net/ntpclient/
13788 13792 4 0.03% 5384 5384 0 0.00% tinygo build -size short -o ./build/test.hex -target=badger2040 ./examples/uc8151/main.go
13332 13336 4 0.03% 5388 5388 0 0.00% tinygo build -size short -o ./build/test.hex -target=macropad-rp2040 ./examples/sh1106/macropad_spi
253224 253232 8 0.00% 15024 15024 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-rp2040 -stack-size 8kb ./examples/net/websocket/dial/
5766874 5766810 -64 -0.00% 914402 914402 0 0.00%
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eliasnaur
reviewed
Jun 20, 2025
Comment on lines
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| // Convert the pointer to a uintptr, to be used for memory I/O (DMA for | ||
| // example). It also means the pointer is "gone" as far as the compiler is | ||
| // concerned, and a GC cycle might deallocate the object. To prevent this from | ||
| // happening, also call keepAliveNoEscape at a point after the address isn't | ||
| // accessed anymore by the hardware. | ||
| // The only exception is if the pointer is accessed later in a volatile way | ||
| // (volatile read/write), which also forces the value to stay alive until that | ||
| // point. | ||
| // | ||
| // This function is treated specially by the compiler to mark the 'ptr' | ||
| // parameter as not escaping. | ||
| // | ||
| // TODO: this function should eventually be replaced with the proposed ptrtoaddr | ||
| // instruction in LLVM. See: | ||
| // https://discourse.llvm.org/t/clarifiying-the-semantics-of-ptrtoint/83987/10 | ||
| // https://github.com/llvm/llvm-project/pull/139357 | ||
| func unsafeNoEscape(ptr unsafe.Pointer) uintptr { | ||
| return uintptr(ptr) | ||
| } | ||
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| // Make sure the given pointer stays alive until this point. This is similar to | ||
| // runtime.KeepAlive, with the difference that it won't let the pointer escape. | ||
| // This is typically used together with unsafeNoEscape. | ||
| // | ||
| // This is a compiler intrinsic. | ||
| func keepAliveNoEscape(ptr unsafe.Pointer) |
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This is, as you say, hacky and won't help external drivers that don't have access to the unexported unsafeNoEscape and keepAliveNoEscape.
Can't runtime.KeepAlive be made to not move the allocation to the heap in TinyGo? If so, that leaves unsafeNoEscape. I suggest the more drastical solution of accepting #4889 that relaxes uintptr(unsafe.Pointer(&x)) to not escape. My reasoning is that for something like DMA, you need something like runtime.KeepAlive to keep the pointer alive anyway (it's not enough for the pointer to be kept alive at the point of conversion to uintptr).
That way, all code can use the same tricks to avoid allocations.
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This is, as you say, hacky and won't help external drivers that don't have access to the unexported
unsafeNoEscapeandkeepAliveNoEscape.
I intentionally kept them unexported. Drivers (like the tinygo.org/x/drivers/* packages) won't need it as long as they don't access these hardware registers directly - which is the vast majority. If there are drivers which really need these functions, we can export these functions.
Can't
runtime.KeepAlivebe made to not move the allocation to the heap in TinyGo?
Yes, but that won't help the machine package due to a circular dependency (machine -> runtime -> machine).
I suggest the more drastical solution of accepting #4889 that relaxes
uintptr(unsafe.Pointer(&x))to not escape.
The only way to implement that at the moment is to let the compiler do something exactly like unsafeNoEscape: insert a call at the point of the cast. I much prefer to keep this explicit and keep the default (escaping) behavior for these casts. In the future there might be ptrtoaddr but not today.
My reasoning is that for something like DMA, you need something like
runtime.KeepAliveto keep the pointer alive anyway (it's not enough for the pointer to be kept alive at the point of conversion touintptr).
Yeah that's the goal of this PR.
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Any idea why it fails on Windows? |
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Do we have a test that proves this helps? |
I agree with this sentiment. Why avoid escaping buffers that could surely be scratch space in some larger, already allocated, structure? |
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Writing the pointer of a buffer to memory-mapped I/O will normally cause it to escape, which forces the compiler to heap-allocate the buffer. But we do know how long the value stays alive, so we can tell the compiler to keep it alive exactly until it is not needed anymore - and tell it to not treat the pointer-to-uintptr cast as escaping.
This PR tries to solve the same problem as #4889 but in a different way. In fact, see #4889 (comment) where I first came up with this idea. Basically, with this PR, the allocation inside
legacy.ReadRegister(but probably notlegacy.WriteRegister!) should be fixed. See: tinygo-org/drivers#766.It's perhaps not the cleanest solution, but it seems to work in my tests.
@ysoldak can you take a look?
@dgryski @eliasnaur you may also be interested in this PR.