machine: make sure DMA buffers do not escape unnecessarily #4930
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Size difference with the dev branch: Binary size differenceflash ram before after diff before after diff 14784 14724 -60 -0.41% 6580 6580 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/hts221/main.go 11896 11856 -40 -0.34% 6580 6580 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/apds9960/proximity/main.go 14140 14112 -28 -0.20% 6580 6580 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/lps22hb/main.go 18480 18480 0 0.00% 6236 6236 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/adafruit4650 61676 61676 0 0.00% 6180 6180 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/adt7410/main.go 8848 8848 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/adxl345/main.go 13584 13584 0 0.00% 6796 6796 0 0.00% tinygo build -size short -o ./build/test.hex -target=pybadge ./examples/amg88xx 9012 9012 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/apa102/main.go 9272 9272 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 7588 7588 0 0.00% 2320 2320 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/at24cx/main.go 8096 8096 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bh1750/main.go 7456 7456 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/blinkm/main.go 71564 71564 0 0.00% 3656 3656 0 0.00% tinygo build -size short -o ./build/test.hex -target=pinetime ./examples/bma42x/main.go 64388 64388 0 0.00% 6196 6196 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmi160/main.go 27736 27736 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmp180/main.go 64216 64216 0 0.00% 6220 6220 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmp280/main.go 11956 11956 0 0.00% 4812 4812 0 0.00% tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/bmp388/main.go 7872 7872 0 0.00% 3352 3352 0 0.00% tinygo build -size short -o ./build/test.hex -target=bluepill ./examples/ds1307/sram/main.go 21788 21788 0 0.00% 3556 3556 0 0.00% tinygo build -size short -o ./build/test.hex -target=bluepill ./examples/ds1307/time/main.go 69576 69576 0 0.00% 6368 6368 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/ds3231/main.go 4640 4640 0 0.00% 2280 2280 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/easystepper/main.go 70240 70240 0 0.00% 6980 6980 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/flash/console/spi 67032 67032 0 0.00% 9020 9020 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/flash/console/qspi 7312 7312 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/gc9a01/main.go 67912 67912 0 0.00% 6360 6360 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/i2c/main.go 68360 68360 0 0.00% 6504 6504 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/uart/main.go 8432 8432 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/hcsr04/main.go 5768 5768 0 0.00% 2280 2280 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hd44780/customchar/main.go 5808 5808 0 0.00% 2280 2280 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hd44780/text/main.go 10432 10432 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/hd44780i2c/main.go 16220 16220 0 0.00% 2364 2364 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hub75/main.go 10400 10400 0 0.00% 6916 6916 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/basic 11196 11196 0 0.00% 4876 4876 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/ili9341/basic 29792 29792 0 0.00% 38076 38076 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/pyportal_boing 10432 10432 0 0.00% 6916 6916 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/scroll 11280 11280 0 0.00% 4876 4876 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/ili9341/scroll 263900 263900 0 0.00% 46772 46772 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/slideshow 11080 11080 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/lis3dh/main.go 26464 26464 0 0.00% 2328 2328 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/lsm303agr/main.go 28136 28136 0 0.00% 6828 6828 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m4 ./examples/lsm303dlhc/main.go 12400 12400 0 0.00% 4788 4788 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/lsm6ds3/main.go 10104 10104 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mag3110/main.go 9244 9244 0 0.00% 4772 4772 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp23017/main.go 9648 9648 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp23017-multiple/main.go 9496 9496 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp3008/main.go 70444 70444 0 0.00% 6196 6196 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp2515/main.go 27516 27516 0 0.00% 3832 3832 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/microbitmatrix/main.go 27332 27332 0 0.00% 5812 5812 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit-v2 ./examples/microbitmatrix/main.go 7548 7548 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mma8653/main.go 7452 7452 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mpu6050/main.go 76232 76232 0 0.00% 7452 7452 0 0.00% tinygo build -size short -o ./build/test.hex -target=p1am-100 ./examples/p1am/main.go 14076 14076 0 0.00% 5416 5416 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/pca9685/main.go 6280 6280 0 0.00% 3292 3292 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/pcd8544/setbuffer/main.go 4660 4660 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/pcd8544/setpixel/main.go 12460 12460 0 0.00% 5392 5392 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/seesaw/soil-sensor 13720 13720 0 0.00% 5400 5400 0 0.00% tinygo build -size short -o ./build/test.hex -target=qtpy-rp2040 ./examples/seesaw/rotary-encoder 2841 2841 0 0.00% 558 558 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino ./examples/servo 15780 15780 0 0.00% 5464 5464 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/sgp30 8224 8224 0 0.00% 6788 6788 0 0.00% tinygo build -size short -o ./build/test.hex -target=pybadge ./examples/shifter/main.go 57808 57808 0 0.00% 3688 3688 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/sht3x/main.go 57800 57800 0 0.00% 3696 3696 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/sht4x/main.go 57808 57808 0 0.00% 3688 3688 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/shtc3/main.go 5912 5912 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1331/main.go 6820 6820 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/st7735/main.go 6716 6716 0 0.00% 2284 2284 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/st7789/main.go 16864 16864 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/thermistor/main.go 10132 10132 0 0.00% 4532 4532 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-bluefruit ./examples/tone 10192 10192 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/tm1637/main.go 12624 12624 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 12692 12692 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 15764 15764 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/vl53l1x/main.go 14396 14396 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/vl6180x/main.go 24796 24796 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 6544 6544 0 0.00% 2324 2324 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd2in13/main.go 6180 6180 0 0.00% 2316 2316 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd2in13x/main.go 6464 6464 0 0.00% 2324 2324 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd4in2/main.go 27956 27956 0 0.00% 18476 18476 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/waveshare-epd/epd2in66b/main.go 6976 6976 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/ws2812 5622 5622 0 0.00% 9538 9538 0 0.00% '-xesppie' is not a recognized feature for this target (ignoring feature) 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 32204 32204 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/bme280/main.go 16440 16440 0 0.00% 4724 4724 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/microphone/main.go 11620 11620 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/buzzer/main.go 12332 12332 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/veml6070/main.go 6868 6868 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l293x/simple/main.go 8788 8788 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l293x/speed/main.go 6844 6844 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l9110x/simple/main.go 9192 9192 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/l9110x/speed/main.go 7428 7428 0 0.00% 3324 3324 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-f103rb ./examples/shiftregister/main.go 6796 6796 0 0.00% 2272 2272 0 0.00% '-xesppie' is not a recognized feature for this target (ignoring feature) 13364 13364 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/lis2mdl/main.go 9896 9896 0 0.00% 4764 4764 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/max72xx/main.go 76816 76816 0 0.00% 6336 6336 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/dht/main.go 37720 37720 0 0.00% 6048 6048 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/pcf8523/ 71212 71212 0 0.00% 6344 6344 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/alarm/ 7264 7264 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/clkout/ 70644 70644 0 0.00% 6340 6340 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/time/ 71036 71036 0 0.00% 6344 6344 0 0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/pcf8563/timer/ 14100 14100 0 0.00% 5368 5368 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/qmi8658c/main.go 12632 12632 0 0.00% 5352 5352 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/pcf8591/ 8768 8768 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/ina260/main.go 12376 12376 0 0.00% 4780 4780 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/ina219/main.go 9420 9420 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/ 62144 62144 0 0.00% 8228 8228 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-m4 ./examples/i2csoft/adt7410/ 10400 10400 0 0.00% 6788 6788 0 0.00% tinygo build -size short -o ./build/test.elf -target=wioterminal ./examples/axp192/m5stack-core2-blinky/ 10800 10800 0 0.00% 5340 5340 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/xpt2046/main.go 13252 13252 0 0.00% 4936 4936 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-wl55jc ./examples/sx126x/lora_rxtx/ 33352 33352 0 0.00% 6796 6796 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/ssd1289/main.go 13020 13020 0 0.00% 6308 6308 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/irremote/main.go 12312 12312 0 0.00% 5412 5412 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/scd4x/main.go 8036 8036 0 0.00% 4748 4748 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=circuitplay-express ./examples/makeybutton/main.go 9584 9584 0 0.00% 4764 4764 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/ds18b20/main.go 122176 122176 0 0.00% 8068 8068 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-wl55jc ./examples/lora/lorawan/atcmd/ 17860 17860 0 0.00% 7012 7012 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/as560x/main.go 11680 11680 0 0.00% 5360 5360 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/mpu6886/main.go 7852 7852 0 0.00% 4740 4740 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/ttp229/main.go 69072 69072 0 0.00% 6892 6892 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/ndir/main_ndir.go 62388 62388 0 0.00% 3784 3784 0 0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ndir/main_ndir.go 65424 65424 0 0.00% 6252 6252 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/ndir/main_ndir.go 11128 11128 0 0.00% 5352 5352 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/mpu9150/main.go 10156 10156 0 0.00% 5824 5824 0 0.00% tinygo build -size short -o ./build/test.hex -target=macropad-rp2040 ./examples/encoders/quadrature-interrupt 68576 68576 0 0.00% 6860 6860 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/mcp9808/main.go 44192 44192 0 0.00% 7144 7144 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/tmc2209/main.go 15092 15092 0 0.00% 5348 5348 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/tmc5160/main.go 12472 12472 0 0.00% 4544 4544 0 0.00% tinygo build -size short -o ./build/test.uf2 -target=nicenano ./examples/sharpmem/main.go 14748 14748 0 0.00% 5408 5408 0 0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/ens160/main.go 88224 88224 0 0.00% 7260 7260 0 0.00% tinygo build -size short -o ./build/test.hex -target=challenger-rp2040 ./examples/net/ntpclient/ 347056 347056 0 0.00% 16764 16764 0 0.00% tinygo build -size short -o ./build/test.hex -target=pyportal -stack-size 8kb ./examples/net/http-get/ 119928 119928 0 0.00% 8020 8020 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 -stack-size 8kb ./examples/net/tcpclient/ 103568 103568 0 0.00% 10000 10000 0 0.00% tinygo build -size short -o ./build/test.hex -target=metro-m4-airlift -stack-size 8kb ./examples/net/socket/ 388420 388420 0 0.00% 18772 18772 0 0.00% tinygo build -size short -o ./build/test.hex -target=matrixportal-m4 -stack-size 8kb ./examples/net/webstatic/ 166364 166364 0 0.00% 9992 9992 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-mkrwifi1010 -stack-size 8kb ./examples/net/tlsclient/ 155780 155780 0 0.00% 8812 8812 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-rp2040 -stack-size 8kb ./examples/net/mqttclient/natiu/ 116732 116732 0 0.00% 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5344 5344 0 0.00% tinygo build -size short -o ./build/test.hex -target=thumby ./examples/ssd1306/ 13832 13836 4 0.03% 5384 5384 0 0.00% tinygo build -size short -o ./build/test.hex -target=badger2040 ./examples/uc8151/main.go 13408 13412 4 0.03% 5388 5388 0 0.00% tinygo build -size short -o ./build/test.hex -target=macropad-rp2040 ./examples/sh1106/macropad_spi 63096 63104 8 0.01% 5948 5948 0 0.00% tinygo build -size short -o ./build/test.hex -target=feather-nrf52840 ./examples/is31fl3731/main.go 308248 308256 8 0.00% 15924 15924 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-rp2040 -stack-size 8kb ./examples/net/websocket/dial/ 60640 62424 1784 2.94% 5968 5976 8 0.13% tinygo build -size short -o ./build/test.hex -target=feather-nrf52840 ./examples/max6675/main.go 6254988 6256680 1692 0.00% 963434 963442 8 0.00% |
eliasnaur
reviewed
Jun 20, 2025
Comment on lines
+69
to
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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) | ||
| } | ||
|
|
||
| // 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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What about drivers written on top of an interface, say drivers.I2C? AFAIK, Unless TinyGo can see through the interface indirection, any buffers passed to |
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Rebased, and added tests.
Yeah, this is only a partial solution. Callers that use the |
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eliasnaur
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src/machine/machine_nrf528xx.go
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| // Make sure the w and r buffers stay alive until this point, so they won't | ||
| // be garbage collected while the buffers are used by the hardware. | ||
| if len(w) > 0 { | ||
| keepAliveNoEscape(unsafe.Pointer(&w[0])) |
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Nit: why not use unsafe.SliceData and drop the len(w) > 0 check? Here and elsewhere.
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Because it's an old PR that I rebased.
I've updated the PR to use unsafe.SliceData instead where possible.
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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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.