pbio/os: Number protothread checkpoints from one. - #487
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Protothread checkpoints used __LINE__ as the resume state, so the switch that dispatches to them spanned the whole line range of the function. GCC emits a jump table covering that range, one entry per line, with most entries pointing at the default case. Where the range exceeded 255 the table also doubled in width, since __gnu_thumb1_case_uqi can only address a byte. Use __COUNTER__ instead, and capture its value in PBIO_OS_ASYNC_BEGIN() so that each protothread numbers its checkpoints from one. The case labels are then dense and start at zero, so the compiler indexes the table directly with no range offset. On the Move Hub this takes the firmware from 105632 to 104112 bytes, which matters because only 864 bytes of the 104K region were left. For example, the dispatch in init_device_information_service() goes from a 42 entry table to 15 entries, and the one in pbdrv_bluetooth_spi_process_thread() from 79 two byte entries to 12 single byte entries. This also means source line numbers no longer affect the size of the binary, so adding a comment to a protothread does not move code around. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Protothread checkpoints used
__LINE__as the resume state, so the switch that dispatches to them spanned the whole line range of the function. GCC emits a jump table covering that range, one entry per line, with most entries pointing at the default case. Where the range exceeded 255 the table also doubled in width, since__gnu_thumb1_case_uqican only address a byte.Use
__COUNTER__instead, and capture its value inPBIO_OS_ASYNC_BEGIN()so that each protothread numbers its checkpoints from one. The case labels are then dense and start at zero, so the compiler indexes the table directly with no range offset.On the Move Hub this takes the firmware from 105632 to 104112 bytes, which matters because only 864 bytes of the 104K region were left. For example, the dispatch in
init_device_information_service()goes from a 42 entry table to 15 entries, and the one inpbdrv_bluetooth_spi_process_thread()from 79 two byte entries to 12 single byte entries.This also means source line numbers no longer affect the size of the binary, so adding a comment to a protothread does not move code around.