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py/asmthumb: Implement long jumps on Thumb/armv6m architecture.#17293
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py/asmthumb: Implement long jumps on Thumb/armv6m architecture.#17293
dpgeorge wants to merge1 commit intomicropython:masterfromdpgeorge:py-asmthumb-implement-armv6m-long-jump
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With this change, all tests (except thread tests) now pass on RPI_PICO whenusing the native emitter: (plug in RPI_PICO) $ cd tests $ ./run-tests.py -t a0 --via-mpy --emit nativeSigned-off-by: Damien George <damien@micropython.org>
@agatti FYI |
Code size report: |
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@## master #17293 +/- ##======================================= Coverage 98.54% 98.54% ======================================= Files 169 169 Lines 21897 21897 ======================================= Hits 21579 21579 Misses 318 318 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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Summary
Implement long jumps (greater than +/- 2k code distance) for armv6m targets, eg RPI_PICO.
With this change, all tests (except thread tests) now pass on RPI_PICO when using the native emitter:
Testing
Tested on an RPI_PICO as above. Prior to this PR 8 tests would fail due to large jumps not being implemented. Now they pass.
Trade-offs and Alternatives
All forwards jumps now take 8 or 10 bytes, whereas previously they took only 2 bytes. That's just because it's not possible to know in advance how long the jump is, and the emitter must commit to the size of the instruction in early passes (one day that could be improved by adding more assembler passes).
The jump can now clobber register
r1, which it uses as a temporary to calculate the long jump. Clobbering this register is OK, it's anyway used as a temporary in the native emitter and is never needed across jumps (butr0is because it's used to return a value from the function, so that can't be used here as a temporary).