tools/mpy_ld.py: Optimise entry trampoline for x86/x64.#19309
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This commit allows natmod entry trampolines to possibly be smaller depending on the offset between the `mpy_init` from the beginning of the text segment. x64 and x86 shared the same, fixed-size entry point opcode that covered the whole 32-bits offset range. With changes introduced in 0fd0843 the entry point may change its length once all segments are laid out in the file, so optimised entry point code sequences can be emitted depending on the jump distance. These changes generate optimised entry point jump opcodes for 8-, and 32- bit offsets. Depending on the size of the natmod and where the compiler decides to put the `mpy_init` symbol this can help shortening the output file by three bytes. Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
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Summary
This PR allows natmod entry trampolines to possibly be smaller depending on the offset between the
mpy_initfrom the beginning of the text segment.x64 and x86 shared the same, fixed-size entry point opcode that covered the whole 32-bits offset range. With changes introduced in 0fd0843 the entry point may change its length once all segments are laid out in the file, so optimised entry point code sequences can be emitted depending on the jump distance.
These changes generate optimised entry point jump opcodes for 8-, and 32- bit offsets. Depending on the size of the natmod and where the compiler decides to put the
mpy_initsymbol this can help shortening the output file by three bytes. Clang seems to prefer placingmpy_initat the beginning of the text segment on x86, whilst GCC sort of does it on x64. In both cases, a 2 bytes opcode is used instead of a 6 bytes one.This is derived from the work being carried out in #19308, as this change won't really fit the parent PR's scope.
Testing
This should be tested by CI, as x86 and x64 natmod tests should be covered. In addition, the
features0natmod is small enough to trigger the generation of a 8-bit jump. Importing that module on either a x86 or x64 interpreter and running itsfactorialfunction works as expected.Generative AI
I did not use generative AI tools when creating this PR.