IRGen: make the autolink work better in COFF environments #14493
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CC: @aschwaighofer |
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@swift-ci please test |
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Build failed |
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Yeah, this is probably worth it, especially since it'll end up in the text section anyway. If we can think of anything even better to force linking, we can switch to that later. |
This was obscured due to local workarounds. Because the reference is cross-module, and the symbol itself will be rebased, it cannot serve as a constant initializer (the value is not known until runtime). However, using a function pointer is permissible. The linker will materialize a thunk for the function itself and cause the module to be force linked. This also works on ELF and MachO as well. The overhead associated with this is pretty minimal as the function itself has an empty body, and flags will differentiate between a function and data symbol. The slight penalty in size (on the order of 2-4 bytes) allows for the same pattern to be used across all the targets.
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@swift-ci please test and merge |
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This was obscured due to local workarounds. Because the reference is
cross-module, and the symbol itself will be rebased, it cannot serve as
a constant initializer (the value is not known until runtime). However,
using a function pointer is permissible. The linker will materialize a
thunk for the function itself and cause the module to be force linked.
This also works on ELF and MachO as well. The overhead associated with
this is pretty minimal as the function itself has an empty body, and
flags will differentiate between a function and data symbol. The slight
penalty in size (on the order of 2-4 bytes) allows for the same pattern
to be used across all the targets.
Replace this paragraph with a description of your changes and rationale. Provide links to external references/discussions if appropriate.
Resolves SR-NNNN.