Remove a hack to change linkage from public_external to shared. #9736
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The linkage change let the compiler generate code for public functions which are imported from the stdlib - and are also available in the swiftCore library. This got worse since we use public linkage for @_versioned internal functions in the stdlib. Getting rid of the linkage change reduces code size a lot: up to 40% for some projects. I didn’t see any significant impact on benchmark performance.
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@swift-ci test |
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Explanation: This change fixes a big code duplication problem. The compiler generated code for public functions which are imported from the stdlib - and are also available in the swiftCore library.
This got worse since we use public linkage for @_versioned internal functions in the stdlib.
The code size overhead by this duplication is up to 40% for some projects. Which means that by fixing this, we get up to 40% code size reduction.
There is no significant impact on benchmark performance.
Scope: This problem has a big effect on the code size.
Radar: rdar://problem/32265845
Risk: Low. It has no effect on generated code (it only removes duplicated functions). And it has no effect on generated swiftmodule files.
Testing: There is a specific test for swift-ci. Also it's implicitly tested by all tests/projects which link an executable.