[4.2] Some string performance changes #16542
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Beside the general goal to remove inlinable functions, this reduces code size and also improves performance for several benchmarks. The performance problem was that by inlining top-level String API functions into client code (like String.count) it ended up calling non-inlinable internal String functions eventually. This is much slower than to make a single call at the top-level API boundary into the library. Inside the library all the internal String functions can be specialized and inlined. rdar://problem/39921548
Re-wrote the inner memcpy loops so that they can be vectorized. Also added a few inline(__always). Since we removed some @inlineable attributes this string-append code is not code generated in the client anymore. The code generation in the stdlib binary is different because all the precondition checks are not folded away. Using explicit loop control statements instead of for-in-range removes the precondition-overhead for those time critical memcpy loops.
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@swift-ci test and merge |
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@swift-ci test and merge |
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@swift-ci test and merge |
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@swift-ci test OS X |
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@swift-ci test OS X |
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