[Foundation] Performance improvements for IndexPath bridging and comparison#9339
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phausler merged 4 commits intoswiftlang:masterfrom May 6, 2017
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…ions The previous implementation of IndexPath would cause a malloc of the underlying array buffer upon bridging from ObjectiveC. This impacts graphical APIs (such as UICollectionView or AppKit equivalents) when calling delegation patterns. Since IndexPath itself can be a tagged pointer and most often just a pair of elements it can be represented as an enum of common cases. Those common cases of empty, single, or pair can be represented respectively as no associated value, a single Int, and a tuple of Ints. These cases will be exclusively stack allocations, which is markably faster than the allocating code-path. IndexPaths that have a count greater than 2 will still fall into the array storage case. As an added performance benefit, accessing count and subscripting is now faster by aproximately 30% due to more tightly coupled inlining potential under whole module optimizations. Accessing count is also faster since it has better cache-line effeciency (lesson learned: the branch predictor is more optimized than pointer indirection chasing). Benchmarks performed on x86_64, arm and arm64 still pending results but should be applicable across the board. Resolves the following issues: https://bugs.swift.org/browse/SR-3655 https://bugs.swift.org/browse/SR-2769 Resolves the following radars: rdar://problem/28207534 rdar://problem/28209456
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@swift-ci please test |
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StringIndex should not have any interaction with IndexPath |
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thomasvl
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May 10, 2017
| let totalBits = MemoryLayout<Int>.size * 8 | ||
| let lengthBits = 8 | ||
| let firstIndexBits = (totalBits - lengthBits) / 2 | ||
| return count + (first << lengthBits) + (last << (lengthBits + firstIndexBits)) |
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Shouldn't this have been:
return count &+ (first << lengthBits) &+ (last << (lengthBits + firstIndexBits))i.e. if the first/last value are large, you can overflow.
phausler
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May 16, 2017
…arison (swiftlang#9339) * [Foundation] Refactor the backing of IndexPath to favor stack allocations The previous implementation of IndexPath would cause a malloc of the underlying array buffer upon bridging from ObjectiveC. This impacts graphical APIs (such as UICollectionView or AppKit equivalents) when calling delegation patterns. Since IndexPath itself can be a tagged pointer and most often just a pair of elements it can be represented as an enum of common cases. Those common cases of empty, single, or pair can be represented respectively as no associated value, a single Int, and a tuple of Ints. These cases will be exclusively stack allocations, which is markably faster than the allocating code-path. IndexPaths that have a count greater than 2 will still fall into the array storage case. As an added performance benefit, accessing count and subscripting is now faster by aproximately 30% due to more tightly coupled inlining potential under whole module optimizations. Accessing count is also faster since it has better cache-line effeciency (lesson learned: the branch predictor is more optimized than pointer indirection chasing). Benchmarks performed on x86_64, arm and arm64 still pending results but should be applicable across the board. Resolves the following issues: https://bugs.swift.org/browse/SR-3655 https://bugs.swift.org/browse/SR-2769 Resolves the following radars: rdar://problem/28207534 rdar://problem/28209456 * [Foundation] remove temp IndexPath hashing that required bridging to ref types * [Foundation] IndexPath does not guarentee hashing to be the same as objc # Conflicts: # stdlib/public/SDK/Foundation/IndexPath.swift
tkremenek
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May 17, 2017
[Foundation] Performance improvements for IndexPath bridging and comparison (#9339)
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The previous implementation of IndexPath would cause a malloc of the underlying array buffer upon bridging from ObjectiveC. This impacts graphical APIs (such as UICollectionView or AppKit equivalents) when calling delegation patterns. Since IndexPath itself can be a tagged pointer and most often just a pair of elements it can be represented as an enum of common cases. Those common cases of empty, single, or pair can be represented respectively as no associated value, a single Int, and a tuple of Ints. These cases will be exclusively stack allocations, which is markably faster than the allocating code-path. IndexPaths that have a count greater than 2 will still fall into the array storage case. As an added performance benefit, accessing count and subscripting is now faster by aproximately 30% due to more tightly coupled inlining potential under whole module optimizations. Accessing count is also faster since it has better cache-line effeciency (lesson learned: the branch predictor is more optimized than pointer indirection chasing).
Benchmarks performed on x86_64, arm and arm64 still pending results but should be applicable across the board.
Resolves the following issues:
https://bugs.swift.org/browse/SR-3655
https://bugs.swift.org/browse/SR-2769
Resolves the following radars:
rdar://problem/28207534
rdar://problem/28209456
This was re-opened since the CI server decided it didn't like the previous PR