String.range is much slower than NSString.range [macOS m1]

[750]

Description

String.range performs about 20 times slower than NSString(string: String).range for the same string

Reproduction

code

import Foundation

var test_string: String? = nil;
var test_string_ns: NSString? = nil;
var len = 1024;
for power in stride(from: 10, to: 29, by: 2) {
      len = Int(pow(Double(2), Double(power)));

      test_string = String(repeating: "1", count: len) + "zu";
      test_string_ns = NSString(string: test_string!);

      print("string size: 2^\(power) (\(len))")

      var ts = Date().timeIntervalSince1970;
      NSString(string: test_string!).range(of: "zu", options: NSString.CompareOptions.caseInsensitive)
      print("  NSString(String)", "total seconds:", Date().timeIntervalSince1970-ts)

      ts = Date().timeIntervalSince1970;
      test_string_ns!.range(of: "zu", options: NSString.CompareOptions.caseInsensitive)
      print("  NSString        ", "total seconds:", Date().timeIntervalSince1970-ts)

      ts = Date().timeIntervalSince1970;
      test_string!.range(of: "zu", options: NSString.CompareOptions.caseInsensitive)
      print("  String          ", "total seconds:", Date().timeIntervalSince1970-ts)
}

result

string size: 2^10 (1024)
  NSString(String) total seconds: 2.9087066650390625e-05
  NSString         total seconds: 1.6689300537109375e-05
  String           total seconds: 0.0015459060668945312
string size: 2^12 (4096)
  NSString(String) total seconds: 7.414817810058594e-05
  NSString         total seconds: 5.507469177246094e-05
  String           total seconds: 0.0013251304626464844
string size: 2^14 (16384)
  NSString(String) total seconds: 0.0002551078796386719
  NSString         total seconds: 0.00021004676818847656
  String           total seconds: 0.0048809051513671875
string size: 2^16 (65536)
  NSString(String) total seconds: 0.0009019374847412109
  NSString         total seconds: 0.0006799697875976562
  String           total seconds: 0.014341115951538086
string size: 2^18 (262144)
  NSString(String) total seconds: 0.0029938220977783203
  NSString         total seconds: 0.0017380714416503906
  String           total seconds: 0.036461830139160156
string size: 2^20 (1048576)
  NSString(String) total seconds: 0.006340980529785156
  NSString         total seconds: 0.005095005035400391
  String           total seconds: 0.12430882453918457
string size: 2^22 (4194304)
  NSString(String) total seconds: 0.024969816207885742
  NSString         total seconds: 0.01906609535217285
  String           total seconds: 0.4754300117492676
string size: 2^24 (16777216)
  NSString(String) total seconds: 0.09792113304138184
  NSString         total seconds: 0.07473611831665039
  String           total seconds: 2.0220470428466797
string size: 2^26 (67108864)
  NSString(String) total seconds: 0.41455817222595215
  NSString         total seconds: 0.29911088943481445
  String           total seconds: 7.661313056945801
string size: 2^28 (268435456)
  NSString(String) total seconds: 1.6104252338409424
  NSString         total seconds: 1.2524471282958984
  String           total seconds: 31.029043912887573

Expected behavior

String.range is at least as fast as NSString.range

Environment

╰─>$ swiftc --version
swift-driver version: 1.115 Apple Swift version 6.0.2 (swiftlang-6.0.2.1.2 clang-1600.0.26.4)
Target: arm64-apple-macosx14.0

sonoma 14.5

Additional information

No response

[750]

I can't reproduce this issue in online swift compilers like https://swiftfiddle.com/vryzorl7avd3fac6q3bwpfkv4y

Probably because they are running linux swift

But i can reproduce it on another mac, sonoma 14.4.1

Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-darwin23.4.0

[itingliu]

Thanks for reporting. It looks like we're spending a good chunk of time in String/Substring.subscript.getter

11.00 ms  84.6%	0               specialized _StringCompareOptionsIterable._range<A>(of:toHalfWidth:diacriticsInsensitive:caseFold:anchored:backwards:)
5.00 ms   38.5%	1.00 ms	            specialized Collection.first.getter
4.00 ms   30.8%	1.00 ms	                String.subscript.getter
3.00 ms   23.1%	1.00 ms	            Character.asciiValue.getter
2.00 ms   15.4%	1.00 ms	            Substring.subscript.getter
1.00 ms   7.7%	1.00 ms	            _stringCompareWithSmolCheck(_:_:expecting:)

I suppose that's here. I'm not sure what exactly is taking so long though from this trace though.