class func v. static func in Swift4 ref: https://qiita.com/YutoMizutani/items/040d8af5bfc38d9f1fac

class-func.swift

class Main {
    class func say() {
        print("Hello, world!!")
    }
}
Main.say()

diff.sh

diff ./sil/final-class-func.sil ./sil/static-func.sil
diff ./sil/final-class-func.sil ./sil/open-class-func.sil
diff ./sil/final-class-func.sil ./sil/public-class-func.sil
diff ./sil/final-class-func.sil ./sil/internal-class-func.sil
diff ./sil/final-class-func.sil ./sil/fileprivate-class-func.sil
diff ./sil/final-class-func.sil ./sil/private-class-func.sil

file0.txt

$ swiftc -v
Apple Swift version 4.1 (swiftlang-902.0.48 clang-902.0.37.1)
Target: x86_64-apple-darwin17.5.0

file1.swift

class Main {
    class func say() {
        print("Hello, world!!")
    }
}
Main.say()

file10.swift

class Main {
    init() {
        Main.say()
    }

    <foo> class func say() {
        print("Hello, world!!")
    }
}
let _ = Main()

file14.txt

xcrun swiftc -wmo -O ./final-class-func.swift
xcrun swiftc -wmo -O ./static-func.swift
xcrun swiftc -wmo -O ./open-func.swift
xcrun swiftc -wmo -O ./public-class-func.swift
xcrun swiftc -wmo -O ./internal-class-func.swift
xcrun swiftc -wmo -O ./fileprivate-class-func.swift
xcrun swiftc -wmo -O ./private-class-func.swift

file2.swift

class Main {
    static func say() {
        print("Hello, world!!")
    }
}
Main.say()

file3.txt

$ swiftc -emit-silgen class-func.swift > class-func.sil
$ swiftc -emit-silgen static-func.swift > static-func.sil

file4.txt

diff class-func.sil static-func.sil
@@ -7,8 +7,9 @@ import SwiftShims
 // main
 sil @main : $@convention(c) (Int32, UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>) -> Int32 {
 bb0(%0 : $Int32, %1 : $UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>):
-  %2 = metatype $@thick Main.Type                 // users: %4, %3
-  %3 = class_method %2 : $@thick Main.Type, #Main.say!1 : (Main.Type) -> () -> (), $@convention(method) (@thick Main.Type) -> () // user: %4
+  %2 = metatype $@thick Main.Type                 // user: %4
+  // function_ref static Main.say()
+  %3 = function_ref @_T04main4MainC3sayyyFZ : $@convention(method) (@thick Main.Type) -> () // user: %4
   %4 = apply %3(%2) : $@convention(method) (@thick Main.Type) -> ()
   %5 = integer_literal $Builtin.Int32, 0          // user: %6
   %6 = struct $Int32 (%5 : $Builtin.Int32)        // user: %7
@@ -117,7 +118,6 @@ bb0(%0 : $Main):
 } // end sil function '_T04main4MainCACycfc'

 sil_vtable Main {
-  #Main.say!1: (Main.Type) -> () -> () : _T04main4MainC3sayyyFZ        // static Main.say()
   #Main.init!initializer.1: (Main.Type) -> () -> Main : _T04main4MainCACycfc   // Main.init()
   #Main.deinit!deallocator: _T04main4MainCfD   // Main.__deallocating_deinit
 }

file5.txt

$ swiftc -emit-assembly class-func.swift > class-func.s
$ swiftc -emit-assembly static-func.swift > static-func.s

file6.txt

diff class-func.s static-func.s
@@ -385,7 +385,7 @@ l___unnamed_4:
 __T04main4MainCMn:
        .long   l___unnamed_3-__T04main4MainCMn
        .long   0
-       .long   12
+       .long   11
        .long   (l___unnamed_4-__T04main4MainCMn)-12
        .long   (l_get_field_types_Main-__T04main4MainCMn)-16
        .long   0
@@ -397,10 +397,8 @@ __T04main4MainCMn:
        .short  4
        .long   0
        .long   10
-       .long   2
-       .long   (__T04main4MainC3sayyyFZ-__T04main4MainCMn)-56
-       .long   0
-       .long   (__T04main4MainCACycfc-__T04main4MainCMn)-64
+       .long   1
+       .long   (__T04main4MainCACycfc-__T04main4MainCMn)-56
        .long   1

 .zerofill __DATA,__bss,__T04main4MainCML,8,3
@@ -419,11 +417,10 @@ __T04main4MainCMf:
        .long   16
        .short  7
        .short  0
-       .long   112
+       .long   104
        .long   16
        .quad   __T04main4MainCMn
        .quad   0
-       .quad   __T04main4MainC3sayyyFZ
        .quad   __T04main4MainCACycfc

        .section        __TEXT,__swift3_typeref,regular,no_dead_strip

file7.swift

class Main {
    final class func say() {
        print("Hello, world!!")
    }
}
Main.say()

file8.swift

class Main {
    static func say() {
        print("Hello, world!!")
    }
}
Main.say()

file9.txt

$ swiftc -emit-silgen final-class-func.swift > final-class-func.sil
$ swiftc -emit-silgen static-func.swift > static-func.sil

final-class-func.swift

class Main {
    final class func say() {
        print("Hello, world!!")
    }
}
Main.say()

generate.sh

swiftc -emit-silgen -wmo -O final-class-func.swift > ./sil/final-class-func.sil
swiftc -emit-silgen -wmo -O static-func.swift > ./sil/static-func.sil
swiftc -emit-silgen -wmo -O open-class-func.swift > ./sil/open-class-func.sil
swiftc -emit-silgen -wmo -O public-class-func.swift > ./sil/public-class-func.sil
swiftc -emit-silgen -wmo -O internal-class-func.swift > ./sil/internal-class-func.sil
swiftc -emit-silgen -wmo -O fileprivate-class-func.swift > ./sil/fileprivate-class-func.sil
swiftc -emit-silgen -wmo -O private-class-func.swift > ./sil/private-class-func.sil

sed.sh

sed -n 43p ./sil/final-class-func.sil
sed -n 43p ./sil/static-func.sil
sed -n 43p ./sil/open-class-func.sil
sed -n 43p ./sil/public-class-func.sil
sed -n 43p ./sil/internal-class-func.sil
sed -n 43p ./sil/fileprivate-class-func.sil
sed -n 43p ./sil/private-class-func.sil

static-func.swift

class Main {
    static func say() {
        print("Hello, world!!")
    }
}
Main.say()