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working on issue 13
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‎issue13/README.md‎

Lines changed: 191 additions & 78 deletions
Original file line numberDiff line numberDiff line change
@@ -52,84 +52,94 @@ func traditionalForLoop() {
5252
It doesn't really do anything special but it allows us to get the assembled code by searching for its name in the code segment and then analyzing the results. Here is the ARM64 generated code from *xcodebuild*:
5353

5454
```asm
55-
0x00000001000060b0 FFC301D1 sub sp, sp, #0x70
56-
0x00000001000060b4 FC6F01A9 stp x28, x27, [sp, #0x10]
57-
0x00000001000060b8 FA6702A9 stp x26, x25, [sp, #0x20]
58-
0x00000001000060bc F85F03A9 stp x24, x23, [sp, #0x30]
59-
0x00000001000060c0 F65704A9 stp x22, x21, [sp, #0x40]
60-
0x00000001000060c4 F44F05A9 stp x20, x19, [sp, #0x50]
61-
0x00000001000060c8 FD7B06A9 stp x29, x30, [sp, #0x60]
62-
0x00000001000060cc FD830191 add x29, sp, #0x60
63-
0x00000001000060d0 170080D2 movz x23, #0x0
64-
0x00000001000060d4 180000F0 adrp x24, #0x100009000
65-
0x00000001000060d8 FA030032 orr w26, wzr, #0x1
66-
0x00000001000060dc FC031F32 orr w28, wzr, #0x2
67-
0x00000001000060e0 1F2003D5 nop
68-
0x00000001000060e4 3BF90058 ldr x27, #0x100008008
69-
0x00000001000060e8 B9D5BB52 movz w25, #0xdead, lsl #16
70-
0x00000001000060ec F9DD9772 movk w25, #0xbeef
71-
72-
0x00000001000060f0 D7040037 tbnz w23, #0x0, 0x100006188
73-
74-
0x00000001000060f4 002B43F9 ldr x0, [x24, #0x650]
75-
0x00000001000060f8 000200B5 cbnz x0, 0x100006138
76-
77-
0x00000001000060fc 1F2003D5 nop
78-
0x0000000100006100 40AA0158 ldr x0, #0x100009648
79-
0x0000000100006104 200100B5 cbnz x0, 0x100006128
80-
81-
0x0000000100006108 E0030032 orr w0, wzr, #0x1
82-
0x000000010000610c E3230091 add x3, sp, #0x8
83-
0x0000000100006110 010080D2 movz x1, #0x0
84-
0x0000000100006114 020080D2 movz x2, #0x0 ; argument #1 for method _swift_rt_swift_getExistentialTypeMetadata
85-
0x0000000100006118 2A000094 bl _swift_rt_swift_getExistentialTypeMetadata
86-
0x000000010000611c 68A90110 adr x8, #0x100009648
87-
0x0000000100006120 1F2003D5 nop
88-
0x0000000100006124 00FD9FC8 stlr x0, [x8]
89-
90-
0x0000000100006128 52000094 bl imp___stubs___T0s23_ContiguousArrayStorageCMa
91-
0x000000010000612c 28A90110 adr x8, #0x100009650
92-
0x0000000100006130 1F2003D5 nop
93-
0x0000000100006134 00FD9FC8 stlr x0, [x8]
94-
95-
0x0000000100006138 E1031A32 orr w1, wzr, #0x40
96-
0x000000010000613c E20B0032 orr w2, wzr, #0x7
97-
0x0000000100006140 25000094 bl _swift_rt_swift_allocObject
98-
0x0000000100006144 F30300AA mov x19, x0
99-
0x0000000100006148 7A7201A9 stp x26, x28, [x19, #0x10]
100-
0x000000010000614c 7B1E00F9 str x27, [x19, #0x38]
101-
0x0000000100006150 771200F9 str x23, [x19, #0x20]
102-
0x0000000100006154 4D000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortFfA0_
103-
0x0000000100006158 F40300AA mov x20, x0
104-
0x000000010000615c F50301AA mov x21, x1
105-
0x0000000100006160 F60302AA mov x22, x2
106-
0x0000000100006164 4C000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortFfA1_
107-
0x0000000100006168 E40300AA mov x4, x0
108-
0x000000010000616c E50301AA mov x5, x1
109-
0x0000000100006170 E60302AA mov x6, x2
110-
0x0000000100006174 E00313AA mov x0, x19
111-
0x0000000100006178 E10314AA mov x1, x20
112-
0x000000010000617c E20315AA mov x2, x21
113-
0x0000000100006180 E30316AA mov x3, x22
114-
0x0000000100006184 3E000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortF
115-
116-
0x0000000100006188 FF0219EB cmp x23, x25
117-
0x000000010000618c A0000054 b.eq 0x1000061a0
118-
119-
0x0000000100006190 FF0600B1 cmn x23, #0x1
120-
0x0000000100006194 F7060091 add x23, x23, #0x1
121-
0x0000000100006198 C7FAFF54 b.vc 0x1000060f0
122-
123-
0x000000010000619c 200020D4 brk #0x1
124-
125-
0x00000001000061a0 FD7B46A9 ldp x29, x30, [sp, #0x60]
126-
0x00000001000061a4 F44F45A9 ldp x20, x19, [sp, #0x50]
127-
0x00000001000061a8 F65744A9 ldp x22, x21, [sp, #0x40]
128-
0x00000001000061ac F85F43A9 ldp x24, x23, [sp, #0x30]
129-
0x00000001000061b0 FA6742A9 ldp x26, x25, [sp, #0x20]
130-
0x00000001000061b4 FC6F41A9 ldp x28, x27, [sp, #0x10]
131-
0x00000001000061b8 FFC30191 add sp, sp, #0x70
132-
0x00000001000061bc C0035FD6 ret
55+
0x0000000100005f78 FFC301D1 sub sp, sp, #0x70 ; XREF=-[_TtC12swift_weekly11AppDelegate application:didFinishLaunchingWithOptions:]+200
56+
0x0000000100005f7c FC6F01A9 stp x28, x27, [sp, #0x10]
57+
0x0000000100005f80 FA6702A9 stp x26, x25, [sp, #0x20]
58+
0x0000000100005f84 F85F03A9 stp x24, x23, [sp, #0x30]
59+
0x0000000100005f88 F65704A9 stp x22, x21, [sp, #0x40]
60+
0x0000000100005f8c F44F05A9 stp x20, x19, [sp, #0x50]
61+
0x0000000100005f90 FD7B06A9 stp x29, x30, [sp, #0x60]
62+
0x0000000100005f94 FD830191 add x29, sp, #0x60
63+
0x0000000100005f98 170080D2 movz x23, #0x0
64+
0x0000000100005f9c B85FF2D2 movz x24, #0x92fd, lsl #48
65+
0x0000000100005fa0 1834D3F2 movk x24, #0x99a0, lsl #32
66+
0x0000000100005fa4 B8FCA0F2 movk x24, #0x7e5, lsl #16
67+
0x0000000100005fa8 38E083F2 movk x24, #0x1f01
68+
0x0000000100005fac B9DD9B52 movz w25, #0xdeed
69+
0x0000000100005fb0 FB031F32 orr w27, wzr, #0x2
70+
0x0000000100005fb4 1F2003D5 nop
71+
0x0000000100005fb8 9A020158 ldr x26, #0x100008008
72+
0x0000000100005fbc BCD5BB52 movz w28, #0xdead, lsl #16
73+
0x0000000100005fc0 FCDD9772 movk w28, #0xbeef
74+
75+
0x0000000100005fc4 E87E589B smulh x8, x23, x24 ; XREF=__T012swift_weekly11AppDelegateC18traditionalForLoopyyFTf4d_n+272
76+
0x0000000100005fc8 0801178B add x8, x8, x23
77+
0x0000000100005fcc 09FD4F93 asr x9, x8, #0xf
78+
0x0000000100005fd0 28FD488B add x8, x9, x8, lsr #63
79+
0x0000000100005fd4 08DD199B msub x8, x8, x25, x23
80+
0x0000000100005fd8 080500B5 cbnz x8, 0x100006078
81+
82+
0x0000000100005fdc 1F2003D5 nop
83+
0x0000000100005fe0 C0B30158 ldr x0, #0x100009658
84+
0x0000000100005fe4 000200B5 cbnz x0, 0x100006024
85+
86+
0x0000000100005fe8 1F2003D5 nop
87+
0x0000000100005fec 20B30158 ldr x0, #0x100009650
88+
0x0000000100005ff0 200100B5 cbnz x0, 0x100006014
89+
90+
0x0000000100005ff4 E0030032 orr w0, wzr, #0x1
91+
0x0000000100005ff8 E3230091 add x3, sp, #0x8
92+
0x0000000100005ffc 010080D2 movz x1, #0x0
93+
0x0000000100006000 020080D2 movz x2, #0x0 ; argument #1 for method _swift_rt_swift_getExistentialTypeMetadata
94+
0x0000000100006004 6F000094 bl _swift_rt_swift_getExistentialTypeMetadata
95+
0x0000000100006008 48B20110 adr x8, #0x100009650
96+
0x000000010000600c 1F2003D5 nop
97+
0x0000000100006010 00FD9FC8 stlr x0, [x8]
98+
99+
0x0000000100006014 97000094 bl imp___stubs___T0s23_ContiguousArrayStorageCMa ; XREF=__T012swift_weekly11AppDelegateC18traditionalForLoopyyFTf4d_n+120
100+
0x0000000100006018 08B20110 adr x8, #0x100009658
101+
0x000000010000601c 1F2003D5 nop
102+
0x0000000100006020 00FD9FC8 stlr x0, [x8]
103+
104+
0x0000000100006024 E1031A32 orr w1, wzr, #0x40 ; XREF=__T012swift_weekly11AppDelegateC18traditionalForLoopyyFTf4d_n+108
105+
0x0000000100006028 E20B0032 orr w2, wzr, #0x7
106+
0x000000010000602c 6A000094 bl _swift_rt_swift_allocObject
107+
0x0000000100006030 F30300AA mov x19, x0
108+
0x0000000100006034 E8030032 orr w8, wzr, #0x1
109+
0x0000000100006038 686E01A9 stp x8, x27, [x19, #0x10]
110+
0x000000010000603c 7A1E00F9 str x26, [x19, #0x38]
111+
0x0000000100006040 771200F9 str x23, [x19, #0x20]
112+
0x0000000100006044 91000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortFfA0_
113+
0x0000000100006048 F40300AA mov x20, x0
114+
0x000000010000604c F50301AA mov x21, x1
115+
0x0000000100006050 F60302AA mov x22, x2
116+
0x0000000100006054 90000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortFfA1_
117+
0x0000000100006058 E40300AA mov x4, x0
118+
0x000000010000605c E50301AA mov x5, x1
119+
0x0000000100006060 E60302AA mov x6, x2
120+
0x0000000100006064 E00313AA mov x0, x19
121+
0x0000000100006068 E10314AA mov x1, x20
122+
0x000000010000606c E20315AA mov x2, x21
123+
0x0000000100006070 E30316AA mov x3, x22
124+
0x0000000100006074 82000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortF
125+
126+
0x0000000100006078 FF021CEB cmp x23, x28 ; XREF=__T012swift_weekly11AppDelegateC18traditionalForLoopyyFTf4d_n+96
127+
0x000000010000607c A0000054 b.eq 0x100006090
128+
129+
0x0000000100006080 FF0600B1 cmn x23, #0x1
130+
0x0000000100006084 F7060091 add x23, x23, #0x1
131+
0x0000000100006088 E7F9FF54 b.vc 0x100005fc4
132+
133+
0x000000010000608c 200020D4 brk #0x1
134+
135+
0x0000000100006090 FD7B46A9 ldp x29, x30, [sp, #0x60] ; XREF=__T012swift_weekly11AppDelegateC18traditionalForLoopyyFTf4d_n+260
136+
0x0000000100006094 F44F45A9 ldp x20, x19, [sp, #0x50]
137+
0x0000000100006098 F65744A9 ldp x22, x21, [sp, #0x40]
138+
0x000000010000609c F85F43A9 ldp x24, x23, [sp, #0x30]
139+
0x00000001000060a0 FA6742A9 ldp x26, x25, [sp, #0x20]
140+
0x00000001000060a4 FC6F41A9 ldp x28, x27, [sp, #0x10]
141+
0x00000001000060a8 FFC30191 add sp, sp, #0x70
142+
0x00000001000060ac C0035FD6 ret
133143
```
134144

135145
I will have to fire up ARM's reference manual to be able to understand all these instructions but I don't think it's a good idea to just put some assembly code in here and analyze it. Instead, we will look at some of the calls which are executed in this code and find out how they work and what they do.
@@ -259,6 +269,109 @@ class HighPriority {
259269
}
260270
```
261271

272+
TO BE CONTINUED
273+
274+
275+
`forEach{}` Loop
276+
===
277+
Let's rewrite the previous code by calling the `forEach` function on our array:
278+
279+
```swift
280+
@inline(never)
281+
func forEachLoop() {
282+
283+
(0...0xDEADBEEF).forEach {value in
284+
if value % 2 == 0 {
285+
print(value)
286+
}
287+
}
288+
289+
}
290+
```
291+
292+
Let's look at the generated assembly code to get some hints as to how this loop differs from the traditional `for` loop:
293+
294+
```asm
295+
0x00000001000060b0 FFC301D1 sub sp, sp, #0x70 ; XREF=-[_TtC12swift_weekly11AppDelegate application:didFinishLaunchingWithOptions:]+204
296+
0x00000001000060b4 FC6F01A9 stp x28, x27, [sp, #0x10]
297+
0x00000001000060b8 FA6702A9 stp x26, x25, [sp, #0x20]
298+
0x00000001000060bc F85F03A9 stp x24, x23, [sp, #0x30]
299+
0x00000001000060c0 F65704A9 stp x22, x21, [sp, #0x40]
300+
0x00000001000060c4 F44F05A9 stp x20, x19, [sp, #0x50]
301+
0x00000001000060c8 FD7B06A9 stp x29, x30, [sp, #0x60]
302+
0x00000001000060cc FD830191 add x29, sp, #0x60
303+
0x00000001000060d0 170080D2 movz x23, #0x0
304+
0x00000001000060d4 180000F0 adrp x24, #0x100009000
305+
0x00000001000060d8 FA030032 orr w26, wzr, #0x1
306+
0x00000001000060dc FC031F32 orr w28, wzr, #0x2
307+
0x00000001000060e0 1F2003D5 nop
308+
0x00000001000060e4 3BF90058 ldr x27, #0x100008008
309+
0x00000001000060e8 B9D5BB52 movz w25, #0xdead, lsl #16
310+
0x00000001000060ec F9DD9772 movk w25, #0xbeef
311+
312+
0x00000001000060f0 D7040037 tbnz w23, #0x0, 0x100006188 ; XREF=__T012swift_weekly11AppDelegateC11forEachLoopyyFTf4d_n+232
313+
314+
0x00000001000060f4 002F43F9 ldr x0, [x24, #0x658]
315+
0x00000001000060f8 000200B5 cbnz x0, 0x100006138
316+
317+
0x00000001000060fc 1F2003D5 nop
318+
0x0000000100006100 80AA0158 ldr x0, #0x100009650
319+
0x0000000100006104 200100B5 cbnz x0, 0x100006128
320+
321+
0x0000000100006108 E0030032 orr w0, wzr, #0x1
322+
0x000000010000610c E3230091 add x3, sp, #0x8
323+
0x0000000100006110 010080D2 movz x1, #0x0
324+
0x0000000100006114 020080D2 movz x2, #0x0 ; argument #1 for method _swift_rt_swift_getExistentialTypeMetadata
325+
0x0000000100006118 2A000094 bl _swift_rt_swift_getExistentialTypeMetadata
326+
0x000000010000611c A8A90110 adr x8, #0x100009650
327+
0x0000000100006120 1F2003D5 nop
328+
0x0000000100006124 00FD9FC8 stlr x0, [x8]
329+
330+
0x0000000100006128 52000094 bl imp___stubs___T0s23_ContiguousArrayStorageCMa ; XREF=__T012swift_weekly11AppDelegateC11forEachLoopyyFTf4d_n+84
331+
0x000000010000612c 68A90110 adr x8, #0x100009658
332+
0x0000000100006130 1F2003D5 nop
333+
0x0000000100006134 00FD9FC8 stlr x0, [x8]
334+
335+
0x0000000100006138 E1031A32 orr w1, wzr, #0x40 ; XREF=__T012swift_weekly11AppDelegateC11forEachLoopyyFTf4d_n+72
336+
0x000000010000613c E20B0032 orr w2, wzr, #0x7
337+
0x0000000100006140 25000094 bl _swift_rt_swift_allocObject
338+
0x0000000100006144 F30300AA mov x19, x0
339+
0x0000000100006148 7A7201A9 stp x26, x28, [x19, #0x10]
340+
0x000000010000614c 7B1E00F9 str x27, [x19, #0x38]
341+
0x0000000100006150 771200F9 str x23, [x19, #0x20]
342+
0x0000000100006154 4D000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortFfA0_
343+
0x0000000100006158 F40300AA mov x20, x0
344+
0x000000010000615c F50301AA mov x21, x1
345+
0x0000000100006160 F60302AA mov x22, x2
346+
0x0000000100006164 4C000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortFfA1_
347+
0x0000000100006168 E40300AA mov x4, x0
348+
0x000000010000616c E50301AA mov x5, x1
349+
0x0000000100006170 E60302AA mov x6, x2
350+
0x0000000100006174 E00313AA mov x0, x19
351+
0x0000000100006178 E10314AA mov x1, x20
352+
0x000000010000617c E20315AA mov x2, x21
353+
0x0000000100006180 E30316AA mov x3, x22
354+
0x0000000100006184 3E000094 bl imp___stubs___T0s5printySayypGd_SS9separatorSS10terminatortF
355+
356+
0x0000000100006188 FF0219EB cmp x23, x25 ; XREF=__T012swift_weekly11AppDelegateC11forEachLoopyyFTf4d_n+64
357+
0x000000010000618c A0000054 b.eq 0x1000061a0
358+
359+
0x0000000100006190 FF0600B1 cmn x23, #0x1
360+
0x0000000100006194 F7060091 add x23, x23, #0x1
361+
0x0000000100006198 C7FAFF54 b.vc 0x1000060f0
362+
363+
0x000000010000619c 200020D4 brk #0x1
364+
365+
0x00000001000061a0 FD7B46A9 ldp x29, x30, [sp, #0x60] ; XREF=__T012swift_weekly11AppDelegateC11forEachLoopyyFTf4d_n+220
366+
0x00000001000061a4 F44F45A9 ldp x20, x19, [sp, #0x50]
367+
0x00000001000061a8 F65744A9 ldp x22, x21, [sp, #0x40]
368+
0x00000001000061ac F85F43A9 ldp x24, x23, [sp, #0x30]
369+
0x00000001000061b0 FA6742A9 ldp x26, x25, [sp, #0x20]
370+
0x00000001000061b4 FC6F41A9 ldp x28, x27, [sp, #0x10]
371+
0x00000001000061b8 FFC30191 add sp, sp, #0x70
372+
0x00000001000061bc C0035FD6 ret
373+
```
374+
262375

263376

264377

‎issue13/exampleCode/swift-weekly.xcodeproj/project.xcworkspace/xcuserdata/vandadnp.xcuserdatad/UserInterfaceState.xcuserstate‎

-12 Bytes
Binary file not shown.

‎issue13/exampleCode/swift-weekly/AppDelegate.swift‎

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -24,9 +24,21 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
2424

2525
}
2626

27+
@inline(never)
28+
func forEachLoop() {
29+
30+
(0...0xDEADBEEF).forEach {value in
31+
if value % 2 == 0 {
32+
print(value)
33+
}
34+
}
35+
36+
}
37+
2738
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
2839
// Override point for customization after application launch.
2940
traditionalForLoop()
41+
forEachLoop()
3042
return true
3143
}
3244

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