SwiftcKaigi#1 Videp is here -> https://www.youtube.com/watch?v=QBXcCTfwyZ8

1. Tutorial for developing SILOptimizer Pass
freddi - Yuki.Aki
at SwiftcKaigi #1 (16th.Nov)

2. About Me
- I’m freddi
- iOS Engineer @ Fukuoka
- twitter: _ _ _freddi_ _ _

3. Before Start
- This presentation is written in English
- This session will be talked in Japanese

4. Before Start
- This session is mainly for Beginner
- Better to listen previous SIL session
- Better to be familiar with C++ grammar

5. Today’s Aim
- Understand What SILOptimizer and Pass are.
- Understand How Pass optmize SIL Code
- Understand How Can we Play developing Pass

6. Flow of Compiling Swift Code,
with SILOptimizer

7. Flow of Compiling Swift Code

8. Flow of Compiling Swift Code
SILGen generates SIL from type-checked AST

9. SIL
- "Swift Intermediate Language” = SIL
- between type-checked AST and LLVM IR
- SIL Code is used for optimization of program

10. Between SILGen and IRGen
canonical
SIL
raw SIL SILOptimizer

11. raw SIL
- raw SIL code is generated from SILGen
- raw SIL has not been optimized and diagnosed
- optimized and diagnosed on SILOptimizer phase
raw SIL

12. canonical SIL
- Optimized and diagnosed SIL code is canonical SIL
- on SILOptimizer phase
canonical
SIL

13. canonical
SIL
raw SIL
Flow of raw SIL to canonical SIL
SILOptimizer

14. SILOptimizer
- SILOptimizer is one of phase in swiftc
- raw SIL is optimized and diagnosed on this phase
- It is consist of many module which called Pass
SILOptimizer

15. canonical
SIL
raw SIL SILOptimizer
Flow from raw SIL to canonical SIL

16. SILOptimizer
canonical
SIL
raw SIL Pass Pass Pass Pass
Flow from raw SIL to canonical SIL
= “PipeLine of Pass”

17. Pass in SILOptimizer
- Pass diagnoses and optimizes received ras SIL
- Some of Passes are called definitely
Pass

18. Pass Pipeline
- Pass Pipeline has info which Passes must be called
- Pipeline is created before starting optimizing
- Pass in Pipeline is decided by …
- swiftc Option (e.g.-O,-Onone) etc …

19. Pass in SILOptimizer
- Example of Optimizer Pass
- Memory Promotion
- Assuming Single Thread (Optional Optimizer)
Pass

20. Pass in SILOptimizer
- Example of Diagnostic Pass
- Overflow checking of Numeric Type
Pass

21. Pass in SILOptimizer
- Example of Diagnostic Pass
- Overflow checking of Numeric Type
Let's check it by Demo!
by using -Xllvm -sil-print-pass-name option
Pass

22. Pass in SILOptimizer
-Xllvm -sil-print-pass-name

23. SIL
- SIL is generated from our Swift Code
- via type-checked AST
- raw SIL and canonical SIL
- canonical SIL is optimized and diagnosed SIL

24. SILOptimizer and Pass
- SILOptimizer is phase of optimizing and diagnosing
- SILOptimizer is consist of many Pass
- raw SIL is optimized and diagnosed by Pass

25. How can we add optimize Pass to compiler?

26. To add original Pass to swiftc
1. Create your C++ file (because Pass is C++ class)
@ lib/SILOptimizer/Transforms/*.cpp

27. To add original Pass to swiftc
2. Add location of C++ source for Pass Class
to lib/SILOptimizer/Transforms/CMakeLists.txt
3. Generate swiftc Xcode Project
※ You must do 2.before generating Xcode Project

28. 4. Register Pass info
@ include/swift/SILOptimizer/PassManager/Passes.def
5. Rebuild on Xcode
6. Add code which adding Pass to Pipeline
@ lib/SILOptimizer/PassManager/PassPipeline.cpp
To add original Pass to swiftc

29. 7. Write Pass Class and Creating Pass object func
@ on your C++ file which is added on 1.
To add original Pass to swiftc

30. Demo

31. Get Swift Compiler Code
$ mkdir swift-source
$ cd swift-source
$ git clone https://github.com/apple/swift

32. Create your C++ file (because Pass is C++ class)

33. Add location of C++ source for Pass Class

34. Generate swiftc Xcode Project
$ cd swift-source
$ utils/update-checkout --clone
$ utils/build-script
—debug
—xcode --skip-build-benchmarks

35. Register Pass info and Rebuild on Xcode

36. Add code which adding Pass to Pipeline

37. Write Pass Class and Creating Pass object func

38. Demo

40. Understand structural unit of SIL Code
treated by SILOptimizer Pass

41. SIL Component
- SILModule
- SILGlobalVariable-s
- SILFunction-s
- SILBasicBlock-s
- SILInstruction-s
- etc …

42. Demo again :)

43. SILModule

44. SILFunction-sSILModule

45. SILBasicBlock-sSILFunctions

46. SILBasicBlock-s SILInstruction-s

47. Basic Structure of SILInstruction
What instruction is using it (or Instruction’s id)
Instruction’s id
(Some instruction has no id on left of =)

48. Kind of SILInstruction
Integer Literal Instruction
Function Ref Instruction
Apply Literal Instruction

49. Understand structural unit of SIL Code
treated by SILOptimizer Pass

50. Understand structural unit of SIL Code
treated by SILOptimizer Pass
==
We can use these unit as C++ Class
on writing Pass

51. Demo time XD

52. AssumeSingleThreaded

53. SILFunctionTransform

54. Check Option

55. getFunction = Collection of BasicBlock

56. Basic Block = Collection of Instruction

57. Checking the Instruction is kind of Ref Count

58. Set Instruction non atomic

59. Invalidate Analysis

60. Now,we can read easy Pass!

61. Let’s play Pass by Demo!