Как CLR гарантирует, что память в стеке будет очищена? В этом докладе мы обсудим процесс преобразования C# кода в машинный код и то, как это связано с управлением памятью в стеке. Увидим разные трюки, которые JIT-компилятор делает, чтобы код работал быстрее. Доклад будет интересен тем, кто хочет знать, что скрывается под капотом привычных вещей и предпочитает понимать, как в деталях работает его код.

1. .NET Internals
stack memory management

2. Compilation flow
var hello = "Hello";
var world = "World";
Console.WriteLine(hello + world);
ldstr "Hello"
ldstr "World"
call System.String::Concat
call System.Console::WriteLine
movabs rdi, 0x196af5078
mov rdi, qword ptr [rdi]
movabs rsi, 0x196af5080
mov rsi, qword ptr [rsi]
call 0x10d5ad380
mov rdi, rax
call 0x10dbb1d40

3. Notation types
• Infix
• Suffix
• Postfix
2 + 3
+ 2 3
2 3 +

4. Notation types
• Infix
• Suffix
• Postfix
builder.Append("Hello!")
Append builder "Hello!"
builder "Hello!" Append

5. Stack machine

6. 2 + 3 * 4
Stack machine

7. 2 2
3
4
3
2 2
12
14
2 + 3 * 4
Stack machine
Stack
head

8. Stack machine
C#
var i = 2 + 2;
2 2 + i;
Forth

9. Developer Forth was Yoda just

10. Stack machine
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone);
C#
call Contact GetPhoneNumber()
dup
call void SendMessage(Contact)
call void MakeCall(Contact)
CIL

11. Stack machine
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone);
call Contact GetPhoneNumber()
dup
call void SendMessage(Contact)
call void MakeCall(Contact)
C# CIL
Stack phone
top

12. Stack machine
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone);
call Contact GetPhoneNumber()
dup
call void SendMessage(Contact)
call void MakeCall(Contact)
C# CIL
Stack phone
phone
top

13. Stack machine
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone);
call Contact GetPhoneNumber()
dup
call void SendMessage(Contact)
call void MakeCall(Contact)
C# CIL
Stack phone
phone
top

14. Stack machine
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone);
call Contact GetPhoneNumber()
dup
call void SendMessage(Contact)
call void MakeCall(Contact)
C# CIL
Stack phone
top

15. Stack machine
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone);
call Contact GetPhoneNumber()
dup
call void SendMessage(Contact)
call void MakeCall(Contact)
C# CIL
Stack
top

16. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
C#
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
CIL

17. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack 1
top

18. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack 1
Locals mode
top

19. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack phone
Locals mode
top

20. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack phone
Locals mode
phone
top

21. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack phone
Locals mode
phone
top

22. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack phone
Locals mode
phone
top

23. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack phone
Locals mode
phone
top

24. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack phone
mode
Locals mode
phone
top

25. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack phone
mode
Locals mode
phone
top

26. Stack machine
var mode = Mode.Default
var phone = GetPhoneNumber();
SendMessage(phone);
MakeCall(phone, mode);
ldc.i4.1
stloc.0
call Contact GetPhoneNumber()
stloc.1
ldloc.1
call void SendMessage(Contact)
ldloc.1
ldloc.0
call void MakeCall(Contact, valuetype Mode)
C# CIL
Stack Locals mode
phone
top

27. JIT compiler

28. Demo

29. JIT compiler
LdVar Sorting
& Tree
Ordering
Loop
Optimizations
Range Check
Elimination
Rationalization
Importer Inliner Morph
Flowgraph
Analysis
EmitterLowering LSRA CodeGen
Rationalized
LIR
Native
Code
GenTrees IR with reference counts
& evaluation order
Instr
Descs
Real
registers
Reg
Reqts
GenTrees
(IR)
IL
(bytecode)
Copy
Propagation
CSE
Assertion
Propagation
Loop
Optimizations
Range Check
Elimination
Copy
Propagation
CSE
Assertion
Propagation

30. JIT optimizations
• Not saving variables
• Method call inlining
• Range check elimination
• Jump instead of call
• …

31. Demo

32. .NET Internals
stack memory management
Nikolay Balakin
nikolay@balakin.me