This document discusses IronSmalltalk, which aims to provide a Smalltalk environment that runs on the Microsoft .NET DLR framework. It covers the history and motivation behind IronSmalltalk, provides an overview of key .NET DLR concepts like message sends, call sites, and call site binders. It also discusses how IronSmalltalk implements expression trees, the code pipeline from Smalltalk to MSIL, and techniques like polymorphic inline caching. The presentation concludes by discussing the project's goals and some future directions.

1. IronSmalltalk
August 24th 2011
Todor Todorov

2. IronSmalltalk
Smalltalk for the
Microsoft .Net DLR

3. Agenda
• History
• Motivation and Background
• Microsoft .Net DLR
• Message Sends and CallSites
• CallSite Binders
• Expression Trees
• Code Pipeline
• Polymorphic Inline Caching
• Conclusion
• Extras / Bonus
24 August 2011 Todor Todorov 3 / 111

5. Smalltalk 1980

6. Smalltalk 1980

7. Smalltalk 1981

8. Smalltalk 2011

9. Smalltalk 2005

10. The World Today

11. The World Today

13. Smalltalking
since 1998
Todor Todorov

14. Business
Applications

15. Microsoft
.Net Platform

16. Costly vs. Free?

17. Commodity!

18. Goal
• X3J20 Compliant Smalltalk
• First Class Member of the
DLR Family
• Easy interop. with .Net
• Decent Performance

19. Personal
Challenge

22. .NET DLR

23. .NET DLR

24. .NET DLR

25. Message Send

26. Message Send
Communication

27. Message Send
Transcript show:
'Hello, Edinburgh!'.

28. Message Send
Transcript show: 'Hello, Edinburgh!'.
TranscriptStream >> show: anObject
self
nextPutAll: anObject asString;
endEntry.

29. Method Lookup
Transcript show: 'Hello, Edinburgh!'.
TranscriptStream >> show: anObject
self
nextPutAll: anObject asString;
endEntry.

30. Call Site
Transcript show: 'Hello, Edinburgh!'.
call1 := Message receiver: Transcript
selector: #show:
arguments: #('Hello, Edinb… ').
call1 evaluate.

31. Call Site
Transcript show: 'Hello, Edinburgh!'.
call1 := CallSite receiver: Transcript
selector: #show:
arguments: #('Hello, Edinb… ').
call1 evaluate.

32. Call Site
Transcript show: 'Hello, Edinburgh!'.
call1 := CallSite selector: #show:.
call1
evaluateWithReceiver: Transcript
andArgs: #('Hello, Edinburgh').

33. Call Site Binders
Transcript show: 'Hello, Edinburgh!'.
call1 := CallSite onBinder:
(Binder selector: #show:).
call1
evaluateWithReceiver: Transcript
andArgs: #('Hello, Edinburgh').

34. Call Site Binders
Binder >> bindFor: aReceiver
arguments: anArray
^BindingRule for:
(aReceiver compiledMethodAt:
#show).

35. Dynamic Objects
Reflective Objects

36. Call Site Binders
Binder >> bindFor: aReceiver
arguments: anArray
^BindingRule for:
(aReceiver compiledMethodAt:
#show).

37. Call Site Binders
Binder >> bindFor: aReceiver
arguments: anArray
^aReceiver bindEvaluateFor: self
arguments: anArray.

38. Call Site Binders
Object >> bindEvaluateFor: aBinder
arguments: anArray
^BindingRule for:
(self compiledMethodAt:
aBinder selector).
” or return whatever it wants! ”

39. Call Site Binders
… receiver can’t help us, then …
fallbackBindInvokeFor: aReceiver
arguments: anArray
^BindingRule for:
… some compiled method …

40. Expression Trees

41. Expression Trees
Abstract Semantic Tree

42. Expression Trees
Abstract Semantic Tree
Abstract Syntax Tree

43. Expression Trees
Abstract Semantic Tree
Abstract Syntax Tree
Expression trees model code

44. Expression Trees
Abstract Semantic Tree
Abstract Syntax Tree
Expression trees model code
Expressions are used to
represent the implementation
of certain code or logic

45. Expression Trees
signString
^self < 0
ifTrue: [ 'Negative' ]
ifFalse: [ 'Positive' ].

46. Expression Trees
signString
^Expression
condition: (Expression
lowerThan: self value: 0)
true: 'Negative'
false: 'Positive'.

47. Expression Trees
signString
selfArg := Expression parameter: 'self'.
^Expression
condition: (Expression
lowerThan: selfArg
value: (Expression constant: 0))
true: (Expression constant: 'Negative')
false: (Expression constant: 'Positive').

48. Expression Trees
TranscriptStream>>show: anObject
self
nextPutAll: anObject.

49. Expression Trees
self
nextPutAll: anObject.
selfArg := Expression parameter: 'self'.
arg1 := Expression parameter: 'anObject'.
^Expression
dynamic: (Binder selector: #nextPutAll:)
receiver: selfArg
arguments: (Array with: arg1).

50. Expression Trees
Binder >> bindFor: aReceiver
arguments: anArray
^BindingRule for:
(aReceiver compiledMethodAt:
#nextPutAll).

51. Expression Trees
Binder >> bindFor: aReceiver
arguments: anArray
^BindingRule expression: (Expression
dynamic: (Binder selector: #nextPutAll:)
receiver: aReceiver expression
arguments: (Array
with: anArray first expression).

52. Code Pipeline

53. Code Pipeline
Smalltalk Sources

54. Code Pipeline
Smalltalk Sources Smalltalk
AST
Smalltalk Parser

55. Code Pipeline
Smalltalk Sources Smalltalk Expression
AST Tree
Smalltalk JIT-
Smalltalk Parser
Compiler

56. Code Pipeline
Smalltalk Sources Smalltalk Expression MSIL
AST Tree (Bytecode)
Smalltalk JIT- DLR / Linq
Smalltalk Parser
Compiler Compiler

57. Code Pipeline
Smalltalk Sources Smalltalk Expression MSIL
Machine Code
AST Tree (Bytecode)
Smalltalk JIT- DLR / Linq .NET CLR
Smalltalk Parser
Compiler Compiler (JIT Compiler)

58. Polymorphic
Inline Caching

59. Caching
Transcript show: 'Hello, Edinburgh!'.
call1 := CallSite onBinder:
(Binder selector: #show:).
call1
evaluateWithReceiver: Transcript
andArgs: #('Hello, Edinburgh').

60. Caching
Binder >> bindFor: aReceiver
arguments: anArray
method := aReceiver value compiledMethodAt: #show:.
” … magic … to generate expression from method … ”
^BindingRule expression: (Expression
dynamic: (Binder selector: #nextPutAll:)
receiver: aReceiver expression
arguments: (Array
with: anArray first expression).

61. Caching
Transcript show: 'Hello, Edinburgh!'.
call1 := CallSite onBinder:
(Binder selector: #show:).
call1
evaluateWithReceiver: Transcript
andArgs: #('Hello, Edinburgh').

62. Caching
Binder >> bindFor: aReceiver
arguments: anArray
method := aReceiver value compiledMethodAt: #show:.
” … magic … to generate expression from method … ”
^BindingRule expression: ” … expression … ”
restriction: [ :obj |
obj class = TranscriptStream ].

63. Caching
Transcript show: 'Hello, Edinburgh!'.
call1 := CallSite onBinder:
(Binder selector: #show:).
call1
evaluateWithReceiver: Transcript
andArgs: #('Hello, Edinburgh').

64. Restrictions
• Restrictions can be more complex
• For example, instance specific or object
version specific
• Restrictions determine the
polymorphism of objects
• Restrictions are the key to
polymorphic inline caching!

65. The Cache
• 3 Levels of Caching:
• Level 0 : Rule for last call
• Level 1 : Last 10 rules
• Level 2 : 100 rules, shares
across similar call sites

66. .NET DLR

68. Common Vocabulary
• None Defined
• De-Facto, the .Net class library
• We aim at reusing the common
classes
– Example: System.Char => Character
• Not everything maps easily, but most
do
– Example: System.String ~= String

69. Demo

70. Summary

71. Components
Hosting
Interchange Installer
IC Encoder AST JIT Compiler DefinitionInstaller
Runtime
Compiler Core IC JitCompiler
Common

72. Hosting
Windows Process
.Net AppDomain .Net AppDomain
DLR Script Scope Smalltalk Runtime
Smalltalk (Runtime)
Smalltalk Runtime
Ruby / Python
Smalltalk Runtime DLR Script Scope

73. Specifics
Symbols
Strings
Smalltalk Process
#sender
#respondsTo:
Events

74. Object Space
No Object Space Reflection
No #allInstances
No #allReferences
No #become:
But #behaveLike: is possible!
Debugger inspection is possible.

75. Major Tech Companies

76. Good News
Unicode
Multi Threaded
Large Class Library
Web-Hostable
MIT License

77. Near Future
Generics
Class Library Importer
(or auto-integration)
Finish Version 1.0
Write Tests (…)

78. Future
GUI Integration (WinForms + WPF)
SubSystems
(Interactive) Debugger
Visual Studio Integration
Mixins
SubSystems / Namespaces
Instance Specific Behavior

79. Questions
http://ironsmalltalk.codeplex.com/
mailto:todor@scientia.dk

80. Callbacks
List showItems:
#( 'TT' 'ST' ).
Workspace >> evaluate
Smalltalk >> run

81. Callbacks
List >> showItems: anArray
“ AddItems(anArray, self) ”
<Windows API>
List >> showItems:
Workspace >> evaluate
Smalltalk >> run

82. Callbacks
List.AddItems(string[] keys,
dynamic stList)
{
for(i=0; i<…;i++)
this.AddItem(
keys[i],
List.AddItems() stList);
List >> showItems: }
Workspace >> evaluate
Smalltalk >> run

83. Callbacks
List.AddItem(string[] keys,
dynamic stList)
{
string text = stList.
.GetItemText(key);
List.AddItem()
List.AddItems() ” …somehow add it… ”
List >> showItems: }
Workspace >> evaluate
Smalltalk >> run

84. Callbacks
List >> getItemText:
aString
^self itemTexts
List >> getItemText: at: aString.
List.AddItem()
List.AddItems()
List >> showItems:
Workspace >> evaluate
Smalltalk >> run

85. Callbacks
.Net 4.0 has the dynamic
keyword used for invoking
method on dynamic objects.
List >> getItemText: IronSmalltalk objects can
List.AddItem()
transparently be used by any
DLR aware language.
List.AddItems()
List >> showItems:
Workspace >> evaluate
Smalltalk >> run

86. Callbacks
Native Name: GetItemText
List >> getItemText:
aString
List >> getItemText:
List.AddItem()
List.AddItems() The native name is the
List >> showItems: method name (selector) that
Workspace >> evaluate
is exposed to the other DLR
languages.
Smalltalk >> run

87. Exceptions
[ Transcript show:
'Hello, Edinburgh!' ]
on: Error do: [ … ].
Workspace >> evaluate
Smalltalk >> run

88. Exceptions
BlockClosure >>
on: exception
do: handlerAction
” Some magic … ”
BlockClosure >> on:do:
^self value.
Workspace >> evaluate
Smalltalk >> run

89. Exceptions
BlockClosure >> value
< Primitive >
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

90. Exceptions
TranscriptStream >>
show: anObject
self
nextPutAll:
TranscriptStream >> show: anObject asString;
BlockClosure >> value endEntry.
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

91. Exceptions
String >> asString
^self.
String >> asString
TranscriptStream >> show:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

92. Exceptions
TranscriptStream >>
show: anObject
self
nextPutAll:
TranscriptStream >> show: anObject asString;
BlockClosure >> value endEntry.
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

93. Exceptions
TranscriptStream >>
nextPutAll: aString
” … some code here … ”
TranscriptStream >>nextPutAll:
TranscriptStream >> show:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

94. Exceptions
TranscriptStream >>
show: anObject
self
nextPutAll:
TranscriptStream >> show: anObject asString;
BlockClosure >> value endEntry.
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

95. Exceptions
TranscriptStream >>
endEntry
” … some code here … ”
TranscriptStream >> endEntry
TranscriptStream >> show:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

96. Exceptions
TranscriptStream >>
show: anObject
self
nextPutAll:
TranscriptStream >> show: anObject asString;
BlockClosure >> value endEntry.
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

97. Exceptions
BlockClosure >> value
< Primitive >
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

98. Exceptions
BlockClosure >>
on: exception
do: handlerAction
” Some magic … ”
BlockClosure >> on:do:
^self value.
Workspace >> evaluate
Smalltalk >> run

99. Exceptions
Transcript show:
'Hello, Edinburgh!'.
Workspace >> evaluate
Smalltalk >> run

100. Exceptions
TranscriptStream >>
nextPutAll: aString
” Transcript Window cannot
TranscriptStream >>nextPutAll: hold more text! ”
TranscriptStream >> show:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

101. Exceptions
TranscriptStream >>
nextPutAll: aString
” Transcript Window cannot
TranscriptStream >>nextPutAll: hold more text! ”
TranscriptStream >> show:
BlockClosure >> value
FAIL !
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

102. Exceptions
.Net Exceptions
unwind the stack
TranscriptStream >>nextPutAll: when thrown!
TranscriptStream >> show:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

103. Exceptions
Smalltalk expects
resumable
TranscriptStream >>nextPutAll: exceptions!
TranscriptStream >> show:
BlockClosure >> value
BlockClosure >> on:do: Stack is gone!
Workspace >> evaluate
Smalltalk >> run

104. Exceptions
Must keep stack!
Extra code here …
BlockClosure >> value
TranscriptStream >>nextPutAll: Code executes as
TranscriptStream >> show:
BlockClosure >> value
usually.
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

105. Exceptions
Unwinding is
executes as
TranscriptStream >>nextPutAll:
usually.
TranscriptStream >> show:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

106. Exceptions
List >> getItemText:
aString
List >> getItemText:
List.AddItem() ^self itemTexts
List.AddItems() at: aString.
List >> showItems:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

107. Exceptions
List >> getItemText:
aString
List >> getItemText:
List.AddItem() ^self itemTexts
List.AddItems() at: aString.
List >> showItems:
BlockClosure >> value
BlockClosure >> on:do:
KEY IS MISSING
Workspace >> evaluate
Smalltalk >> run

108. Exceptions
List >> getItemText:
aString
List >> getItemText:
List.AddItem() ^self itemTexts
List.AddItems() at: aString.
List >> showItems:
BlockClosure >> value
BlockClosure >> on:do:
KEY IS MISSING
Workspace >> evaluate
Smalltalk >> run

109. Exceptions
List >> getItemText:
aString
List >> getItemText:
List.AddItem() ^self itemTexts
List.AddItems() at: aString.
List >> showItems:
BlockClosure >> value
BlockClosure >> on:do:
KEY IS MISSING
Workspace >> evaluate
Smalltalk >> run

110. Exceptions
List >> getItemText:
Exceptions must
List.AddItem() integrate with the
try { … } catch { … }
rest of the .Net!
List.AddItems()
List >> showItems:
BlockClosure >> value
BlockClosure >> on:do:
Workspace >> evaluate
Smalltalk >> run

111. Exceptions
Non-Resumable exceptions can be
mapped to native .Net exceptions

112. Exceptions
Non-Resumable exceptions can be
mapped to native .Net exceptions
Resumable exceptions cannot be
mapped to native .Net exceptions
and will need a IronSmalltalk
special implementation.