Late Data Layout: Unifying Data Representation Transformations

Late Data Layout presentation given at the Virtual Machines Meetup at ETH Zürich, Switzerland. Website: http://vmmeetup.github.io/2014/

Project website: http://scala-ldl.org

1. scala-miniboxing.org/ldl Late Data Layout: Unifying Data Representation Transformations 11th of September 2014 Virtual Machine Meetup ETH Zürich, Switzerland
2. scala-miniboxing.org/ldl Vlad URECHE PhD student in the Scala Team @ EPFL Miniboxing guy. Also worked on specialization, the backend and scaladoc. @ @VladUreche @VladUreche vlad.ureche@epfl.ch
3. scala-miniboxing.org/ldl Late Data Layout: Unifying Data Representation Transformations
4. 4 scala-miniboxing.org/ldl
5. 5 scala-miniboxing.org/ldl OOPSLA 2014, Portland, OR
6. scala-miniboxing.org/ldl Late Data Layout: Unifying Data Representation Transformations
7. scala-miniboxing.org/ldl Late Data Layout: Unifying Data Representation Transformations • compiler transformations • separate compilation • global scope
8. scala-miniboxing.org/ldl Late Data Layout: Unifying Data Representation Transformations • unboxing, value classes • how data is represented
9. scala-miniboxing.org/ldl Late Data Layout: Unifying Data Representation Transformations • what is there to unify? • why bother?
10. scala-miniboxing.org/ldl Motivation Transformation Conclusion
11. scala-miniboxing.org/ldl Representation Transformations
12. scala-miniboxing.org/ldl Unboxing Primitive Types Representation Transformations
13. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Representation Transformations
14. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations
15. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations motivated by erased generics
16. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations Staging (Multi-Stage Programming) motivated by erased generics
17. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations Staging (Multi-Stage Programming) Function Representation motivated by erased generics
18. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations Staging (Multi-Stage Programming) Function Representation motivated by erased generics
19. 19 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types def identity[T](t: T): T = t
20. 20 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types def identity[T](t: T): T = t scalac / javac
21. 21 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types def identity[T](t: T): T = t def identity(t: Object): Object = t scalac / javac
22. 22 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types identity(5)
23. 23 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types identity(5) scalac / javac
24. 24 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types identity(5) identity(j.l.Integer.valueOf(5)).intValue scalac / javac
25. 25 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types identity(5) identity(j.l.Integer.valueOf(5)).intValue scalac / javac Object representation
26. 26 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types identity(5) identity(j.l.Integer.valueOf(5)).intValue scalac / javac produces garbage breaks locality guarantees inflates heap requirements indirect (slow) access to the value Object representation
27. 27 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = 5
28. 28 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = 5 scala.Int behaves like an object (has methods, can be used with generics)
29. 29 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = 5 scalac scala.Int behaves like an object (has methods, can be used with generics)
30. 30 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = 5 val five: int = 5 scalac scala.Int behaves like an object (has methods, can be used with generics)
31. 31 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = 5 val five: int = 5 scalac Unboxed integer scala.Int behaves like an object (has methods, can be used with generics)
32. 32 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = identity(5)
33. 33 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = identity(5) scalac
34. 34 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = identity(5) val five: int = scalac
35. 35 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = identity(5) val five: int = identity(I.valueOf(5)).intValue scalac
36. 36 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = identity(5) val five: int = identity(I.valueOf(5)).intValue scalac Boxing coercion
37. 37 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types val five: Int = identity(5) val five: int = identity(I.valueOf(5)).intValue scalac Boxing coercion Unboxing coercion
38. 38 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types scala.Int
39. 39 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types scala.Int
40. 40 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types scala.Int int • fast access • no garbage collection • locality
41. 41 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types scala.Int int • fast access • no garbage collection • locality • indirect access • object allocation • and thus garbage collection • no locality guarantees • compatible with erased generics java.lang.Integer
42. 42 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types scala.Int int • fast access • no garbage collection • locality • indirect access • object allocation • and thus garbage collection • no locality guarantees • compatible with erased generics java.lang.Integer incompatible → coercions
43. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations Staging (Multi-Stage Programming) Function Representation
44. 44 scala-miniboxing.org/ldl Specialization Specialization def identity[T](t: T): T = t
45. 45 scala-miniboxing.org/ldl Specialization Specialization def identity[T](t: T): T = t specialization
46. 46 scala-miniboxing.org/ldl Specialization Specialization def identity[T](t: T): T = t def identity(t: Object): Object = t specialization
47. 47 scala-miniboxing.org/ldl Specialization Specialization def identity[T](t: T): T = t def identity(t: Object): Object = t specialization def identity_Z(t: bool): bool = t
48. 48 scala-miniboxing.org/ldl Specialization Specialization def identity[T](t: T): T = t def identity(t: Object): Object = t specialization def identity_Z(t: bool): bool = t def identity_C(t: char): char = t
49. 49 scala-miniboxing.org/ldl Specialization Specialization def identity[T](t: T): T = t def identity(t: Object): Object = t specialization def identity_Z(t: bool): bool = t def identity_C(t: char): char = t … (7 other variants)
50. 50 scala-miniboxing.org/ldl Specialization Specialization identity(5)
51. 51 scala-miniboxing.org/ldl Specialization Specialization identity(5) specialization
52. 52 scala-miniboxing.org/ldl Specialization Specialization identity(5) identity_I(5) specialization
53. 53 scala-miniboxing.org/ldl Specialization Specialization identity(5) identity_I(5) specialization The variant of identity specialized for int
54. 54 scala-miniboxing.org/ldl Specialization Specialization identity(5) identity_I(5) specialization The variant of identity specialized for int // no boxing!
55. 55 scala-miniboxing.org/ldl Specialization Specialization def tupled[T1, T2](t1: T1, t2: T2) ...
56. 56 scala-miniboxing.org/ldl Specialization Specialization def tupled[T1, T2](t1: T1, t2: T2) ... specialization
57. 57 scala-miniboxing.org/ldl Specialization Specialization def tupled[T1, T2](t1: T1, t2: T2) ... // 100 methods (102) specialization
58. 58 scala-miniboxing.org/ldl Specialization Specialization def tupled[T1, T2](t1: T1, t2: T2) ... // 100 methods (102) specialization
59. 59 scala-miniboxing.org/ldl Specialization Specialization def tupled[T1, T2](t1: T1, t2: T2) ... // 100 methods (102) specialization Can we do better?
60. 60 scala-miniboxing.org/ldl Specialization Specialization def tupled[T1, T2](t1: T1, t2: T2) ... // 100 methods (102) specialization Can we do better?
61. 61 scala-miniboxing.org/ldl Miniboxing Miniboxing def identity[T](t: T): T = t
62. 62 scala-miniboxing.org/ldl Miniboxing Miniboxing def identity[T](t: T): T = t miniboxing
63. 63 scala-miniboxing.org/ldl Miniboxing Miniboxing def identity[T](t: T): T = t def identity(t: Object): Object = t miniboxing
64. 64 scala-miniboxing.org/ldl Miniboxing Miniboxing def identity[T](t: T): T = t def identity(t: Object): Object = t miniboxing def identity_M(..., t: long): long = t
65. 65 scala-miniboxing.org/ldl Miniboxing Miniboxing def identity[T](t: T): T = t def identity(t: Object): Object = t miniboxing def identity_M(..., t: long): long = t long encodes all primitive types
66. 66 scala-miniboxing.org/ldl Miniboxing Miniboxing def identity[T](t: T): T = t def identity(t: Object): Object = t miniboxing def identity_M(..., t: long): long = t Only 2n variants long encodes all primitive types
67. 67 scala-miniboxing.org/ldl Miniboxing Miniboxing identity(3)
68. 68 scala-miniboxing.org/ldl Miniboxing Miniboxing identity(3) miniboxing
69. 69 scala-miniboxing.org/ldl Miniboxing Miniboxing identity(3) identity_M(..., int2minibox(3)) miniboxing
70. 70 scala-miniboxing.org/ldl Miniboxing Miniboxing identity(3) identity_M(..., int2minibox(3)) miniboxing The miniboxed variant of identity
71. 71 scala-miniboxing.org/ldl Miniboxing Miniboxing identity(3) identity_M(..., int2minibox(3)) miniboxing Coercion The miniboxed variant of identity
72. 72 scala-miniboxing.org/ldl Miniboxing Miniboxing T
73. 73 scala-miniboxing.org/ldl Miniboxing Miniboxing T
74. 74 scala-miniboxing.org/ldl Miniboxing Miniboxing T long • preferred encoding
75. 75 scala-miniboxing.org/ldl Miniboxing Miniboxing T long • preferred encoding • fallback encoding • compatible with • virtual dispatch • subtyping • erased generics T (erased to Object)
76. 76 scala-miniboxing.org/ldl Miniboxing Miniboxing T long • preferred encoding • fallback encoding • compatible with • virtual dispatch • subtyping • erased generics T (erased to Object) incompatible → coercions
77. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations Staging (Multi-Stage Programming) Function Representation
78. 78 scala-miniboxing.org/ldl Value Classes Value Classes def abs(c: Complex): Double = ...
79. 79 scala-miniboxing.org/ldl Value Classes Value Classes def abs(c: Complex): Double = ... value class transformation
80. 80 scala-miniboxing.org/ldl Value Classes Value Classes def abs(c: Complex): Double = ... def abs(c_re: Double, c_im: Double): Double = ... value class transformation
81. 81 scala-miniboxing.org/ldl Value Classes Value Classes def abs(c: Complex): Double = ... def abs(c_re: Double, c_im: Double): Double = ... value class transformation No object created!
82. 82 scala-miniboxing.org/ldl Value Classes Value Classes val c: Complex = Complex(2,1)
83. 83 scala-miniboxing.org/ldl Value Classes Value Classes val c: Complex = Complex(2,1) value class transformation
84. 84 scala-miniboxing.org/ldl Value Classes Value Classes val c: Complex = Complex(2,1) val c_re: Double = 2 val c_im: Double = 1 value class transformation
85. 85 scala-miniboxing.org/ldl Value Classes Value Classes val c: Complex = Complex(2,1) val c_re: Double = 2 val c_im: Double = 1 value class transformation No object created!
86. 86 scala-miniboxing.org/ldl Value Classes Value Classes val a: Any = c
87. 87 scala-miniboxing.org/ldl Value Classes Value Classes val a: Any = c value class transformation
88. 88 scala-miniboxing.org/ldl Value Classes Value Classes val a: Any = c val a: Any = new Complex(c_re, c_im) value class transformation
89. 89 scala-miniboxing.org/ldl Value Classes Value Classes val a: Any = c val a: Any = new Complex(c_re, c_im) value class transformation Coercion!
90. 90 scala-miniboxing.org/ldl Value Classes Value Classes value class
91. 91 scala-miniboxing.org/ldl Value Classes Value Classes value class
92. 92 scala-miniboxing.org/ldl Value Classes Value Classes value class structure (by-val) • preferred encoding
93. 93 scala-miniboxing.org/ldl Value Classes Value Classes value class structure (by-val) • preferred encoding • fallback encoding • compatible with • subtyping • erased generics class (by-ref)
94. 94 scala-miniboxing.org/ldl Value Classes Value Classes value class structure (by-val) • preferred encoding • fallback encoding • compatible with • subtyping • erased generics class (by-ref) incompatible → coercions
95. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations Staging (Multi-Stage Programming) Function Representation
96. 96 scala-miniboxing.org/ldl Staging Staging T
97. 97 scala-miniboxing.org/ldl Staging Staging T
98. 98 scala-miniboxing.org/ldl Staging Staging T T (direct) • executed in this stage • stores a value
99. 99 scala-miniboxing.org/ldl Staging Staging T T (direct) • executed in this stage • stores a value • executed in the next stage • stores the expression that produces the value Rep[T] (lifted)
100. 100 scala-miniboxing.org/ldl Staging Staging T T (direct) • executed in this stage • stores a value • executed in the next stage • stores the expression that produces the value Rep[T] (lifted) incompatible → coercions
101. scala-miniboxing.org/ldl Unboxing Primitive Types Specialization (Miniboxing) Value Classes Representation Transformations Staging (Multi-Stage Programming) Function Representation
102. 102 scala-miniboxing.org/ldl Function Representation Function Representation scala.FunctionX
103. 103 scala-miniboxing.org/ldl Function Representation Function Representation scala.FunctionX
104. 104 scala-miniboxing.org/ldl Function Representation Function Representation scala.FunctionX FunctionX • compatible with the library • does not have all specializations • slow when used by miniboxed code
105. 105 scala-miniboxing.org/ldl Function Representation Function Representation scala.FunctionX FunctionX • compatible with the library • does not have all specializations • slow when used by miniboxed code • fast calling from miniboxed code • all specializations are there MbFunctionX
106. 106 scala-miniboxing.org/ldl Function Representation Function Representation scala.FunctionX FunctionX • compatible with the library • does not have all specializations • slow when used by miniboxed code • fast calling from miniboxed code • all specializations are there MbFunctionX incompatible → coercions
107. scala-miniboxing.org/ldl Motivation Transformation Conclusion
108. scala-miniboxing.org/ldl Motivation Transformation Conclusion
109. 109 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL)
110. 110 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL) concept
111. 111 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL) concept
112. 112 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL) concept repr. 1
113. 113 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL) concept repr. 1 repr. 2
114. 114 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL) concept repr. 1 … repr. n repr. 2
115. 115 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL) concept repr. 1 … repr. n repr. 2 Constraints from the interaction with other language features: • generics • subtyping • virtual dispatch • DSL semantics (staging)
116. 116 scala-miniboxing.org/ldl Late Data Layout (LDL) Late Data Layout (LDL) concept repr. 1 … repr. n repr. 2 Constraints from the interaction with other language features: • generics • subtyping • virtual dispatch • DSL semantics (staging) incompatible → coercions
117. scala-miniboxing.org/ldl How to transform a program?
118. scala-miniboxing.org/ldl How to transform a program? We'll use primitive unboxing as the running example, to keep things simple
119. 119 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types scala.Int int • fast access • no garbage collection • locality • indirect access • object allocation • and thus garbage collection • no locality guarantees • compatible with erased generics java.lang.Integer
120. 120 scala-miniboxing.org/ldl Unboxing Primitive Types Unboxing Primitive Types scala.Int int • fast access • no garbage collection • locality • indirect access • object allocation • and thus garbage collection • no locality guarantees • compatible with erased generics java.lang.Integer incompatible → coercions
121. scala-miniboxing.org/ldl Naive transformation Syntax-based transformation Type-based LDL transformation
122. 122 scala-miniboxing.org/ldl Naive transformation Naive transformation val x: Int = List[Int](1, 2, 3).head val y: List[Int] = List[Int](x) naive unboxing
123. 123 scala-miniboxing.org/ldl Naive transformation Naive transformation val x: Int = List[Int](1, 2, 3).head val y: List[Int] = List[Int](x) val x: int = List[Int](1, 2, 3).head val y: List[Int] = List[Int](x) naive unboxing
124. 124 scala-miniboxing.org/ldl Naive transformation Naive transformation val x: Int = List[Int](1, 2, 3).head val y: List[Int] = List[Int](x) val x: int = List[Int](1, 2, 3).head val y: List[Int] = List[Int](x) naive unboxing representation mismatch: expected: int (unboxed) found: Int (boxed)
125. 125 scala-miniboxing.org/ldl Naive transformation Naive transformation val x: Int = List[Int](1, 2, 3).head val y: List[Int] = List[Int](x) val x: int = List[Int](1, 2, 3).head val y: List[Int] = List[Int](x) naive unboxing representation mismatch: expected: int (unboxed) found: Int (boxed) representation mismatch: expected: Int (boxed) found: int (unboxed)
126. 126 scala-miniboxing.org/ldl Naive transformation Naive transformation • naively replacing representations – leads to mismatches – which are hard to recover (impossible for value classes and miniboxing) • we need coercions between representations
127. scala-miniboxing.org/ldl Naive transformation Syntax-based transformation Type-based LDL transformation
128. 128 scala-miniboxing.org/ldl Syntax-based Syntax-based • when transforming a value – coerce the definition right-hand side – coerce all references to it
129. 129 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head
130. 130 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head syntax-based unboxing
131. 131 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val x: int = syntax-based unboxing
132. 132 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val x: int = unbox(List[Int](1, 2, 3).head) syntax-based unboxing
133. 133 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val x: int = unbox(List[Int](1, 2, 3).head) syntax-based unboxing There are no references to x, so there's nothing else to do.
134. 134 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val x: int = unbox(List[Int](1, 2, 3).head) syntax-based unboxing There are no references to x, so there's nothing else to do.
135. 135 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val z: Int = x
136. 136 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val z: Int = x Transform one by one
137. 137 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val z: Int = x syntax-based unboxing Transform one by one
138. 138 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val z: Int = x val x: int = unbox(List[Int](1, 2, 3).head) syntax-based unboxing Transform one by one
139. 139 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: Int = List[Int](1, 2, 3).head val z: Int = x val x: int = unbox(List[Int](1, 2, 3).head) val z: Int = box(x) syntax-based unboxing Transform one by one
140. 140 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: int = unbox(List[Int](1, 2, 3).head) val z: Int = box(x)
141. 141 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: int = unbox(List[Int](1, 2, 3).head) val z: Int = box(x) syntax-based unboxing
142. 142 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: int = unbox(List[Int](1, 2, 3).head) val z: Int = box(x) val x: int = unbox(List[Int](1, 2, 3).head) val z: int = syntax-based unboxing
143. 143 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: int = unbox(List[Int](1, 2, 3).head) val z: Int = box(x) val x: int = unbox(List[Int](1, 2, 3).head) val z: int = unbox(box(x)) syntax-based unboxing
144. 144 scala-miniboxing.org/ldl Syntax-based Syntax-based val x: int = unbox(List[Int](1, 2, 3).head) val z: Int = box(x) val x: int = unbox(List[Int](1, 2, 3).head) val z: int = unbox(box(x)) syntax-based unboxing suboptimal
145. 145 scala-miniboxing.org/ldl Peephole Optimization Peephole Optimization val z: int = unbox(box(x))
146. 146 scala-miniboxing.org/ldl Peephole Optimization Peephole Optimization val z: int = unbox(box(x)) peephole
147. 147 scala-miniboxing.org/ldl Peephole Optimization Peephole Optimization val z: int = unbox(box(x)) val z: int = x peephole
148. 148 scala-miniboxing.org/ldl Peephole Optimization Peephole Optimization val z: int = unbox(box(x)) val z: int = x peephole
149. 149 scala-miniboxing.org/ldl Peephole Optimization Peephole Optimization val z: int = unbox(box(x)) val z: int = x peephole Okay, let's add the peephole transformation in the pipeline.
150. 150 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: Int, t2: Int): Int = if (Random.nextBoolean()) t1 else t2
151. 151 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: Int, t2: Int): Int = if (Random.nextBoolean()) t1 else t2 Transform one by one
152. 152 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: Int): Int = if (Random.nextBoolean()) box(t1) else t2
153. 153 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): Int = if (Random.nextBoolean()) box(t1) else box(t2)
154. 154 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): Int = if (Random.nextBoolean()) box(t1) else box(t2) Anything missing?
155. 155 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = unbox(if (Random.nextBoolean()) box(t1) else box(t2))
156. 156 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = unbox(if (Random.nextBoolean()) box(t1) else box(t2))
157. 157 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = unbox(if (Random.nextBoolean()) box(t1) else box(t2)) new peephole rule
158. 158 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = unbox(if (Random.nextBoolean()) box(t1) else box(t2)) new peephole rule sink outside coercions into the if branches
159. 159 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = if (Random.nextBoolean()) unbox(box(t1)) else unbox(box(t2))
160. 160 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = if (Random.nextBoolean()) unbox(box(t1)) else unbox(box(t2))
161. 161 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = if (Random.nextBoolean()) t1 else t2
162. 162 scala-miniboxing.org/ldl Syntax-based Syntax-based def choice(t1: int, t2: int): int = if (Random.nextBoolean()) t1 else t2 complicated
163. 163 scala-miniboxing.org/ldl Syntax-based Syntax-based • peephole transformation does not scale – needs multiple rules for each node – needs stateful rewrites – leads to an explosion of rules x states Details in the paper
164. scala-miniboxing.org/ldl Naive transformation Syntax-based transformation Type-based LDL transformation
165. 165 scala-miniboxing.org/ldl LDL Transformation LDL Transformation • propagate representation information – into the type system (based on annotated types) – allows selective marking of values to be unboxed
166. 166 scala-miniboxing.org/ldl LDL Transformation LDL Transformation • re-typecheck the tree – exposes inconsistencies in the representation • based on backward type propagation • from local type inference – so we introduce coercions • optimally, only when representations don't match
167. 167 scala-miniboxing.org/ldl LDL Transformation LDL Transformation • three-stage mechanism – inject annotate the values to be unboxed → – coerce introduce coercion markers → – commit commit to the alternative representations →
168. 168 scala-miniboxing.org/ldl LDL Transformation LDL Transformation Warning! Throughout the presentation we'll be writing annotations written before types (e.g. “@unboxed Int”), although in the Scala syntax they are written after the type (e.g.“Int @unboxed”). This makes it easier to read the types aloud.
169. 169 scala-miniboxing.org/ldl LDL Transformation LDL Transformation inject coerce commit
170. 170 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: Int, t2: Int): Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
171. 171 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: Int, t2: Int): Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
172. 172 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit configurable introduction of annotations based on external constraints
173. 173 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
174. 174 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
175. 175 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit the return type of choice is @unboxed Int
176. 176 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit the return type of choice is @unboxed Int
177. 177 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int the return type of choice is @unboxed Int
178. 178 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int expected type (part of local type inference) the return type of choice is @unboxed Int
179. 179 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int
180. 180 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : Boolean
181. 181 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : Boolean matches: expected: Boolean found: Boolean
182. 182 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int
183. 183 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int matches: expected: @unboxed Int found: @unboxed Int
184. 184 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int
185. 185 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit matches: ... : @unboxed Int
186. 186 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
187. 187 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit all okay, next phase
188. 188 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
189. 189 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: @unboxed Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit Replace: @unboxed Int → int (not showing Int → j.l.Integer)
190. 190 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: int, t2: int): int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
191. 191 scala-miniboxing.org/ldl LDL Transformation LDL Transformation def choice(t1: int, t2: int): int = if (Random.nextBoolean()) t1 else t2 inject coerce commit that's it!
192. 192 scala-miniboxing.org/ldl LDL Transformation LDL Transformation • three-stage mechanism – inject: add annotations – coerce: add coercions (based on the annotations) – commit: final representation semantics
193. 193 scala-miniboxing.org/ldl LDL Transformation LDL Transformation • Scalac's erasure – similar transformation – less flexible (no annotations) – entangled with other transformations • we took what's good – and allowed the transformation to work on other use cases as well
194. scala-miniboxing.org/ldl Consistency Selectivity Optimality (not formally proven yet) Properties Type-based LDL transformation
195. 195 scala-miniboxing.org/ldl Consistency Consistency inject coerce commit • representations become explicit in types – representation mismatches • become type mismatches • are exposed by the type system – mismatches lead to coercions • explicit bridges between representations • are introduced automatically – regardless of the representations • at a meta-level
196. scala-miniboxing.org/ldl Consistency Selectivity Optimality (not formally proven yet) Properties Type-based LDL transformation
197. 197 scala-miniboxing.org/ldl Selectivity Selectivity inject coerce commit • annotations allow selectively picking the values to be transformed – value classes • cannot unbox multi-param values in return position (not supported by the JVM platform) • bridge methods – staging • annotations signal domain-specific knowledge – can occur inside generics (List[@staged Int])
198. 198 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: Int): Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit
199. 199 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: Int): Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit what if we did not annotate t1?
200. 200 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit what if we did not annotate t1?
201. 201 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int
202. 202 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int
203. 203 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int mismatch: expected: @unboxed Int found: Int
204. 204 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) t1 else t2 inject coerce commit : @unboxed Int mismatch: expected: @unboxed Int found: Int coercion
205. 205 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) unbox(t1) else t2 inject coerce commit
206. 206 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) unbox(t1) else t2 inject coerce commit
207. 207 scala-miniboxing.org/ldl Selectivity Selectivity def choice(t1: Int, t2: int): int = if (Random.nextBoolean()) t1.intValue else t2 inject coerce commit
208. scala-miniboxing.org/ldl Consistency Selectivity Optimality (not formally proven yet) Properties Type-based LDL transformation
209. 209 scala-miniboxing.org/ldl Optimality Optimality def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) unbox(t1) else t2 inject coerce commit
210. 210 scala-miniboxing.org/ldl Optimality Optimality def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) unbox(t1) else t2 inject coerce commit
211. 211 scala-miniboxing.org/ldl Optimality Optimality def choice(t1: Int, t2: @unboxed Int): @unboxed Int = if (Random.nextBoolean()) unbox(t1) else t2 inject coerce commit Coercions are sunk in the tree → excute only if necessary
212. scala-miniboxing.org/ldl Motivation Transformation Conclusion
213. scala-miniboxing.org/ldl Motivation Transformation Conclusion
214. 214 scala-miniboxing.org/ldl Conclusion Conclusion LDL is a LDL is a • compile-time transformation – compatible with separate compilation – compatible with partial transformation
215. 215 scala-miniboxing.org/ldl Conclusion Conclusion LDL is a LDL is a • compile-time transformation – compatible with separate compilation – compatible with partial transformation – global scope (Graal/Truffle: local scope) • optimizes all data in a program
216. 216 scala-miniboxing.org/ldl Conclusion Conclusion LDL is a LDL is a • compile-time transformation – compatible with separate compilation – compatible with partial transformation – global scope (Graal/Truffle: local scope) • optimizes all data in a program / containers – conservative (Graal/Truffle: speculative)
217. 217 scala-miniboxing.org/ldl Conclusion Conclusion LDL is a LDL is a • compile-time transformation – compatible with separate compilation – compatible with partial transformation – global scope (Graal/Truffle: local scope) • optimizes all data in a program / containers – conservative (Graal/Truffle: speculative) Complementary optimizations
218. 218 scala-miniboxing.org/ldl Conclusion Conclusion LDL allows LDL allows • splitting a high-level concept – into multiple representations – in a consistent way (through coercions) – in a selective way (through annotations) – in an optimal way (coerce only if necessary)
219. 219 scala-miniboxing.org/ldl Conclusion Conclusion LDL is used in LDL is used in • the miniboxing plugin – for specialization – for function representation • other prototypes – value classes – staging
220. 220 scala-miniboxing.org/ldl Conclusion Conclusion LDL is used in LDL is used in • the miniboxing plugin – for specialization – for function representation • other prototypes – value classes – staging Don't take my word for it
221. 221 scala-miniboxing.org/ldl Conclusion Conclusion LDL is used in LDL is used in • the miniboxing plugin – for specialization – for function representation • other prototypes – value classes – staging Don't take my word for it Sources on github, artifact online.
222. 222 scala-miniboxing.org/ldl
223. 223 scala-miniboxing.org/ldl Conclusion Conclusion What's your use-case? What's your use-case? concept repr. 1 … repr. n repr. 2
224. scala-miniboxing.org/ldl Credits and Thank you-s • Cristian Talau - developed the initial prototype, as a semester project • Eugene Burmako - the value class plugin based on the LDL transformation • Aymeric Genet - developing collection-like benchmarks for the miniboxing plugin • Martin Odersky, for his patient guidance • Eugene Burmako, for trusting the idea enough to develop the value-plugin based on the LDL transformation • Iulian Dragos, for his work on specialization and many explanations • Miguel Garcia, for his original insights that spawned the miniboxing idea • Michel Schinz, for his wonderful comments and enlightening ACC course • Andrew Myers and Roland Ducournau for the discussions we had and the feedback provided • Heather Miller for the eye-opening discussions we had • Vojin Jovanovic, Sandro Stucki, Manohar Jonalagedda and the whole LAMP laboratory in EPFL for the extraordinary atmosphere • Adriaan Moors, for the miniboxing name which stuck :)) • Thierry Coppey, Vera Salvisberg and George Nithin, who patiently listened to many presentations and provided valuable feedback • Grzegorz Kossakowski, for the many brainstorming sessions on specialization • Erik Osheim, Tom Switzer and Rex Kerr for their guidance on the Scala community side • OOPSLA paper and artifact reviewers, who reshaped the paper with their feedback • Sandro, Vojin, Nada, Heather, Manohar - reviews and discussions on the LDL paper • Hubert Plociniczak for the type notation in the LDL paper • Denys Shabalin, Dmitry Petrashko for their patient reviews of the LDL paper Special thanks to the Scala Community for their support! (@StuHood, @vpatryshev and everyone else!)
225. scala-miniboxing.org/ldl Thank you! concept repr. 1 … repr. n repr. 2