OPTIMIZING THE JAVA VIRTUAL MACHINE INSTRUCTION SET BY ...

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16 iadd ladd fadd dadd isub lsub fsub dsub imul lmul fmul dmul idiv ldiv fdiv ddiv irem lrem frem drem ineg lneg fneg dneg ishr ishl lshr lshl iushr lushr iand land ior lor ixor lxor Table 2.6: Arithmetic Operation Bytecodes i2l l2i f2i d2i i2b i2f l2f f2l d2l i2c i2d l2d f2d d2f i2s Table 2.7: Numeric Casting Bytecodes from the operand stack. The result of the computation is pushed onto the operand stack. For example, the bytecode dmul pops two double precision floating point numbers from the stack, multiplies them together and then pushes their product onto the stack as a double precision floating point number. 2.3.6 Casting Values are converted between numeric data types using casting bytecodes. These bytecodes follow the general form 2 where and are each a type abbreviation from Table 2.2. In addition, when the input type denoted by is integer, the output type, , can also be byte (b), char (c) or short (s). When a casting bytecode executes, a value of the input data type is popped from the operand stack. Then the value is converted into the output type and pushed back onto the operand stack. Performing these casting operations may result in a loss of data when the input value is too large to be expressed in the output data type or the output data type is unable to represent the input value precisely. Examples of casting bytecodes include f2l, which converts a floating point number into a long integer, and i2s, which converts a 32-bit integer into a 16-bit integer. All of the 15 casting bytecodes defined by the Java Virtual Machine Specification are listed in Table 2.7. The Java Virtual Machine instruction set also includes two bytecodes for casting values with class types. The instanceof bytecode determines if an object reference
17 Condition Equal Unequal Greater Than Greater Than or Equal Less Than Less Than or Equal Abbreviation eq ne gt ge lt le Table 2.8: Branch Condition Abbreviations can be treated as an instance of a specific class. The checkcast bytecode performs a similar check. However, unlike instanceof, which pushes a result value onto the operand stack to indicate the result of the comparison, checkcast throws an exception when the test fails. 2.3.7 Branching Branching bytecodes are used to change the flow of control within the method. The goto and goto w bytecodes are unconditional branches which jump to a new location within the method independent of the values on the operand stack. Other conditional branch bytecodes consider one or more values on the operand stack. These bytecodes branch if the condition specified by the bytecode is true. If the condition is false, execution continues at the bytecode immediately after the branch bytecode. Branch bytecodes can be used to change the flow of control within the method based on the values of integer or object reference operands at the top of the stack. Branch bytecodes that compare an integer at the top of the operand stack with 0 follow the format if where is a two letter abbreviation that indicates the condition being tested. The conditions that can be tested and their abbreviations are listed in Table 2.8. Two integer values stored on the stack can be tested using bytecodes of the form if icmp. These bytecodes allow an integer to be compared against an arbitrary value. In addition, object references can also be compared using bytecodes of the form if acmp. When object references are compared the only conditions that are supported are eq and ne. An object reference located at the top of the operand stack can be tested against null using the bytecodes ifnull and ifnonnull which branch if the object reference is null or non-null respectively. Two additional branch bytecodes are provided which branch based on the value of an integer. These bytecodes, denoted by lookupswitch and tableswitch, allow for
Page 1 and 2: OPTIMIZING THE JAVA VIRTUAL MACHINE
Page 3 and 4: Abstract Since its public introduct
Page 5 and 6: Acknowledgments While my name is th
Page 7 and 8: 2.4.4 Direct Threading . . . . . .
Page 9 and 10: 7.2 An Overview of Multicodes . . .
Page 11 and 12: List of Figures 2.1 Core Virtual Ma
Page 13 and 14: 7.11 201 compress Performance by Mu
Page 15 and 16: B.1 The Steps Followed to Evaluate
Page 17 and 18: 6.1 Most Frequently Occurring Const
Page 19 and 20: 1 Chapter 1 Introduction When Moore
Page 21 and 22: 3 Studies were conducted that consi
Page 23 and 24: 5 Chapter 2 An Overview of Java Thi
Page 25 and 26: 7 Addressing this need led to the d
Page 27 and 28: 9 performs garbage collection, a cl
Page 29 and 30: 11 also has the ability to contain
Page 31 and 32: 13 ... i − 1 iload 0x04 dstore 0x
Page 33: 15 ... aload 3 iconst 2 faload ...
Page 37 and 38: 19 transfered to the start of a new
Page 39 and 40: 21 piled into machine language inst
Page 41 and 42: 23 Figure 2.6: Interpreter Engine C
Page 43 and 44: 25 Figure 2.8: Interpreter Engine C
Page 45 and 46: 27 The following section examines t
Page 47 and 48: 29 execute (JMethod * method, Slot
Page 49 and 50: 31 codelets shown in this example a
Page 51 and 52: 33 3.1 Instruction Set Design The a
Page 53 and 54: 35 is replaced with a new opcode if
Page 55 and 56: 37 method. However, the Java Virtua
Page 57 and 58: 39 3.2.5 Bytecode Optimization Tool
Page 59 and 60: 41 each bytecode executed as was ac
Page 61 and 62: 43 executing the application. The a
Page 63 and 64: 45 Chapter 4 Despecialization The J
Page 65 and 66: 47 ... i − 1 iload 3 iload 0x04 i
Page 67 and 68: 49 purpose bytecodes. The notation,
Page 69 and 70: 51 is present in the constant pool
Page 71 and 72: 53 ... iload 3 iflt ... i − 1 i i
Page 73 and 74: 55 the stack challenging in some ca
Page 75 and 76: Figure 4.7: Despecialization of Bra
Page 77 and 78: 59 Specialized Bytecode load store
Page 79 and 80: 61 tual machine (RVM). Version 2.3.
Page 81 and 82: 63 Test Total Weighted Condition Pe
Page 83 and 84: 65 Test Total Weighted Condition Pe
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67 Test Total Weighted Condition Pe
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69 4.2.6 Performance Summary Compar
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71 Category Original Desp. Percent
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73 the maximum value encountered af
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75 • Efficient support of new lan
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77 difference in the performance of
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79 JGF RayTracer: A 150 by 150 pixe
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81 # Average % of Specialized Despe
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83 provided by only two vendors. IB
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Figure 5.1: Average Performance Res
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87 Figure 5.4: Performance Results
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89 Figure 5.8: Performance Results
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91 ences in background processes, m
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93 difference in performance due to
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95 when a pure interpreter virtual
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97 It is observed that many of the
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99 Within this category, it was als
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101 machine code for the idioms. As
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103 were performed was less than 0.
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105 these despecializations in a me
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107 Chapter 6 Operand Profiling Cha
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109 the applications. In addition,
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111 The aload 0 bytecode was the mo
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113 function being integrated. Beca
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115 Implementing alignment rules un
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117 these data types in the list of
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Figure 6.3: Distribution of Local V
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121 are never executed by any of th
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123 load and store bytecodes. It is
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125 the time because the index bein
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127 6.2.5 Fields Only four bytecode
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129 Figure 6.8: Data types Accessed
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131 lar, the new set of specialized
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133 multicode block is defined to b
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135 Figure 7.1: Two Bytecodes and t
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137 because of the presence of the
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139 cache performance. As a result,
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141 Block 1: Block 2: aload 0 → g
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143 Sequence Count Score getfield a
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Figure 7.3: Iterative Multicode Ide
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147 number of bytecodes that will b
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149 BlockList: A list of the byteco
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151 Both the Total Bytecodes Score
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153 ... i − 1 ❄ ifeq 0x00 0x15
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155 Figure 7.7: Number of Unique Ca
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Figure 7.9: Cumulative Multicode Bl
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159 However, while considering long
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161 Figure 7.10: 201 compress Perfo
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163 Figure 7.14: Length 209 db Perf
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165 Figure 7.18: 222 mpegaudio Perf
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167 7.6.2 Overall Performance Acros
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169 a larger portion of the instruc
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171 // iload_1: stack[sp+1] = local
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173 // iload_1: // iconst_1: // iad
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175 Such bytecodes have a variable
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177 ∆ x1 /x 2 /x 3 /.../x n→ an
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179 Popping any values left on the
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181 7.9 Conclusion This chapter has
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183 ated will differ from that occu
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185 Figure 8.1: A Comparison of the
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187 performed impacts the sequences
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189 Figure 8.2: 201 compress Perfor
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191 Figure 8.5: 213 javac Performan
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193 Compared to the complete despec
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195 Figure 8.10: 209 db Performance
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197 performing multicode substituti
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199 Chapter 9 An Efficient Multicod
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201 alphabet employed by each of th
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9.4 An Algorithm for the Most Contr
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Figure 9.3: The Impact of Algorithm
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207 Algorithm NonOverlappingScore(n
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209 Algorithm CountUniqueOccurrence
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211 this algorithm did not consider
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213 exceptions if the value being c
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215 Figure 10.1: Multicode Blocks u
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217 approximately 30 percent of the
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219 a strategy other than direct th
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221 10.2.6 Combining Multicodes and
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223 10.2.9 Expanding the Class File
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225 revealed that none of the const
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227 based on these profile results
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229 stitution were performed. It co
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231 [13] B. Alpern, C. R. Attanasio
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233 [33] K. Casey, D. Gregg, M. A.
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235 [55] D. Gregg and J. Waldron. P
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237 [78] E. M. McCreight. A space-e
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239 [100] L. A. Smith, J. M. Bull,
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241 [120] T. A. Welch. A technique
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243 # Len Score Multicode % 1 30 10
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253 Table A.5 continued: # Len Scor
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259 the level of entropy within the
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261 there are no pointers to these
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263 information for each method so
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265 to emit four files that were su
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Figure B.1: The Steps Followed to E
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269 B.7 Summary This Chapter has de
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271 Selected Honors and Awards Cont
Page 291:
273 Departmental and University Pre
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