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Peephole Contest 2008. COMP 520. Final Ranking (Total). A-. Submissions. Sound or unsound?. Constant folding iconst_x iconst_y iadd || isub || imul || idiv || irem ---------> ldc x op y. Sound or unsound?. StringBuffer aload x dup ifnull label_1 goto label_2

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Presentation Transcript
sound or unsound
Sound or unsound?

Constant folding

iconst_x

iconst_y

iadd || isub || imul || idiv || irem

--------->

ldc x op y

sound or unsound1
Sound or unsound?

StringBuffer

aload x

dup

ifnull label_1

goto label_2

label_1:

pop

ldc "null"

label_2:

------------------------>

new j/l/StringBuffer

dup

invokenonvirtual j/l/StringBuffer/<init>()V

aload x

invokevirtual j/l/StringBuffer/append(Lj/l/String;)Lj/l/StringBuffer;

invokevirtual j/l/StringBuffer/toString()Lj/l/String;

sound or unsound2
Sound or unsound?

StringBuffer

invokevirtual j/l/String/concat(Lj/l/String;)Lj/l/String;

dup

ifnonnull lbl1

pop

ldc "null"

label lbl1

--------->

invokevirtual j/l/String/concat(Lj/l/String;)Lj/l/String;

sound or unsound3
Sound or unsound?

Dead code elimination

rules to keep in mind
Rules to keep in mind
  • Ok to assume “sensible code”, i.e. verifyable code
  • Should not assume certain code-generation scheme
  • Why? Times change, and code generation schemes, too!
results
Results

Tatatataaaaa….

2004 benchmarks
2004 Benchmarks

Group 5

javac

Group 1

Group 4

A+

A-

2007 benchmarks
2007 Benchmarks

javac

Group 5

Group 4

Group 1

A+

A-

2008 benchmarks
2008 Benchmarks

Group 5

javac

Group 1

A+

Group 2

A-

most gain for the pain
Most gain for the pain

Group 4

Group 3

Group 2

final ranking total1
Final Ranking (Total)

Group 5

javac

Group 1

Group 4

A+

A-

slide15

COMP 520 PRESENTS

Winners of the Peephole Contestof the Year 2008

GROUP 5

NingJia

Alexis Malozemoff

Wei Wu

November 21st, 2008

Eric Bodden & ReehanShaikh