Reducing Code Size Using Outlining Jessica Paquette Apple Outline - PowerPoint PPT Presentation

Reducing Code Size Using Outlining Jessica Paquette Apple

Outline • Code size • Outlining • Results • Future work

Motivating Example

callq _printf movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp) … movl -20(%rbp), %ecx movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp) … movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp)

callq _printf movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp) … NEW_FUNC: movl -20(%rbp), %ecx movl $2, %edx movl $2, %edx movl -8(%rbp), %esi movl -8(%rbp), %esi addl $1, %esi addl $1, %esi movl %esi, -8(%rbp) movl %esi, -8(%rbp) retq … movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp)

callq _printf movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp) callq _printf … callq NEW_FUNC NEW_FUNC: movl -20(%rbp), %ecx movl $2, %edx … movl $2, %edx movl -8(%rbp), %esi movl -20(%rbp), %ecx movl -8(%rbp), %esi addl $1, %esi addl $1, %esi callq NEW_FUNC movl %esi, -8(%rbp) … movl %esi, -8(%rbp) retq … callq NEW_FUNC movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp)

callq _printf callq NEW_FUNC NEW_FUNC: movl $2, %edx … movl -8(%rbp), %esi movl -20(%rbp), %ecx addl $1, %esi callq NEW_FUNC movl %esi, -8(%rbp) … retq callq NEW_FUNC

Outlining Replacing repeated sequences of instructions with calls to equivalent functions

Outliner A pass that finds repeated instruction sequences and outlines them.

G callq _printf G movl $2, %edx C movl -8(%rbp), %esi A addl $1, %esi T movl %esi, -8(%rbp) … C movl -20(%rbp), %ecx G movl $2, %edx C movl -8(%rbp), %esi A addl $1, %esi T movl %esi, -8(%rbp) … G movl $2, %edx C movl -8(%rbp), %esi A addl $1, %esi T movl %esi, -8(%rbp)

A callq _printf B movl $2, %edx C movl -8(%rbp), %esi D addl $1, %esi E movl %esi, -8(%rbp) … F movl -20(%rbp), %ecx B movl $2, %edx movl -8(%rbp), %esi C addl $1, %esi D movl %esi, -8(%rbp) E … movl $2, %edx B movl -8(%rbp), %esi C addl $1, %esi D movl %esi, -8(%rbp) E

Programs are like strings

Find repeated substrings

Suffix Tree A data structure for string searching (Not a suffix trie!)

A B C A B $0 $0 C A B B $ AB 0 C A B $ 0 CAB$0 $0 0 $

Advantages Given a string of length L… • O(L) construction • O(L) longest repeated substring • O(L) time most frequent substring

Simplified Suffix Tree Construction

A B C A B $0 Su ffi xes

A B C A B $0 Su ffi xes A

A B C A B $0 Su ffi xes B, AB A

A B C A B $0 Su ffi xes B AB

A B C A B $0 Su ffi xes C C ABC B

A B C A B $0 Su ffi xes A C A A ABCA C B

A B C A B $0 Su ffi xes A B B B C ABCAB A A C B B

A B C A B $0 Su ffi xes A B $0 0 ABCAB$0 $ B $0 B C A A C B B $0 $ 0

A B C A B $0 Su ffi xes B $0 0 $ $0 B C A A C B B $ AB 0 CAB$0 0 $

A B C A B $0 Su ffi xes $0 C A B B $ AB 0 C A B $ 0 CAB$0 $0 0 $

A B C A B $0 $0 Su ffi xes C A B B $ AB 0 C A B $ 0 CAB$0 $0 0 $

$0 *Note: Real construction is more complex C A B B $ AB 0 Need to store links C A B $ 0 between internal nodes CAB$0 $0 0 $

Representation

Su ffi x Tree Struct struct SuffixTree { Node *Root; size_t LeafEnd; ActiveState Active; … };

Su ffi x Tree Struct struct SuffixTree { Node *Root; size_t LeafEnd; ActiveState Active; StringType longestRepeatedSubstring(); void findOccurrences(std::vector<int> &Occurrences, const StringType &QueryStr); void prune(const StringType &Str); … };

Node Struct struct Node { Node *Parent; std::map<CharacterType, Node *> Children; size_t StartIdx; size_t EndIdx; size_t SuffixIndex; … };

Node Struct struct Node { Node *Parent; std::map<CharacterType, Node *> Children; size_t StartIdx; size_t EndIdx; size_t SuffixIndex; bool Valid; … };

Outlining Example

FOO ( ) A R1 = 0xDEADBEEF B R3 = R2 + R1 C R1 = *R5 D R7 = 0xFEEDFACE E R1 = R1 - 1 BAR ( ) F R7 = R3 + R2 A R1 = 0xDEADBEEF B R3 = R2 + R1 C R1 = *R5 G R7 = 0xFACEFEED A R1 = 0xDEADBEEF B R3 = R2 + R1 C R1 = *R5 E R1 = R1 - 1

FOO ( ) String Encoding A R1 = 0xDEADBEEF B R3 = R2 + R1 C R1 = *R5 A B C D E D R7 = 0xFEEDFACE E R1 = R1 - 1 BAR ( ) F R7 = R3 + R2 A R1 = 0xDEADBEEF F A B C G A B C E B R3 = R2 + R1 C R1 = *R5 G R7 = 0xFACEFEED A R1 = 0xDEADBEEF B R3 = R2 + R1 C R1 = *R5 E R1 = R1 - 1

FOO ( ) String Encoding A R1 = 0xDEADBEEF B R3 = R2 + R1 C R1 = *R5 A B C D E $0 Unique terminators D R7 = 0xFEEDFACE E R1 = R1 - 1 BAR ( ) F R7 = R3 + R2 A R1 = 0xDEADBEEF F A B C G A B C E $1 B R3 = R2 + R1 C R1 = *R5 G R7 = 0xFACEFEED A R1 = 0xDEADBEEF B R3 = R2 + R1 C R1 = *R5 E R1 = R1 - 1

String Encoding A B C D E $0 F A B C G A B C E $1

Find Candidates

A B C D E $0 F A B C G A B C E $1 D E $0 F A B C G A B C E $1 G A B C E $1 G A B C E $ 1 E$1 D E $0 F A B C G A B C E $1 C G A B C E $1 A B C E$1 D E $0 F A B C G A B C E $1 B C D E $0 F A B C G A B C E $1 G A B C E $1 E$1 E F A B C G A B C E $0 F A B C G A B C E $1 $1

Occurrences Length Longest repeated substring A B C D E $0 F A B C G A B C E $1 D E $0 F A B C G A B C E $1 G A B C E $1 G A B C E $ 1 E$1 0 0 None D E $0 F A B C G A B C E $1 C G A B C E $1 A B C E$1 D E $0 F A B C G A B C E $1 B C D E $0 F A B C G A B C E $1 G A B C E $1 E$1 E F A B C G A B C E $0 F A B C G A B C E $1 $1

Occurrences Length Longest repeated substring A B C D E $0 F A B C G A B C E $1 D E $0 F A B C G A B C E $1 G A B C E $1 G A B C E $ 1 E$1 3 1 C D E $0 F A B C G A B C E $1 C G A B C E $1 A B C E$1 D E $0 F A B C G A B C E $1 B C D E $0 F A B C G A B C E $1 G A B C E $1 E$1 E F A B C G A B C E $0 F A B C G A B C E $1 $1

Occurrences Length Longest repeated substring A B C D E $0 F A B C G A B C E $1 D E $0 F A B C G A B C E $1 G A B C E $1 G A B C E $ 1 E$1 3 3 ABC D E $0 F A B C G A B C E $1 C G A B C E $1 A B C E$1 D E $0 F A B C G A B C E $1 B C D E $0 F A B C G A B C E $1 G A B C E $1 E$1 E F A B C G A B C E $0 F A B C G A B C E $1 $1

Reducing Code Size Using Outlining Jessica Paquette Apple Outline - PowerPoint PPT Presentation

Reducing Code Size Using Outlining Jessica Paquette Apple Outline Code size Outlining Results Future work Motivating Example callq _printf movl $2, %edx movl -8(%rbp), %esi addl $1, %esi movl %esi, -8(%rbp) movl

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