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Investigation of flow graphs optimization methods used in optimizing compilers. Eugene Gavrin – MSc student. Universal compiler back-end. Tasks. Develop an universal internal representation of the program based on formal computational model - PowerPoint PPT Presentation
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Investigation of flow graphs optimization methods used in optimizing compilers
Eugene Gavrin – MSc student
Universal compiler back-end
Load IR
Common optimizations
Program analysis
Unload to IR
IR
IR
Program analysis
Tasks
• Develop an universal internal representation of the program based on formal computational model
• Implement the set of common compiler optimizations
Internal representation
• AST• Control flow graph• Data flow graph• Call graph• Dependency graph• ...
Internal representation
• AST• Control flow graph• Data flow graph• Call graph• Dependency graph• ...
Internal representation
• AST• Control flow graph• Data flow graph• Call graph• Dependency graph• ...
Internal representation
• AST• Control flow graph• Data flow graph• Call graph• Dependency graph• ...
Internal representation
• AST• Control flow graph• Data flow graph• Call graph• Dependency graph• ...
Internal representation
• AST• Control flow graph• Data flow graph• Call graph• Dependency graph• ...
Internal representation
• Oriented graph• Nodes are functional
operators• Vertexes are data
dependencies• Each operator stores:
– Operation name– Input and output data
links– Meta data
31 86
10
Functional40
10
Functional197
69
81
116
7
Condition
TRUE100
P
3
106
114
4
X
Left
FALSE66
P
7
94
99
4
X
Right
TRUE FALSE
TRUE
3
7
If47
Internal representation (branching)
• Extended data flow model by Davis & Keller
• Selector and Distributor represents conditional statements
• Enough to represent any control operator– If / Switch– For / While
Optimizing transformations
• Constant folding;• Sub-expression evaluation;• Strength reduction;• Null sequences;• Combine operators;• Loop optimizations;• Branch Elimination;
Constant folding
Before After
printf
6
7 5
+
–
*
printf
3 2
Sub-expression evaluation
Before After
1
1
2
2
3
3
4
5
1
2
3
4
5
[1] (0/1)
var
Dead code elimination
Before
In
Hello World
Out
main
R
R
Dead code
After
In
Hello World
Out
main
R
R
Direct conversion
Before After
1
Slow op
Slow op
2
1
Fast op
2
Future plans
• СIL processing (.NET assembly)– Load– Unload– Compare results with MSFT .NET compiler
• Static program analysis
Q&A
