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Enabling cross-library optimization and compile-time error checking in the presence of procedural macros
Andrew W. Keep R. Kent Dybvig
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Library Groups
Andrew W. Keep R. Kent Dybvig
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Enabling cross-library optimization and compile-time error checking - - PowerPoint PPT Presentation
Enabling cross-library optimization and compile-time error checking - - PowerPoint PPT Presentation
Enabling cross-library optimization and compile-time error checking in the presence of procedural macros Andrew W. Keep R. Kent Dybvig 1 1 Library Groups Andrew W. Keep R. Kent Dybvig 2 2 Goals Cross-library
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Goals
- Cross-library optimizations
- Type checking across library boundaries
- Single binary for multiple libraries
- Unchanged development process
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Library Groups
- Explicitly combine libraries
- Optionally add a top-level program
- A new form: library-group
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Example
(library (tree) (export make-tree ---) (import (rnrs)) (define make-tree ---)
- --)
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(library (tree constants) (export quote-tree t0 ---) (import (rnrs) (tree)) (define-syntax quote-tree
- -- (make-tree ---) ---)
(define t0 (quote-tree))
- --)
Example
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(import (rnrs) (tree) (tree constants)) (define tree->list ---) (tree->list t0) (tree-value (tree-children t2)) (tree->list (quote-tree 5 (7 9)))
Example
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(library-group (library (tree) (export make-tree ---) (import (rnrs)) (define make-tree ---)
- --)
(library (tree constants) (export quote-tree t0 ---) (import (rnrs) (tree)) (define-syntax quote-tree
- -- (make-tree ---) ---)
(define t0 (quote-tree))
- --)
(import (rnrs) (tree) (tree constants)) (define tree->list ---) (tree->list t0) (tree-value (tree-children t2)) (tree->list (quote-tree 5 (7 9))))
Example
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Example
(library-group (include “tree.sls”) (include “tree/constants.sls”) (include “app.sps”))
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Library Group Syntax
library-group -> (library-group (library-group (library-group lglib* lgprog) | (library-group (library-group (library-group lglib*) lglib
- > library | (include filename)
lgprog
- > program | (include filename)
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Challenges
- Achieving proper phasing
- Handling cyclic dependencies
- Enabling cross-library optimization/checking
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Implementation: Libraries
- Visit code, invoke code, metadata
- Import dependencies form a DAG
- Invoke code body uses letrec* semantics
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(letrec* ([make-tree ---]
- --)
(set-top-level! $make-tree make-tree)
- --)
Example
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(letrec* ([t0 tree-constant]
- --)
(set-top-level! $t0 t0)
- --)
Example
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(letrec* ([tree->list ---]) (tree->list $t0) ($tree-value ($tree-children $t2)) (tree->list tree-constant))
Example
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Implementation: Library Groups
- Combine letrec* expressions
- Preserve existing library exports
- Invoke libraries needed during expansion
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Library Group 1
(lambda (uid) (case uid [(tree) (letrec* ([make-tree ―]
- --)
- --)]
[(constants) (letrec* ([t0 ---] ---)
- --)]
[else (letrec* ([tree->list ---]) (tree->list $t0) ($tree-value (car ($tree-children $t2))) (tree->list ---))]))
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Library Group 1
- Advantages:
- Single output binary
- Matches existing library semantics
- Disadvantages:
- Hinders cross-library optimizations
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Library Group 2
(letrec* ([make-tree ---] ---) (set-top-level! $make-tree make-tree)
- (letrec* ([t0 tree-constant] ---)
(set-top-level! $t0 t0)
- (letrec* ([tree->list ---])
(tree->list $t0) ($tree-value (car ($tree-children $t2)))) (tree->list tree-constant)))
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Library Group 2
- Advantages:
- Creates a single invoke code
- Allows optimizations and checking
- Disadvantage:
- Causes dependency problems
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Dependency Problems
(A) (B) (C)
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Dependency Problems
(A) (B) (C)
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Dependency Problems
(A) (B) (C)
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(lambda (uid) (letrec* ([make-tree ---] ---)
- (mark-invoked! ‘tree)
(let ([nested-lib (lambda (uid) (letrec* ([t0 ---] ---)
- (mark-invoked! ‘constants)
(let ([nested-lib program code]) (if (eq? uid ‘constants) nested-lib (nested-lib uid)))))]) (if (eq? uid ‘tree) nested-lib (nested-lib uid)))))
Library Group 3
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Library Group 3
- Advantages:
- Avoids synthetic cycles
- Allows optimization and checking
- Single output binary
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Caveat: Dynamic Dependencies
- Arises from use of eval in init expressions
- Library groups allow explicit ordering
- Work arounds
- Transform into import dependency
- Move into initialization function
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Fixing Dynamic Dependencies
- Start with case-based library-group
- Lift “simple” letrec* bindings
- Requires letrec* style optimization
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Library Phasing
- Retain phasing between libraries in group
- Cannot simply recompile from source
- Relatively straightforward solution
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Summary
- Library groups meet our goals:
- Cross-library optimization
- Type checking across library boundaries
- Single output binary
- Maintains proper phasing order
- Avoids synthetic import dependency cycles
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Thanks
Questions?
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