From: Chris Hanson <org/chris-hanson/cph>
Date: Fri, 9 Nov 2001 21:38:47 +0000 (+0000)
Subject: Implement substitution optimizer, which does a kind of data-flow
X-Git-Tag: 20090517-FFI~2455
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=1f48268ff41f0741e3b42322bbe305726c554e0b;p=mit-scheme.git
Implement substitution optimizer, which does a kind of data-flow
analysis to eliminate unnecessary lambda expressions.
---
diff --git a/v7/src/star-parser/matcher.scm b/v7/src/star-parser/matcher.scm
index cf14763ba..828c53c58 100644
--- a/v7/src/star-parser/matcher.scm
+++ b/v7/src/star-parser/matcher.scm
@@ -1,6 +1,6 @@
;;; -*-Scheme-*-
;;;
-;;; $Id: matcher.scm,v 1.20 2001/11/09 21:37:53 cph Exp $
+;;; $Id: matcher.scm,v 1.21 2001/11/09 21:38:47 cph Exp $
;;;
;;; Copyright (c) 2001 Massachusetts Institute of Technology
;;;
@@ -277,6 +277,7 @@
,(delay-call ks kf)))
(define-matcher (with-pointer identifier expression)
+ pointer
`((LAMBDA (,identifier)
,(compile-matcher-expression expression identifier ks kf))
,(fetch-pointer)))
diff --git a/v7/src/star-parser/parser.scm b/v7/src/star-parser/parser.scm
index b5d9b1cc6..6f4a76c68 100644
--- a/v7/src/star-parser/parser.scm
+++ b/v7/src/star-parser/parser.scm
@@ -1,6 +1,6 @@
;;; -*-Scheme-*-
;;;
-;;; $Id: parser.scm,v 1.23 2001/11/09 21:37:55 cph Exp $
+;;; $Id: parser.scm,v 1.24 2001/11/09 21:38:43 cph Exp $
;;;
;;; Copyright (c) 2001 Massachusetts Institute of Technology
;;;
@@ -282,6 +282,7 @@
(procedure ks v kf)))))
(define-parser (with-pointer identifier expression)
+ pointer
`((LAMBDA (,identifier)
,(compile-parser-expression expression identifier ks kf))
,(fetch-pointer)))
diff --git a/v7/src/star-parser/shared.scm b/v7/src/star-parser/shared.scm
index b5f6dc439..22c6d6f56 100644
--- a/v7/src/star-parser/shared.scm
+++ b/v7/src/star-parser/shared.scm
@@ -1,6 +1,6 @@
;;; -*-Scheme-*-
;;;
-;;; $Id: shared.scm,v 1.13 2001/10/16 17:52:33 cph Exp $
+;;; $Id: shared.scm,v 1.14 2001/11/09 21:37:58 cph Exp $
;;;
;;; Copyright (c) 2001 Massachusetts Institute of Technology
;;;
@@ -32,68 +32,64 @@
(preprocessor expression external-bindings internal-bindings)))
(maybe-make-let (map (lambda (b) (list (cdr b) (car b)))
(cdr external-bindings))
- `(LAMBDA (,b)
- ,(fluid-let ((*buffer-name* b))
- (maybe-make-let (map (lambda (b)
- (list (cdr b) (car b)))
- (cdr internal-bindings))
- (generator expression)))))))))
+ `(LAMBDA (,b)
+ ,(fluid-let ((*buffer-name* `(PROTECT ,b)))
+ (maybe-make-let (map (lambda (b)
+ (list (cdr b) (car b)))
+ (cdr internal-bindings))
+ (strip-protection-wrappers
+ (let ((expression (generator expression)))
+ (if debug:disable-substitution-optimizer?
+ expression
+ (optimize-by-substitution expression))))))))))))
(define *buffer-name*)
+(define debug:disable-substitution-optimizer? #f)
+(define debug:disable-peephole-optimizer? #f)
+(define debug:trace-substitution? #f)
(define (maybe-make-let bindings body)
(if (pair? bindings)
- `(LET ,bindings ,body)
+ `((LAMBDA ,(map car bindings) ,body)
+ ,@(map cadr bindings))
body))
-(define (wrap-matcher generate-body)
- (let ((ks (make-ks-identifier))
- (kf (make-kf-identifier)))
- `(LAMBDA (,ks ,kf)
- ,(generate-body ks kf))))
-
-(define wrap-parser wrap-matcher)
-
-(define (wrap-external-matcher matcher)
- (wrap-matcher
- (lambda (ks kf)
- `(IF ,matcher
- (,ks ,kf)
- (,kf)))))
-
-(define (wrap-external-parser expression)
- (wrap-matcher
- (lambda (ks kf)
- (handle-parser-value expression ks kf))))
-
-(define (handle-parser-value expression ks kf)
- (with-value-binding expression
- (lambda (v)
- `(IF ,v
- (,ks ,v ,kf)
- (,kf)))))
-
(define (with-value-binding expression generator)
- (let ((v (make-value-identifier)))
- `(LET ((,v ,expression))
- ,(generator v))))
+ `(,(let ((v (make-value-identifier)))
+ `(LAMBDA (,v)
+ ,(generator v)))
+ ,expression))
(define (call-with-pointer pointer procedure)
(if pointer
(procedure pointer)
- (let ((p (make-ptr-identifier)))
- `(LET ((,p ,(fetch-pointer)))
- ,(procedure p)))))
+ `(,(let ((p (make-ptr-identifier)))
+ `(LAMBDA (,p)
+ ,(procedure p)))
+ ,(fetch-pointer))))
(define (fetch-pointer)
`(GET-PARSER-BUFFER-POINTER ,*buffer-name*))
(define (backtracking-kf pointer generate-body)
- (call-with-pointer pointer
- (lambda (p)
- `(LAMBDA ()
- (SET-PARSER-BUFFER-POINTER! ,*buffer-name* ,p)
- ,(generate-body p)))))
+ (make-kf-lambda
+ (lambda ()
+ `(BEGIN
+ (SET-PARSER-BUFFER-POINTER! ,*buffer-name* ,pointer)
+ ,(generate-body)))))
+
+(define (make-kf-lambda generator)
+ (make-delayed-lambda make-kf-identifier (list) generator))
+
+(define (make-matcher-ks-lambda generator)
+ (make-delayed-lambda make-ks-identifier
+ (list make-kf-identifier)
+ generator))
+
+(define (make-parser-ks-lambda generator)
+ (make-delayed-lambda make-ks-identifier
+ (list make-value-identifier make-kf-identifier)
+ generator))
(define (make-kf-identifier)
(generate-identifier 'KF))
@@ -239,34 +235,370 @@
(define *parser-macros*
*global-parser-macros*)
+;;;; Substitution optimization
+
+(define (bind-delayed-lambdas body-generator . operands)
+ `(,(let ((parameters (map (lambda (operand) ((car operand))) operands)))
+ `(LAMBDA ,parameters
+ ,(apply body-generator parameters)))
+ ,@(map cadr operands)))
+
+(define (make-delayed-lambda name-generator
+ parameter-name-generators
+ body-generator)
+ (list name-generator
+ (let ((parameters
+ (map (lambda (generator) (generator))
+ parameter-name-generators)))
+ `(LAMBDA ,parameters
+ ,(apply body-generator parameters)))))
+
+(define (delay-call operator . operands)
+ `(,operator ,@operands))
+
+(define (delay-reference object)
+ object)
+
+(define (lambda-expression? expression)
+ (and (pair? expression)
+ (eq? (car expression) 'LAMBDA)))
+
+(define (optimize-by-substitution expression)
+ (if (pair? expression)
+ (case (car expression)
+ ((LAMBDA)
+ `(LAMBDA ,(cadr expression)
+ ,(optimize-by-substitution (caddr expression))))
+ ((LET)
+ (maybe-resubstitute
+ (let ((identifier (cadr expression))
+ (bindings
+ (map (lambda (binding)
+ `(,(car binding)
+ ,(optimize-by-substitution (cadr binding))))
+ (caddr expression)))
+ (body (optimize-by-substitution (cadddr expression))))
+ (let ((discards
+ (map (lambda (count operand)
+ (and (= 0 count)
+ (operand-discardable? operand)))
+ (count-references (map car bindings) body)
+ (map cadr bindings))))
+ (if (there-exists? discards (lambda (discard) discard))
+ `(LET ,identifier
+ ,(apply-discards discards bindings)
+ ,(discard-unused-operands-1 identifier discards body))
+ `(LET ,identifier ,bindings ,body))))
+ expression))
+ ((PROTECT)
+ expression)
+ ((VECTOR-APPEND)
+ (optimize-group-expression (map optimize-by-substitution expression)
+ '(VECTOR)))
+ (else
+ (let ((expression (map optimize-by-substitution expression)))
+ (if (lambda-expression? (car expression))
+ (let ((body (caddr (car expression))))
+ (call-with-values
+ (lambda ()
+ (compute-bindings-and-substitutions
+ (cadr (car expression))
+ (cdr expression)
+ body))
+ (lambda (bindings substitutions)
+ (maybe-resubstitute
+ (call-with-values
+ (lambda ()
+ (discard-unused-operands
+ bindings
+ (maybe-apply-substitutions substitutions
+ body)))
+ maybe-make-let)
+ expression))))
+ expression))))
+ expression))
+
+(define (maybe-resubstitute result expression)
+ (if (equal? result expression)
+ expression
+ (begin
+ (if debug:trace-substitution?
+ (begin
+ (pp expression)
+ (newline)
+ (write-string "==>")
+ (pp result)
+ (newline)
+ (newline)))
+ (optimize-by-substitution result))))
+
+(define (discard-unused-operands bindings body)
+ (let loop ((bindings bindings) (body body) (bindings* '()))
+ (if (pair? bindings)
+ (let ((identifier (car (car bindings)))
+ (operand (cadr (car bindings))))
+ (if (lambda-expression? operand)
+ (let ((discards
+ (map (lambda (count) (= 0 count))
+ (count-references (cadr operand) (caddr operand)))))
+ (if (there-exists? discards (lambda (discard) discard))
+ (loop (cdr bindings)
+ (discard-unused-operands-1 identifier discards body)
+ (cons (list identifier
+ `(LAMBDA ,(apply-discards discards
+ (cadr operand))
+ ,(caddr operand)))
+ bindings*))
+ (loop (cdr bindings)
+ body
+ (cons (car bindings) bindings*))))
+ (loop (cdr bindings)
+ body
+ (cons (car bindings) bindings*))))
+ (values (reverse! bindings*) body))))
+
+(define (apply-discards discards items)
+ (if (pair? discards)
+ (if (car discards)
+ (apply-discards (cdr discards) (cdr items))
+ (cons (car items) (apply-discards (cdr discards) (cdr items))))
+ '()))
+
+(define (discard-unused-operands-1 identifier discards expression)
+ (let loop ((expression expression))
+ (if (pair? expression)
+ (if (eq? identifier (car expression))
+ (call-with-values
+ (lambda ()
+ (discard-unused-operands-2 discards (cdr expression)))
+ (lambda (kept not-discarded)
+ (let ((call (cons identifier kept)))
+ (if (pair? not-discarded)
+ `(BEGIN ,@not-discarded ,call)
+ call))))
+ (case (car expression)
+ ((LAMBDA)
+ (if (memq identifier (cadr expression))
+ expression
+ `(LAMBDA ,(cadr expression)
+ ,(loop (caddr expression)))))
+ ((LET)
+ `(LET ,(cadr expression)
+ ,(map (lambda (binding)
+ `(,(car binding) ,(loop (cadr binding))))
+ (caddr expression))
+ ,(if (or (eq? identifier (cadr expression))
+ (assq identifier (caddr expression)))
+ (cadddr expression)
+ (loop (cadddr expression)))))
+ ((PROTECT)
+ expression)
+ (else
+ (map loop expression))))
+ expression)))
+
+(define (discard-unused-operands-2 discards operands)
+ (let loop
+ ((discards discards)
+ (operands operands)
+ (kept '())
+ (not-discarded '()))
+ (if (pair? discards)
+ (if (car discards)
+ (loop (cdr discards)
+ (cdr operands)
+ kept
+ (if (operand-discardable? (car operands))
+ not-discarded
+ (cons (car operands) not-discarded)))
+ (loop (cdr discards)
+ (cdr operands)
+ (cons (car operands) kept)
+ not-discarded))
+ (values (reverse! kept) (reverse! not-discarded)))))
+
+(define (compute-bindings-and-substitutions identifiers operands body)
+ (let loop
+ ((identifiers identifiers)
+ (operands operands)
+ (counts (count-references identifiers body))
+ (bindings '())
+ (substitutions '()))
+ (if (pair? identifiers)
+ (let ((identifier (car identifiers))
+ (operand (car operands))
+ (count (car counts)))
+ (cond ((and (= 0 count)
+ (operand-discardable? operand))
+ (loop (cdr identifiers)
+ (cdr operands)
+ (cdr counts)
+ bindings
+ substitutions))
+ ((or (operand-copyable? operand)
+ (and (= 1 count)
+ (operand-substitutable? operand body)))
+ (loop (cdr identifiers)
+ (cdr operands)
+ (cdr counts)
+ bindings
+ (cons (cons identifier operand) substitutions)))
+ (else
+ (loop (cdr identifiers)
+ (cdr operands)
+ (cdr counts)
+ (cons (list identifier operand) bindings)
+ substitutions))))
+ (values (reverse! bindings) substitutions))))
+
+(define (operand-copyable? operand)
+ (or (symbol? operand)
+ (and (lambda-expression? operand)
+ (or (boolean? (caddr operand))
+ (symbol? (caddr operand))))
+ (equal? operand '(VECTOR))))
+
+(define (operand-substitutable? operand body)
+ (or (lambda-expression? operand)
+ (not (and (tree-memq 'PROTECT operand)
+ (tree-memq 'PROTECT body)))))
+
+(define (operand-discardable? operand)
+ (not (tree-memq 'PROTECT operand)))
+
+(define (tree-memq item tree)
+ (let loop ((tree tree))
+ (if (pair? tree)
+ (or (loop (car tree))
+ (loop (cdr tree)))
+ (eq? item tree))))
+
+(define (maybe-apply-substitutions substitutions expression)
+ (if (pair? substitutions)
+ (let loop ((expression expression) (substitutions substitutions))
+ (cond ((pair? expression)
+ (case (car expression)
+ ((LAMBDA)
+ `(LAMBDA ,(cadr expression)
+ ,(loop (caddr expression)
+ (delete-matching-items substitutions
+ (lambda (s)
+ (memq (car s) (cadr expression)))))))
+ ((LET)
+ `(LET ,(cadr expression)
+ ,(map (lambda (binding)
+ `(,(car binding)
+ ,(loop (cadr binding) substitutions)))
+ (caddr expression))
+ ,(loop (cadddr expression)
+ (delete-matching-items substitutions
+ (lambda (s)
+ (or (eq? (car s) (cadr expression))
+ (assq (car s) (caddr expression))))))))
+ ((PROTECT)
+ expression)
+ (else
+ (let ((expression
+ (map (lambda (expression)
+ (loop expression substitutions))
+ expression)))
+ (if (and (lambda-expression? (car expression))
+ (null? (cadr (car expression)))
+ (null? (cdr expression)))
+ (caddr (car expression))
+ expression)))))
+ ((symbol? expression)
+ (let ((entry (assq expression substitutions)))
+ (if entry
+ (cdr entry)
+ expression)))
+ (else expression)))
+ expression))
+
+(define (count-references identifiers expression)
+ (let ((alist
+ (map (lambda (identifier)
+ (cons identifier 0))
+ identifiers)))
+ (let loop ((expression expression) (alist alist))
+ (cond ((pair? expression)
+ (case (car expression)
+ ((LAMBDA)
+ (loop (caddr expression)
+ (delete-matching-items alist
+ (lambda (entry)
+ (memq (car entry) (cadr expression))))))
+ ((LET)
+ (for-each (lambda (binding)
+ (loop (cadr binding) alist))
+ (caddr expression))
+ (loop (cadddr expression)
+ (delete-matching-items alist
+ (lambda (entry)
+ (or (eq? (car entry) (cadr expression))
+ (assq (car entry) (caddr expression)))))))
+ ((PROTECT)
+ unspecific)
+ (else
+ (for-each (lambda (expression)
+ (loop expression alist))
+ expression))))
+ ((symbol? expression)
+ (let ((entry (assq expression alist)))
+ (if entry
+ (set-cdr! entry (+ (cdr entry) 1)))))))
+ (map cdr alist)))
+
+(define (strip-protection-wrappers expression)
+ (if (pair? expression)
+ (case (car expression)
+ ((LAMBDA)
+ `(LAMBDA ,(cadr expression)
+ ,(strip-protection-wrappers (caddr expression))))
+ ((LET)
+ `(LET ,(cadr expression)
+ ,(map (lambda (binding)
+ (list (car binding)
+ (strip-protection-wrappers (cadr binding))))
+ (caddr expression))
+ ,(strip-protection-wrappers (cadddr expression))))
+ ((PROTECT)
+ (cadr expression))
+ (else
+ (map strip-protection-wrappers expression)))
+ expression))
+
;;;; Code optimizer
(define (optimize-expression expression)
- (let loop ((entries optimizer-patterns))
- (cond ((pair? entries)
- (if (and (syntax-match? (caar entries) expression)
- (or (not (cadar entries))
- ((cadar entries) expression)))
- (let ((expression* ((cddar entries) expression)))
+ (if debug:disable-peephole-optimizer?
+ expression
+ (let loop ((entries optimizer-patterns))
+ (cond ((pair? entries)
+ (if (and (syntax-match? (caar entries) expression)
+ (or (not (cadar entries))
+ ((cadar entries) expression)))
+ (let ((expression* ((cddar entries) expression)))
+ (if (equal? expression* expression)
+ expression
+ (optimize-expression expression*)))
+ (loop (cdr entries))))
+ ((and (pair? expression)
+ (symbol? (car expression)))
+ (let ((expression*
+ (let ((optimizer
+ (hash-table/get default-optimizers
+ (car expression)
+ #f)))
+ (if optimizer
+ (optimizer expression)
+ (cons (car expression)
+ (map optimize-expression
+ (cdr expression)))))))
(if (equal? expression* expression)
expression
- (optimize-expression expression*)))
- (loop (cdr entries))))
- ((and (pair? expression)
- (symbol? (car expression)))
- (let ((expression*
- (let ((optimizer
- (hash-table/get default-optimizers
- (car expression)
- #f)))
- (if optimizer
- (optimizer expression)
- (cons (car expression)
- (map optimize-expression (cdr expression)))))))
- (if (equal? expression* expression)
- expression
- (optimize-expression expression*))))
- (else expression))))
+ (optimize-expression expression*))))
+ (else expression)))))
(define (define-optimizer pattern predicate optimizer)
(let ((entry (assoc pattern optimizer-patterns))
@@ -278,15 +610,12 @@
(cons (cons pattern datum) optimizer-patterns))
unspecific))))
-(define optimizer-patterns
- '())
-
(define (define-default-optimizer keyword optimizer)
(hash-table/put! default-optimizers keyword optimizer)
keyword)
-(define default-optimizers
- (make-eq-hash-table))
+(define optimizer-patterns '())
+(define default-optimizers (make-eq-hash-table))
(define (predicate-not-or expression)
(not (and (pair? (cadr expression))