| 4e987026 |
;;; optimize.scm -- flic optimizer
;;;
;;; author : Sandra Loosemore
;;; date : 7 May 1992
;;;
;;;
;;; The optimizer does these kinds of program transformations:
;;;
;;; * remove unreferenced variable bindings.
;;;
;;; * constant folding and various other kinds of compile-time
;;; evaluation.
;;;
;;; * beta reduction (replace references to variables bound to simple
;;; expressions with the expression)
;;;
;;; Since some of the optimizations can make additional transformations
;;; possible, we want to make multiple iteration passes. But since each
;;; pass is likely to have diminishing benefits, we don't want to keep
;;; iterating indefinitely. So establish a fairly arbitrary cutoff point.
;;; The value is based on empirical results from compiling the prelude.
(define *max-optimize-iterations* 5)
(define *optimize-foldr-iteration* 0) ; when to inline foldr
(define *optimize-build-iteration* 0) ; when to inline build
(define *current-optimize-iteration* 0)
;;; Flags for enabling various optimizations
(define *all-optimizers* '(foldr inline constant lisp))
(define *optimizers* *all-optimizers*)
;;; Used to note whether we are doing the various optimizations
(define-local-syntax (do-optimization? o)
`(memq ,o (dynamic *optimizers*)))
(define *do-foldr-optimizations* (do-optimization? 'foldr))
(define *do-inline-optimizations* (do-optimization? 'inline))
(define *do-constant-optimizations* (do-optimization? 'constant))
;;; If the foldr optimization is enabled, bind the corresponding
;;; variables to these values instead of the defaults.
(define *foldr-max-optimize-iterations* 15)
(define *foldr-optimize-foldr-iteration* 8)
(define *foldr-optimize-build-iteration* 5)
;;; Some random other variables
(define *structured-constants* '())
(define *structured-constants-table* '#f)
(define *lambda-depth* 0)
(define *local-bindings* '())
;;; This is for doing some crude profiling.
;;; Comment out the body of the macro to disable profiling.
;;; Here are current counts from compiling the prelude:
;;; (LET-REMOVE-UNUSED-BINDING . 5835)
;;; (REF-INLINE-SINGLE-REF . 2890)
;;; (REF-INLINE . 2692)
;;; (LET-EMPTY-BINDINGS . 2192)
;;; (APP-LAMBDA-TO-LET . 1537)
;;; (APP-MAKE-SATURATED . 416)
;;; (LET-HOIST-RETURN-FROM . 310)
;;; (CASE-BLOCK-IDENTITY . 273)
;;; (CASE-BLOCK-DEAD-CODE . 234)
;;; (CASE-BLOCK-TO-IF . 212)
;;; (SEL-FOLD-VAR . 211)
;;; (APP-HOIST-LET . 190)
;;; (LET-HOIST-LAMBDA . 181)
;;; (FOLDR-INLINE . 176)
;;; (AND-UNARY . 172)
;;; (LAMBDA-COMPRESS . 168)
;;; (APP-FOLD-SELECTOR . 141)
;;; (BUILD-INLINE-LAMBDA . 134)
;;; (LET-COMPRESS . 134)
;;; (IF-FOLD . 128)
;;; (INTEGER-TO-INT-CONSTANT-FOLD . 124)
;;; (AND-COMPRESS . 94)
;;; (APP-COMPRESS . 93)
;;; (FOLDR-CONS-IDENTITY . 69)
;;; (IF-COMPRESS-TEST . 65)
;;; (IF-HOIST-LAMBDA . 61)
;;; (APP-HOIST-STRUCTURED-CONSTANT . 60)
;;; (FOLDR-PRIM-APPEND-INLINE . 55)
;;; (FOLDR-BUILD-IDENTITY . 40)
;;; (CASE-BLOCK-DISCARD-REDUNDANT-TEST . 37)
;;; (FOLDR-NIL-IDENTITY . 36)
;;; (LET-HOIST-INVARIANT-ARGS . 30)
;;; (FOLDR-HOIST-LET . 28)
;;; (CON-NUMBER-FOLD-TUPLE . 21)
;;; (FOLDR-CONS-NIL-IDENTITY . 15)
;;; (AND-CONTAINS-TRUE . 14)
;;; (IF-IDENTITY-INVERSE . 8)
;;; (IF-HOIST-RETURN-FROM . 7)
;;; (CASE-BLOCK-HOIST-LET . 7)
;;; (INTEGER-TO-INT-IDENTITY . 7)
;;; (APP-PACK-IDENTITY . 2)
;;; (CON-NUMBER-FOLD . 2)
;;; (IF-IDENTITY . 2)
;;; (INT-TO-INTEGER-CONSTANT-FOLD . 2)
;;; (LET-HOIST-STRUCTURED-CONSTANT . 1)
(define-local-syntax (record-hack type . args)
(declare (ignore args))
`',type
; `(record-hack-aux ,type ,@args)
)
(define *hacks-done* '())
(define (record-hack-aux type . args)
;; *** debug
;; (format '#t "~s ~s~%" type args)
(declare (ignore args))
(let ((stuff (assq type (car (dynamic *hacks-done*)))))
(if stuff
(incf (cdr stuff))
(push (cons type 1) (car (dynamic *hacks-done*))))))
(define (total-hacks)
(let ((totals '()))
(dolist (alist *hacks-done*)
(dolist (entry alist)
(let ((stuff (assq (car entry) totals)))
(if stuff
(setf (cdr stuff) (+ (cdr stuff) (cdr entry)))
(push (cons (car entry) (cdr entry)) totals)))))
totals))
;;; This is the main entry point.
(define (optimize-top object)
(dynamic-let ((*structured-constants* '())
(*structured-constants-table* (make-table))
(*lambda-depth* 0)
(*local-bindings* '())
(*do-inline-optimizations*
(do-optimization? 'inline))
(*do-constant-optimizations*
(do-optimization? 'constant))
(*max-optimize-iterations*
(if (do-optimization? 'foldr)
(dynamic *foldr-max-optimize-iterations*)
(dynamic *max-optimize-iterations*)))
(*optimize-foldr-iteration*
(if (do-optimization? 'foldr)
(dynamic *foldr-optimize-foldr-iteration*)
(dynamic *optimize-foldr-iteration*)))
(*optimize-build-iteration*
(if (do-optimization? 'foldr)
(dynamic *foldr-optimize-build-iteration*)
(dynamic *optimize-build-iteration*))))
(setf *hacks-done* '())
(dotimes (i (dynamic *max-optimize-iterations*))
(dynamic-let ((*current-optimize-iteration* i))
;; debug (*duplicate-object-table* (make-table)))
(when (memq 'optimize-extra (dynamic *printers*))
(format '#t "~%Optimize pass ~s:" i)
(pprint object))
(push '() *hacks-done*)
(setf object (optimize-flic-let-aux object '#t))))
(setf (flic-let-bindings object)
(nconc (nreverse (dynamic *structured-constants*))
(flic-let-bindings object))))
(install-uninterned-globals (flic-let-bindings object))
(postoptimize object)
object)
(define-flic-walker optimize (object))
;;; debugging stuff
;;;
;;; (define *duplicate-object-table* (make-table))
;;;
;;; (define (new-optimize object)
;;; (if (table-entry (dynamic *duplicate-object-table*) object)
;;; (error "Duplicate object ~s detected." object)
;;; (begin
;;; (setf (table-entry (dynamic *duplicate-object-table*) object) '#t)
;;; (old-optimize object))))
;;;
;;; (lisp:setf (lisp:symbol-function 'old-optimize)
;;; (lisp:symbol-function 'optimize))
;;; (lisp:setf (lisp:symbol-function 'optimize)
;;; (lisp:symbol-function 'new-optimize))
(define (optimize-list objects)
(optimize-list-aux objects)
objects)
(define (optimize-list-aux objects)
(if (null? objects)
'()
(begin
(setf (car objects) (optimize (car objects)))
(optimize-list-aux (cdr objects)))))
;;; Compress nested lambdas. This hack is desirable because saturating
;;; applications within the lambda body effectively adds additional
;;; parameters to the function.
;;; *** Maybe this should look for hoistable constant lambdas too.
(define-optimize flic-lambda (object)
(let ((vars (flic-lambda-vars object)))
(dynamic-let ((*lambda-depth* (1+ (dynamic *lambda-depth*)))
(*local-bindings* (cons vars (dynamic *local-bindings*))))
(dolist (var vars)
(setf (var-referenced var) 0))
(let ((new-body (optimize (flic-lambda-body object))))
(setf (flic-lambda-body object) new-body)
(cond ((is-type? 'flic-lambda new-body)
(record-hack 'lambda-compress)
(setf (flic-lambda-vars object)
(nconc (flic-lambda-vars object)
(flic-lambda-vars new-body)))
(setf (flic-lambda-body object) (flic-lambda-body new-body)))
(else
'#f))
object))))
;;; For let, first mark all variables as unused and check for "simple"
;;; binding values that permit beta reduction. Then walk the subexpressions.
;;; Finally discard any bindings that are still marked as unused.
;;; *** This fails to detect unused recursive variables.
(define-optimize flic-let (object)
(optimize-flic-let-aux object '#f))
(define (optimize-flic-let-aux object toplevel?)
(let ((bindings (flic-let-bindings object))
(recursive? (flic-let-recursive? object)))
;; *** This handling of *local-bindings* isn't quite right since
;; *** it doesn't account for the sequential nature of bindings
;; *** in a non-recursive let, but it's close enough. We won't
;; *** get any semantic errors, but it might miss a few optimizations.
(dynamic-let ((*local-bindings*
(if (and recursive? (not toplevel?))
(cons bindings (dynamic *local-bindings*))
(dynamic *local-bindings*))))
(optimize-flic-let-bindings bindings recursive? toplevel?)
(dynamic-let ((*local-bindings*
(if (and (not recursive?) (not toplevel?))
(cons bindings (dynamic *local-bindings*))
(dynamic *local-bindings*))))
(setf (flic-let-body object) (optimize (flic-let-body object))))
;; Check for unused bindings and other rewrites.
;; Only do this for non-toplevel lets.
(if toplevel?
object
(optimize-flic-let-rewrite object bindings recursive?)))))
(define (optimize-flic-let-bindings bindings recursive? toplevel?)
;; Initialize
(dolist (var bindings)
(setf (var-referenced var) 0)
(setf (var-fn-referenced var) 0)
(when (is-type? 'flic-lambda (var-value var))
(dolist (v (flic-lambda-vars (var-value var)))
(setf (var-arg-invariant? v) '#t)
(setf (var-arg-invariant-value v) '#f))))
;; Traverse value subforms
(do ((bindings bindings (cdr bindings)))
((null? bindings) '#f)
(let* ((var (car bindings))
(val (var-value var)))
(if (and (is-type? 'flic-app val)
(dynamic *do-constant-optimizations*)
(let ((fn (flic-app-fn val))
(args (flic-app-args val)))
(if recursive?
(structured-constant-app-recursive?
fn args bindings (list var))
(structured-constant-app? fn args))))
;; Variable is bound to a structured constant. If this
;; isn't already a top-level binding, replace the value
;; of the constant with a reference to a top-level variable
;; that is in turn bound to the constant expression.
;; binding to top-level if this is a new constant.
;; *** Maybe we should also look for variables bound
;; *** to lambdas, that can also be hoisted to top level.
(when (not toplevel?)
(multiple-value-bind (con args cvar)
(enter-structured-constant-aux val '#t)
(record-hack 'let-hoist-structured-constant)
(if cvar
(setf (var-value var) (make-flic-ref cvar))
(add-new-structured-constant var con args))))
(begin
;; If this is a function that's a candidate for foldr/build
;; optimization, stash the value away prior to
;; inlining the calls.
;; *** We might try to automagically detect functions
;; *** that are candidates for these optimizations here,
;; *** but have to watch out for infinite loops!
(when (and (var-force-inline? var)
(eqv? (the fixnum
(dynamic *current-optimize-iteration*))
(the fixnum
(dynamic *optimize-build-iteration*)))
(is-type? 'flic-lambda val)
(or (is-foldr-or-build-app? (flic-lambda-body val))))
(setf (var-inline-value var) (copy-flic-top val)))
;; Then walk value normally.
(let ((new-val (optimize val)))
(setf (var-value var) new-val)
(setf (var-simple? var)
(or (var-force-inline? var)
(and (not (var-selector-fn? var))
(can-inline?
new-val
(if recursive? bindings '())
toplevel?))))))
))))
(define (is-foldr-or-build-app? exp)
(typecase exp
(flic-app
(let ((fn (flic-app-fn exp)))
(and (is-type? 'flic-ref fn)
(or (eq? (flic-ref-var fn) (core-symbol "foldr"))
(eq? (flic-ref-var fn) (core-symbol "build"))))))
(flic-let
(is-foldr-or-build-app? (flic-let-body exp)))
(flic-ref
(let ((val (var-value (flic-ref-var exp))))
(and val (is-foldr-or-build-app? val))))
(else
'#f)))
(define (optimize-flic-let-rewrite object bindings recursive?)
;; Delete unused variables from the list.
(setf bindings
(list-delete-if
(lambda (var)
(cond ((var-toplevel? var)
;; This was a structured constant hoisted to top-level.
'#t)
((eqv? (the fixnum (var-referenced var)) (the fixnum 0))
(record-hack 'let-remove-unused-binding var)
'#t)
((eqv? (the fixnum (var-referenced var)) (the fixnum 1))
(setf (var-single-ref var) (dynamic *lambda-depth*))
'#f)
(else
(setf (var-single-ref var) '#f)
'#f)))
bindings))
;; Add extra bindings for reducing functions with invariant
;; arguments. Hopefully some of the extra bindings will go
;; away in future passes!
(setf (flic-let-bindings object)
(setf bindings (add-stuff-for-invariants bindings)))
;; Look for other special cases.
(cond ((null? bindings)
;; Simplifying the expression by getting rid of the LET may
;; make it possible to do additional optimizations on the
;; next pass.
(record-hack 'let-empty-bindings)
(flic-let-body object))
((is-type? 'flic-return-from (flic-let-body object))
;; Hoist return-from outside of LET. This may permit
;; further optimizations by an enclosing case-block.
(record-hack 'let-hoist-return-from)
(let* ((body (flic-let-body object))
(inner-body (flic-return-from-exp body)))
(setf (flic-return-from-exp body) object)
(setf (flic-let-body object) inner-body)
body))
((and (not recursive?)
(is-type? 'flic-let (flic-let-body object))
(not (flic-let-recursive? (flic-let-body object))))
;; This is purely to produce more compact code.
(record-hack 'let-compress)
(let ((body (flic-let-body object)))
(setf (flic-let-bindings object)
(nconc bindings (flic-let-bindings body)))
(setf (flic-let-body object) (flic-let-body body))
object))
((is-type? 'flic-lambda (flic-let-body object))
;; Hoist lambda outside of LET. This may permit
;; merging of nested lambdas on a future pass.
(record-hack 'let-hoist-lambda)
(let* ((body (flic-let-body object))
(inner-body (flic-lambda-body body)))
(setf (flic-lambda-body body) object)
(setf (flic-let-body object) inner-body)
body))
(else
object))
)
;;; Look for constant-folding and structured constants here.
(define-optimize flic-app (object)
(optimize-flic-app-aux object))
(define (optimize-flic-app-aux object)
(let ((new-fn (optimize (flic-app-fn object)))
(new-args (optimize-list (flic-app-args object))))
(typecase new-fn
(flic-ref
;; The function is a variable.
(let* ((var (flic-ref-var new-fn))
(val (var-value var))
(n (length new-args))
(arity (guess-function-arity var)))
(cond ((and arity (< (the fixnum n) (the fixnum arity)))
;; This is a first-class call that is not fully saturated.
;; Make it saturated by wrapping a lambda around it.
(setf new-fn
(do-app-make-saturated object new-fn new-args arity n))
(setf new-args '()))
((var-selector-fn? var)
;; This is a saturated call to a selector. We might
;; be able to inline the call.
(multiple-value-bind (fn args)
(try-to-fold-selector var new-fn new-args)
(setf new-fn fn)
(setf new-args args)))
((and (not (var-toplevel? var))
(is-type? 'flic-lambda val))
;; This is a saturated call to a local function.
;; Increment its reference count and note if any of
;; the arguments are invariant.
(incf (var-fn-referenced var))
(note-invariant-args new-args (flic-lambda-vars val)))
(else
(let ((magic (magic-optimize-function var)))
(when magic
(multiple-value-bind (fn args)
(funcall magic new-fn new-args)
(setf new-fn fn)
(setf new-args args)))))
)))
(flic-lambda
;; Turn application of lambda into a let.
(multiple-value-bind (fn args)
(do-lambda-to-let-aux new-fn new-args)
(setf new-fn fn)
(setf new-args args)))
(flic-pack
(let ((con (flic-pack-con new-fn))
(temp '#f))
(when (eqv? (length new-args) (con-arity con))
(cond ((and (dynamic *do-constant-optimizations*)
(every-1 (function structured-constant?) new-args))
;; This is a structured constant that
;; can be replaced with a top-level binding.
(setf (flic-app-fn object) new-fn)
(setf (flic-app-args object) new-args)
(record-hack 'app-hoist-structured-constant object)
(setf new-fn (enter-structured-constant object '#t))
(setf new-args '()))
((and (setf temp (is-selector? con 0 (car new-args)))
(is-selector-list? con 1 temp (cdr new-args)))
;; This is an expression like (cons (car x) (cdr x)).
;; Replace it with just plain x to avoid reconsing.
(record-hack 'app-pack-identity new-fn)
(setf new-fn (copy-flic-top temp))
(setf new-args '()))
))))
(flic-let
;; Hoist let to surround entire application.
;; Simplifying the function being applied may permit further
;; optimizations on next pass.
;; (We might try to hoist lets in the argument expressions, too,
;; but I don't think that would lead to any real simplification
;; of the code.)
(record-hack 'app-hoist-let)
(setf (flic-app-fn object) (flic-let-body new-fn))
(setf (flic-app-args object) new-args)
(setf new-args '())
(setf (flic-let-body new-fn) object)
)
(flic-app
;; Try to compress nested applications.
;; This may make the call saturated and permit further optimizations
;; on the next pass.
(record-hack 'app-compress)
(setf new-args (nconc (flic-app-args new-fn) new-args))
(setf new-fn (flic-app-fn new-fn)))
)
(if (null? new-args)
new-fn
(begin
(setf (flic-app-fn object) new-fn)
(setf (flic-app-args object) new-args)
object))
))
(define (guess-function-arity var)
(or (let ((value (var-value var)))
(and value
(is-type? 'flic-lambda value)
(length (flic-lambda-vars value))))
(var-arity var)))
(define (do-app-make-saturated app fn args arity nargs)
(declare (type fixnum arity nargs))
(record-hack 'app-make-saturated fn args)
(let ((newvars '())
(newargs '()))
(dotimes (i (- arity nargs))
(declare (type fixnum i))
(let ((v (init-flic-var (create-temp-var 'arg) '#f '#f)))
(push v newvars)
(push (make-flic-ref v) newargs)))
(setf (flic-app-fn app) fn)
(setf (flic-app-args app) (nconc args newargs))
(make-flic-lambda newvars app)))
;;; If the function is a selector applied to a literal dictionary,
;;; inline it.
(define (try-to-fold-selector var new-fn new-args)
(let ((exp (car new-args)))
(if (or (and (is-type? 'flic-ref exp)
;; *** should check that var is top-level?
(is-bound-to-constructor-app? (flic-ref-var exp)))
(and (is-type? 'flic-app exp)
(is-constructor-app-prim? exp)))
(begin
(record-hack 'app-fold-selector)
(setf new-fn (copy-flic-top (var-value var)))
(do-lambda-to-let-aux new-fn new-args))
(values new-fn new-args))))
;;; Various primitive functions have special optimizer functions
;;; associated with them, that do constant folding and certain
;;; other identities. The optimizer function is called with the
;;; function expression and list of argument expressions (at least
;;; as many arguments as the arity of the function) and should return
;;; the two values.
;;; *** This should really use some kind of hash table, but we'd
;;; *** have to initialize the table dynamically because core-symbols
;;; *** aren't defined when this file is loaded.
(define (magic-optimize-function var)
(cond ((eq? var (core-symbol "foldr"))
(function optimize-foldr-aux))
((eq? var (core-symbol "build"))
(function optimize-build))
((eq? var (core-symbol "primIntegerToInt"))
(function optimize-integer-to-int))
((eq? var (core-symbol "primIntToInteger"))
(function optimize-int-to-integer))
((eq? var (core-symbol "primRationalToFloat"))
(function optimize-rational-to-float))
((eq? var (core-symbol "primRationalToDouble"))
(function optimize-rational-to-double))
((or (eq? var (core-symbol "primNegInt"))
(eq? var (core-symbol "primNegInteger"))
(eq? var (core-symbol "primNegFloat"))
(eq? var (core-symbol "primNegDouble")))
(function optimize-neg))
(else
'#f)))
;;; Foldr identities for deforestation
(define (optimize-foldr fn args)
(multiple-value-bind (fn args)
(optimize-foldr-aux fn args)
(maybe-make-app fn args)))
(define (optimize-foldr-aux fn args)
(let ((k (car args))
(z (cadr args))
(l (caddr args))
(tail (cdddr args)))
(cond ((and (is-type? 'flic-pack k)
(eq? (flic-pack-con k) (core-symbol ":"))
(is-type? 'flic-pack z)
(eq? (flic-pack-con z) (core-symbol "Nil")))
;; foldr (:) [] l ==> l
;; (We arrange for build to be inlined before foldr
;; so that this pattern can be detected.)
(record-hack 'foldr-cons-nil-identity)
(values l tail))
((and (is-type? 'flic-app l)
(is-type? 'flic-ref (flic-app-fn l))
(eq? (flic-ref-var (flic-app-fn l))
(core-symbol "build"))
(null? (cdr (flic-app-args l))))
;; foldr k z (build g) ==> g k z
(record-hack 'foldr-build-identity)
(values
(car (flic-app-args l))
(cons k (cons z tail))))
((and (is-type? 'flic-pack l)
(eq? (flic-pack-con l) (core-symbol "Nil")))
;; foldr k z [] ==> z
(record-hack 'foldr-nil-identity)
(values z tail))
((short-string-constant? l)
;; If the list argument is a string constant, expand it inline.
;; Only do this if the string is fairly short, though.
(optimize-foldr-aux
fn
(cons k (cons z (cons (expand-string-constant l) tail)))))
((and (is-type? 'flic-app l)
(is-type? 'flic-pack (flic-app-fn l))
(eq? (flic-pack-con (flic-app-fn l)) (core-symbol ":"))
(eqv? (length (flic-app-args l)) 2))
;; foldr k z x:xs ==> let c = k in c x (foldr c z xs)
(record-hack 'foldr-cons-identity)
(let ((x (car (flic-app-args l)))
(xs (cadr (flic-app-args l))))
(values
(if (can-inline? k '() '#f)
(do-foldr-cons-identity k z x xs)
(let ((cvar (init-flic-var (create-temp-var 'c) k '#f)))
(make-flic-let
(list cvar)
(do-foldr-cons-identity (make-flic-ref cvar) z x xs)
'#f)))
tail)))
((is-type? 'flic-let l)
;; foldr k z (let bindings in body) ==>
;; let bindings in foldr k z body
(record-hack 'foldr-hoist-let)
(setf (flic-let-body l)
(optimize-foldr fn (list k z (flic-let-body l))))
(values l tail))
((not (eqv? (the fixnum (dynamic *current-optimize-iteration*))
(the fixnum (dynamic *optimize-foldr-iteration*))))
;; Hope for more optimizations later.
(values fn args))
((and (is-type? 'flic-pack k)
(eq? (flic-pack-con k) (core-symbol ":")))
;; Inline to special case, highly optimized append primitive.
;; Could also look for (++ (++ l1 l2) l3) => (++ l1 (++ l2 l3))
;; here, but I don't think that happens very often.
(record-hack 'foldr-prim-append-inline)
(values
(make-flic-ref (core-symbol "primAppend"))
(cons l (cons z tail))))
(else
;; Default inline.
(record-hack 'foldr-inline k z)
(let ((new-fn
(copy-flic-top (var-value (core-symbol "inlineFoldr")))))
(if (is-type? 'flic-lambda new-fn)
(do-lambda-to-let-aux new-fn args)
(values new-fn args))))
)))
;;; Mess with compile-time expansion of short string constants.
(define-integrable max-short-string-length 3)
(define (short-string-constant? l)
(and (is-type? 'flic-const l)
(let ((string (flic-const-value l)))
(and (string? string)
(<= (the fixnum (string-length string))
(the fixnum max-short-string-length))))))
(define (expand-string-constant l)
(let* ((string (flic-const-value l))
(length (string-length string)))
(expand-string-constant-aux string 0 length)))
(define (expand-string-constant-aux string i length)
(declare (type fixnum i length))
(if (eqv? i length)
(make-flic-pack (core-symbol "Nil"))
(make-flic-app
(make-flic-pack (core-symbol ":"))
(list (make-flic-const (string-ref string i))
(expand-string-constant-aux string (+ 1 i) length))
'#f)))
;;; Helper function for the case of expanding foldr applied to cons call.
(define (do-foldr-cons-identity c z x xs)
(make-flic-app
c
(list x
(optimize-foldr
(make-flic-ref (core-symbol "foldr"))
(list (copy-flic-top c) z xs)))
'#f))
;;; Short-circuit build inlining for the usual case where the
;;; argument is a lambda. (It would take several optimizer passes
;;; for this simplification to fall out, otherwise.)
(define (optimize-build fn args)
(let ((arg (car args)))
(cond ((not (eqv? (dynamic *current-optimize-iteration*)
(dynamic *optimize-build-iteration*)))
(values fn args))
((is-type? 'flic-lambda arg)
(record-hack 'build-inline-lambda)
(do-lambda-to-let-aux
arg
(cons (make-flic-pack (core-symbol ":"))
(cons (make-flic-pack (core-symbol "Nil"))
(cdr args)))))
(else
(record-hack 'build-inline-other)
(let ((new-fn
(copy-flic-top (var-value (core-symbol "inlineBuild")))))
(if (is-type? 'flic-lambda new-fn)
(do-lambda-to-let-aux new-fn args)
(values new-fn args))))
)))
;;; Various simplifications on numeric functions.
;;; *** Obviously, could get much fancier about this.
(define (optimize-integer-to-int fn args)
(let ((arg (car args)))
(cond ((is-type? 'flic-const arg)
(record-hack 'integer-to-int-constant-fold)
(if (is-type? 'integer (flic-const-value arg))
(let ((value (flic-const-value arg)))
(when (not (is-type? 'fixnum value))
;; Overflow is a user error, not an implementation error.
(phase-error 'int-overflow
"Int overflow in primIntegerToInt: ~s"
value))
(values arg (cdr args)))
(error "Bad argument ~s to primIntegerToInt." arg)))
((and (is-type? 'flic-app arg)
(is-type? 'flic-ref (flic-app-fn arg))
(eq? (flic-ref-var (flic-app-fn arg))
(core-symbol "primIntToInteger"))
(null? (cdr (flic-app-args arg))))
(record-hack 'integer-to-int-identity)
(values (car (flic-app-args arg)) (cdr args)))
(else
(values fn args)))))
(define (optimize-int-to-integer fn args)
(let ((arg (car args)))
(cond ((is-type? 'flic-const arg)
(record-hack 'int-to-integer-constant-fold)
(if (is-type? 'integer (flic-const-value arg))
(values arg (cdr args))
(error "Bad argument ~s to primIntToInteger." arg)))
((and (is-type? 'flic-app arg)
(is-type? 'flic-ref (flic-app-fn arg))
(eq? (flic-ref-var (flic-app-fn arg))
(core-symbol "primIntegerToInt"))
(null? (cdr (flic-app-args arg))))
(record-hack 'int-to-integer-identity)
(values (car (flic-app-args arg)) (cdr args)))
(else
(values fn args)))))
(predefine (prim.rational-to-float-aux n d)) ; in prims.scm
(predefine (prim.rational-to-double-aux n d)) ; in prims.scm
(define (optimize-rational-to-float fn args)
(let ((arg (car args)))
(cond ((is-type? 'flic-const arg)
(record-hack 'rational-to-float-constant-fold)
(if (is-type? 'list (flic-const-value arg))
(let ((value (flic-const-value arg)))
(setf (flic-const-value arg)
(prim.rational-to-float-aux (car value) (cadr value)))
(values arg (cdr args)))
(error "Bad argument ~s to primRationalToFloat." arg)))
(else
(values fn args)))))
(define (optimize-rational-to-double fn args)
(let ((arg (car args)))
(cond ((is-type? 'flic-const arg)
(record-hack 'rational-to-double-constant-fold)
(if (is-type? 'list (flic-const-value arg))
(let ((value (flic-const-value arg)))
(setf (flic-const-value arg)
(prim.rational-to-double-aux (car value) (cadr value)))
(values arg (cdr args)))
(error "Bad argument ~s to primRationalToDouble." arg)))
(else
(values fn args)))))
(define (optimize-neg fn args)
(let ((arg (car args)))
(cond ((is-type? 'flic-const arg)
(record-hack 'neg-constant-fold)
(if (is-type? 'number (flic-const-value arg))
(begin
(setf (flic-const-value arg) (- (flic-const-value arg)))
(values arg (cdr args)))
(error "Bad argument ~s to ~s." arg fn)))
(else
(values fn args)))))
;;; Convert lambda applications to lets.
;;; If application is not saturated, break it up into two nested
;;; lambdas before doing the transformation.
;;; It's better to do this optimization immediately than hoping
;;; the call will become fully saturated on the next pass.
;;; Maybe we could also look for a flic-let with a flic-lambda as
;;; the body to catch the cases where additional arguments can
;;; be found on a later pass.
(define (do-lambda-to-let new-fn new-args)
(multiple-value-bind (fn args)
(do-lambda-to-let-aux new-fn new-args)
(maybe-make-app fn args)))
(define (maybe-make-app fn args)
(if (null? args)
fn
(make-flic-app fn args '#f)))
(define (do-lambda-to-let-aux new-fn new-args)
(let ((vars (flic-lambda-vars new-fn))
(body (flic-lambda-body new-fn))
(matched '()))
(record-hack 'app-lambda-to-let)
(do ()
((or (null? new-args) (null? vars)))
(let ((var (pop vars))
(arg (pop new-args)))
(setf (var-value var) arg)
(setf (var-simple? var) (can-inline? arg '() '#t))
(if (eqv? (var-referenced var) 1)
(setf (var-single-ref var) (dynamic *lambda-depth*)))
(push var matched)))
(setf matched (nreverse matched))
(if (not (null? vars))
(setf body (make-flic-lambda vars body)))
(setf new-fn (make-flic-let matched body '#f))
(values new-fn new-args)))
;;; For references, check to see if we can beta-reduce.
;;; Don't increment reference count for inlineable vars, but do
;;; traverse the new value expression.
(define-optimize flic-ref (object)
(optimize-flic-ref-aux object))
(define (optimize-flic-ref-aux object)
(let ((var (flic-ref-var object)))
(cond ((var-single-ref var)
;; (or (eqv? (var-single-ref var) (dynamic *lambda-depth*)))
;; *** The lambda-depth test is too conservative to handle
;; *** inlining of stuff necessary for foldr/build optimizations.
;; Can substitute value no matter how hairy it is.
;; Note that this is potentially risky; if the single
;; reference detected on the previous pass appeared as
;; the value of a variable binding that is being inlined
;; on the current pass, it might turn into multiple
;; references again!
;; We copy the value anyway to avoid problems with shared
;; structure in the multiple reference case.
(record-hack 'ref-inline-single-ref var)
(optimize (copy-flic-top (var-value var))))
((and (var-inline-value var) (dynamic *do-inline-optimizations*))
;; Use the previously saved value in preference to the current
;; value of the variable.
(record-hack 'ref-inline-foldr-hack)
(optimize (copy-flic-top (var-inline-value var))))
((and (var-simple? var)
(or (dynamic *do-inline-optimizations*)
(not (var-toplevel? var))))
;; Can substitute, but must copy.
(record-hack 'ref-inline var)
(optimize (copy-flic-top (var-value var))))
((eq? var (core-symbol "foldr"))
;; Magic stuff for deforestation
(if (> (the fixnum (dynamic *current-optimize-iteration*))
(the fixnum (dynamic *optimize-foldr-iteration*)))
(begin
(record-hack 'ref-inline-foldr)
(optimize (make-flic-ref (core-symbol "inlineFoldr"))))
object))
((eq? var (core-symbol "build"))
;; Magic stuff for deforestation
(if (> (the fixnum (dynamic *current-optimize-iteration*))
(the fixnum (dynamic *optimize-build-iteration*)))
(begin
(record-hack 'ref-inline-build)
(optimize (make-flic-ref (core-symbol "inlineBuild"))))
object))
((var-toplevel? var)
object)
(else
(incf (var-referenced var))
object))))
;;; Don't do anything exciting with constants.
(define-optimize flic-const (object)
object)
(define-optimize flic-pack (object)
object)
;;; Various simplifications on and
(define-optimize flic-and (object)
(maybe-simplify-and
object
(optimize-and-exps (flic-and-exps object) '())))
(define (maybe-simplify-and object exps)
(cond ((null? exps)
(record-hack 'and-empty)
(make-flic-pack (core-symbol "True")))
((null? (cdr exps))
(record-hack 'and-unary)
(car exps))
(else
(setf (flic-and-exps object) exps)
object)))
(define (optimize-and-exps exps result)
(if (null? exps)
(nreverse result)
(let ((exp (optimize (car exps))))
(typecase exp
(flic-pack
(cond ((eq? (flic-pack-con exp) (core-symbol "True"))
;; True appears in subexpressions.
;; Discard this test only.
(record-hack 'and-contains-true)
(optimize-and-exps (cdr exps) result))
((eq? (flic-pack-con exp) (core-symbol "False"))
;; False appears in subexpressions.
;; Discard remaining tests as dead code.
;; Can't replace the whole and expression with false because
;; of possible strictness side-effects.
(record-hack 'and-contains-false)
(nreverse (cons exp result)))
(else
;; Should never happen.
(error "Non-boolean con ~s in and expression!" exp))))
(flic-and
;; Flatten nested ands.
(record-hack 'and-compress)
(optimize-and-exps
(cdr exps)
(nconc (nreverse (flic-and-exps exp)) result)))
(else
;; No optimization possible.
(optimize-and-exps (cdr exps) (cons exp result)))
))))
;;; Case-block optimizations. These optimizations are possible because
;;; of the restricted way this construct is used; return-froms are
;;; never nested, etc.
(define-optimize flic-case-block (object)
(let* ((sym (flic-case-block-block-name object))
(exps (optimize-case-block-exps
sym (flic-case-block-exps object) '())))
(optimize-flic-case-block-aux object sym exps)))
(define (optimize-flic-case-block-aux object sym exps)
(cond ((null? exps)
;; This should never happen. It means all of the tests were
;; optimized away, including the failure case!
(error "No exps left in case block ~s!" object))
((and (is-type? 'flic-and (car exps))
(is-return-from-block?
sym
(car (last (flic-and-exps (car exps))))))
;; The first clause is a simple and. Hoist it out of the
;; case-block and rewrite as if/then/else.
(record-hack 'case-block-to-if)
(let ((then-exp (car (last (flic-and-exps (car exps))))))
(setf (flic-case-block-exps object) (cdr exps))
(make-flic-if
(maybe-simplify-and
(car exps)
(butlast (flic-and-exps (car exps))))
(flic-return-from-exp then-exp)
(optimize-flic-case-block-aux object sym (cdr exps)))))
((is-return-from-block? sym (car exps))
;; Do an identity reduction.
(record-hack 'case-block-identity)
(flic-return-from-exp (car exps)))
((is-type? 'flic-let (car exps))
;; The first clause is a let. Since this clause is going
;; to be executed anyway, hoisting the bindings to surround
;; the entire case-block should not change their strictness
;; properties, and it may permit some further optimizations.
(record-hack 'case-block-hoist-let)
(let* ((exp (car exps))
(body (flic-let-body exp)))
(setf (flic-let-body exp)
(optimize-flic-case-block-aux
object sym (cons body (cdr exps))))
exp))
(else
(setf (flic-case-block-exps object) exps)
object)
))
(define (optimize-case-block-exps sym exps result)
(if (null? exps)
(nreverse result)
(let ((exp (optimize (car exps))))
(cond ((is-return-from-block? sym exp)
;; Any remaining clauses are dead code and should be removed.
(if (not (null? (cdr exps)))
(record-hack 'case-block-dead-code))
(nreverse (cons exp result)))
((is-type? 'flic-and exp)
;; See if we can remove redundant tests.
(push (maybe-simplify-and
exp
(look-for-redundant-tests (flic-and-exps exp) result))
result)
(optimize-case-block-exps sym (cdr exps) result))
(else
;; No optimization possible.
(optimize-case-block-exps sym (cdr exps) (cons exp result)))
))))
;;; Look for case-block tests that are known to be either true or false
;;; because of tests made in previous clauses.
;;; For now, we only look at is-constructor tests. Such a test is known
;;; to be true if previous clauses have eliminated all other possible
;;; constructors. And such a test is known to be false if a previous
;;; clause has already matched this constructor.
(define (look-for-redundant-tests exps previous-clauses)
(if (null? exps)
'()
(let ((exp (car exps)))
(cond ((and (is-type? 'flic-is-constructor exp)
(constructor-test-redundant? exp previous-clauses))
;; Known to be true.
(record-hack 'case-block-discard-redundant-test)
(cons (make-flic-pack (core-symbol "True"))
(look-for-redundant-tests (cdr exps) previous-clauses)))
((and (is-type? 'flic-is-constructor exp)
(constructor-test-duplicated? exp previous-clauses))
;; Known to be false.
(record-hack 'case-block-discard-duplicate-test)
(list (make-flic-pack (core-symbol "False"))))
(else
;; No optimization.
(cons exp
(look-for-redundant-tests (cdr exps) previous-clauses)))
))))
;;; In looking for redundant/duplicated tests, only worry about
;;; is-constructor tests that have an argument that is a variable.
;;; It's too hairy to consider any other cases.
(define (constructor-test-duplicated? exp previous-clauses)
(let ((con (flic-is-constructor-con exp))
(arg (flic-is-constructor-exp exp)))
(and (is-type? 'flic-ref arg)
(constructor-test-present? con arg previous-clauses))))
(define (constructor-test-redundant? exp previous-clauses)
(let ((con (flic-is-constructor-con exp))
(arg (flic-is-constructor-exp exp)))
(and (is-type? 'flic-ref arg)
(every-1 (lambda (c)
(or (eq? c con)
(constructor-test-present? c arg previous-clauses)))
(algdata-constrs (con-alg con))))))
(define (constructor-test-present? con arg previous-clauses)
(cond ((null? previous-clauses)
'#f)
((constructor-test-present-1? con arg (car previous-clauses))
'#t)
(else
(constructor-test-present? con arg (cdr previous-clauses)))))
;;; The tricky thing here is that, even if the constructor test is
;;; present in the clause, we have to make sure that the entire clause won't
;;; fail due to the presence of some other test which fails. So look
;;; for a very specific pattern here, namely
;;; (and (is-constructor con arg) (return-from ....))
(define (constructor-test-present-1? con arg clause)
(and (is-type? 'flic-and clause)
(let ((exps (flic-and-exps clause)))
(and (is-type? 'flic-is-constructor (car exps))
(is-type? 'flic-return-from (cadr exps))
(null? (cddr exps))
(let* ((inner-exp (car exps))
(inner-con (flic-is-constructor-con inner-exp))
(inner-arg (flic-is-constructor-exp inner-exp)))
(and (eq? inner-con con)
(flic-exp-eq? arg inner-arg)))))))
;;; No fancy optimizations for return-from by itself.
(define-optimize flic-return-from (object)
(setf (flic-return-from-exp object)
(optimize (flic-return-from-exp object)))
object)
;;; Obvious simplification on if
(define-optimize flic-if (object)
(let ((test-exp (optimize (flic-if-test-exp object)))
(then-exp (optimize (flic-if-then-exp object)))
(else-exp (optimize (flic-if-else-exp object))))
(cond ((and (is-type? 'flic-pack test-exp)
(eq? (flic-pack-con test-exp) (core-symbol "True")))
;; Fold constant test
(record-hack 'if-fold)
then-exp)
((and (is-type? 'flic-pack test-exp)
(eq? (flic-pack-con test-exp) (core-symbol "False")))
;; Fold constant test
(record-hack 'if-fold)
else-exp)
((and (is-type? 'flic-is-constructor test-exp)
(eq? (flic-is-constructor-con test-exp) (core-symbol "True")))
;; Remove redundant is-constructor test.
;; Doing this as a general is-constructor identity
;; backfires because it prevents some of the important case-block
;; optimizations from being recognized, but it works fine here.
(record-hack 'if-compress-test)
(setf (flic-if-test-exp object) (flic-is-constructor-exp test-exp))
(setf (flic-if-then-exp object) then-exp)
(setf (flic-if-else-exp object) else-exp)
object)
((and (is-type? 'flic-is-constructor test-exp)
(eq? (flic-is-constructor-con test-exp) (core-symbol "False")))
;; Remove redundant is-constructor test, flip branches.
(record-hack 'if-compress-test)
(setf (flic-if-test-exp object) (flic-is-constructor-exp test-exp))
(setf (flic-if-then-exp object) else-exp)
(setf (flic-if-else-exp object) then-exp)
object)
((and (is-type? 'flic-return-from then-exp)
(is-type? 'flic-return-from else-exp)
(eq? (flic-return-from-block-name then-exp)
(flic-return-from-block-name else-exp)))
;; Hoist return-from outside of IF.
;; This may permit further case-block optimizations.
(record-hack 'if-hoist-return-from)
(let ((return-exp then-exp))
(setf (flic-if-test-exp object) test-exp)
(setf (flic-if-then-exp object) (flic-return-from-exp then-exp))
(setf (flic-if-else-exp object) (flic-return-from-exp else-exp))
(setf (flic-return-from-exp return-exp) object)
return-exp))
((and (is-type? 'flic-pack then-exp)
(is-type? 'flic-pack else-exp)
(eq? (flic-pack-con then-exp) (core-symbol "True"))
(eq? (flic-pack-con else-exp) (core-symbol "False")))
;; This if does nothing useful at all!
(record-hack 'if-identity)
test-exp)
((and (is-type? 'flic-pack then-exp)
(is-type? 'flic-pack else-exp)
(eq? (flic-pack-con then-exp) (core-symbol "False"))
(eq? (flic-pack-con else-exp) (core-symbol "True")))
;; Inverse of previous case
(record-hack 'if-identity-inverse)
(make-flic-is-constructor (core-symbol "False") test-exp))
((or (is-type? 'flic-lambda then-exp)
(is-type? 'flic-lambda else-exp))
;; Hoist lambdas to surround entire if. This allows us to
;; do a better job of saturating them.
(record-hack 'if-hoist-lambda)
(multiple-value-bind (vars then-exp else-exp)
(do-if-hoist-lambda then-exp else-exp)
(setf (flic-if-test-exp object) test-exp)
(setf (flic-if-then-exp object) then-exp)
(setf (flic-if-else-exp object) else-exp)
(make-flic-lambda vars object)))
(else
;; No optimization possible
(setf (flic-if-test-exp object) test-exp)
(setf (flic-if-then-exp object) then-exp)
(setf (flic-if-else-exp object) else-exp)
object)
)))
;;; Try to pull as many variables as possible out to surround the entire
;;; let.
(define (do-if-hoist-lambda then-exp else-exp)
(let ((vars '())
(then-args '())
(else-args '()))
(do ((then-vars (if (is-type? 'flic-lambda then-exp)
(flic-lambda-vars then-exp)
'())
(cdr then-vars))
(else-vars (if (is-type? 'flic-lambda else-exp)
(flic-lambda-vars else-exp)
'())
(cdr else-vars)))
((and (null? then-vars) (null? else-vars)) '#f)
(let ((var (init-flic-var (create-temp-var 'arg) '#f '#f)))
(push var vars)
(push (make-flic-ref var) then-args)
(push (make-flic-ref var) else-args)))
(values
vars
(if (is-type? 'flic-lambda then-exp)
(do-lambda-to-let then-exp then-args)
(make-flic-app then-exp then-args '#f))
(if (is-type? 'flic-lambda else-exp)
(do-lambda-to-let else-exp else-args)
(make-flic-app else-exp else-args '#f)))))
;;; Look for (sel (pack x)) => x
(define-optimize flic-sel (object)
(optimize-flic-sel-aux object))
(define (optimize-flic-sel-aux object)
(let ((new-exp (optimize (flic-sel-exp object))))
(setf (flic-sel-exp object) new-exp)
(typecase new-exp
(flic-ref
;; Check to see whether this is bound to a pack application
(let ((val (is-bound-to-constructor-app? (flic-ref-var new-exp))))
(if val
;; Yup, it is. Now extract the appropriate component,
;; provided it is inlineable.
(let* ((i (flic-sel-i object))
(args (flic-app-args val))
(newval (list-ref args i)))
(if (can-inline? newval '() '#t)
(begin
(record-hack 'sel-fold-var)
(optimize (copy-flic-top newval)))
object))
;; The variable was bound to something else.
object)))
(flic-app
;; The obvious optimization.
(if (is-constructor-app-prim? new-exp)
(begin
(record-hack 'sel-fold-app)
(list-ref (flic-app-args new-exp) (flic-sel-i object)))
object))
(else
object))))
;;; Do similar stuff for is-constructor.
(define-optimize flic-is-constructor (object)
(let ((con (flic-is-constructor-con object))
(exp (optimize (flic-is-constructor-exp object)))
(exp-con '#f))
(cond ((algdata-tuple? (con-alg con))
;; Tuples have only one constructor, so this is always true
(record-hack 'is-constructor-fold-tuple)
(make-flic-pack (core-symbol "True")))
((setf exp-con (is-constructor-app? exp))
;; The expression is a constructor application.
(record-hack 'is-constructor-fold)
(make-flic-pack
(if (eq? exp-con con)
(core-symbol "True")
(core-symbol "False"))))
(else
;; No optimization possible
(setf (flic-is-constructor-exp object) exp)
object)
)))
(define-optimize flic-con-number (object)
(let ((exp (flic-con-number-exp object))
(type (flic-con-number-type object)))
;; ***Maybe ast-to-flic should look for this one.
(if (algdata-tuple? type)
(begin
(record-hack 'con-number-fold-tuple)
(make-flic-const 0))
(let* ((new-exp (optimize exp))
(con (is-constructor-app? new-exp)))
(if con
(begin
(record-hack 'con-number-fold)
(make-flic-const (con-tag con)))
(begin
(setf (flic-con-number-exp object) new-exp)
object)))
)))
(define-optimize flic-void (object)
object)
;;;===================================================================
;;; General helper functions
;;;===================================================================
;;; Lucid's built-in every function seems to do a lot of unnecessary
;;; consing. This one is much faster.
(define (every-1 fn list)
(cond ((null? list)
'#t)
((funcall fn (car list))
(every-1 fn (cdr list)))
(else
'#f)))
;;; Equality predicate on flic expressions
(define (flic-exp-eq? a1 a2)
(typecase a1
(flic-const
(and (is-type? 'flic-const a2)
(equal? (flic-const-value a1) (flic-const-value a2))))
(flic-ref
(and (is-type? 'flic-ref a2)
(eq? (flic-ref-var a1) (flic-ref-var a2))))
(flic-pack
(and (is-type? 'flic-pack a2)
(eq? (flic-pack-con a1) (flic-pack-con a2))))
(flic-sel
(and (is-type? 'flic-sel a2)
(eq? (flic-sel-con a1) (flic-sel-con a2))
(eqv? (flic-sel-i a1) (flic-sel-i a2))
(flic-exp-eq? (flic-sel-exp a1) (flic-sel-exp a2))))
(else
'#f)))
;;; Predicates for testing whether an expression matches a pattern.
(define (is-constructor-app? exp)
(typecase exp
(flic-app
;; See if we have a saturated call to a constructor.
(is-constructor-app-prim? exp))
(flic-ref
;; See if we can determine anything about the value the variable
;; is bound to.
(let ((value (var-value (flic-ref-var exp))))
(if value
(is-constructor-app? value)
'#f)))
(flic-let
;; See if we can determine anything about the body of the let.
(is-constructor-app? (flic-let-body exp)))
(flic-pack
;; See if this is a nullary constructor.
(let ((con (flic-pack-con exp)))
(if (eqv? (con-arity con) 0)
con
'#f)))
(else
'#f)))
(define (is-return-from-block? sym exp)
(and (is-type? 'flic-return-from exp)
(eq? (flic-return-from-block-name exp) sym)))
(define (is-constructor-app-prim? exp)
(let ((fn (flic-app-fn exp))
(args (flic-app-args exp)))
(if (and (is-type? 'flic-pack fn)
(eqv? (length args) (con-arity (flic-pack-con fn))))
(flic-pack-con fn)
'#f)))
(define (is-bound-to-constructor-app? var)
(let ((val (var-value var)))
(if (and val
(is-type? 'flic-app val)
(is-constructor-app-prim? val))
val
'#f)))
(define (is-selector? con i exp)
(or (and (is-type? 'flic-ref exp)
(is-selector? con i (var-value (flic-ref-var exp))))
(and (is-type? 'flic-sel exp)
(eq? (flic-sel-con exp) con)
(eqv? (the fixnum i) (the fixnum (flic-sel-i exp)))
(flic-sel-exp exp))
))
(define (is-selector-list? con i subexp exps)
(declare (type fixnum i))
(if (null? exps)
subexp
(let ((temp (is-selector? con i (car exps))))
(and (flic-exp-eq? subexp temp)
(is-selector-list? con (+ 1 i) subexp (cdr exps))))))
;;;===================================================================
;;; Inlining criteria
;;;===================================================================
;;; Expressions that can be inlined unconditionally are constants, variable
;;; references, and some functions.
;;; I've made some attempt here to arrange the cases in the order they
;;; are likely to occur.
(define (can-inline? exp recursive-vars toplevel?)
(typecase exp
(flic-sel
;; Listed first because it happens more frequently than
;; anything else.
;; *** Inlining these is an experiment.
;; *** This transformation interacts with the strictness
;; *** analyzer; if the variable referenced is not strict, then
;; *** it is probably not a good thing to do since it adds extra
;; *** forces.
;; (let ((subexp (flic-sel-exp exp)))
;; (and (is-type? 'flic-ref subexp)
;; (not (memq (flic-ref-var subexp) recursive-vars))))
'#f)
(flic-lambda
;; Do not try to inline lambdas if the fancy inline optimization
;; is disabled.
;; Watch for problems with infinite loops with recursive variables.
(if (dynamic *do-inline-optimizations*)
(simple-function-body? (flic-lambda-body exp)
(flic-lambda-vars exp)
recursive-vars
toplevel?)
'#f))
(flic-ref
;; We get into infinite loops trying to inline recursive variables.
(not (memq (flic-ref-var exp) recursive-vars)))
((or flic-pack flic-const)
'#t)
(else
'#f)))
;;; Determining whether to inline a function is difficult. This is
;;; very conservative to avoid code bloat. What we need to do is
;;; compare the cost (in program size mainly) of the inline call with
;;; an out of line call. For an out of line call, we pay for one function
;;; call and a setup for each arg. When inlining, we pay for function
;;; calls in the body and for args referenced more than once. In terms of
;;; execution time, we win big when a functional parameter is called
;;; since this `firstifies' the program.
;;; Here's the criteria:
;;; An inline function gets to reference no more that 2 non-parameter
;;; values (including constants and repeated parameter references).
;;; For non-toplevel functions, be slightly more generous since the
;;; fixed overhead of binding the local function would go away.
(define (simple-function-body? exp lambda-vars recursive-vars toplevel?)
(let ((c (if toplevel? 2 4)))
(>= (the fixnum (simple-function-body-1 exp lambda-vars recursive-vars c))
0)))
;;; I've made some attempt here to order the cases by how frequently
;;; they appear.
(define (simple-function-body-1 exp lambda-vars recursive-vars c)
(declare (type fixnum c))
(if (< c 0)
(values c '())
(typecase exp
(flic-ref
(let ((var (flic-ref-var exp)))
(cond ((memq var lambda-vars)
(values c (list-remove-1 var lambda-vars)))
((memq var recursive-vars)
(values -1 '()))
(else
(values (the fixnum (1- c)) lambda-vars)))))
(flic-app
(simple-function-body-1/l
(cons (flic-app-fn exp) (flic-app-args exp))
lambda-vars recursive-vars c))
(flic-sel
(simple-function-body-1
(flic-sel-exp exp)
lambda-vars recursive-vars (the fixnum (1- c))))
(flic-is-constructor
(simple-function-body-1
(flic-is-constructor-exp exp)
lambda-vars recursive-vars (the fixnum (1- c))))
((or flic-const flic-pack)
(values (the fixnum (1- c)) lambda-vars))
(else
;; case & let & lambda not allowed.
(values -1 '())))))
(define (list-remove-1 item list)
(cond ((null? list)
'())
((eq? item (car list))
(cdr list))
(else
(cons (car list) (list-remove-1 item (cdr list))))
))
(define (simple-function-body-1/l exps lambda-vars recursive-vars c)
(declare (type fixnum c))
(if (or (null? exps) (< c 0))
(values c lambda-vars)
(multiple-value-bind (c-1 lambda-vars-1)
(simple-function-body-1 (car exps) lambda-vars recursive-vars c)
(simple-function-body-1/l
(cdr exps) lambda-vars-1 recursive-vars c-1))))
;;;===================================================================
;;; Constant structured data detection
;;;===================================================================
;;; Look to determine whether an object is a structured constant,
;;; recursively examining its components if it's an app. This is
;;; necessary in order to detect constants with arbitrary circular
;;; reference to the vars in recursive-vars.
(define (structured-constant-recursive? object recursive-vars stack)
(typecase object
(flic-const
'#t)
(flic-ref
(let ((var (flic-ref-var object)))
(or (memq var stack)
(var-toplevel? var)
(and (memq var recursive-vars)
(structured-constant-recursive?
(var-value var) recursive-vars (cons var stack))))))
(flic-pack
'#t)
(flic-app
(structured-constant-app-recursive?
(flic-app-fn object)
(flic-app-args object)
recursive-vars
stack))
(flic-lambda
(lambda-hoistable? object))
(else
'#f)))
(define (structured-constant-app-recursive? fn args recursive-vars stack)
(and (is-type? 'flic-pack fn)
(eqv? (length args) (con-arity (flic-pack-con fn)))
(every-1 (lambda (a)
(structured-constant-recursive? a recursive-vars stack))
args)))
;;; Here's a non-recursive (and more efficient) version of the above.
;;; Instead of looking at the whole structure, it only looks one level
;;; deep. This can't detect circular constants, but is useful in
;;; contexts where circularities cannot appear.
(define (structured-constant? object)
(typecase object
(flic-ref
(var-toplevel? (flic-ref-var object)))
(flic-const
'#t)
(flic-pack
'#t)
(flic-lambda
(lambda-hoistable? object))
(else
'#f)))
(define (structured-constant-app? fn args)
(and (is-type? 'flic-pack fn)
(eqv? (length args) (con-arity (flic-pack-con fn)))
(every-1 (function structured-constant?) args)))
;;; Determine whether a lambda can be hoisted to top-level.
;;; The main purpose of this code is to mark structured constants
;;; containing simple lambdas to permit later folding of sel expressions
;;; on those constants. Since the latter expression is permissible
;;; only on inlinable functions, stop if we hit an expression that
;;; would make the function not inlinable.
(define (lambda-hoistable? object)
(and (can-inline? object '() '#t)
(lambda-hoistable-aux
(flic-lambda-body object)
(flic-lambda-vars object))))
(define (lambda-hoistable-aux object local-vars)
(typecase object
(flic-ref
(or (var-toplevel? (flic-ref-var object))
(memq (flic-ref-var object) local-vars)))
((or flic-const flic-pack)
'#t)
(flic-sel
(lambda-hoistable-aux (flic-sel-exp object) local-vars))
(flic-is-constructor
(lambda-hoistable-aux (flic-is-constructor-exp object) local-vars))
(flic-app
(and (lambda-hoistable-aux (flic-app-fn object) local-vars)
(every-1 (lambda (x) (lambda-hoistable-aux x local-vars))
(flic-app-args object))))
(else
'#f)))
;;; Having determined that something is a structured constant,
;;; enter it (and possibly its subcomponents) in the hash table
;;; and return a var-ref.
(define (enter-structured-constant value recursive?)
(multiple-value-bind (con args var)
(enter-structured-constant-aux value recursive?)
(when (not var)
(setf var (create-temp-var 'constant))
(add-new-structured-constant var con args))
(make-flic-ref var)))
(define (enter-structured-constant-aux value recursive?)
(let* ((fn (flic-app-fn value))
(con (flic-pack-con fn))
(args (if recursive?
(map (function enter-structured-constant-arg)
(flic-app-args value))
(flic-app-args value))))
(values con args (lookup-structured-constant con args))))
(define (enter-structured-constant-arg a)
(if (is-type? 'flic-app a)
(enter-structured-constant a '#t)
a))
(define (lookup-structured-constant con args)
(lookup-structured-constant-aux
(table-entry *structured-constants-table* con) args))
(define (lookup-structured-constant-aux alist args)
(cond ((null? alist)
'#f)
((every (function flic-exp-eq?) (car (car alist)) args)
(cdr (car alist)))
(else
(lookup-structured-constant-aux (cdr alist) args))))
(define (add-new-structured-constant var con args)
(push (cons args var) (table-entry *structured-constants-table* con))
(setf (var-toplevel? var) '#t)
(setf (var-value var) (make-flic-app (make-flic-pack con) args '#t))
(push var *structured-constants*)
var)
;;;===================================================================
;;; Invariant argument stuff
;;;===================================================================
;;; When processing a saturated call to a locally defined function,
;;; note whether any of the arguments are always passed the same value.
(define (note-invariant-args args vars)
(when (and (not (null? args)) (not (null? vars)))
(let* ((arg (car args))
(var (car vars))
(val (var-arg-invariant-value var)))
(cond ((not (var-arg-invariant? var))
;; This argument already marked as having more than one
;; value.
)
((and (is-type? 'flic-ref arg)
(eq? (flic-ref-var arg) var))
;; This is a recursive call with the same argument.
;; Don't update the arg-invariant-value slot.
)
((or (not val)
(flic-exp-eq? arg val))
;; Either this is the first call, or a second call with
;; the same argument.
(setf (var-arg-invariant-value var) arg))
(else
;; Different values for this argument are passed in
;; different places, so we can't mess with it.
(setf (var-arg-invariant? var) '#f)))
(note-invariant-args (cdr args) (cdr vars)))))
;;; After processing a let form, check to see if any of the bindings
;;; are for local functions with invariant arguments.
;;; Suppose we have something like
;;; let foo = \ x y z -> <fn-body>
;;; in <let-body>
;;; and y is known to be invariant; then we rewrite this as
;;; let foo1 = \ x z -> let y = <invariant-value> in <fn-body>
;;; foo = \ x1 y1 z1 -> foo1 x1 z1
;;; in <let-body>
;;; The original foo binding is inlined on subsequent passes and
;;; should go away. Likewise, the binding of y should be inlined also.
;;; *** This is kind of bogus because of the way it depends on the
;;; *** magic force-inline bit. It would be better to do a code walk
;;; *** now on the entire let expression to rewrite all the calls to foo.
(define (add-stuff-for-invariants bindings)
(if (null? bindings)
'()
(let* ((var (car bindings))
(val (var-value var)))
(setf (cdr bindings)
(add-stuff-for-invariants (cdr bindings)))
(if (and (is-type? 'flic-lambda val)
;; Don't mess with single-reference variable bindings,
;; or things we are going to inline anyway.
(not (var-single-ref var))
(not (var-simple? var))
;; All references must be in saturated calls to do this.
(eqv? (var-referenced var) (var-fn-referenced var))
;; There is at least one argument marked invariant.
(some (function var-arg-invariant?) (flic-lambda-vars val))
;; Every argument marked invariant must also be hoistable.
(every-1 (function arg-hoistable?) (flic-lambda-vars val)))
(hoist-invariant-args
var
val
bindings)
bindings))))
(define (arg-hoistable? var)
(if (var-arg-invariant? var)
(or (not (var-arg-invariant-value var))
(flic-invariant? (var-arg-invariant-value var)
(dynamic *local-bindings*)))
'#t))
(define (hoist-invariant-args var val bindings)
(let ((foo1-var (copy-temp-var (def-name var)))
(foo1-def-vars '())
(foo1-app-args '())
(foo1-let-vars '())
(foo-def-vars '()))
(push foo1-var bindings)
(dolist (v (flic-lambda-vars val))
(let ((new-v (copy-temp-var (def-name v))))
(push (init-flic-var new-v '#f '#f) foo-def-vars)
(if (var-arg-invariant? v)
(when (var-arg-invariant-value v)
(push (init-flic-var
v (copy-flic-top (var-arg-invariant-value v)) '#f)
foo1-let-vars))
(begin
(push v foo1-def-vars)
(push (make-flic-ref new-v) foo1-app-args))
)))
(setf foo1-def-vars (nreverse foo1-def-vars))
(setf foo1-app-args (nreverse foo1-app-args))
(setf foo1-let-vars (nreverse foo1-let-vars))
(setf foo-def-vars (nreverse foo-def-vars))
(record-hack 'let-hoist-invariant-args var foo1-let-vars)
;; Fix up the value of foo1
(init-flic-var
foo1-var
(let ((body (make-flic-let foo1-let-vars (flic-lambda-body val) '#f)))
(if (null? foo1-def-vars)
;; *All* of the arguments were invariant.
body
;; Otherwise, make a new lambda
(make-flic-lambda foo1-def-vars body)))
'#f)
;; Fix up the value of foo and arrange for it to be inlined.
(setf (flic-lambda-vars val) foo-def-vars)
(setf (flic-lambda-body val)
(if (null? foo1-app-args)
(make-flic-ref foo1-var)
(make-flic-app (make-flic-ref foo1-var) foo1-app-args '#t)))
(setf (var-simple? var) '#t)
(setf (var-force-inline? var) '#t)
;; Return modified list of bindings
bindings))
;;;===================================================================
;;; Install globals
;;;===================================================================
;;; The optimizer, CFN, etc. can introduce new top-level variables that
;;; are not installed in the symbol table. This causes problems if
;;; those variables are referenced in the .hci file (as in the inline
;;; expansion of some other variables). So we need to fix up the
;;; symbol table before continuing.
(define (install-uninterned-globals vars)
(dolist (v vars)
(let* ((module (locate-module (def-module v)))
(name (def-name v))
(table (module-symbol-table module))
(def (table-entry table name)))
(cond ((not def)
;; This def was not installed. Rename it if it's a gensym
;; and install it.
(when (gensym? name)
(setf name (rename-gensym-var v name table)))
(setf (table-entry table name) v))
((eq? def v)
;; Already installed.
'#t)
(else
;; Ooops! The symbol installed in the symbol table isn't
;; this one!
(error "Duplicate defs ~s and ~s in symbol table for ~s!"
v def module))
))))
(define (rename-gensym-var var name table)
(setf name (string->symbol (symbol->string name)))
(if (table-entry table name)
;; This name already in use; gensym a new one!
(rename-gensym-var var (gensym (symbol->string name)) table)
;; OK, no problem
(setf (def-name var) name)))
;;;===================================================================
;;; Postoptimizer
;;;===================================================================
;;; This is another quick traversal of the structure to determine
;;; whether references to functions are fully saturated or not.
;;; Also makes sure that reference counts on variables are correct;
;;; this is needed so the code generator can generate ignore declarations
;;; for unused lambda variables.
(define-flic-walker postoptimize (object))
(define-postoptimize flic-lambda (object)
(dolist (var (flic-lambda-vars object))
(setf (var-referenced var) 0))
(postoptimize (flic-lambda-body object)))
(define-postoptimize flic-let (object)
(dolist (var (flic-let-bindings object))
(setf (var-referenced var) 0)
(let ((val (var-value var)))
(setf (var-arity var)
(if (is-type? 'flic-lambda val)
(length (flic-lambda-vars val))
0))))
(dolist (var (flic-let-bindings object))
(postoptimize (var-value var)))
(postoptimize (flic-let-body object)))
(define-postoptimize flic-app (object)
(let ((fn (flic-app-fn object)))
(typecase fn
(flic-ref
(let* ((var (flic-ref-var fn))
(arity (var-arity var)))
(if (not (var-toplevel? var)) (incf (var-referenced var)))
(when (not (eqv? arity 0))
(postoptimize-app-aux object var arity (flic-app-args object)))))
(flic-pack
(let* ((con (flic-pack-con fn))
(arity (con-arity con)))
(postoptimize-app-aux object '#f arity (flic-app-args object))))
(else
(postoptimize fn)))
(dolist (a (flic-app-args object))
(postoptimize a))))
(define (postoptimize-app-aux object var arity args)
(declare (type fixnum arity))
(let ((nargs (length args)))
(declare (type fixnum nargs))
(cond ((< nargs arity)
;; not enough arguments
(when var (setf (var-standard-refs? var) '#t)))
((eqv? nargs arity)
;; exactly the right number of arguments
(when var (setf (var-optimized-refs? var) '#t))
(setf (flic-app-saturated? object) '#t))
(else
;; make the fn a nested flic-app
(multiple-value-bind (arghead argtail)
(split-list args arity)
(setf (flic-app-fn object)
(make-flic-app (flic-app-fn object) arghead '#t))
(setf (flic-app-args object) argtail)
(when var (setf (var-optimized-refs? var) '#t))
(dolist (a arghead)
(postoptimize a))))
)))
(define-postoptimize flic-ref (object)
(let ((var (flic-ref-var object)))
(if (not (var-toplevel? var)) (incf (var-referenced var)))
(setf (var-standard-refs? var) '#t)))
(define-postoptimize flic-const (object)
object)
(define-postoptimize flic-pack (object)
object)
(define-postoptimize flic-and (object)
(for-each (function postoptimize) (flic-and-exps object)))
(define-postoptimize flic-case-block (object)
(for-each (function postoptimize) (flic-case-block-exps object)))
(define-postoptimize flic-if (object)
(postoptimize (flic-if-test-exp object))
(postoptimize (flic-if-then-exp object))
(postoptimize (flic-if-else-exp object)))
(define-postoptimize flic-return-from (object)
(postoptimize (flic-return-from-exp object)))
(define-postoptimize flic-sel (object)
(postoptimize (flic-sel-exp object)))
(define-postoptimize flic-is-constructor (object)
(postoptimize (flic-is-constructor-exp object)))
(define-postoptimize flic-con-number (object)
(postoptimize (flic-con-number-exp object)))
(define-postoptimize flic-void (object)
object)
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