--- /dev/null
+;;; Effects analysis on CPS
+
+;; Copyright (C) 2011, 2012, 2013 Free Software Foundation, Inc.
+
+;;;; This library is free software; you can redistribute it and/or
+;;;; modify it under the terms of the GNU Lesser General Public
+;;;; License as published by the Free Software Foundation; either
+;;;; version 3 of the License, or (at your option) any later version.
+;;;;
+;;;; This library is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;;;; Lesser General Public License for more details.
+;;;;
+;;;; You should have received a copy of the GNU Lesser General Public
+;;;; License along with this library; if not, write to the Free Software
+;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+;;; Commentary:
+;;;
+;;; A helper module to compute the set of effects that an expression
+;;; depends on and causes. This information is useful when writing
+;;; algorithms that move code around, while preserving the semantics of
+;;; an input program.
+;;;
+;;; The effects set is represented by a bitfield, as a fixnum. The set
+;;; of possible effects is modelled rather coarsely. For example, a
+;;; "car" call modelled as depending on the &car effect, and causing a
+;;; &type-check effect. If any intervening code sets the car of any
+;;; pair, that will block motion of the "car" call.
+;;;
+;;; For each effect, two bits are reserved: one to indicate that an
+;;; expression depends on the effect, and the other to indicate that an
+;;; expression causes the effect.
+;;;
+;;; Since we have more bits in a fixnum on 64-bit systems, we can be
+;;; more precise without losing efficiency. On a 32-bit system, some of
+;;; the more precise effects map to fewer bits.
+;;;
+;;; Code:
+
+(define-module (language cps effects-analysis)
+ #:use-module (language cps)
+ #:use-module (language cps dfg)
+ #:use-module (ice-9 match)
+ #:export (expression-effects
+ compute-effects
+
+ &fluid
+ &prompt
+ &definite-bailout
+ &possible-bailout
+ &allocation
+ &car
+ &cdr
+ &vector
+ &box
+ &module
+ &struct
+ &string
+ &bytevector
+ &type-check
+
+ &no-effects
+ &all-effects
+ &all-effects-but-bailout
+
+ effects-commute?
+ exclude-effects
+ effect-free?
+ constant?
+ depends-on-effects?
+ causes-effects?))
+
+(define-syntax define-effects
+ (lambda (x)
+ (syntax-case x ()
+ ((_ all name ...)
+ (with-syntax (((n ...) (iota (length #'(name ...)))))
+ #'(begin
+ (define-syntax name (identifier-syntax (ash 1 (* n 2))))
+ ...
+ (define-syntax all (identifier-syntax (logior name ...)))))))))
+
+(define-syntax compile-time-cond
+ (lambda (x)
+ (syntax-case x (else)
+ ((_ (else body ...))
+ #'(begin body ...))
+ ((_ (exp body ...) clause ...)
+ (if (eval (syntax->datum #'exp) (current-module))
+ #'(begin body ...)
+ #'(compile-time-cond clause ...))))))
+
+;; Here we define the effects, indicating the meaning of the effect.
+;;
+;; Effects that are described in a "depends on" sense can also be used
+;; in the "causes" sense.
+;;
+;; Effects that are described as causing an effect are not usually used
+;; in a "depends-on" sense. Although the "depends-on" sense is used
+;; when checking for the existence of the "causes" effect, the effects
+;; analyzer will not associate the "depends-on" sense of these effects
+;; with any expression.
+;;
+(compile-time-cond
+ ((>= (logcount most-positive-fixnum) 60)
+ (define-effects &all-effects
+ ;; Indicates that an expression depends on the value of a fluid
+ ;; variable.
+ &fluid
+
+ ;; Indicates that an expression depends on the current prompt
+ ;; stack.
+ &prompt
+
+ ;; Indicates that an expression definitely causes a non-local,
+ ;; non-resumable exit -- a bailout. Only used in the "changes" sense.
+ &definite-bailout
+
+ ;; Indicates that an expression may cause a bailout.
+ &possible-bailout
+
+ ;; Indicates that an expression may return a fresh object -- a
+ ;; "causes" effect.
+ &allocation
+
+ ;; Indicates that an expression depends on the value of the car of a
+ ;; pair.
+ &car
+
+ ;; Indicates that an expression depends on the value of the cdr of a
+ ;; pair.
+ &cdr
+
+ ;; Indicates that an expression depends on the value of a vector
+ ;; field. We cannot be more precise, as vectors may alias other
+ ;; vectors.
+ &vector
+
+ ;; Indicates that an expression depends on the value of a variable
+ ;; cell.
+ &box
+
+ ;; Indicates that an expression depends on the current module.
+ &module
+
+ ;; Indicates that an expression depends on the value of a particular
+ ;; struct field.
+ &struct-0 &struct-1 &struct-2 &struct-3 &struct-4 &struct-5 &struct-6+
+
+ ;; Indicates that an expression depends on the contents of a string.
+ &string
+
+ ;; Indicates that an expression depends on the contents of a
+ ;; bytevector. We cannot be more precise, as bytevectors may alias
+ ;; other bytevectors.
+ &bytevector
+
+ ;; Indicates that an expression may cause a type check. A type check,
+ ;; for the purposes of this analysis, is the possibility of throwing
+ ;; an exception the first time an expression is evaluated. If the
+ ;; expression did not cause an exception to be thrown, users can
+ ;; assume that evaluating the expression again will not cause an
+ ;; exception to be thrown.
+ ;;
+ ;; For example, (+ x y) might throw if X or Y are not numbers. But if
+ ;; it doesn't throw, it should be safe to elide a dominated, common
+ ;; subexpression (+ x y).
+ &type-check)
+
+ ;; Indicates that an expression depends on the contents of an unknown
+ ;; struct field.
+ (define-syntax &struct
+ (identifier-syntax
+ (logior &struct-1 &struct-2 &struct-3 &struct-4 &struct-5 &struct-6+))))
+
+ (else
+ ;; For systems with smaller fixnums, be less precise regarding struct
+ ;; fields.
+ (define-effects &all-effects
+ &fluid
+ &prompt
+ &definite-bailout
+ &possible-bailout
+ &allocation
+ &car
+ &cdr
+ &vector
+ &box
+ &module
+ &struct
+ &string
+ &bytevector
+ &type-check)
+ (define-syntax &struct-0 (identifier-syntax &struct))
+ (define-syntax &struct-1 (identifier-syntax &struct))
+ (define-syntax &struct-2 (identifier-syntax &struct))
+ (define-syntax &struct-3 (identifier-syntax &struct))
+ (define-syntax &struct-4 (identifier-syntax &struct))
+ (define-syntax &struct-5 (identifier-syntax &struct))
+ (define-syntax &struct-6+ (identifier-syntax &struct))))
+
+(define-syntax &no-effects (identifier-syntax 0))
+
+;; Definite bailout is an oddball effect. Since it indicates that an
+;; expression definitely causes bailout, it's not in the set of effects
+;; of a call to an unknown procedure. At the same time, it's also
+;; special in that a definite bailout in a subexpression doesn't always
+;; cause an outer expression to include &definite-bailout in its
+;; effects. For that reason we have to treat it specially.
+;;
+(define-syntax &all-effects-but-bailout
+ (identifier-syntax
+ (logand &all-effects (lognot &definite-bailout))))
+
+(define-inlinable (cause effect)
+ (ash effect 1))
+
+(define-inlinable (&depends-on a)
+ (logand a &all-effects))
+(define-inlinable (&causes a)
+ (logand a (cause &all-effects)))
+
+(define (exclude-effects effects exclude)
+ (logand effects (lognot (cause exclude))))
+(define (effect-free? effects)
+ (zero? (&causes effects)))
+(define (constant? effects)
+ (zero? effects))
+
+(define-inlinable (depends-on-effects? x effects)
+ (not (zero? (logand (&depends-on x) effects))))
+(define-inlinable (causes-effects? x effects)
+ (not (zero? (logand (&causes x) (cause effects)))))
+
+(define-inlinable (effects-commute? a b)
+ (and (not (causes-effects? a (&depends-on b)))
+ (not (causes-effects? b (&depends-on a)))))
+
+(define (lookup-constant-index sym dfg)
+ (call-with-values (lambda () (find-constant-value sym dfg))
+ (lambda (has-const? val)
+ (and has-const? (integer? val) (exact? val) (<= 0 val) val))))
+
+(define *primitive-effects* (make-hash-table))
+
+(define-syntax-rule (define-primitive-effects* dfg ((name . args) effects) ...)
+ (begin
+ (hashq-set! *primitive-effects* 'name
+ (case-lambda* ((dfg . args) effects)
+ (_ (logior (cause &possible-bailout)
+ (cause &definite-bailout)))))
+ ...))
+
+(define-syntax-rule (define-primitive-effects ((name . args) effects) ...)
+ (define-primitive-effects* dfg ((name . args) effects) ...))
+
+;; Miscellaneous.
+(define-primitive-effects
+ ((values . _) &no-effects)
+ ((not arg) &no-effects))
+
+;; Generic predicates.
+(define-primitive-effects
+ ((eq? . _) &no-effects)
+ ((eqv? . _) &no-effects)
+ ((equal? . _) &no-effects)
+ ((pair? arg) &no-effects)
+ ((null? arg) &no-effects)
+ ((nil? arg ) &no-effects)
+ ((list? arg) &no-effects)
+ ((symbol? arg) &no-effects)
+ ((variable? arg) &no-effects)
+ ((vector? arg) &no-effects)
+ ((struct? arg) &no-effects)
+ ((string? arg) &no-effects)
+ ((number? arg) &no-effects)
+ ((char? arg) &no-effects)
+ ((procedure? arg) &no-effects)
+ ((thunk? arg) &no-effects))
+
+;; Fluids.
+(define-primitive-effects
+ ((fluid-ref f) (logior (cause &type-check) &fluid))
+ ((fluid-set! f v) (logior (cause &type-check) (cause &fluid)))
+ ((push-fluid f v) (logior (cause &type-check) (cause &fluid)))
+ ((pop-fluid) (logior (cause &fluid))))
+
+;; Prompts.
+(define-primitive-effects
+ ((make-prompt-tag #:optional arg) (cause &allocation)))
+
+;; Bailout.
+(define-primitive-effects
+ ((error . _) (logior (cause &definite-bailout) (cause &possible-bailout)))
+ ((scm-error . _) (logior (cause &definite-bailout) (cause &possible-bailout)))
+ ((throw . _) (logior (cause &definite-bailout) (cause &possible-bailout))))
+
+;; Pairs.
+(define-primitive-effects
+ ((cons a b) (cause &allocation))
+ ((list . _) (cause &allocation))
+ ((car x) (logior (cause &type-check) &car))
+ ((set-car! x y) (logior (cause &type-check) (cause &car)))
+ ((cdr x) (logior (cause &type-check) &cdr))
+ ((set-cdr! x y) (logior (cause &type-check) (cause &cdr)))
+ ((memq x y) (logior (cause &type-check) &car &cdr))
+ ((memv x y) (logior (cause &type-check) &car &cdr))
+ ((length l) (logior (cause &type-check) &car &cdr)))
+
+;; Vectors.
+(define-primitive-effects
+ ((vector . _) (cause &allocation))
+ ((vector-ref v n) (logior (cause &type-check) &vector))
+ ((vector-set! v n x) (logior (cause &type-check) (cause &vector)))
+ ((vector-length v) (cause &type-check)))
+
+;; Variables.
+(define-primitive-effects
+ ((box v) (cause &allocation))
+ ((box-ref v) (logior (cause &type-check) &box))
+ ((box-set! v x) (logior (cause &type-check) (cause &box))))
+
+;; Structs.
+(define-primitive-effects* dfg
+ ((allocate-struct vtable nfields) (logior (cause &type-check)
+ (cause &allocation)))
+ ((make-struct vtable ntail . args) (logior (cause &type-check)
+ (cause &allocation)))
+ ((make-struct/no-tail vtable . args) (logior (cause &type-check)
+ (cause &allocation)))
+ ((struct-ref s n)
+ (logior (cause &type-check)
+ (match (lookup-constant-index n dfg)
+ (#f &struct)
+ (0 &struct-0)
+ (1 &struct-1)
+ (2 &struct-2)
+ (3 &struct-3)
+ (4 &struct-4)
+ (5 &struct-5)
+ (_ &struct-6+))))
+ ((struct-set! s n x)
+ (logior (cause &type-check)
+ (match (lookup-constant-index n dfg)
+ (#f (cause &struct))
+ (0 (cause &struct-0))
+ (1 (cause &struct-1))
+ (2 (cause &struct-2))
+ (3 (cause &struct-3))
+ (4 (cause &struct-4))
+ (5 (cause &struct-5))
+ (_ (cause &struct-6+)))))
+ ((struct-vtable s) (cause &type-check)))
+
+;; Strings.
+(define-primitive-effects
+ ((string-ref s n) (logior (cause &type-check) &string))
+ ((string-set! s n c) (logior (cause &type-check) (cause &string)))
+ ((number->string _) (cause &type-check))
+ ((string->number _) (logior (cause &type-check) &string))
+ ((string-length s) (cause &type-check)))
+
+;; Bytevectors.
+(define-primitive-effects
+ ((bv-u8-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-s8-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-u16-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-s16-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-u32-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-s32-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-u64-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-s64-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-f32-ref bv n) (logior (cause &type-check) &bytevector))
+ ((bv-f64-ref bv n) (logior (cause &type-check) &bytevector))
+
+ ((bv-u8-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-s8-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-u16-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-s16-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-u32-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-s32-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-u64-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-s64-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-f32-set! bv n x) (logior (cause &type-check) (cause &bytevector)))
+ ((bv-f64-set! bv n x) (logior (cause &type-check) (cause &bytevector))))
+
+;; Numbers.
+(define-primitive-effects
+ ((= . _) (cause &type-check))
+ ((< . _) (cause &type-check))
+ ((> . _) (cause &type-check))
+ ((<= . _) (cause &type-check))
+ ((>= . _) (cause &type-check))
+ ((zero? . _) (cause &type-check))
+ ((add . _) (cause &type-check))
+ ((mul . _) (cause &type-check))
+ ((sub . _) (cause &type-check))
+ ((div . _) (cause &type-check))
+ ((sub1 . _) (cause &type-check))
+ ((add1 . _) (cause &type-check))
+ ((quo . _) (cause &type-check))
+ ((rem . _) (cause &type-check))
+ ((mod . _) (cause &type-check))
+ ((complex? _) (cause &type-check))
+ ((real? _) (cause &type-check))
+ ((rational? _) (cause &type-check))
+ ((inf? _) (cause &type-check))
+ ((nan? _) (cause &type-check))
+ ((integer? _) (cause &type-check))
+ ((exact? _) (cause &type-check))
+ ((inexact? _) (cause &type-check))
+ ((even? _) (cause &type-check))
+ ((odd? _) (cause &type-check))
+ ((ash n m) (cause &type-check))
+ ((logand . _) (cause &type-check))
+ ((logior . _) (cause &type-check))
+ ((logior . _) (cause &type-check))
+ ((lognot . _) (cause &type-check)))
+
+;; Characters.
+(define-primitive-effects
+ ((char<? . _) (cause &type-check))
+ ((char<=? . _) (cause &type-check))
+ ((char>=? . _) (cause &type-check))
+ ((char>? . _) (cause &type-check))
+ ((integer->char _) (cause &type-check))
+ ((char->integer _) (cause &type-check)))
+
+;; Modules.
+(define-primitive-effects
+ ((current-module) &module)
+ ((cache-current-module! mod scope) (cause &box))
+ ((resolve name bound?) (logior &box &module (cause &type-check)))
+ ((cached-toplevel-box scope name bound?) (logior &box (cause &type-check)))
+ ((cached-module-box scope name bound?) (logior &box (cause &type-check)))
+ ((define! name val) (logior &module (cause &box))))
+
+(define (primitive-effects dfg name args)
+ (let ((proc (hashq-ref *primitive-effects* name)))
+ (if proc
+ (apply proc dfg args)
+ (logior &all-effects-but-bailout (cause &all-effects-but-bailout)))))
+
+(define (expression-effects exp dfg)
+ (match exp
+ ((or ($ $void) ($ $const) ($ $prim) ($ $values))
+ &no-effects)
+ (($ $fun)
+ (cause &allocation))
+ (($ $prompt)
+ (cause &prompt))
+ (($ $call)
+ (logior &all-effects-but-bailout (cause &all-effects-but-bailout)))
+ (($ $primcall name args)
+ (primitive-effects dfg name args))))
+
+(define (compute-effects cfa dfg)
+ (let ((effects (make-vector (cfa-k-count cfa) &no-effects)))
+ (let lp ((n 0))
+ (when (< n (vector-length effects))
+ (vector-set!
+ effects
+ n
+ (match (lookup-cont (cfa-k-sym cfa n) (dfg-cont-table dfg))
+ (($ $kargs names syms body)
+ (expression-effects (find-expression body) dfg))
+ (($ $ktrunc arity kargs)
+ (match arity
+ (($ $arity _ () #f () #f) (cause &type-check))
+ (($ $arity () () _ () #f) (cause &allocation))
+ (($ $arity _ () _ () #f) (logior (cause &allocation)
+ (cause &type-check)))))
+ (($ $kif) &no-effects)
+ (($ $kentry) &type-check)
+ (($ $kclause) &type-check)
+ (($ $ktail) &no-effects)))
+ (lp (1+ n))))
+ effects))
HCoop / bpt / guile.git / commitdiff