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;;; Continuation-passing style (CPS) intermediate language (IL)
;; Copyright (C) 2015-2020 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:
;;;
;;; Some arithmetic operations have multiple implementations: one
;;; polymorphic implementation that works on all kinds of numbers, like
;;; `add', and one or more specialized variants for unboxed numbers of
;;; some kind, like `fadd'. If we can replace a polymorphic
;;; implementation with a monomorphic implementation, we should do so --
;;; it will speed up the runtime and avoid boxing numbers.
;;;
;;; A polymorphic operation can be specialized if its result is
;;; specialized. To specialize an operation, we manually unbox its
;;; arguments and box its return value, relying on CSE to remove boxes
;;; where possible.
;;;
;;; We also want to specialize phi variables. A phi variable is bound
;;; by a continuation with more than one predecessor. For example in
;;; this code:
;;;
;;; (+ 1.0 (if a 2.0 3.0))
;;;
;;; We want to specialize this code to:
;;;
;;; (f64->scm (fl+ (scm->f64 1.0) (if a (scm->f64 2.0) (scm->f64 3.0))))
;;;
;;; Hopefully later passes will remove the conversions. In any case,
;;; specialization will likely result in a lower heap-number allocation
;;; rate, and that cost is higher than the extra opcodes to do
;;; conversions. This transformation is especially important for loop
;;; variables.
;;;
;;; Code:
(define-module (language cps specialize-numbers)
#:use-module (ice-9 match)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-11)
#:use-module (system base target)
#:use-module (language cps)
#:use-module (language cps intmap)
#:use-module (language cps intset)
#:use-module (language cps renumber)
#:use-module (language cps types)
#:use-module (language cps utils)
#:use-module (language cps with-cps)
#:export (specialize-numbers))
;; A note on how to represent unboxing and boxing operations. We want
;; to avoid diamond control flows here, like:
;;
;; s64 x = (if (fixnum? x*) (untag-fixnum x*) (untag-bignum x*))
;;
;; The reason is that the strategy that this specialize-numbers pass
;; uses to unbox values is to reify unboxing and boxing conversions
;; around every newly reified unboxed operation; it then relies heavily
;; on DCE and CSE to remove redundant conversions. However DCE and CSE
;; really work best when there's a linear control flow, so instead we
;; use a mid-level primcall:
;;
;; (define (scm->s64 x*)
;; (if (fixnum? x*) (untag-fixnum x*) (untag-bignum x*)))
;;
;; Then, unless we know that we can reduce directly to `untag-fixnum`,
;; we do:
;;
;; s64 x = (scm->s64 x*)
;;
;; That way we keep DCE and CSE happy. We can inline scm->s64 at the
;; backend if we choose to (though we might choose to not do so, for
;; code size reasons).
(define (simple-primcall cps k src op arg)
(with-cps cps
(build-term
($continue k src
($primcall op #f (arg))))))
(define-syntax-rule (define-simple-primcall name)
(define (name cps k src arg) (simple-primcall cps k src 'name arg)))
(define-simple-primcall untag-fixnum)
(define-simple-primcall scm->s64)
(define-simple-primcall tag-fixnum)
(define-simple-primcall s64->scm)
(define-simple-primcall tag-fixnum/unlikely)
(define-simple-primcall s64->scm/unlikely)
(define (fixnum->u64 cps k src fx)
(with-cps cps
(letv s64)
(letk kcvt ($kargs ('s64) (s64)
($continue k src ($primcall 's64->u64 #f (s64)))))
($ (untag-fixnum kcvt src fx))))
(define (u64->fixnum cps k src u64)
(with-cps cps
(letv s64)
(let$ tag-body (tag-fixnum k src s64))
(letk ks64 ($kargs ('s64) (s64) ,tag-body))
(build-term
($continue ks64 src ($primcall 'u64->s64 #f (u64))))))
(define-simple-primcall scm->u64)
(define-simple-primcall u64->scm)
(define-simple-primcall u64->scm/unlikely)
(define-simple-primcall scm->f64)
(define-simple-primcall f64->scm)
(define (fixnum->f64 cps k src fx)
(with-cps cps
(letv s64)
(letk kcvt ($kargs ('s64) (s64)
($continue k src ($primcall 's64->f64 #f (s64)))))
($ (untag-fixnum kcvt src fx))))
(define (specialize-unop cps k src op param a unbox-a box-result)
(with-cps cps
(letv a* result)
(let$ box-result-body (box-result k src result))
(letk kbox ($kargs ('result) (result) ,box-result-body))
(letk kop ($kargs ('a) (a*)
($continue kbox src ($primcall op param (a*)))))
($ (unbox-a kop src a))))
(define* (specialize-binop cps k src op a b
unbox-a unbox-b box-result)
(with-cps cps
(letv a* b* result)
(let$ box-result-body (box-result k src result))
(letk kbox ($kargs ('result) (result) ,box-result-body))
(letk kop ($kargs ('b) (b*)
($continue kbox src ($primcall op #f (a* b*)))))
(let$ unbox-b-body (unbox-b kop src b))
(letk kunbox-b ($kargs ('a) (a*) ,unbox-b-body))
($ (unbox-a kunbox-b src a))))
(define (specialize-comparison cps kf kt src op a b unbox-a unbox-b)
(with-cps cps
(letv a* b*)
(letk kop ($kargs ('b) (b*) ($branch kf kt src op #f (a* b*))))
(let$ unbox-b-body (unbox-b kop src b))
(letk kunbox-b ($kargs ('a) (a*) ,unbox-b-body))
($ (unbox-a kunbox-b src a))))
(define* (specialize-comparison/immediate cps kf kt src op a imm
unbox-a)
(with-cps cps
(letv ia)
(letk kop ($kargs ('ia) (ia) ($branch kf kt src op imm (ia))))
($ (unbox-a kop src a))))
(define (specialize-comparison/s64-integer cps kf kt src op a-s64 b-int
unbox-a rebox-a)
(let ((s64-op (match op ('= 's64-=) ('< 's64-<))))
(with-cps cps
(letv a b sunk)
(letk kheap ($kargs ('sunk) (sunk)
($branch kf kt src op #f (sunk b-int))))
;; Re-box the variable. FIXME: currently we use a specially
;; marked s64->scm to avoid CSE from hoisting the allocation
;; again. Instead we should just use a-s64 directly and implement
;; an allocation sinking pass that should handle this..
(let$ rebox-a-body (rebox-a kheap src a))
(letk kretag ($kargs () () ,rebox-a-body))
(letk kb ($kargs ('b) (b) ($branch kf kt src s64-op #f (a b))))
(letk kfix ($kargs () ()
($continue kb src
($primcall 'untag-fixnum #f (b-int)))))
(letk ka ($kargs ('a) (a)
($branch kretag kfix src 'fixnum? #f (b-int))))
($ (unbox-a ka src a-s64)))))
(define (specialize-comparison/integer-s64 cps kf kt src op a-int b-s64
unbox-b rebox-b)
(match op
('= (specialize-comparison/s64-integer cps kf kt src op b-s64 a-int
unbox-b rebox-b))
('<
(with-cps cps
(letv a b sunk)
(letk kheap ($kargs ('sunk) (sunk)
($branch kf kt src '< #f (a-int sunk))))
;; FIXME: We should just use b-s64 directly and implement an
;; allocation sinking pass so that the box op that creates b-64
;; should float down here. Instead, for now we just rebox the
;; variable, relying on the reboxing op not being available for
;; CSE.
(let$ rebox-b-body (rebox-b kheap src b))
(letk kretag ($kargs () () ,rebox-b-body))
(letk ka ($kargs ('a) (a) ($branch kf kt src 's64-< #f (a b))))
(letk kfix ($kargs () ()
($continue ka src
($primcall 'untag-fixnum #f (a-int)))))
(letk kb ($kargs ('b) (b)
($branch kretag kfix src 'fixnum? #f (a-int))))
($ (unbox-b kb src b-s64))))))
(define (specialize-comparison/immediate-s64-integer cps kf kt src op a b-int
compare-integers)
(with-cps cps
(letv b sunk)
(letk kheap ($kargs ('sunk) (sunk) ,(compare-integers kf kt src sunk)))
;; Re-box the variable. FIXME: currently we use a specially marked
;; load-const to avoid CSE from hoisting the constant. Instead we
;; should just use a $const directly and implement an allocation
;; sinking pass that should handle this..
(letk kretag ($kargs () ()
($continue kheap src
($primcall 'load-const/unlikely a ()))))
(letk kb ($kargs ('b) (b)
($branch kf kt src op a (b))))
(letk kfix ($kargs () ()
($continue kb src
($primcall 'untag-fixnum #f (b-int)))))
(build-term ($branch kretag kfix src 'fixnum? #f (b-int)))))
;; compute-significant-bits solves a flow equation to compute a
;; least-fixed-point over the lattice VAR -> BITMASK, where X > Y if
;; X[VAR] > Y[VAR] for any VAR. Adjoining VAR -> BITMASK to X results
;; in a distinct value X' (in the sense of eq?) if and only if X' > X.
;; This property is used in compute-significant-bits to know when to
;; stop iterating, and is ensured by intmaps, provided that the `meet'
;; function passed to `intmap-add' and so on also preserves this
;; property.
;;
;; The meet function for adding bits is `sigbits-union'; the first
;; argument is the existing value, and the second is the bitmask to
;; adjoin. For fixnums, BITMASK' will indeed be distinct if and only if
;; bits were added. However for bignums it's possible that (= X' X) but
;; not (eq? X' X). This preserve-eq? helper does the impedance matching
;; for bignums, returning the first value if the values are =.
(define (preserve-eq? x x*)
(if (= x x*)
x
x*))
(define (sigbits-union x y)
(and x y
(preserve-eq? x (logior x y))))
(define (sigbits-intersect x y)
(cond
((not x) y)
((not y) x)
(else (logand x y))))
(define (sigbits-intersect3 a b c)
(sigbits-intersect a (sigbits-intersect b c)))
(define (next-power-of-two n)
(let lp ((out 1))
(if (< n out)
out
(lp (ash out 1)))))
(define (range->sigbits min max)
(cond
((or (< min 0) (> max #xffffFFFFffffFFFF)) #f)
((eqv? min max) min)
(else (1- (next-power-of-two max)))))
(define (inferred-sigbits types label var)
(call-with-values (lambda () (lookup-pre-type types label var))
(lambda (type min max)
(and (type<=? type (logior &exact-integer &u64 &s64))
(range->sigbits min max)))))
(define significant-bits-handlers (make-hash-table))
(define-syntax-rule (define-significant-bits-handler
((primop label types out def ...) arg ...)
body ...)
(hashq-set! significant-bits-handlers 'primop
(lambda (label types out param args defs)
(match args ((arg ...) (match defs ((def ...) body ...)))))))
(define-significant-bits-handler ((logand label types out res) a b)
(let ((sigbits (sigbits-intersect3 (inferred-sigbits types label a)
(inferred-sigbits types label b)
(intmap-ref out res (lambda (_) 0)))))
(intmap-add (intmap-add out a sigbits sigbits-union)
b sigbits sigbits-union)))
(define (significant-bits-handler primop)
(hashq-ref significant-bits-handlers primop))
(define (compute-significant-bits cps types kfun)
"Given the locally inferred types @var{types}, compute a map of VAR ->
BITS indicating the significant bits needed for a variable. BITS may be
#f to indicate all bits, or a non-negative integer indicating a bitmask."
(let ((preds (invert-graph (compute-successors cps kfun))))
(let lp ((worklist (intmap-keys preds)) (visited empty-intset)
(out empty-intmap))
(match (intset-prev worklist)
(#f out)
(label
(let ((worklist (intset-remove worklist label))
(visited* (intset-add visited label)))
(define (continue out*)
(if (and (eq? out out*) (eq? visited visited*))
(lp worklist visited out)
(lp (intset-union worklist (intmap-ref preds label))
visited* out*)))
(define (add-def out var)
(intmap-add out var 0 sigbits-union))
(define (add-defs out vars)
(match vars
(() out)
((var . vars) (add-defs (add-def out var) vars))))
(define (add-unknown-use out var)
(intmap-add out var (inferred-sigbits types label var)
sigbits-union))
(define (add-unknown-uses out vars)
(match vars
(() out)
((var . vars)
(add-unknown-uses (add-unknown-use out var) vars))))
(continue
(match (intmap-ref cps label)
(($ $kfun src meta self)
(if self (add-def out self) out))
(($ $kargs names vars term)
(let ((out (add-defs out vars)))
(match term
(($ $continue k src exp)
(match exp
((or ($ $const) ($ $prim) ($ $fun) ($ $const-fun)
($ $code) ($ $rec))
;; No uses, so no info added to sigbits.
out)
(($ $values args)
(match (intmap-ref cps k)
(($ $kargs _ vars)
(if (intset-ref visited k)
(fold (lambda (arg var out)
(intmap-add out arg (intmap-ref out var)
sigbits-union))
out args vars)
out))
(($ $ktail)
(add-unknown-uses out args))))
(($ $call proc args)
(add-unknown-use (add-unknown-uses out args) proc))
(($ $callk label proc args)
(let ((out (add-unknown-uses out args)))
(if proc
(add-unknown-use out proc)
out)))
(($ $primcall name param args)
(let ((h (significant-bits-handler name)))
(if h
(match (intmap-ref cps k)
(($ $kargs _ defs)
(h label types out param args defs)))
(add-unknown-uses out args))))))
(($ $branch kf kt src op param args)
(add-unknown-uses out args))
(($ $switch kf kt src arg)
(add-unknown-use out arg))
(($ $prompt k kh src escape? tag)
(add-unknown-use out tag))
(($ $throw src op param args)
(add-unknown-uses out args)))))
(_ out)))))))))
(define (specialize-operations cps)
(define (u6-parameter? param)
(<= 0 param 63))
(define (s64-parameter? param)
(<= (ash -1 63) param (1- (ash 1 63))))
(define (u64-parameter? param)
(<= 0 param (1- (ash 1 64))))
(define (visit-cont label cont cps types sigbits)
(define (operand-in-range? var &type &min &max)
(call-with-values (lambda ()
(lookup-pre-type types label var))
(lambda (type min max)
(and (type<=? type &type) (<= &min min max &max)))))
(define (u64-operand? var)
(operand-in-range? var &exact-integer 0 (1- (ash 1 64))))
(define (u6-operand? var)
;; This predicate is only used for the "count" argument to
;; rsh/lsh, which is already unboxed to &u64.
(operand-in-range? var &u64 0 63))
(define (s64-operand? var)
(operand-in-range? var &exact-integer (ash -1 63) (1- (ash 1 63))))
(define (fixnum-operand? var)
(operand-in-range? var &exact-integer
(target-most-negative-fixnum)
(target-most-positive-fixnum)))
(define (exact-integer-operand? var)
(operand-in-range? var &exact-integer -inf.0 +inf.0))
(define (all-u64-bits-set? var)
(operand-in-range? var &exact-integer (1- (ash 1 64)) (1- (ash 1 64))))
(define (only-fixnum-bits-used? var)
(let ((bits (intmap-ref sigbits var)))
(and bits (= bits (logand bits (target-most-positive-fixnum))))))
(define (fixnum-result? result)
(or (only-fixnum-bits-used? result)
(call-with-values
(lambda ()
(lookup-post-type types label result 0))
(lambda (type min max)
(and (type<=? type &exact-integer)
(<= (target-most-negative-fixnum)
min max
(target-most-positive-fixnum)))))))
(define (only-u64-bits-used? var)
(let ((bits (intmap-ref sigbits var)))
(and bits (= bits (logand bits (1- (ash 1 64)))))))
(define (u64-result? result)
(or (only-u64-bits-used? result)
(call-with-values
(lambda ()
(lookup-post-type types label result 0))
(lambda (type min max)
(and (type<=? type &exact-integer)
(<= 0 min max (1- (ash 1 64))))))))
(define (s64-result? result)
(call-with-values
(lambda ()
(lookup-post-type types label result 0))
(lambda (type min max)
(and (type<=? type &exact-integer)
(<= (ash -1 63) min max (1- (ash 1 63)))))))
(define (f64-result? result)
(call-with-values
(lambda ()
(lookup-post-type types label result 0))
(lambda (type min max)
(eqv? type &flonum))))
(define (f64-operands? vara varb)
(let-values (((typea mina maxa) (lookup-pre-type types label vara))
((typeb minb maxb) (lookup-pre-type types label varb)))
(and (type<=? (logior typea typeb) &real)
(or (eqv? typea &flonum)
(eqv? typeb &flonum)))))
(define (constant-arg arg)
(let-values (((type min max) (lookup-pre-type types label arg)))
(and (= min max) min)))
(define (fixnum-range? min max)
(<= (target-most-negative-fixnum) min max (target-most-positive-fixnum)))
(define (unbox-u64 arg)
(if (fixnum-operand? arg) fixnum->u64 scm->u64))
(define (unbox-s64 arg)
(if (fixnum-operand? arg) untag-fixnum scm->s64))
(define (rebox-s64 arg)
(if (fixnum-operand? arg) tag-fixnum/unlikely s64->scm/unlikely))
(define (unbox-f64 arg)
;; Could be more precise here.
(if (fixnum-operand? arg) fixnum->f64 scm->f64))
(define (box-s64 result)
(if (fixnum-result? result) tag-fixnum s64->scm))
(define (box-u64 result)
(if (fixnum-result? result) u64->fixnum u64->scm))
(define (box-f64 result)
f64->scm)
(define (specialize-primcall cps k src op param args)
(match (intmap-ref cps k)
(($ $kargs (_) (result))
(match (cons* op result param args)
(((or 'add 'sub 'mul 'div 'atan2)
(? f64-result?) #f a b)
(let ((op (match op
('add 'fadd) ('sub 'fsub) ('mul 'fmul) ('div 'fdiv)
('atan2 'fatan2))))
(specialize-binop cps k src op a b
(unbox-f64 a) (unbox-f64 b) (box-f64 result))))
(((or 'sqrt 'abs 'floor 'ceiling 'sin 'cos 'tan 'asin 'acos 'atan)
(? f64-result?) #f a)
(let ((op (match op
('sqrt 'fsqrt) ('abs 'fabs)
('floor 'ffloor) ('ceiling 'fceiling)
('sin 'fsin) ('cos 'fcos) ('tan 'ftan)
('asin 'fasin) ('acos 'facos) ('atan 'fatan))))
(specialize-unop cps k src op #f a
(unbox-f64 a) (box-f64 result))))
(((or 'add 'sub 'mul 'logand 'logior 'logxor 'logsub)
(? u64-result?) #f (? u64-operand? a) (? u64-operand? b))
(let ((op (match op
('add 'uadd) ('sub 'usub) ('mul 'umul)
('logand 'ulogand) ('logior 'ulogior)
('logxor 'ulogxor) ('logsub 'ulogsub))))
(specialize-binop cps k src op a b
(unbox-u64 a) (unbox-u64 b) (box-u64 result))))
(((or 'logand 'logior 'logxor 'logsub)
(? u64-result?) #f (? s64-operand? a) (? s64-operand? b))
(let ((op (match op
('logand 'ulogand) ('logior 'ulogior)
('logxor 'ulogxor) ('logsub 'ulogsub))))
(define (unbox-u64* x)
(let ((unbox-s64 (unbox-s64 x)))
(lambda (cps k src x)
(with-cps cps
(letv s64)
(letk ks64 ($kargs ('s64) (s64)
($continue k src
($primcall 's64->u64 #f (s64)))))
($ (unbox-s64 k src x))))))
(specialize-binop cps k src op a b
(unbox-u64* a) (unbox-u64* b) (box-u64 result))))
(((or 'add 'sub 'mul)
(? s64-result?) #f (? s64-operand? a) (? s64-operand? b))
(let ((op (match op
('add 'sadd) ('sub 'ssub) ('mul 'smul))))
(specialize-binop cps k src op a b
(unbox-s64 a) (unbox-s64 b) (box-s64 result))))
(('sub/immediate
(? f64-result?) param a)
(specialize-unop cps k src 'fadd/immediate (- param) a
(unbox-f64 a) (box-f64 result)))
(((or 'add/immediate 'mul/immediate)
(? f64-result?) param a)
(let ((op (match op
('add/immediate 'fadd/immediate)
('mul/immediate 'fmul/immediate))))
(specialize-unop cps k src op param a
(unbox-f64 a) (box-f64 result))))
(((or 'add/immediate 'sub/immediate 'mul/immediate)
(? u64-result?) (? u64-parameter?) (? u64-operand? a))
(let ((op (match op
('add/immediate 'uadd/immediate)
('sub/immediate 'usub/immediate)
('mul/immediate 'umul/immediate))))
(specialize-unop cps k src op param a
(unbox-u64 a) (box-u64 result))))
(((or 'add/immediate 'sub/immediate 'mul/immediate)
(? s64-result?) (? s64-parameter?) (? s64-operand? a))
(let ((op (match op
('add/immediate 'sadd/immediate)
('sub/immediate 'ssub/immediate)
('mul/immediate 'smul/immediate))))
(specialize-unop cps k src op param a
(unbox-s64 a) (box-s64 result))))
(((or 'lsh 'rsh)
(? u64-result?) #f (? u64-operand? a) (? u6-operand? b))
(let ((op (match op ('lsh 'ulsh) ('rsh 'ursh))))
(define (pass-u64 cps k src b)
(with-cps cps
(build-term ($continue k src ($values (b))))))
(specialize-binop cps k src op a b
(unbox-u64 a) pass-u64 (box-u64 result))))
(((or 'lsh 'rsh)
(? s64-result?) #f (? s64-operand? a) (? u6-operand? b))
(let ((op (match op ('lsh 'slsh) ('rsh 'srsh))))
(define (pass-u64 cps k src b)
(with-cps cps
(build-term ($continue k src ($values (b))))))
(specialize-binop cps k src op a b
(unbox-s64 a) pass-u64 (box-s64 result))))
(((or 'lsh/immediate 'rsh/immediate)
(? u64-result?) (? u6-parameter?) (? u64-operand? a))
(let ((op (match op
('lsh/immediate 'ulsh/immediate)
('rsh/immediate 'ursh/immediate))))
(specialize-unop cps k src op param a
(unbox-u64 a) (box-u64 result))))
(((or 'lsh/immediate 'rsh/immediate)
(? s64-result?) (? u6-parameter?) (? s64-operand? a))
(let ((op (match op
('lsh/immediate 'slsh/immediate)
('rsh/immediate 'srsh/immediate))))
(specialize-unop cps k src op param a
(unbox-s64 a) (box-s64 result))))
(_ (with-cps cps #f))))
(_ (with-cps cps #f))))
(define (specialize-branch cps kf kt src op param args)
(match (cons op args)
(('<= a b)
(cond
((f64-operands? a b)
(specialize-comparison cps kf kt src 'f64-<= a b
(unbox-f64 a) (unbox-f64 b)))
((and (exact-integer-operand? a) (exact-integer-operand? b))
;; If NaN is impossible, reduce (<= a b) to (not (< b a)) and
;; try again.
(specialize-branch cps kt kf src '< param (list b a)))
(else
(with-cps cps #f))))
(((or '< '=) a b)
(cond
((f64-operands? a b)
(let ((op (match op ('= 'f64-=) ('< 'f64-<))))
(specialize-comparison cps kf kt src op a b
(unbox-f64 a) (unbox-f64 b))))
((and (s64-operand? a) (s64-operand? b))
(cond
((constant-arg a)
=> (lambda (a)
(let ((op (match op ('= 's64-imm-=) ('< 'imm-s64-<))))
(specialize-comparison/immediate cps kf kt src op b a
(unbox-s64 b)))))
((constant-arg b)
=> (lambda (b)
(let ((op (match op ('= 's64-imm-=) ('< 's64-imm-<))))
(specialize-comparison/immediate cps kf kt src op a b
(unbox-s64 a)))))
(else
(let ((op (match op ('= 's64-=) ('< 's64-<))))
(specialize-comparison cps kf kt src op a b
(unbox-s64 a) (unbox-s64 b))))))
((and (u64-operand? a) (u64-operand? b))
(cond
((constant-arg a)
=> (lambda (a)
(let ((op (match op ('= 'u64-imm-=) ('< 'imm-u64-<))))
(specialize-comparison/immediate cps kf kt src op b a
(unbox-u64 b)))))
((constant-arg b)
=> (lambda (b)
(let ((op (match op ('= 'u64-imm-=) ('< 'u64-imm-<))))
(specialize-comparison/immediate cps kf kt src op a b
(unbox-u64 a)))))
(else
(let ((op (match op ('= 'u64-=) ('< 'u64-<))))
(specialize-comparison cps kf kt src op a b
(unbox-u64 a) (unbox-u64 b))))))
((and (exact-integer-operand? a) (exact-integer-operand? b))
(cond
((s64-operand? a)
(cond
((constant-arg a)
=> (lambda (a)
(let ((imm-op (match op ('= 's64-imm-=) ('< 'imm-s64-<))))
(specialize-comparison/immediate-s64-integer
cps kf kt src imm-op a b
(lambda (kf kt src a)
(build-term ($branch kf kt src op #f (a b))))))))
(else
(specialize-comparison/s64-integer cps kf kt src op a b
(unbox-s64 a)
(rebox-s64 a)))))
((s64-operand? b)
(cond
((constant-arg b)
=> (lambda (b)
(let ((imm-op (match op ('= 's64-imm-=) ('< 's64-imm-<))))
(specialize-comparison/immediate-s64-integer
cps kf kt src imm-op b a
(lambda (kf kt src b)
(build-term ($branch kf kt src op #f (a b))))))))
(else
(specialize-comparison/integer-s64 cps kf kt src op a b
(unbox-s64 b)
(rebox-s64 b)))))
(else (with-cps cps #f))))
(else (with-cps cps #f))))
(_ (with-cps cps #f))))
(match cont
(($ $kfun)
(let* ((types (infer-types cps label))
(sigbits (compute-significant-bits cps types label)))
(values cps types sigbits)))
(($ $kargs names vars ($ $continue k src ($ $primcall op param args)))
(call-with-values
(lambda () (specialize-primcall cps k src op param args))
(lambda (cps term)
(values (if term
(with-cps cps
(setk label ($kargs names vars ,term)))
cps)
types sigbits))))
(($ $kargs names vars ($ $branch kf kt src op param args))
(call-with-values
(lambda () (specialize-branch cps kf kt src op param args))
(lambda (cps term)
(values (if term
(with-cps cps
(setk label ($kargs names vars ,term)))
cps)
types sigbits))))
(_ (values cps types sigbits))))
(values (intmap-fold visit-cont cps cps #f #f)))
;; Compute a map from VAR -> LABEL, where LABEL indicates the cont that
;; binds VAR.
(define (compute-defs conts labels)
(intset-fold
(lambda (label defs)
(match (intmap-ref conts label)
(($ $kfun src meta self tail clause)
(if self (intmap-add defs self label) defs))
(($ $kargs names vars)
(fold1 (lambda (var defs)
(intmap-add defs var label))
vars defs))
(_ defs)))
labels empty-intmap))
;; Compute vars whose definitions are all unboxable and whose uses
;; include an unbox operation.
(define (compute-specializable-vars cps body preds defs
exp-result-unboxable?
unbox-ops)
;; Compute a map of VAR->LABEL... indicating the set of labels that
;; define VAR with unboxable values, given the set of vars
;; UNBOXABLE-VARS which is known already to be unboxable.
(define (collect-unboxable-def-labels unboxable-vars)
(define (add-unboxable-def unboxable-defs var label)
(intmap-add unboxable-defs var (intset label) intset-union))
(intset-fold (lambda (label unboxable-defs)
(match (intmap-ref cps label)
(($ $kargs _ _ ($ $continue k _ exp))
(match exp
((? exp-result-unboxable?)
(match (intmap-ref cps k)
(($ $kargs (_) (def))
(add-unboxable-def unboxable-defs def label))))
(($ $values vars)
(match (intmap-ref cps k)
(($ $kargs _ defs)
(fold
(lambda (var def unboxable-defs)
(if (intset-ref unboxable-vars var)
(add-unboxable-def unboxable-defs def label)
unboxable-defs))
unboxable-defs vars defs))
;; Could be $ktail for $values.
(_ unboxable-defs)))
(_ unboxable-defs)))
(_ unboxable-defs)))
body empty-intmap))
;; Compute the set of vars which are always unboxable.
(define (compute-unboxable-defs)
(fixpoint
(lambda (unboxable-vars)
(intmap-fold
(lambda (def unboxable-pred-labels unboxable-vars)
(if (and (not (intset-ref unboxable-vars def))
;; Are all defining expressions unboxable?
(and-map (lambda (pred)
(intset-ref unboxable-pred-labels pred))
(intmap-ref preds (intmap-ref defs def))))
(intset-add unboxable-vars def)
unboxable-vars))
(collect-unboxable-def-labels unboxable-vars)
unboxable-vars))
empty-intset))
;; Compute the set of vars that may ever be unboxed.
(define (compute-unbox-uses unboxable-defs)
(intset-fold
(lambda (label unbox-uses)
(match (intmap-ref cps label)
(($ $kargs _ _ ($ $continue k _ exp))
(match exp
(($ $primcall (? (lambda (op) (memq op unbox-ops))) #f (var))
(intset-add unbox-uses var))
(($ $values vars)
(match (intmap-ref cps k)
(($ $kargs _ defs)
(fold (lambda (var def unbox-uses)
(if (intset-ref unboxable-defs def)
(intset-add unbox-uses var)
unbox-uses))
unbox-uses vars defs))
(($ $ktail)
;; Assume return is rare and that any unboxable def can
;; be reboxed when leaving the procedure.
(fold (lambda (var unbox-uses)
(intset-add unbox-uses var))
unbox-uses vars))))
(_ unbox-uses)))
(_ unbox-uses)))
body empty-intset))
(let ((unboxable-defs (compute-unboxable-defs)))
(intset-intersect unboxable-defs (compute-unbox-uses unboxable-defs))))
;; Compute vars whose definitions are all inexact reals and whose uses
;; include an unbox operation.
(define (compute-specializable-f64-vars cps body preds defs)
;; Can the result of EXP definitely be unboxed as an f64?
(define (exp-result-f64? exp)
(match exp
((or ($ $primcall 'f64->scm #f (_))
($ $const (and (? number?) (? inexact?) (? real?))))
#t)
(_ #f)))
(compute-specializable-vars cps body preds defs exp-result-f64? '(scm->f64)))
;; Compute vars whose definitions are all exact integers in the u64
;; range and whose uses include an unbox operation.
(define (compute-specializable-u64-vars cps body preds defs)
;; Can the result of EXP definitely be unboxed as a u64?
(define (exp-result-u64? exp)
(define (u64? n)
(and (number? n) (exact-integer? n)
(<= 0 n #xffffffffffffffff)))
(match exp
((or ($ $primcall 'u64->scm #f (_))
($ $primcall 'u64->scm/unlikely #f (_))
($ $primcall 'load-const/unlikely (? u64?) ())
($ $const (? u64?)))
#t)
(_ #f)))
(compute-specializable-vars cps body preds defs exp-result-u64?
'(scm->u64 'scm->u64/truncate)))
;; Compute vars whose definitions are all exact integers in the fixnum
;; range and whose uses include an untag operation.
(define (compute-specializable-fixnum-vars cps body preds defs)
;; Is the result of EXP definitely a fixnum?
(define (exp-result-fixnum? exp)
(define (fixnum? n)
(and (number? n) (exact-integer? n)
(<= (target-most-negative-fixnum)
n
(target-most-positive-fixnum))))
(match exp
((or ($ $primcall 'tag-fixnum #f (_))
($ $primcall 'tag-fixnum/unlikely #f (_))
($ $const (? fixnum?))
($ $primcall 'load-const/unlikely (? fixnum?) ()))
#t)
(_ #f)))
(compute-specializable-vars cps body preds defs exp-result-fixnum?
'(untag-fixnum)))
;; Compute vars whose definitions are all exact integers in the s64
;; range and whose uses include an untag operation.
(define (compute-specializable-s64-vars cps body preds defs)
;; Is the result of EXP definitely a fixnum?
(define (exp-result-fixnum? exp)
(define (s64? n)
(and (number? n) (exact-integer? n)
(<= (ash -1 63) n (1- (ash 1 63)))))
(match exp
((or ($ $primcall 's64->scm #f (_))
($ $const (? s64?))
($ $primcall 'load-const/unlikely (? s64?) ()))
#t)
(_ #f)))
(compute-specializable-vars cps body preds defs exp-result-fixnum?
'(scm->s64)))
(define (compute-phi-vars cps preds)
(intmap-fold (lambda (label preds phis)
(match preds
(() phis)
((_) phis)
(_
(match (intmap-ref cps label)
(($ $kargs names vars)
(fold1 (lambda (var phis)
(intset-add phis var))
vars phis))
(_ phis)))))
preds empty-intset))
;; Compute the set of variables which have more than one definition,
;; whose definitions are always f64-valued or u64-valued, and which have
;; at least one use that is an unbox operation.
(define (compute-specializable-phis cps body preds defs)
(let ((phi-vars (compute-phi-vars cps preds)))
(fold1 (lambda (in out)
(match in
((kind vars)
(intset-fold
(lambda (var out)
(intmap-add out var kind (lambda (old new) old)))
(intset-intersect phi-vars vars)
out))))
`((f64 ,(compute-specializable-f64-vars cps body preds defs))
(fx ,(compute-specializable-fixnum-vars cps body preds defs))
(s64 ,(compute-specializable-s64-vars cps body preds defs))
(u64 ,(compute-specializable-u64-vars cps body preds defs)))
empty-intmap)))
;; Each definition of a f64/u64 variable should unbox that variable.
;; The cont that binds the variable should re-box it under its original
;; name, and rely on CSE to remove the boxing as appropriate.
(define (apply-specialization cps kfun body preds defs phis)
(define (compute-unbox-labels)
(intmap-fold (lambda (phi kind labels)
(fold1 (lambda (pred labels)
(intset-add labels pred))
(intmap-ref preds (intmap-ref defs phi))
labels))
phis empty-intset))
(define (unbox-op var)
(match (intmap-ref phis var)
('f64 'scm->f64)
('fx 'untag-fixnum)
('s64 'scm->s64)
('u64 'scm->u64)))
(define (box-op var)
(match (intmap-ref phis var)
('f64 'f64->scm)
('fx 'tag-fixnum)
('s64 's64->scm)
('u64 'u64->scm)))
(define (unbox-operands)
(define (unbox-arg cps arg def-var have-arg)
(if (intmap-ref phis def-var (lambda (_) #f))
(with-cps cps
(letv unboxed)
(let$ body (have-arg unboxed))
(letk kunboxed ($kargs ('unboxed) (unboxed) ,body))
(build-term
($continue kunboxed #f ($primcall (unbox-op def-var) #f (arg)))))
(have-arg cps arg)))
(define (unbox-args cps args def-vars have-args)
(match args
(() (have-args cps '()))
((arg . args)
(match def-vars
((def-var . def-vars)
(unbox-arg cps arg def-var
(lambda (cps arg)
(unbox-args cps args def-vars
(lambda (cps args)
(have-args cps (cons arg args)))))))))))
(intset-fold
(lambda (label cps)
(match (intmap-ref cps label)
(($ $kargs names vars ($ $continue k src exp))
(match (intmap-ref cps k)
(($ $kargs _ defs)
(match exp
;; For expressions that define a single value, we know we need
;; to unbox that value. For $values though we might have to
;; unbox just a subset of values.
(($ $values args)
(with-cps cps
(let$ term (unbox-args
args defs
(lambda (cps args)
(with-cps cps
(build-term
($continue k src ($values args)))))))
(setk label ($kargs names vars ,term))))
(_
(match defs
((def)
(with-cps cps
(letv boxed)
(letk kunbox ($kargs ('boxed) (boxed)
($continue k src
($primcall (unbox-op def) #f (boxed)))))
(setk label ($kargs names vars
($continue kunbox src ,exp)))))))))))))
(compute-unbox-labels)
cps))
(define (compute-box-labels)
(intmap-fold (lambda (phi kind labels)
(intset-add labels (intmap-ref defs phi)))
phis empty-intset))
(define (box-results cps)
(intset-fold
(lambda (label cps)
(match (intmap-ref cps label)
(($ $kargs names vars term)
(let* ((boxed (fold1 (lambda (var boxed)
(if (intmap-ref phis var (lambda (_) #f))
(intmap-add boxed var (fresh-var))
boxed))
vars empty-intmap))
(bound-vars (map (lambda (var)
(intmap-ref boxed var (lambda (var) var)))
vars)))
(define (box-var cps name var done)
(let ((unboxed (intmap-ref boxed var (lambda (_) #f))))
(if unboxed
(with-cps cps
(let$ term (done))
(letk kboxed ($kargs (name) (var) ,term))
(build-term
($continue kboxed #f
($primcall (box-op var) #f (unboxed)))))
(done cps))))
(define (box-vars cps names vars done)
(match vars
(() (done cps))
((var . vars)
(match names
((name . names)
(box-var cps name var
(lambda (cps)
(box-vars cps names vars done))))))))
(with-cps cps
(let$ box-term (box-vars names vars
(lambda (cps)
(with-cps cps term))))
(setk label ($kargs names bound-vars ,box-term)))))))
(compute-box-labels)
cps))
(box-results (unbox-operands)))
(define (specialize-phis cps)
(intmap-fold
(lambda (kfun body cps)
(let* ((preds (compute-predecessors cps kfun #:labels body))
(defs (compute-defs cps body))
(phis (compute-specializable-phis cps body preds defs)))
(if (eq? phis empty-intmap)
cps
(apply-specialization cps kfun body preds defs phis))))
(compute-reachable-functions cps)
cps))
(define (specialize-numbers cps)
;; Type inference wants a renumbered graph; OK.
(let ((cps (renumber cps)))
(with-fresh-name-state cps
(specialize-phis (specialize-operations cps)))))