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|
;; Copyright (c) Eduardo Julian. All rights reserved.
;; This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
;; If a copy of the MPL was not distributed with this file,
;; You can obtain one at http://mozilla.org/MPL/2.0/.
(ns lux.optimizer
(:require (lux [base :as & :refer [|let |do return fail return* fail* |case defvariant]])
(lux.analyser [base :as &a]
[case :as &a-case])))
;; [Tags]
(defvariant
;; These tags just have a one-to-one correspondence with Analysis data-structures.
("bool" 1)
("nat" 1)
("int" 1)
("frac" 1)
("real" 1)
("char" 1)
("text" 1)
("variant" 3)
("tuple" 1)
("apply" 2)
("case" 2)
("function" 4)
("ann" 2)
("var" 1)
("captured" 3)
("proc" 3)
;; These other tags represent higher-order constructs that manifest
;; themselves as patterns in the code.
;; Lux doesn't formally provide these features, but some macros
;; expose ways to implement them in terms of the other (primitive)
;; features.
;; The optimizer looks for those usage patterns and transforms them
;; into explicit constructs, which are then subject to specialized optimizations.
;; This is loop iteration, as expected in imperative programming.
("iter" 1)
;; This is a simple let-expression, as opposed to the more general pattern-matching.
("let" 3)
;; This is an access to a record's member. It can be multi-level:
;; e.g. record.l1.l2.l3
;; The record-get token stores the path, for simpler compilation.
("record-get" 2)
;; Regular, run-of-the-mill if expressions.
("if" 3)
)
;; [Utils]
;; [[Pattern-Matching Traversal Optimization]]
;; This represents an alternative way to view pattern-matching.
;; The PM that Lux provides has declarative semantics, with the user
;; specifying how his data is shaped, but not how to traverse it.
;; The optimizer's PM is operational in nature, and relies on
;; specifying a path of traversal, with a variety of operations that
;; can be done along the way.
;; The algorithm relies on looking at pattern-matching as traversing a
;; (possibly) branching path, where each step along the path
;; corresponds to a value, the ends of the path are the jumping-off
;; points for the bodies of branches, and branching decisions can be
;; backtracked, if they don't result in a valid jump.
(defvariant
;; Throw away the current data-node (CDN). It's useless.
("PopPM" 0)
;; Store the CDN in a register.
("BindPM" 1)
;; Compare the CDN with a boolean value.
("BoolPM" 1)
;; Compare the CDN with a natural value.
("NatPM" 1)
;; Compare the CDN with an integer value.
("IntPM" 1)
;; Compare the CDN with a fractional value.
("FracPM" 1)
;; Compare the CDN with a real value.
("RealPM" 1)
;; Compare the CDN with a character value.
("CharPM" 1)
;; Compare the CDN with a text value.
("TextPM" 1)
;; Compare the CDN with a variant value. If valid, proceed to test
;; the variant's inner value.
("VariantPM" 1)
;; Access a tuple value at a given index, for further examination.
("TuplePM" 1)
;; Creates an instance of the backtracking info, as a preparatory
;; step to exploring one of the branching paths.
("AltPM" 2)
;; Allows to test the CDN, while keeping a copy of it for more
;; tasting later on.
;; If necessary when doing multiple tests on a single value, like
;; when testing multiple parts of a tuple.
("SeqPM" 2)
;; This is the jumping-off point for the PM part, where the PM
;; data-structure is thrown away and the program jumps to the
;; branch's body.
("ExecPM" 1))
;; This function does a simple transformation from the declarative
;; model of PM of the analyser, to the operational model of PM of the
;; optimizer.
;; You may notice that all branches end in PopPM.
;; The reason is that testing does not immediately imply throwing away
;; the data to be tested, which is why a popping step must immediately follow.
(defn ^:private transform-pm* [test]
(|case test
(&a-case/$NoTestAC)
(&/|list $PopPM)
(&a-case/$StoreTestAC _register)
(&/|list ($BindPM _register))
(&a-case/$BoolTestAC _value)
(&/|list ($BoolPM _value)
$PopPM)
(&a-case/$NatTestAC _value)
(&/|list ($NatPM _value)
$PopPM)
(&a-case/$IntTestAC _value)
(&/|list ($IntPM _value)
$PopPM)
(&a-case/$FracTestAC _value)
(&/|list ($FracPM _value)
$PopPM)
(&a-case/$RealTestAC _value)
(&/|list ($RealPM _value)
$PopPM)
(&a-case/$CharTestAC _value)
(&/|list ($CharPM _value)
$PopPM)
(&a-case/$TextTestAC _value)
(&/|list ($TextPM _value)
$PopPM)
(&a-case/$VariantTestAC _idx _num-options _sub-test)
(&/|++ (&/|list ($VariantPM (if (= _idx (dec _num-options))
(&/$Right _idx)
(&/$Left _idx))))
(&/|++ (transform-pm* _sub-test)
(&/|list $PopPM)))
(&a-case/$TupleTestAC _sub-tests)
(|case _sub-tests
;; An empty tuple corresponds to unit, which can't be tested in
;; any meaningful way, so it's just popped.
(&/$Nil)
(&/|list $PopPM)
;; A tuple of a single element is equivalent to the element
;; itself, to the element's PM is generated.
(&/$Cons _only-test (&/$Nil))
(transform-pm* _only-test)
;; Single tuple PM features the tests of each tuple member
;; inlined, it's operational equivalent is interleaving the
;; access to each tuple member, followed by the testing of said
;; member.
;; That is way each sequence of access+subtesting gets generated
;; and later they all get concatenated.
_
(|let [tuple-size (&/|length _sub-tests)]
(&/|++ (&/flat-map (fn [idx+test*]
(|let [[idx test*] idx+test*]
(&/$Cons ($TuplePM (if (< idx (dec tuple-size))
(&/$Left idx)
(&/$Right idx)))
(transform-pm* test*))))
(&/zip2 (&/|range tuple-size)
_sub-tests))
(&/|list $PopPM))))))
;; It will be common for pattern-matching on a very nested
;; data-structure to require popping all the intermediate
;; data-structures that were visited once it's all done.
;; However, the PM infrastructure employs a single data-stack to keep
;; all data nodes in the trajectory, and that data-stack can just be
;; thrown again entirely, in just one step.
;; Because of that, any ending POPs prior to throwing away the
;; data-stack would be completely useless.
;; This function cleans them all up, to avoid wasteful computation later.
(defn ^:private clean-unnecessary-pops [steps]
(|case steps
(&/$Cons ($PopPM) _steps)
(clean-unnecessary-pops _steps)
_
steps))
;; This transforms a single branch of a PM tree into it's operational
;; equivalent, while also associating the PM of the branch with the
;; jump to the branch's body.
(defn ^:private transform-pm [test body-id]
(&/fold (fn [right left] ($SeqPM left right))
($ExecPM body-id)
(clean-unnecessary-pops (&/|reverse (transform-pm* test)))))
(defn ^:private pattern->text [pattern]
(|case pattern
($PopPM)
"$PopPM"
($BindPM _id)
(str "($BindPM " _id ")")
($BoolPM _value)
(str "($BoolPM " (pr-str _value) ")")
($NatPM _value)
(str "($NatPM " (pr-str _value) ")")
($IntPM _value)
(str "($IntPM " (pr-str _value) ")")
($FracPM _value)
(str "($FracPM " (pr-str _value) ")")
($RealPM _value)
(str "($RealPM " (pr-str _value) ")")
($CharPM _value)
(str "($CharPM " (pr-str _value) ")")
($TextPM _value)
(str "($TextPM " (pr-str _value) ")")
($TuplePM (&/$Left _idx))
(str "($TuplePM L" _idx ")")
($TuplePM (&/$Right _idx))
(str "($TuplePM R" _idx ")")
($VariantPM (&/$Left _idx))
(str "($VariantPM L" _idx ")")
($VariantPM (&/$Right _idx))
(str "($VariantPM R" _idx ")")
($SeqPM _left _right)
(str "($SeqPM " (pattern->text _left) " " (pattern->text _right) ")")
($ExecPM _idx)
(str "($ExecPM " _idx ")")
;; $AltPM is not considered because it's not supposed to be
;; present anywhere at this point in time.
))
;; This function fuses together the paths of the PM traversal, adding
;; branching AltPMs where necessary, and fusing similar paths together
;; as much as possible, when early parts of them coincide.
;; The goal is to minimize rework as much as possible by sharing as
;; much of each path as possible.
(defn ^:private fuse-pms [pre post]
(|case (&/T [pre post])
[($PopPM) ($PopPM)]
$PopPM
[($BindPM _pre-var-id) ($BindPM _post-var-id)]
(if (= _pre-var-id _post-var-id)
($BindPM _pre-var-id)
($AltPM pre post))
[($BoolPM _pre-value) ($BoolPM _post-value)]
(if (= _pre-value _post-value)
($BoolPM _pre-value)
($AltPM pre post))
[($NatPM _pre-value) ($NatPM _post-value)]
(if (= _pre-value _post-value)
($NatPM _pre-value)
($AltPM pre post))
[($IntPM _pre-value) ($IntPM _post-value)]
(if (= _pre-value _post-value)
($IntPM _pre-value)
($AltPM pre post))
[($FracPM _pre-value) ($FracPM _post-value)]
(if (= _pre-value _post-value)
($FracPM _pre-value)
($AltPM pre post))
[($RealPM _pre-value) ($RealPM _post-value)]
(if (= _pre-value _post-value)
($RealPM _pre-value)
($AltPM pre post))
[($CharPM _pre-value) ($CharPM _post-value)]
(if (= _pre-value _post-value)
($CharPM _pre-value)
($AltPM pre post))
[($TextPM _pre-value) ($TextPM _post-value)]
(if (= _pre-value _post-value)
($TextPM _pre-value)
($AltPM pre post))
[($TuplePM (&/$Left _pre-idx)) ($TuplePM (&/$Left _post-idx))]
(if (= _pre-idx _post-idx)
($TuplePM (&/$Left _pre-idx))
($AltPM pre post))
[($TuplePM (&/$Right _pre-idx)) ($TuplePM (&/$Right _post-idx))]
(if (= _pre-idx _post-idx)
($TuplePM (&/$Right _pre-idx))
($AltPM pre post))
[($VariantPM (&/$Left _pre-idx)) ($VariantPM (&/$Left _post-idx))]
(if (= _pre-idx _post-idx)
($VariantPM (&/$Left _pre-idx))
($AltPM pre post))
[($VariantPM (&/$Right _pre-idx)) ($VariantPM (&/$Right _post-idx))]
(if (= _pre-idx _post-idx)
($VariantPM (&/$Right _pre-idx))
($AltPM pre post))
[($SeqPM _pre-pre _pre-post) ($SeqPM _post-pre _post-post)]
(|case (fuse-pms _pre-pre _post-pre)
($AltPM _ _)
($AltPM pre post)
fused-pre
($SeqPM fused-pre (fuse-pms _pre-post _post-post)))
_
($AltPM pre post)
))
(defn ^:private pattern-vars [pattern]
(|case pattern
($BindPM _id)
(&/|list (&/T [_id false]))
($SeqPM _left _right)
(&/|++ (pattern-vars _left) (pattern-vars _right))
_
(&/|list)
;; $AltPM is not considered because it's not supposed to be
;; present anywhere at this point in time.
))
(defn ^:private find-unused-vars [var-table body]
(|let [[meta body-] body]
(|case body-
($var (&/$Local _idx))
(&/|update _idx (fn [_] true) var-table)
($captured _scope _c-idx [_ ($var (&/$Local _idx))])
(&/|update _idx (fn [_] true) var-table)
($variant _idx _is-last? _value)
(find-unused-vars var-table _value)
($tuple _elems)
(&/fold find-unused-vars var-table _elems)
($ann _value-expr _type-expr)
(find-unused-vars var-table _value-expr)
($apply _func _args)
(&/fold find-unused-vars
(find-unused-vars var-table _func)
_args)
($proc _proc-ident _args _special-args)
(&/fold find-unused-vars var-table _args)
($iter _args)
(&/fold find-unused-vars var-table _args)
($let _value _register _body)
(-> var-table
(find-unused-vars _value)
(find-unused-vars _body))
($record-get _value _path)
(find-unused-vars var-table _value)
($if _test _then _else)
(-> var-table
(find-unused-vars _test)
(find-unused-vars _then)
(find-unused-vars _else))
($case _value [_pm _bodies])
(&/fold find-unused-vars
(find-unused-vars var-table _value)
_bodies)
($function _arity _scope _captured _body)
(->> _captured
(&/|map &/|second)
(&/fold find-unused-vars var-table))
_
var-table
)))
(defn ^:private clean-unused-pattern-registers [var-table pattern]
(|case pattern
($BindPM _idx)
(|let [_new-idx (&/|get _idx var-table)]
(cond (= _idx _new-idx)
pattern
(>= _new-idx 0)
($BindPM _new-idx)
:else
$PopPM))
($SeqPM _left _right)
($SeqPM (clean-unused-pattern-registers var-table _left)
(clean-unused-pattern-registers var-table _right))
_
pattern
;; $AltPM is not considered because it's not supposed to be
;; present anywhere at this point in time.
))
;; This function assumes that the var-table has an ascending index
;; order.
;; For example: (2 3 4 5 6 7 8), instead of (8 7 6 5 4 3 2)
(defn ^:private adjust-register-indexes* [offset var-table]
(|case var-table
(&/$Nil)
(&/|list)
(&/$Cons [_idx _used?] _tail)
(if _used?
(&/$Cons (&/T [_idx (- _idx offset)])
(adjust-register-indexes* offset _tail))
(&/$Cons (&/T [_idx -1])
(adjust-register-indexes* (inc offset) _tail))
)))
(defn ^:private adjust-register-indexes [var-table]
(adjust-register-indexes* 0 var-table))
(defn ^:private clean-unused-body-registers [var-table body]
(|let [[meta body-] body]
(|case body-
($var (&/$Local _idx))
(|let [new-idx (or (&/|get _idx var-table)
_idx)]
(&/T [meta ($var (&/$Local new-idx))]))
($captured _scope _c-idx [_sub-meta ($var (&/$Local _idx))])
(|let [new-idx (or (&/|get _idx var-table)
_idx)]
(&/T [meta ($captured _scope _c-idx (&/T [_sub-meta ($var (&/$Local new-idx))]))]))
($variant _idx _is-last? _value)
(&/T [meta ($variant _idx _is-last? (clean-unused-body-registers var-table _value))])
($tuple _elems)
(&/T [meta ($tuple (&/|map (partial clean-unused-body-registers var-table)
_elems))])
($ann _value-expr _type-expr)
(&/T [meta ($ann (clean-unused-body-registers var-table _value-expr) _type-expr)])
($apply _func _args)
(&/T [meta ($apply (clean-unused-body-registers var-table _func)
(&/|map (partial clean-unused-body-registers var-table)
_args))])
($proc _proc-ident _args _special-args)
(&/T [meta ($proc _proc-ident
(&/|map (partial clean-unused-body-registers var-table)
_args)
_special-args)])
($iter _args)
(&/T [meta ($iter (&/|map (partial clean-unused-body-registers var-table)
_args))])
($let _value _register _body)
(&/T [meta ($let (clean-unused-body-registers var-table _value)
_register
(clean-unused-body-registers var-table _body))])
($record-get _value _path)
(&/T [meta ($record-get (clean-unused-body-registers var-table _value)
_path)])
($if _test _then _else)
(&/T [meta ($if (clean-unused-body-registers var-table _test)
(clean-unused-body-registers var-table _then)
(clean-unused-body-registers var-table _else))])
($case _value [_pm _bodies])
(&/T [meta ($case (clean-unused-body-registers var-table _value)
(&/T [_pm
(&/|map (partial clean-unused-body-registers var-table)
_bodies)]))])
($function _arity _scope _captured _body)
(&/T [meta ($function _arity
_scope
(&/|map (fn [capture]
(|let [[_name __var] capture]
(&/T [_name (clean-unused-body-registers var-table __var)])))
_captured)
_body)])
_
body
)))
(defn ^:private simplify-pattern [pattern]
(|case pattern
($SeqPM ($TuplePM _idx) ($SeqPM ($PopPM) pattern*))
(simplify-pattern pattern*)
($SeqPM ($TuplePM _idx) _right)
(|case (simplify-pattern _right)
($SeqPM ($PopPM) pattern*)
pattern*
_right*
($SeqPM ($TuplePM _idx) _right*))
($SeqPM _left _right)
($SeqPM _left (simplify-pattern _right))
_
pattern))
(defn ^:private optimize-register-use [pattern body]
(|let [p-vars (pattern-vars pattern)
p-vars* (find-unused-vars p-vars body)
adjusted-vars (adjust-register-indexes p-vars*)
clean-pattern (clean-unused-pattern-registers adjusted-vars pattern)
simple-pattern (simplify-pattern clean-pattern)
clean-body (clean-unused-body-registers adjusted-vars body)]
(&/T [simple-pattern clean-body])))
;; This is the top-level function for optimizing PM, which transforms
;; each branch and then fuses them together.
(defn ^:private optimize-pm [branches]
(|let [;; branches (&/|reverse branches*)
pms+bodies (&/map2 (fn [branch _body-id]
(|let [[_pattern _body] branch]
(optimize-register-use (transform-pm _pattern _body-id)
_body)))
branches
(&/|range (&/|length branches)))
pms (&/|map &/|first pms+bodies)
bodies (&/|map &/|second pms+bodies)]
(|case (&/|reverse pms)
(&/$Nil)
(assert false)
(&/$Cons _head-pm _tail-pms)
(&/T [(&/fold fuse-pms _head-pm _tail-pms)
bodies])
)))
;; [[Function-Folding Optimization]]
;; The semantics of Lux establish that all functions are of a single
;; argument and the multi-argument functions are actually nested
;; functions being generated and then applied.
;; This, of course, would generate a lot of waste.
;; To avoid it, Lux actually folds function definitions together,
;; thereby creating functions that can be used both
;; one-argument-at-a-time, and also being called with all, or just a
;; partial amount of their arguments.
;; This avoids generating too many artifacts during compilation, since
;; they get "compressed", and it can also lead to faster execution, by
;; enabling optimized function calls later.
;; Functions and captured variables have "scopes", which tell which
;; function they are, or to which function they belong.
;; During the folding, inner functions dissapear, since their bodies
;; are merged into their outer "parent" functions.
;; Their scopes must change accordingy.
(defn ^:private de-scope [old-scope new-scope scope]
"(-> Scope Scope Scope Scope)"
(if (identical? new-scope scope)
old-scope
scope))
;; Also, it must be noted that when folding functions, the indexes of
;; the registers have to be changed accodingly.
;; That is what the following "shifting" functions are for.
;; Shifts the registers for PM operations.
(defn ^:private shift-pattern [pattern]
(|case pattern
($BindPM _var-id)
($BindPM (inc _var-id))
($SeqPM _left-pm _right-pm)
($SeqPM (shift-pattern _left-pm) (shift-pattern _right-pm))
($AltPM _left-pm _right-pm)
($AltPM (shift-pattern _left-pm) (shift-pattern _right-pm))
_
pattern
))
;; Shifts the body of a function after a folding is performed.
(defn shift-function-body [old-scope new-scope own-body? body]
"(-> Scope Scope Bool Optimized Optimized)"
(|let [[meta body-] body]
(|case body-
($variant idx is-last? value)
(&/T [meta ($variant idx is-last? (shift-function-body old-scope new-scope own-body? value))])
($tuple elems)
(&/T [meta ($tuple (&/|map (partial shift-function-body old-scope new-scope own-body?) elems))])
($case value [_pm _bodies])
(&/T [meta ($case (shift-function-body old-scope new-scope own-body? value)
(&/T [(if own-body?
(shift-pattern _pm)
_pm)
(&/|map (partial shift-function-body old-scope new-scope own-body?) _bodies)]))])
($function arity scope captured body*)
(|let [scope* (de-scope old-scope new-scope scope)]
(&/T [meta ($function arity
scope*
(&/|map (fn [capture]
(|let [[_name [_meta ($captured _scope _idx _source)]] capture]
(&/T [_name (&/T [_meta ($captured scope* _idx (shift-function-body old-scope new-scope own-body? _source))])])))
captured)
(shift-function-body old-scope new-scope false body*))]))
($ann value-expr type-expr)
(&/T [meta ($ann (shift-function-body old-scope new-scope own-body? value-expr)
type-expr)])
($var var-kind)
(if own-body?
(|case var-kind
(&/$Local 0)
(&/T [meta ($apply body
(&/|list [meta ($var (&/$Local 1))]))])
(&/$Local idx)
(&/T [meta ($var (&/$Local (inc idx)))])
(&/$Global ?module ?name)
body)
body)
;; This special "apply" rule is for handling recursive calls better.
($apply [meta-0 ($var (&/$Local 0))] args)
(if own-body?
(&/T [meta ($apply (&/T [meta-0 ($var (&/$Local 0))])
(&/$Cons (&/T [meta-0 ($var (&/$Local 1))])
(&/|map (partial shift-function-body old-scope new-scope own-body?) args)))])
(&/T [meta ($apply (&/T [meta-0 ($var (&/$Local 0))])
(&/|map (partial shift-function-body old-scope new-scope own-body?) args))]))
($apply func args)
(&/T [meta ($apply (shift-function-body old-scope new-scope own-body? func)
(&/|map (partial shift-function-body old-scope new-scope own-body?) args))])
($captured scope idx source)
(if own-body?
source
(|case scope
(&/$Cons _ (&/$Cons _ (&/$Nil)))
source
_
(&/T [meta ($captured (de-scope old-scope new-scope scope) idx (shift-function-body old-scope new-scope own-body? source))])))
($proc proc-ident args special-args)
(&/T [meta ($proc proc-ident (&/|map (partial shift-function-body old-scope new-scope own-body?) args) special-args)])
($iter args)
(&/T [meta ($iter (&/|map (partial shift-function-body old-scope new-scope own-body?) args))])
($let _value _register _body)
(&/T [meta ($let (shift-function-body old-scope new-scope own-body? _value)
(if own-body?
(inc _register)
_register)
(shift-function-body old-scope new-scope own-body? _body))])
($record-get _value _path)
(&/T [meta ($record-get (shift-function-body old-scope new-scope own-body? _value)
_path)])
($if _test _then _else)
(&/T [meta ($if (shift-function-body old-scope new-scope own-body? _test)
(shift-function-body old-scope new-scope own-body? _then)
(shift-function-body old-scope new-scope own-body? _else))])
_
body
)))
;; [[Record-Manipulation Optimizations]]
;; If a pattern-matching tree with a single branch is found, and that
;; branch corresponds to a tuple PM, and the body corresponds to a
;; local variable, it's likely that the local refers to some member of
;; the tuple that is being extracted.
;; That is the pattern that is to be expected of record read-access,
;; so this function tries to extract the (possibly nested) path
;; necessary, ending in the data-node of the wanted member.
(defn ^:private record-read-path [pms member-idx]
"(-> (List PM) Idx (List Idx))"
(loop [current-idx 0
pms pms]
(|case pms
(&/$Nil)
&/$None
(&/$Cons _pm _pms)
(|case _pm
(&a-case/$NoTestAC)
(recur (inc current-idx)
_pms)
(&a-case/$StoreTestAC _register)
(if (= member-idx _register)
(&/|list (&/T [current-idx (&/|empty? _pms)]))
(recur (inc current-idx)
_pms))
(&a-case/$TupleTestAC _sub-tests)
(let [sub-path (record-read-path _sub-tests member-idx)]
(if (not (&/|empty? sub-path))
(&/$Cons (&/T [current-idx (&/|empty? _pms)]) sub-path)
(recur (inc current-idx)
_pms)
))
_
(&/|list))
)))
;; [[Loop Optimizations]]
;; Lux doesn't offer any looping constructs, relying instead on
;; recursion.
;; Some common usages of recursion can be written more efficiently
;; just using regular loops/iteration.
;; This optimization looks for tail-calls in the function body,
;; rewriting them as jumps to the beginning of the function, while
;; they also updated the necessary local variables for the next iteration.
(defn ^:private optimize-loop [arity optim]
"(-> Int Optimized Optimized)"
(|let [[meta optim-] optim]
(|case optim-
($apply [meta-0 ($var (&/$Local 0))] _args)
(if (= arity (&/|length _args))
(&/T [meta ($iter _args)])
optim)
($case _value [_pattern _bodies])
(&/T [meta ($case _value
(&/T [_pattern
(&/|map (partial optimize-loop arity)
_bodies)]))])
($let _value _register _body)
(&/T [meta ($let _value _register (optimize-loop arity _body))])
($if _test _then _else)
(&/T [meta ($if _test
(optimize-loop arity _then)
(optimize-loop arity _else))])
($ann _value-expr _type-expr)
(&/T [meta ($ann (optimize-loop arity _value-expr) _type-expr)])
_
optim
)))
;; [[Initial Optimization]]
;; Before any big optimization can be done, the incoming Analysis nodes
;; must be transformed into Optimized nodes, amenable to further transformations.
;; This function does the job, while also detecting (and optimizing)
;; some simple surface patterns it may encounter.
(let [optimize-closure (fn [optimize closure]
(&/|map (fn [capture]
(|let [[_name _analysis] capture]
(&/T [_name (optimize _analysis)])))
closure))]
(defn ^:private pass-0 [top-level-func? analysis]
"(-> Bool Analysis Optimized)"
(|let [[meta analysis-] analysis]
(|case analysis-
(&a/$bool value)
(&/T [meta ($bool value)])
(&a/$nat value)
(&/T [meta ($nat value)])
(&a/$int value)
(&/T [meta ($int value)])
(&a/$frac value)
(&/T [meta ($frac value)])
(&a/$real value)
(&/T [meta ($real value)])
(&a/$char value)
(&/T [meta ($char value)])
(&a/$text value)
(&/T [meta ($text value)])
(&a/$variant idx is-last? value)
(&/T [meta ($variant idx is-last? (pass-0 top-level-func? value))])
(&a/$tuple elems)
(&/T [meta ($tuple (&/|map (partial pass-0 top-level-func?) elems))])
(&a/$apply func args)
(&/T [meta ($apply (pass-0 top-level-func? func) (&/|map (partial pass-0 top-level-func?) args))])
(&a/$case value branches)
(let [normal-case-optim (fn []
(&/T [meta ($case (pass-0 top-level-func? value)
(optimize-pm (&/|map (fn [branch]
(|let [[_pattern _body] branch]
(&/T [_pattern (pass-0 top-level-func? _body)])))
branches)))]))]
(|case branches
;; The pattern for a let-expression is a single branch,
;; tying the value to a register.
(&/$Cons [(&a-case/$StoreTestAC _register) _body] (&/$Nil))
(&/T [meta ($let (pass-0 top-level-func? value) _register (pass-0 top-level-func? _body))])
(&/$Cons [(&a-case/$BoolTestAC false) _else]
(&/$Cons [(&a-case/$BoolTestAC true) _then]
(&/$Nil)))
(&/T [meta ($if (pass-0 top-level-func? value) (pass-0 top-level-func? _then) (pass-0 top-level-func? _else))])
;; The pattern for a record-get is a single branch, with a
;; tuple pattern and a body corresponding to a
;; local-variable extracted from the tuple.
(&/$Cons [(&a-case/$TupleTestAC _sub-tests) [_ (&a/$var (&/$Local _member-idx))]] (&/$Nil))
(|let [_path (record-read-path _sub-tests _member-idx)]
(if (&/|empty? _path)
;; If the path is empty, that means it was a
;; false-positive and normal PM optimization should be
;; done instead.
(normal-case-optim)
;; Otherwise, we've got ourselves a record-get expression.
(&/T [meta ($record-get (pass-0 top-level-func? value) _path)])))
;; If no special patterns are found, just do normal PM optimization.
_
(normal-case-optim)))
(&a/$lambda scope captured body)
(|case (pass-0 false body)
;; If the body of a function is another function, that means
;; no work was done in-between and both layers can be folded
;; into one.
[_ ($function _arity _scope _captured _body)]
(|let [new-arity (inc _arity)
collapsed-body (shift-function-body scope _scope true _body)]
(&/T [meta ($function new-arity
scope
(optimize-closure (partial pass-0 top-level-func?) captured)
(if top-level-func?
(optimize-loop new-arity collapsed-body)
collapsed-body))]))
;; Otherwise, they're nothing to be done and we've got a
;; 1-arity function.
=body
(&/T [meta ($function 1 scope (optimize-closure (partial pass-0 top-level-func?) captured) =body)]))
(&a/$ann value-expr type-expr)
(&/T [meta ($ann (pass-0 top-level-func? value-expr) type-expr)])
(&a/$var var-kind)
(&/T [meta ($var var-kind)])
(&a/$captured scope idx source)
(&/T [meta ($captured scope idx (pass-0 top-level-func? source))])
(&a/$proc proc-ident args special-args)
(&/T [meta ($proc proc-ident (&/|map (partial pass-0 top-level-func?) args) special-args)])
_
(assert false (prn-str 'pass-0 top-level-func? (&/adt->text analysis)))
))))
;; [Exports]
(defn optimize [analysis]
"(-> Analysis Optimized)"
(->> analysis
(pass-0 true)))
|