a029afc127
When the collection-type inference proves an argument's type, number?/ string?/keyword?/record?/nil?/some? fold to a compile-time boolean. A const-fold now runs after inference so a folded predicate propagates and collapses any if it gates to the taken branch. Sound by construction: only a provable answer folds, and only when the argument is side-effect-free (a const or local) so dropping its evaluation is a no-op. Unknown types (:any/:truthy) and impure args keep the call. vector?/set?/map? are left out — the :vec tag conflates a real vector with a range/seq, so vector? could be wrong. 50M-iter loop, same shape isolated with a carry-only control: number? call+ branch 5080ms, predicate folded 1365ms — matching the 1417ms control floor, so the 3.7x is entirely the eliminated call+branch. Co-authored-by: Yogthos <yogthos@gmail.com>
61 lines
3.5 KiB
Text
61 lines
3.5 KiB
Text
# Predicate folding from inference (jolt-wcw): when the collection-type
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# inference PROVES the argument's type, a type predicate (number?/string?/
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# keyword?/nil?/some?/record?) folds to a compile-time boolean constant, which
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# the trailing const-fold then propagates — collapsing any `if` it gates to the
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# taken branch. Sound: only a provable answer folds, and only when the argument
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# is side-effect-free (a local or const), so dropping its evaluation is a no-op.
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# Mirrors type-infer-test.janet's harness (count a marker in the emitted IR to
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# prove the optimization fired, then evaluate to prove it stayed correct).
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(import ../../src/jolt/api :as api)
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(import ../../src/jolt/backend :as backend)
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(import ../../src/jolt/reader :as reader)
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(print "Predicate folding (jolt-wcw)...")
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(os/setenv "JOLT_DIRECT_LINK" "1")
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(def ctx (api/init {:compile? true}))
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(api/eval-string ctx "(ns pf)")
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(defn code [src]
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(string/format "%p" (backend/emit-ir ctx (backend/analyze-form ctx (reader/parse-string src)))))
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(defn occurs [src needle] (length (string/find-all needle (code src))))
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(defn ev [src] (api/eval-string ctx src))
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# --- the predicate call is gone where the type is proven --------------------
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(assert (= 0 (occurs "(fn [] (let [x (+ 1 2)] (number? x)))" "number?"))
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"number? on proven :num -> folded, call eliminated")
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(assert (= 0 (occurs "(fn [] (let [x \"hi\"] (string? x)))" "string?"))
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"string? on proven :str -> folded")
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(assert (= 0 (occurs "(fn [] (let [x :k] (keyword? x)))" "keyword?"))
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"keyword? on proven :kw -> folded")
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(assert (= 0 (occurs "(fn [] (let [x (+ 1 2)] (nil? x)))" "nil?"))
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"nil? on a provably non-nil value -> folded")
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# --- the folded constant collapses an if it gates --------------------------
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# the dead branch's literal (200) must be gone after dead-branch removal
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(assert (= 0 (occurs "(fn [] (let [x (+ 1 2)] (if (number? x) 100 200)))" "200"))
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"true predicate folds the if to its then-branch (dead 200 dropped)")
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(assert (= 0 (occurs "(fn [] (let [x (+ 1 2)] (if (string? x) 100 200)))" "100"))
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"false predicate folds the if to its else-branch (dead 100 dropped)")
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# --- sound fallback: unknown type or impure arg keeps the call -------------
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# a param is :any (Phase 0 doesn't type it) -> no fold
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(assert (= 1 (occurs "(fn [m] (number? m))" "number?"))
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"unknown-type arg keeps the predicate call")
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# arg type is proven :num but the arg has side effects (a call) -> must NOT
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# drop its evaluation, so the predicate is left in place
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(assert (>= (occurs "(fn [g] (number? (+ (g) 1)))" "number?") 1)
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"impure arg (even with proven type) keeps the predicate call")
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# --- correctness: folded path evaluates to the dispatched path -------------
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(assert (= true (ev "((fn [] (let [x (+ 1 2)] (number? x))))")) "number? true value")
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(assert (= false (ev "((fn [] (let [x \"hi\"] (number? x))))")) "number? false value")
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(assert (= true (ev "((fn [] (let [x :k] (keyword? x))))")) "keyword? true value")
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(assert (= false (ev "((fn [] (let [x 5] (nil? x))))")) "nil? false value")
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(assert (= true (ev "((fn [] (let [x 5] (some? x))))")) "some? true value")
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(assert (= :yes (ev "((fn [] (let [x 5] (if (number? x) :yes :no))))")) "gated if takes proven branch")
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(assert (= :no (ev "((fn [] (let [x 5] (if (string? x) :yes :no))))")) "gated if drops false branch")
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# impure arg still runs its side effect and returns the right answer
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(assert (= 6 (ev "((fn [g] (if (number? (+ (g) 1)) (+ (g) 5) 0)) (fn [] 1))")) "impure-arg predicate stays correct")
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(print "Predicate folding (jolt-wcw) passed!")
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