fb5e6a8 · rowtype-yoga/purescript-backend-optimizer

git.iko.soy/rowtype-yoga/purescript-backend-optimizer

Fix analysis and heuristic for derefs. (#40)

Captured derefs shouldn't be indiscriminately inlined, but this was happening due to a missing analysis. This isn't unsound or anything, as it's what the main compiler does, but it can lead to space leaks when an object is captured by a closure, but only certain fields are accessed. For now, I've kept the inlining if the field is known to be a function, or rather always called with arguments, since it results in much better codegen for typeclass code.

commitfb5e6a85d70c3f6346e350e52db868492e8455ee authorNathan Faubion <natefaubion@users.noreply.github.com> dateWed 21 Dec 2022, 09:41 (4 years ago) parentc37b527

4 files changed+34−3

compare with main

unifiedsplit

backend-es/test/snapshots-out/Snapshot.CaptureDerefRegression01.js+12 backend-es/test/snapshots/Snapshot.CaptureDerefRegression01.purs+17 src/PureScript/Backend/Optimizer/Analysis.purs+1−1 src/PureScript/Backend/Optimizer/Semantics.purs+4−2

backend-es/test/snapshots-out/Snapshot.CaptureDerefRegression01.jsnew file+12

@@ -0,0 +1,12 @@

1+const $Box = _1 => ({tag: "Box", _1});

2+const Box = value0 => $Box(value0);

3+const test3 = v => {

4+ const $0 = v._1;

5+ return $Box(b => $0 + b | 0);

6+};

7+const test2 = v => {

8+ const $0 = v._1;

9+ return b => $0 + b | 0;

10+};

11+const test1 = v => b => v._1 + b | 0;

12+export {$Box, Box, test1, test2, test3};

backend-es/test/snapshots/Snapshot.CaptureDerefRegression01.pursnew file+17

@@ -0,0 +1,17 @@

1+module Snapshot.CaptureDerefRegression01 where

3+import Prelude

5+import Data.Identity (Identity(..))

6+import Data.Tuple (Tuple(..))

8+data Box a = Box a

10+test1 :: Tuple Int Int -> Int -> Int

11+test1 (Tuple a _) b = a + b

12+

13+test2 :: Tuple Int Int -> Identity (Int -> Int)

14+test2 (Tuple a _) = Identity \b -> a + b

15+

16+test3 :: Tuple Int Int -> Box (Int -> Int)

17+test3 (Tuple a _) = Box \b -> a + b

src/PureScript/Backend/Optimizer/Analysis.purs+1−1

@@ -341,7 +341,7 @@ analyze externAnalysis expr = case expr of

341341 Just (Accessor _ _) ->

342342 analysis

343343 Just (Local _ lvl) ->

344− accessed lvl analysis

344+ accessed lvl $ complex Deref analysis

345345 Just (Var qi) -> do

346346 let BackendAnalysis { args } = externAnalysis (Tuple qi (Just acc))

347347 withArgs args $ complex Trivial analysis

src/PureScript/Backend/Optimizer/Semantics.purs+4−2

@@ -1475,9 +1475,11 @@ shouldInlineLet level a b = do

14751475 case Map.lookup level s2.usages of

14761476 Nothing ->

14771477 true

1478− Just (Usage { captured, total }) ->

1478+ Just (Usage { captured, total, call }) ->

14791479 (s1.complexity == Trivial)

1480− || (captured == CaptureNone && (total == 1 || (s1.complexity <= Deref && s1.size < 5)))

1480+ || (captured == CaptureNone && total == 1)

1481+ || (captured <= CaptureBranch && s1.complexity <= Deref && s1.size < 5)

1482+ || (s1.complexity == Deref && call == total)

14811483 || (s1.complexity == KnownSize && total == 1)

14821484 || (isAbs a && (total == 1 || Map.isEmpty s1.usages || s1.size < 16))

14831485 || (isKnownEffect a && total == 1)