Inline non-recursive functions with only one call site (#3204)

* Closes #3198

src/Juvix/Compiler/Core/Extra/Utils.hs

@@ -640,3 +640,32 @@ isDirectlyRecursive md sym = ufold (\x xs -> or (x : xs)) go (lookupIdentifierNo
     go = \case
       NIdt Ident {..} -> _identSymbol == sym
       _ -> False
+
+-- Returns a map from symbols to their number of occurrences in the given node.
+getSymbolsMap :: Module -> Node -> HashMap Symbol Int
+getSymbolsMap md = gather go mempty
+  where
+    go :: HashMap Symbol Int -> Node -> HashMap Symbol Int
+    go acc = \case
+      NTyp TypeConstr {..} -> mapInc _typeConstrSymbol acc
+      NIdt Ident {..} -> mapInc _identSymbol acc
+      NCase Case {..} -> mapInc _caseInductive acc
+      NCtr Constr {..}
+        | Just ci <- lookupConstructorInfo' md _constrTag ->
+            mapInc (ci ^. constructorInductive) acc
+      _ -> acc
+
+    mapInc :: Symbol -> HashMap Symbol Int -> HashMap Symbol Int
+    mapInc k = HashMap.insertWith (+) k 1
+
+getTableSymbolsMap :: InfoTable -> HashMap Symbol Int
+getTableSymbolsMap tab =
+  foldr
+    (HashMap.unionWith (+))
+    mempty
+    (map (getSymbolsMap md) (HashMap.elems $ tab ^. identContext))
+  where
+    md = emptyModule {_moduleInfoTable = tab}
+
+getModuleSymbolsMap :: Module -> HashMap Symbol Int
+getModuleSymbolsMap = getTableSymbolsMap . computeCombinedInfoTable

src/Juvix/Compiler/Core/Transformation/Optimize/Inlining.hs

@@ -1,5 +1,6 @@
 module Juvix.Compiler.Core.Transformation.Optimize.Inlining where
 
+import Data.HashMap.Strict qualified as HashMap
 import Data.HashSet qualified as HashSet
 import Juvix.Compiler.Core.Data.BinderList qualified as BL
 import Juvix.Compiler.Core.Data.IdentDependencyInfo
@@ -16,8 +17,8 @@ isInlineableLambda inlineDepth md bl node = case node of
   _ ->
     False
 
-convertNode :: Int -> HashSet Symbol -> Module -> Node -> Node
+convertNode :: Int -> HashSet Symbol -> HashMap Symbol Int -> Module -> Node -> Node
-convertNode inlineDepth nonRecSyms md = dmapL go
+convertNode inlineDepth nonRecSyms symOcc md = dmapL go
   where
     go :: BinderList Binder -> Node -> Node
     go bl node = case node of
@@ -39,7 +40,9 @@ convertNode inlineDepth nonRecSyms md = dmapL go
                   _
                     | HashSet.member _identSymbol nonRecSyms
                         && length args >= argsNum
-                        && isInlineableLambda inlineDepth md bl def ->
+                        && ( HashMap.lookup _identSymbol symOcc == Just 1
+                               || isInlineableLambda inlineDepth md bl def
+                           ) ->
                         mkApps def args
                   _ ->
                     node
@@ -58,7 +61,10 @@ convertNode inlineDepth nonRecSyms md = dmapL go
           Just InlineNever -> node
           _
             | HashSet.member _identSymbol nonRecSyms
-                && isImmediate md def ->
+                && argsNum == 0
+                && ( HashMap.lookup _identSymbol symOcc == Just 1
+                       || isImmediate md def
+                   ) ->
                 def
             | otherwise ->
                 node
@@ -98,10 +104,10 @@ convertNode inlineDepth nonRecSyms md = dmapL go
       where
         (lamsNum, body) = unfoldLambdas' node
 
-inlining' :: Int -> HashSet Symbol -> Module -> Module
+inlining' :: Int -> HashSet Symbol -> HashMap Symbol Int -> Module -> Module
-inlining' inliningDepth nonRecSyms md = mapT (const (convertNode inliningDepth nonRecSyms md)) md
+inlining' inliningDepth nonRecSyms symOcc md = mapT (const (convertNode inliningDepth nonRecSyms symOcc md)) md
 
 inlining :: (Member (Reader CoreOptions) r) => Module -> Sem r Module
 inlining md = do
   d <- asks (^. optInliningDepth)
-  return $ inlining' d (nonRecursiveIdents md) md
+  return $ inlining' d (nonRecursiveIdents md) (getModuleSymbolsMap md) md

src/Juvix/Compiler/Core/Transformation/Optimize/Phase/Main.hs

@@ -1,6 +1,7 @@
 module Juvix.Compiler.Core.Transformation.Optimize.Phase.Main where
 
 import Juvix.Compiler.Core.Data.IdentDependencyInfo
+import Juvix.Compiler.Core.Extra.Utils (getTableSymbolsMap)
 import Juvix.Compiler.Core.Options
 import Juvix.Compiler.Core.Transformation.Base
 import Juvix.Compiler.Core.Transformation.Optimize.CaseFolding
@@ -39,6 +40,9 @@ optimize' opts@CoreOptions {..} md =
     nonRecsReachable :: HashSet Symbol
     nonRecsReachable = nonRecursiveReachableIdents' tab
 
+    symOcc :: HashMap Symbol Int
+    symOcc = getTableSymbolsMap tab
+
     doConstantFolding :: Module -> Module
     doConstantFolding md' = constantFolding' opts nonRecs' tab' md'
       where
@@ -48,7 +52,7 @@ optimize' opts@CoreOptions {..} md =
           | otherwise = nonRecsReachable
 
     doInlining :: Module -> Module
-    doInlining md' = inlining' _optInliningDepth nonRecs' md'
+    doInlining md' = inlining' _optInliningDepth nonRecs' symOcc md'
       where
         nonRecs' =
           if

src/Juvix/Compiler/Core/Transformation/Optimize/Phase/PreLifting.hs

@@ -1,6 +1,7 @@
 module Juvix.Compiler.Core.Transformation.Optimize.Phase.PreLifting where
 
 import Juvix.Compiler.Core.Data.IdentDependencyInfo
+import Juvix.Compiler.Core.Extra.Utils
 import Juvix.Compiler.Core.Options
 import Juvix.Compiler.Core.Transformation.Base
 import Juvix.Compiler.Core.Transformation.Optimize.CaseFolding
@@ -23,8 +24,9 @@ optimize md = do
         2
         ( compose 2 (letFolding' (isInlineableLambda _optInliningDepth))
             . lambdaFolding
-            . inlining' _optInliningDepth nonRecSyms
+            . inlining' _optInliningDepth nonRecSyms symOcc
         )
       . letFolding
   where
     nonRecSyms = nonRecursiveIdents md
+    symOcc = getModuleSymbolsMap md

tests/Compilation/positive/test086.juvix

@@ -1,3 +1,4 @@
+-- Patterns in definitions
 module test086;
 
 import Stdlib.Prelude open;