Add constant inlining to UPLC (#5790)

* Add constant inlining to UPLC

Signed-off-by: Ana Pantilie <[email protected]>

* Regenerate UPLC test output

Signed-off-by: Ana Pantilie <[email protected]>

* Regenerate benchmark test outputs

Signed-off-by: Ana Pantilie <[email protected]>

---------

Signed-off-by: Ana Pantilie <[email protected]>

plutus-benchmark/nofib/test/9.6/clausify-F5.budget.golden

@@ -1,2 +1,2 @@
-({cpu: 86149266650
-| mem: 341062680})
+({cpu: 86149243650
+| mem: 341062580})

plutus-benchmark/nofib/test/9.6/clausify-F5.size.golden

@@ -1 +1 @@
-1633
+1627

plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Simplify.hs

@@ -10,6 +10,7 @@ module UntypedPlutusCore.Simplify (
     soMaxCseIterations,
     soInlineHints,
     soConservativeOpts,
+    soInlineConstants,
     defaultSimplifyOpts,
     InlineHints (..),
 ) where
@@ -36,6 +37,7 @@ data SimplifyOpts name a = SimplifyOpts
     , _soMaxCseIterations        :: Int
     , _soConservativeOpts        :: Bool
     , _soInlineHints             :: InlineHints name a
+    , _soInlineConstants         :: Bool
     }
     deriving stock (Show)
 
@@ -48,6 +50,7 @@ defaultSimplifyOpts =
         , _soMaxCseIterations = 4
         , _soConservativeOpts = False
         , _soInlineHints = mempty
+        , _soInlineConstants = True
         }
 
 simplifyProgram ::
@@ -83,7 +86,7 @@ simplifyTerm opts =
             >=> pure . forceDelayCancel
             >=> pure . caseOfCase'
             >=> pure . caseReduce
-            >=> inline (_soInlineHints opts)
+            >=> inline (_soInlineConstants opts) (_soInlineHints opts)
 
     caseOfCase' :: Term name uni fun a -> Term name uni fun a
     caseOfCase' = case eqT @fun @DefaultFun of

plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Transform/Inline.hs

@@ -117,7 +117,12 @@ type InliningConstraints name uni fun =
   )
 
 -- See Note [Differences from PIR inliner] 2
-data InlineInfo name a = InlineInfo {_usages :: Usages.Usages, _hints :: InlineHints name a}
+data InlineInfo name a = InlineInfo
+  { _iiUsages          :: Usages.Usages
+  , _iiHints           :: InlineHints name a
+  , _iiInlineConstants :: Bool
+  }
+makeLenses ''InlineInfo
 
 -- Using a concrete monad makes a very large difference to the performance of this module
 -- (determined from profiling)
@@ -166,13 +171,15 @@ See Note [Inlining and global uniqueness]
 inline ::
   forall name uni fun m a.
   (ExternalConstraints name uni fun m) =>
+  Bool ->
+  -- ^ inline constants
   InlineHints name a ->
   Term name uni fun a ->
   m (Term name uni fun a)
-inline hints t =
+inline inlineConstants hints t =
   let
     inlineInfo :: InlineInfo name a
-    inlineInfo = InlineInfo usgs hints
+    inlineInfo = InlineInfo usgs hints inlineConstants
     usgs :: Usages.Usages
     usgs = Usages.termUsages t
    in
@@ -274,7 +281,7 @@ maybeAddSubst body a n rhs0 = do
   rhs <- processTerm rhs0
 
   -- Check whether we've been told specifically to inline this
-  hints <- asks _hints
+  hints <- view iiHints
   let hinted = shouldInline hints a n
 
   if hinted -- if we've been told specifically, then do it right away
@@ -299,7 +306,8 @@ shouldUnconditionallyInline ::
   InlineM name uni fun a Bool
 shouldUnconditionallyInline n rhs body = do
   isTermPure <- checkPurity rhs
-  preUnconditional isTermPure ||^ postUnconditional isTermPure
+  inlineConstants <- view iiInlineConstants
+  preUnconditional isTermPure ||^ postUnconditional inlineConstants isTermPure
   where
     -- similar to the paper, preUnconditional inlining checks that the binder is 'OnceSafe'.
     -- I.e., it's used at most once AND it neither duplicate code or work.
@@ -310,7 +318,8 @@ shouldUnconditionallyInline n rhs body = do
     -- See Note [Inlining approach and 'Secrets of the GHC Inliner'] and [Inlining and
     -- purity]. This is the case where we don't know that the number of occurrences is
     -- exactly one, so there's no point checking if the term is immediately evaluated.
-    postUnconditional isTermPure = pure isTermPure &&^ acceptable rhs
+    postUnconditional inlineConstants isTermPure =
+      pure isTermPure &&^ acceptable inlineConstants rhs
 
 -- | Check if term is pure. See Note [Inlining and purity]
 checkPurity :: Term name uni fun a -> InlineM name uni fun a Bool
@@ -322,7 +331,7 @@ nameUsedAtMostOnce ::
   name ->
   InlineM name uni fun a Bool
 nameUsedAtMostOnce n = do
-  usgs <- asks _usages
+  usgs <- view iiUsages
   -- 'inlining' terms used 0 times is a cheap way to remove dead code while we're here
   pure $ Usages.getUsageCount n usgs <= 1
 
@@ -360,10 +369,14 @@ effectSafe body n purity = do
 {- | Should we inline? Should only inline things that won't duplicate work or code.
 See Note [Inlining approach and 'Secrets of the GHC Inliner']
 -}
-acceptable :: Term name uni fun a -> InlineM name uni fun a Bool
-acceptable t =
+acceptable ::
+  Bool ->
+  -- ^ inline constants
+  Term name uni fun a ->
+  InlineM name uni fun a Bool
+acceptable inlineConstants t =
   -- See Note [Inlining criteria]
-  pure $ costIsAcceptable t && sizeIsAcceptable t
+  pure $ costIsAcceptable t && sizeIsAcceptable inlineConstants t
 
 {- | Is the cost increase (in terms of evaluation work) of inlining a variable whose RHS is
 the given term acceptable?
@@ -392,8 +405,12 @@ costIsAcceptable = \case
 {- | Is the size increase (in the AST) of inlining a variable whose RHS is
 the given term acceptable?
 -}
-sizeIsAcceptable :: Term name uni fun a -> Bool
-sizeIsAcceptable = \case
+sizeIsAcceptable ::
+  Bool ->
+  -- ^ inline constants
+  Term name uni fun a ->
+  Bool
+sizeIsAcceptable inlineConstants = \case
   Builtin{} -> True
   Var{} -> True
   Error{} -> True
@@ -402,16 +419,16 @@ sizeIsAcceptable = \case
   -- Inlining constructors of size 1 or 0 seems okay
   Constr _ _ es -> case es of
     []  -> True
-    [e] -> sizeIsAcceptable e
+    [e] -> sizeIsAcceptable inlineConstants e
     _   -> False
   -- Cases are pretty big, due to the case branches
   Case{} -> False
-  -- Constants can be big! We could check the size here and inline if they're
-  -- small, but probably not worth it
-  Constant{} -> False
+  -- Inlining constants is deemed acceptable if the 'inlineConstants'
+  -- flag is turned on, see Note [Inlining constants].
+  Constant{} -> inlineConstants
   Apply{} -> False
-  Force _ t -> sizeIsAcceptable t
-  Delay _ t -> sizeIsAcceptable t
+  Force _ t -> sizeIsAcceptable inlineConstants t
+  Delay _ t -> sizeIsAcceptable inlineConstants t
 
 -- | Fully apply and beta reduce.
 fullyApplyAndBetaReduce ::

plutus-core/untyped-plutus-core/test/Transform/floatDelay1.uplc.golden

@@ -1 +1 @@
-((\a_1 -> addInteger a_1 a_1) 1)
+(addInteger 1 1)

plutus-core/untyped-plutus-core/test/Transform/floatDelay3.uplc.golden

@@ -1 +1 @@
-((\a_2 -> addInteger (force a_2) (force a_2)) (delay 1))
+(addInteger (force (delay 1)) (force (delay 1)))

plutus-core/untyped-plutus-core/test/Transform/inlinePure3.uplc.golden

@@ -1 +1 @@
-(\b_5 -> (\x_8 y_9 -> 1 x_8) 1)
+(\b_5 y_8 -> 1 1)

plutus-core/untyped-plutus-core/test/Transform/interveningLambda.uplc.golden

@@ -1 +1 @@
-(force ((\a_1 -> delay (1 a_1)) 1))
+(force (delay (1 1)))

plutus-tx-plugin/src/PlutusTx/Plugin.hs

@@ -519,6 +519,8 @@ runCompiler moduleName opts expr = do
             & set (PLC.coSimplifyOpts . UPLC.soConservativeOpts)
                 (opts ^. posConservativeOpts)
             & set (PLC.coSimplifyOpts . UPLC.soInlineHints) hints
+            & set (PLC.coSimplifyOpts . UPLC.soInlineConstants)
+                (opts ^. posInlineConstants)
 
     -- GHC.Core -> Pir translation.
     pirT <- original <$> (PIR.runDefT annMayInline $ compileExprWithDefs expr)