Fix #4346 (INLINABLE pragma not behaving consistently)

[ghc-hetmet.git] / compiler / coreSyn / CoreSyn.lhs

diff --git a/compiler/coreSyn/CoreSyn.lhs b/compiler/coreSyn/CoreSyn.lhs
index c74de06..1181931 100644 (file)
--- a/compiler/coreSyn/CoreSyn.lhs
+++ b/compiler/coreSyn/CoreSyn.lhs
@@ -59,6 +59,9 @@ module CoreSyn (
        -- * Annotated expression data types
        AnnExpr, AnnExpr'(..), AnnBind(..), AnnAlt,
        
+        -- ** Operations on annotated expressions
+        collectAnnArgs,
+
        -- ** Operations on annotations
        deAnnotate, deAnnotate', deAnnAlt, collectAnnBndrs,
 
@@ -480,7 +483,20 @@ data UnfoldingSource
                       -- Replace uf_tmpl each time around
 
   | InlineStable       -- From an INLINE or INLINABLE pragma 
-                      -- Do not replace uf_tmpl; instead, keep it unchanged
+                       --   INLINE     if guidance is UnfWhen
+                       --   INLINABLE  if guidance is UnfIfGoodArgs
+                       -- (well, technically an INLINABLE might be made
+                       -- UnfWhen if it was small enough, and then
+                       -- it will behave like INLINE outside the current
+                       -- module, but that is the way automatic unfoldings
+                       -- work so it is consistent with the intended
+                       -- meaning of INLINABLE).
+                       --
+                      -- uf_tmpl may change, but only as a result of
+                       -- gentle simplification, it doesn't get updated
+                       -- to the current RHS during compilation as with
+                       -- InlineRhs.
+                       --
                       -- See Note [InlineRules]
 
   | InlineCompulsory   -- Something that *has* no binding, so you *must* inline it
@@ -1142,6 +1158,17 @@ data AnnBind bndr annot
 \end{code}
 
 \begin{code}
+-- | Takes a nested application expression and returns the the function
+-- being applied and the arguments to which it is applied
+collectAnnArgs :: AnnExpr b a -> (AnnExpr b a, [AnnExpr b a])
+collectAnnArgs expr
+  = go expr []
+  where
+    go (_, AnnApp f a) as = go f (a:as)
+    go e              as = (e, as)
+\end{code}
+
+\begin{code}
 deAnnotate :: AnnExpr bndr annot -> Expr bndr
 deAnnotate (_, e) = deAnnotate' e