+--------------------------------
+-- Top level function inlining
+--------------------------------
+-- This transformation inlines top level bindings that have been generated by
+-- the compiler and are really simple. Really simple currently means that the
+-- normalized form only contains a single binding, which catches most of the
+-- cases where a top level function is created that simply calls a type class
+-- method with a type and dictionary argument, e.g.
+-- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
+-- which is later called using simply
+-- fromInteger (smallInteger 10)
+-- By inlining such calls to simple, compiler generated functions, we prevent
+-- huge amounts of trivial components in the VHDL output, which the user never
+-- wanted. We never inline user-defined functions, since we want to preserve
+-- all structure defined by the user. Currently this includes all functions
+-- that were created by funextract, since we would get loops otherwise.
+--
+-- Note that "defined by the compiler" isn't completely watertight, since GHC
+-- doesn't seem to set all those names as "system names", we apply some
+-- guessing here.
+inlinetoplevel, inlinetopleveltop :: Transform
+-- Any system name is candidate for inlining. Never inline user-defined
+-- functions, to preserve structure.
+inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
+ norm_maybe <- Trans.lift $ getNormalized_maybe f
+ case norm_maybe of
+ -- No body or not normalizeable.
+ Nothing -> return expr
+ Just norm -> if needsInline norm then do
+ -- Regenerate all uniques in the to-be-inlined expression
+ norm_uniqued <- Trans.lift $ genUniques norm
+ -- And replace the variable reference with the unique'd body.
+ change norm_uniqued
+ else
+ -- No need to inline
+ return expr
+
+-- Leave all other expressions unchanged
+inlinetoplevel expr = return expr
+inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
+
+needsInline :: CoreExpr -> Bool
+needsInline expr = case splitNormalized expr of
+ -- Inline any function that only has a single definition, it is probably
+ -- simple enough. This might inline some stuff that it shouldn't though it
+ -- will never inline user-defined functions (inlinetoplevel only tries
+ -- system names) and inlining should never break things.
+ (args, [bind], res) -> True
+ _ -> False
+