diff options
Diffstat (limited to 'compiler/GHC/Unit/Module/ModIface.hs')
| -rw-r--r-- | compiler/GHC/Unit/Module/ModIface.hs | 44 |
1 files changed, 41 insertions, 3 deletions
diff --git a/compiler/GHC/Unit/Module/ModIface.hs b/compiler/GHC/Unit/Module/ModIface.hs index a339df92cc..db7c4ce362 100644 --- a/compiler/GHC/Unit/Module/ModIface.hs +++ b/compiler/GHC/Unit/Module/ModIface.hs @@ -24,6 +24,7 @@ module GHC.Unit.Module.ModIface , emptyFullModIface , mkIfaceHashCache , emptyIfaceHashCache + , forceModIface ) where @@ -55,6 +56,7 @@ import GHC.Utils.Fingerprint import GHC.Utils.Binary import Control.DeepSeq +import Control.Exception {- Note [Interface file stages] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -145,6 +147,9 @@ type family IfaceBackendExts (phase :: ModIfacePhase) where -- except that we explicitly make the 'mi_decls' and a few other fields empty; -- as when reading we consolidate the declarations etc. into a number of indexed -- maps and environments in the 'ExternalPackageState'. +-- +-- See Note [Strictness in ModIface] to learn about why some fields are +-- strict and others are not. data ModIface_ (phase :: ModIfacePhase) = ModIface { mi_module :: !Module, -- ^ Name of the module we are for @@ -228,7 +233,7 @@ data ModIface_ (phase :: ModIfacePhase) -- itself) but imports some trustworthy modules from its own -- package (which does require its own package be trusted). -- See Note [Trust Own Package] in GHC.Rename.Names - mi_complete_matches :: [IfaceCompleteMatch], + mi_complete_matches :: ![IfaceCompleteMatch], mi_doc_hdr :: Maybe HsDocString, -- ^ Module header. @@ -243,7 +248,7 @@ data ModIface_ (phase :: ModIfacePhase) -- ^ Either `()` or `ModIfaceBackend` for -- a fully instantiated interface. - mi_ext_fields :: ExtensibleFields, + mi_ext_fields :: !ExtensibleFields, -- ^ Additional optional fields, where the Map key represents -- the field name, resulting in a (size, serialized data) pair. -- Because the data is intended to be serialized through the @@ -256,6 +261,29 @@ data ModIface_ (phase :: ModIfacePhase) -- ^ Hash of the .hs source, used for recompilation checking. } +{- +Note [Strictness in ModIface] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ModIface is the Haskell representation of an interface (.hi) file. + +* During compilation we write out ModIface values to disk for files + that we have just compiled +* For packages that we depend on we load the ModIface from disk. + +Some fields in the ModIface are deliberately lazy because when we read +an interface file we don't always need all the parts. For example, an +interface file contains information about documentation which is often +not needed during compilation. This is achieved using the lazyPut/lazyGet pair. +If the field was strict then we would pointlessly load this information into memory. + +On the other hand, if we create a ModIface but **don't** write it to +disk then to avoid space leaks we need to make sure to deepseq all these lazy fields +because the ModIface might live for a long time (for instance in a GHCi session). +That's why in GHC.Driver.Main.hscMaybeWriteIface there is the call to +forceModIface. +-} + -- | Old-style accessor for whether or not the ModIface came from an hs-boot -- file. mi_boot :: ModIface -> IsBootInterface @@ -307,7 +335,7 @@ renameFreeHoles fhs insts = -- It wasn't actually a hole | otherwise = emptyUniqDSet - +-- See Note [Strictness in ModIface] about where we use lazyPut vs put instance Binary ModIface where put_ bh (ModIface { mi_module = mod, @@ -532,6 +560,16 @@ instance (NFData (IfaceBackendExts (phase :: ModIfacePhase)), NFData (IfaceDeclE rnf f16 `seq` f17 `seq` rnf f18 `seq` rnf f19 `seq` f20 `seq` f21 `seq` f22 `seq` rnf f23 `seq` rnf f24 `seq` f25 `seq` () +instance NFData (ModIfaceBackend) where + rnf (ModIfaceBackend f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13) + = rnf f1 `seq` rnf f2 `seq` rnf f3 `seq` rnf f4 `seq` + rnf f5 `seq` rnf f6 `seq` rnf f7 `seq` rnf f8 `seq` + rnf f9 `seq` rnf f10 `seq` rnf f11 `seq` rnf f12 `seq` rnf f13 + + +forceModIface :: ModIface -> IO () +forceModIface iface = () <$ (evaluate $ force iface) + -- | Records whether a module has orphans. An \"orphan\" is one of: -- -- * An instance declaration in a module other than the definition |