diff options
Diffstat (limited to 'compiler/types/InstEnv.hs')
| -rw-r--r-- | compiler/types/InstEnv.hs | 33 |
1 files changed, 24 insertions, 9 deletions
diff --git a/compiler/types/InstEnv.hs b/compiler/types/InstEnv.hs index e214f12a65..a8b5f0f8ff 100644 --- a/compiler/types/InstEnv.hs +++ b/compiler/types/InstEnv.hs @@ -41,7 +41,7 @@ import Unify import Outputable import ErrUtils import BasicTypes -import UniqFM +import UniqDFM import Util import Id import Data.Data ( Data ) @@ -330,7 +330,21 @@ or, to put it another way, we have -} --------------------------------------------------- -type InstEnv = UniqFM ClsInstEnv -- Maps Class to instances for that class +{- +Note [InstEnv determinism] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +We turn InstEnvs into a list in some places that don't directly affect +the ABI. That happens when we create output for `:info`. +Unfortunately that nondeterminism is nonlocal and it's hard to tell what it +affects without following a chain of functions. It's also easy to accidentally +make that nondeterminism affect the ABI. Furthermore the envs should be +relatively small, so it should be free to use deterministic maps here. +Testing with nofib and validate detected no difference between UniqFM and +UniqDFM. See also Note [Deterministic UniqFM] +-} + +type InstEnv = UniqDFM ClsInstEnv -- Maps Class to instances for that class + -- See Note [InstEnv determinism] -- | 'InstEnvs' represents the combination of the global type class instance -- environment, the local type class instance environment, and the set of @@ -365,10 +379,11 @@ instance Outputable ClsInstEnv where -- the dfun type. emptyInstEnv :: InstEnv -emptyInstEnv = emptyUFM +emptyInstEnv = emptyUDFM instEnvElts :: InstEnv -> [ClsInst] -instEnvElts ie = [elt | ClsIE elts <- eltsUFM ie, elt <- elts] +instEnvElts ie = [elt | ClsIE elts <- eltsUDFM ie, elt <- elts] + -- See Note [InstEnv determinism] -- | Test if an instance is visible, by checking that its origin module -- is in 'VisibleOrphanModules'. @@ -388,7 +403,7 @@ classInstances :: InstEnvs -> Class -> [ClsInst] classInstances (InstEnvs { ie_global = pkg_ie, ie_local = home_ie, ie_visible = vis_mods }) cls = get home_ie ++ get pkg_ie where - get env = case lookupUFM env cls of + get env = case lookupUDFM env cls of Just (ClsIE insts) -> filter (instIsVisible vis_mods) insts Nothing -> [] @@ -397,20 +412,20 @@ classInstances (InstEnvs { ie_global = pkg_ie, ie_local = home_ie, ie_visible = memberInstEnv :: InstEnv -> ClsInst -> Bool memberInstEnv inst_env ins_item@(ClsInst { is_cls_nm = cls_nm } ) = maybe False (\(ClsIE items) -> any (identicalClsInstHead ins_item) items) - (lookupUFM inst_env cls_nm) + (lookupUDFM inst_env cls_nm) extendInstEnvList :: InstEnv -> [ClsInst] -> InstEnv extendInstEnvList inst_env ispecs = foldl extendInstEnv inst_env ispecs extendInstEnv :: InstEnv -> ClsInst -> InstEnv extendInstEnv inst_env ins_item@(ClsInst { is_cls_nm = cls_nm }) - = addToUFM_C add inst_env cls_nm (ClsIE [ins_item]) + = addToUDFM_C add inst_env cls_nm (ClsIE [ins_item]) where add (ClsIE cur_insts) _ = ClsIE (ins_item : cur_insts) deleteFromInstEnv :: InstEnv -> ClsInst -> InstEnv deleteFromInstEnv inst_env ins_item@(ClsInst { is_cls_nm = cls_nm }) - = adjustUFM adjust inst_env cls_nm + = adjustUDFM adjust inst_env cls_nm where adjust (ClsIE items) = ClsIE (filterOut (identicalClsInstHead ins_item) items) @@ -702,7 +717,7 @@ lookupInstEnv' ie vis_mods cls tys all_tvs = all isNothing rough_tcs -------------- - lookup env = case lookupUFM env cls of + lookup env = case lookupUDFM env cls of Nothing -> ([],[]) -- No instances for this class Just (ClsIE insts) -> find [] [] insts |