diff options
Diffstat (limited to 'compiler/GHC/Core/Opt/CprAnal.hs')
| -rw-r--r-- | compiler/GHC/Core/Opt/CprAnal.hs | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/compiler/GHC/Core/Opt/CprAnal.hs b/compiler/GHC/Core/Opt/CprAnal.hs index 87d9eb2ec7..5199635c4e 100644 --- a/compiler/GHC/Core/Opt/CprAnal.hs +++ b/compiler/GHC/Core/Opt/CprAnal.hs @@ -297,9 +297,16 @@ data TermFlag -- Better than using a Bool -- See Note [Nested CPR] exprTerminates :: CoreExpr -> TermFlag +-- ^ A /very/ simple termination analysis. exprTerminates e - | exprIsHNF e = Terminates -- A /very/ simple termination analysis. - | otherwise = MightDiverge + | exprIsHNF e = Terminates + | exprOkForSpeculation e = Terminates + | otherwise = MightDiverge + -- Annyingly, we have to check both for HNF and ok-for-spec. + -- * `I# (x# *# 2#)` is ok-for-spec, but not in HNF. Still worth CPR'ing! + -- * `lvl` is an HNF if its unfolding is evaluated + -- (perhaps `lvl = I# 0#` at top-level). But, tiresomely, it is never + -- ok-for-spec due to Note [exprOkForSpeculation and evaluated variables]. cprAnalApp :: AnalEnv -> CoreExpr -> [(CprType, CoreArg)] -> (CprType, CoreExpr) -- Main function that takes care of /nested/ CPR. See Note [Nested CPR] |