diff options
Diffstat (limited to 'compiler/simplCore')
| -rw-r--r-- | compiler/simplCore/OccurAnal.hs | 42 |
1 files changed, 29 insertions, 13 deletions
diff --git a/compiler/simplCore/OccurAnal.hs b/compiler/simplCore/OccurAnal.hs index 6628ee70ee..41a6f7fa71 100644 --- a/compiler/simplCore/OccurAnal.hs +++ b/compiler/simplCore/OccurAnal.hs @@ -1104,12 +1104,13 @@ occAnalNonRecRhs :: OccEnv occAnalNonRecRhs env bndr rhs = occAnal rhs_env rhs where + -- See Note [Cascading inlines] + env1 | certainly_inline = env + | otherwise = rhsCtxt env + -- See Note [Use one-shot info] - env1 = env { occ_one_shots = argOneShots OneShotLam dmd } + rhs_env = env1 { occ_one_shots = argOneShots OneShotLam dmd } - -- See Note [Cascading inlines] - rhs_env | certainly_inline = env1 - | otherwise = rhsCtxt env1 certainly_inline -- See Note [Cascading inlines] = case idOccInfo bndr of @@ -1395,19 +1396,29 @@ markManyIf False uds = uds {- Note [Use one-shot information] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The occurrrence analyser propagates one-shot-lambda information in two situation - * Applications: eg build (\cn -> blah) +The occurrrence analyser propagates one-shot-lambda information in two +situations: + + * Applications: eg build (\c n -> blah) + Propagate one-shot info from the strictness signature of 'build' to - the \cn + the \c n. + + This strictness signature can come from a module interface, in the case of + an imported function, or from a previous run of the demand analyser. * Let-bindings: eg let f = \c. let ... in \n -> blah in (build f, build f) + Propagate one-shot info from the demanand-info on 'f' to the lambdas in its RHS (which may not be syntactically at the top) -Some of this is done by the demand analyser, but this way it happens -much earlier, taking advantage of the strictness signature of -imported functions. + This information must have come from a previous run of the demanand + analyser. + +Previously, the demand analyser would *also* set the one-shot information, but +that code was buggy (see #11770), so doing it only in on place, namely here, is +saner. Note [Binders in case alternatives] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -1534,7 +1545,7 @@ oneShotGroup :: OccEnv -> [CoreBndr] -> ( OccEnv , [CoreBndr] ) -- The result binders have one-shot-ness set that they might not have had originally. - -- This happens in (build (\cn -> e)). Here the occurrence analyser + -- This happens in (build (\c n -> e)). Here the occurrence analyser -- linearity context knows that c,n are one-shot, and it records that fact in -- the binder. This is useful to guide subsequent float-in/float-out tranformations @@ -1555,8 +1566,13 @@ oneShotGroup env@(OccEnv { occ_one_shots = ctxt }) bndrs = case ctxt of [] -> go [] bndrs (bndr : rev_bndrs) (one_shot : ctxt) -> go ctxt bndrs (bndr': rev_bndrs) - where - bndr' = updOneShotInfo bndr one_shot + where + bndr' = updOneShotInfo bndr one_shot + -- Use updOneShotInfo, not setOneShotInfo, as pre-existing + -- one-shot info might be better than what we can infer, e.g. + -- due to explicit use of the magic 'oneShot' function. + -- See Note [The oneShot function] + | otherwise = go ctxt bndrs (bndr:rev_bndrs) |