| otherwise = case occ of
IAmDead -> pprTrace "callSiteInline: dead" (ppr id) False
IAmALoopBreaker -> False
- OneOcc in_lam one_br -> (not in_lam || is_cheap) && consider_safe in_lam True one_br
- NoOccInfo -> is_cheap && consider_safe True False False
- consider_safe in_lam once once_in_one_branch
- -- consider_safe decides whether it's a good idea to inline something,
- -- given that there's no work-duplication issue (the caller checks that).
- -- once_in_one_branch = True means there's a unique textual occurrence
- | inline_call = True
+ -- Occurs once in one branch. These are deal with by
+ -- preInlineUnconditionally, so we ignore them here:
+ OneOcc _ True _ -> False
- | once_in_one_branch
- -- Be very keen to inline something if this is its unique occurrence:
- --
- -- a) Inlining gives a good chance of eliminating the original
- -- binding (and hence the allocation) for the thing.
- -- (Provided it's not a top level binding, in which case the
- -- allocation costs nothing.)
- --
- -- b) Inlining a function that is called only once exposes the
- -- body function to the call site.
- --
- -- The only time we hold back is when substituting inside a lambda;
- -- then if the context is totally uninteresting (not applied, not scrutinised)
- -- there is no point in substituting because it might just increase allocation,
- -- by allocating the function itself many times
- -- Note [Jan 2002]: this comment looks out of date. The actual code
- -- doesn't inline *ever* in an uninteresting context. Why not? I
- -- think it's just because we don't want to inline top-level constants
- -- into uninteresting contexts, lest we (for example) re-nest top-level
- -- literal lists.
- --
- -- Note: there used to be a '&& not top_level' in the guard above,
- -- but that stopped us inlining top-level functions used only once,
- -- which is stupid
- = WARN( not is_top && not in_lam, ppr id )
- -- If (not in_lam) && one_br then PreInlineUnconditionally
- -- should have caught it, shouldn't it? Unless it's a top
- -- level thing.
- notNull arg_infos || interesting_cont
+ OneOcc in_lam False _ -> (not in_lam || is_cheap) && consider_safe True
+ other -> is_cheap && consider_safe False
+
+ consider_safe once
+ -- consider_safe decides whether it's a good idea to
+ -- inline something, given that there's no
+ -- work-duplication issue (the caller checks that).
+ | inline_call = True
| otherwise
= case guidance of
where
some_benefit = or arg_infos || really_interesting_cont ||
(not is_top && (once || (n_vals_wanted > 0 && enough_args)))
- -- If it occurs more than once, there must be something interesting
- -- about some argument, or the result context, to make it worth inlining
- --
- -- If a function has a nested defn we also record some-benefit,
- -- on the grounds that we are often able to eliminate the binding,
- -- and hence the allocation, for the function altogether; this is good
- -- for join points. But this only makes sense for *functions*;
- -- inlining a constructor doesn't help allocation unless the result is
- -- scrutinised. UNLESS the constructor occurs just once, albeit possibly
- -- in multiple case branches. Then inlining it doesn't increase allocation,
- -- but it does increase the chance that the constructor won't be allocated at all
- -- in the branches that don't use it.
-
+ -- If it occurs more than once, there must be
+ -- something interesting about some argument, or the
+ -- result context, to make it worth inlining
+ --
+ -- If a function has a nested defn we also record
+ -- some-benefit, on the grounds that we are often able
+ -- to eliminate the binding, and hence the allocation,
+ -- for the function altogether; this is good for join
+ -- points. But this only makes sense for *functions*;
+ -- inlining a constructor doesn't help allocation
+ -- unless the result is scrutinised. UNLESS the
+ -- constructor occurs just once, albeit possibly in
+ -- multiple case branches. Then inlining it doesn't
+ -- increase allocation, but it does increase the
+ -- chance that the constructor won't be allocated at
+ -- all in the branches that don't use it.
+
enough_args = n_val_args >= n_vals_wanted
really_interesting_cont | n_val_args < n_vals_wanted = False -- Too few args
| n_val_args == n_vals_wanted = interesting_cont
projects / ghc-hetmet.git / blobdiff