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| author | Sebastian Graf <sebastian.graf@kit.edu> | 2021-06-24 09:54:33 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-06-27 14:57:39 -0400 |
| commit | b92479f9e367413cd69ff0877579033ab86cde36 (patch) | |
| tree | 1f0e2378e1573f2f8cc4269642f822ea1388930a | |
| parent | e69d070b85a4e911b1245e733e4b95d7d7cd9224 (diff) | |
| download | haskell-b92479f9e367413cd69ff0877579033ab86cde36.tar.gz | |
Inliner: Regard LitRubbish as TrivArg and not ConLike
Part of fixing #19766 required the emission of `LitRubbish` as absent filler in
places where we used `absentError` before. In WWRec we have the situation that
such bindings occur in the argument to functions. With `LitRubbish` we inlined
those functions, because
1. The absent binding was regarded as ConLike. So I fixed `exprIsHNFLike` to
respond `False` to `LitRubbish`.
2. The other source of inlining was that after inlining such an absent
binding, `LitRubbish` itself was regarded `ValueArg` by `interestingArg`,
leading to more inlining. It now responds `TrivArg` to `LitRubbish`.
Fixes #20035.
There's one slight 1.6% ghc/alloc regression left in T15164 that is due to an
additional specialisation `$s$cget`. I've no idea why that happens; the Core
output before is identical and has the call site that we specialise for.
Metric Decrease:
WWRec
| -rw-r--r-- | compiler/GHC/Core/Opt/Simplify/Utils.hs | 5 | ||||
| -rw-r--r-- | compiler/GHC/Core/Utils.hs | 4 |
2 files changed, 7 insertions, 2 deletions
diff --git a/compiler/GHC/Core/Opt/Simplify/Utils.hs b/compiler/GHC/Core/Opt/Simplify/Utils.hs index 15cccfd55b..549ee2365f 100644 --- a/compiler/GHC/Core/Opt/Simplify/Utils.hs +++ b/compiler/GHC/Core/Opt/Simplify/Utils.hs @@ -42,6 +42,7 @@ import GHC.Prelude import GHC.Driver.Session import GHC.Core +import GHC.Types.Literal ( isLitRubbish ) import GHC.Core.Opt.Simplify.Env import GHC.Core.Opt.Monad ( SimplMode(..), Tick(..) ) import qualified GHC.Core.Subst @@ -819,7 +820,9 @@ interestingArg env e = go env 0 e DoneEx e _ -> go (zapSubstEnv env) n e ContEx tvs cvs ids e -> go (setSubstEnv env tvs cvs ids) n e - go _ _ (Lit {}) = ValueArg + go _ _ (Lit l) + | isLitRubbish l = TrivArg -- Leads to unproductive inlining in WWRec, #20035 + | otherwise = ValueArg go _ _ (Type _) = TrivArg go _ _ (Coercion _) = TrivArg go env n (App fn (Type _)) = go env n fn diff --git a/compiler/GHC/Core/Utils.hs b/compiler/GHC/Core/Utils.hs index a120bed3b0..12efdddcd4 100644 --- a/compiler/GHC/Core/Utils.hs +++ b/compiler/GHC/Core/Utils.hs @@ -1907,7 +1907,9 @@ exprIsHNFlike is_con is_con_unf = is_hnf_like -- but otherwise I worry that if an Id's unfolding is just itself, -- we could get an infinite loop - is_hnf_like (Lit _) = True + is_hnf_like (Lit l) = not (isLitRubbish l) + -- Regarding a LitRubbish as ConLike leads to unproductive inlining in + -- WWRec, see #20035 is_hnf_like (Type _) = True -- Types are honorary Values; -- we don't mind copying them is_hnf_like (Coercion _) = True -- Same for coercions |