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| author | Matthew Pickering <matthewtpickering@gmail.com> | 2022-01-05 17:21:28 +0000 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-01-07 18:25:06 -0500 |
| commit | 7b783c9da649899bdce34b6e746fa8704b667f28 (patch) | |
| tree | ddfd706deaa75b307b4a1ad1e220fc50284d8ef1 /compiler/GHC/Unit/Module/ModGuts.hs | |
| parent | 978ea35e37b49ffde28b0536e44362b66f3187b4 (diff) | |
| download | haskell-7b783c9da649899bdce34b6e746fa8704b667f28.tar.gz | |
Thoughtful forcing in CoreUnfolding
We noticed that the structure of CoreUnfolding could leave double the
amount of CoreExprs which were retained in the situation where the
template but not all the predicates were forced. This observation was
then confirmed using ghc-debug:
```
(["ghc:GHC.Core:App","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","THUNK_1_0"],Count 237)
(["ghc:GHC.Core:App","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","ghc-prim:GHC.Types:True"],Count 1)
(["ghc:GHC.Core:Case","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","THUNK_1_0"],Count 12)
(["ghc:GHC.Core:Cast","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","BLACKHOLE"],Count 1)
(["ghc:GHC.Core:Cast","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","THUNK_1_0"],Count 78)
(["ghc:GHC.Core:Cast","ghc-prim:GHC.Types:True","THUNK_1_0","ghc-prim:GHC.Types:False","THUNK_1_0"],Count 1)
(["ghc:GHC.Core:Cast","ghc-prim:GHC.Types:True","ghc-prim:GHC.Types:False","THUNK_1_0","THUNK_1_0"],Count 3)
(["ghc:GHC.Core:Cast","ghc-prim:GHC.Types:True","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0"],Count 1)
(["ghc:GHC.Core:Lam","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","BLACKHOLE"],Count 31)
(["ghc:GHC.Core:Lam","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","THUNK_1_0"],Count 4307)
(["ghc:GHC.Core:Lam","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","ghc-prim:GHC.Types:True"],Count 6)
(["ghc:GHC.Core:Let","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","THUNK_1_0"],Count 29)
(["ghc:GHC.Core:Lit","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","ghc-prim:GHC.Types:True"],Count 1)
(["ghc:GHC.Core:Tick","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","THUNK_1_0"],Count 36)
(["ghc:GHC.Core:Var","ghc-prim:GHC.Types:True","THUNK_1_0","THUNK_1_0","THUNK_1_0"],Count 1)
(["ghc:GHC.Core:Var","ghc-prim:GHC.Types:True","ghc-prim:GHC.Types:False","THUNK_1_0","THUNK_1_0"],Count 6)
(["ghc:GHC.Core:Var","ghc-prim:GHC.Types:True","ghc-prim:GHC.Types:False","ghc-prim:GHC.Types:True","THUNK_1_0"],Count 2)
```
Where we can see that the first argument is forced but there are still
thunks remaining which retain the old expr.
For my test case (a very big module, peak of 3 000 000 core terms) this
reduced peak memory usage by 1G (12G -> 11G).
Fixes #20905
Diffstat (limited to 'compiler/GHC/Unit/Module/ModGuts.hs')
0 files changed, 0 insertions, 0 deletions