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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2021-04-15 15:20:26 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2021-04-22 23:29:32 +0100 |
| commit | 8d135dfb871662f86b522c6fa337d1695f6bfe1a (patch) | |
| tree | f1ac26cda512f01a680f05758fdf7b38f9f46119 /compiler/GHC/Core/Coercion | |
| parent | 7bc7eea3897dcb8a87fdb0921f451b9bc77309f6 (diff) | |
| download | haskell-wip/T19700.tar.gz | |
Eliminate unsafeEqualityProof in CorePrepwip/T19700
The main idea here is to avoid treating
* case e of {}
* case unsafeEqualityProof of UnsafeRefl co -> blah
specially in CoreToStg. Instead, nail them in CorePrep,
by converting
case e of {}
==> e |> unsafe-co
case unsafeEqualityProof of UnsafeRefl cv -> blah
==> blah[unsafe-co/cv]
in GHC.Core.Prep. Now expressions that we want to treat as trivial
really are trivial. We can get rid of cpExprIsTrivial.
And we fix #19700.
A downside is that, at least under unsafeEqualityProof, we substitute
in types and coercions, which is more work. But a big advantage is
that it's all very simple and principled: CorePrep really gets rid of
the unsafeCoerce stuff, as it does empty case, runRW#, lazyId etc.
I've updated the overview in GHC.Core.Prep, and added
Note [Unsafe coercions] in GHC.Core.Prep
Note [Implementing unsafeCoerce] in base:Unsafe.Coerce
We get 3% fewer bytes allocated when compiling perf/compiler/T5631,
which uses a lot of unsafeCoerces. (It's a happy-generated parser.)
Metric Decrease:
T5631
Diffstat (limited to 'compiler/GHC/Core/Coercion')
| -rw-r--r-- | compiler/GHC/Core/Coercion/Opt.hs | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/compiler/GHC/Core/Coercion/Opt.hs b/compiler/GHC/Core/Coercion/Opt.hs index 66ba8ee8ab..72c96c962a 100644 --- a/compiler/GHC/Core/Coercion/Opt.hs +++ b/compiler/GHC/Core/Coercion/Opt.hs @@ -594,6 +594,7 @@ opt_univ env sym prov role oty1 oty2 #endif ProofIrrelProv kco -> ProofIrrelProv $ opt_co4_wrap env sym False Nominal kco PluginProv _ -> prov + CorePrepProv -> prov ------------- opt_transList :: HasDebugCallStack => InScopeSet -> [NormalCo] -> [NormalCo] -> [NormalCo] |