diff options
| author | Simon Peyton Jones <simonpj@microsoft.com> | 2016-05-06 09:49:46 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2016-05-10 14:25:08 +0100 |
| commit | a4717f51433d16e948d102477564e257cdece475 (patch) | |
| tree | 88136a3315bbfc8b1064f3a77cb6ac16ee41bd85 /compiler/coreSyn | |
| parent | b58b0e18a568bbf6381a85eea7adc72679355671 (diff) | |
| download | haskell-a4717f51433d16e948d102477564e257cdece475.tar.gz | |
Comments about static forms
Diffstat (limited to 'compiler/coreSyn')
| -rw-r--r-- | compiler/coreSyn/CoreLint.hs | 28 |
1 files changed, 21 insertions, 7 deletions
diff --git a/compiler/coreSyn/CoreLint.hs b/compiler/coreSyn/CoreLint.hs index b3cec5f22a..2a2284b09d 100644 --- a/compiler/coreSyn/CoreLint.hs +++ b/compiler/coreSyn/CoreLint.hs @@ -1636,18 +1636,32 @@ top-level ones. See Note [Exported LocalIds] and Trac #9857. Note [Checking StaticPtrs] ~~~~~~~~~~~~~~~~~~~~~~~~~~ +See SimplCore Note [Grand plan for static forms] for an overview. -Every occurrence of the data constructor @StaticPtr@ should be moved to the top -level by the FloatOut pass. The linter is checking that no occurrence is left -nested within an expression. +Every occurrence of the data constructor @StaticPtr@ should be moved +to the top level by the FloatOut pass. It's vital that we don't have +nested StaticPtr uses after CorePrep, because we populate the Static +Pointer Table from the top-level bindings. See SimplCore Note [Grand +plan for static forms]. -The check is enabled only if the module uses the StaticPointers language -extension. This optimization arose from the need to compile "GHC.StaticPtr", -which otherwise would be rejected because the following binding +The linter checks that no occurrence is left behind, nested within an +expression. The check is enabled only: + +* After the FloatOut, CorePrep, and CoreTidy passes. + We could check more often, but the condition doesn't hold until + after the first FloatOut pass. + +* When the module uses the StaticPointers language extension. This is + a little hack. This optimization arose from the need to compile + GHC.StaticPtr, which otherwise would be rejected because of the + following binding for the StaticPtr data constructor itself: StaticPtr = \a b1 b2 b3 b4 -> StaticPtr a b1 b2 b3 b4 -contains an application of `StaticPtr` nested within the lambda abstractions. + which contains an application of `StaticPtr` nested within the + lambda abstractions. This binding is injected by CorePrep. + + Note that GHC.StaticPtr is itself compiled without -XStaticPointers. Note [Type substitution] ~~~~~~~~~~~~~~~~~~~~~~~~ |