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| author | George Karachalias <george.karachalias@gmail.com> | 2016-02-01 11:43:12 +0100 |
|---|---|---|
| committer | George Karachalias <george.karachalias@gmail.com> | 2016-02-01 11:43:12 +0100 |
| commit | b5df2cc6cf2af4508a4f34a718320a6d79f9adca (patch) | |
| tree | 525e975eaf60e0200555e7f269fd79b7eaeb227d /docs/users_guide/bugs.rst | |
| parent | a883c1b7b08657102a2081b55c8fe68714d8bf73 (diff) | |
| download | haskell-wip/gadtpm.tar.gz | |
Overhaul the Overhauled Pattern Match Checkerwip/gadtpm
* Changed the representation of Value Set Abstractions. Instead
of using a prefix tree, we now use a list of Value Vector
Abstractions. The set of constraints Delta for every Value
Vector Abstraction is the oracle state so that we solve
everything only once.
* Instead of doing everything lazily, we prune at once (and in
general everything is much stricter). A case writtern with
pattern guards is not checked in almost the same time as the
equivalent with pattern matching.
* Do not store the covered and the divergent sets at all. Since
what we only need is a yes/no (does this clause cover anything?
Does it force any thunk?) We just keep a boolean for each.
* Removed flags `-Wtoo-many-guards` and `-ffull-guard-reasoning`.
Replaced with `fmax-pmcheck-iterations=n`. Still debatable what
should the default `n` be.
* When a guard is for sure not going to contribute anything, we
treat it as such: The oracle is not called and cases `CGuard`,
`UGuard` and `DGuard` from the paper are not happening at all
(the generation of a fresh variable, the unfolding of the
pattern list etc.). his combined with the above seems to be
enough to drop the memory increase for test T783 down to 18.7%.
* Do not export function `dsPmWarn` (it is now called directly
from within `checkSingle` and `checkMatches`).
* Make `PmExprVar` hold a `Name` instead of an `Id`. The term
oracle does not handle type information so using `Id` was a
waste of time/space.
* Added testcases T11195, T11303b (data families) and T11374
The patch addresses at least the following:
#11195, #11276, #11303, #11374, #11162
Diffstat (limited to 'docs/users_guide/bugs.rst')
| -rw-r--r-- | docs/users_guide/bugs.rst | 10 |
1 files changed, 0 insertions, 10 deletions
diff --git a/docs/users_guide/bugs.rst b/docs/users_guide/bugs.rst index 8304e25e78..f0c522cf75 100644 --- a/docs/users_guide/bugs.rst +++ b/docs/users_guide/bugs.rst @@ -358,16 +358,6 @@ Bugs in GHC This flag ensures that yield points are inserted at every function entrypoint (at the expense of a bit of performance). -- GHC's updated exhaustiveness and coverage checker (see - :ref:`options-sanity`) is quite expressive but with a rather high - performance cost (in terms of both time and memory consumption), mainly - due to guards. Two flags have been introduced to give more control to - the user over guard reasoning: :ghc-flag:`-Wtoo-many-guards` - and :ghc-flag:`-ffull-guard-reasoning` (see :ref:`options-sanity`). - When :ghc-flag:`-ffull-guard-reasoning` is on, pattern match checking for guards - runs in full power, which may run out of memory/substantially increase - compilation time. - - GHC does not allow you to have a data type with a context that mentions type variables that are not data type parameters. For example: |