#11162: T783 regresses severely in allocations with new pattern match checker -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: T783 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"e9220daf7dbbd1ee084296a0d486a62aca7f1dcf/ghc" e9220daf/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="e9220daf7dbbd1ee084296a0d486a62aca7f1dcf" Bump allocations for T783 The new pattern match checker increased allocations by over 100%. Tracking in #11162. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11162#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11162: T783 regresses severely in allocations with new pattern match checker -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: T783 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"28f951edfe50ea5182065144340061ec326781f5/ghc" 28f951e/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="28f951edfe50ea5182065144340061ec326781f5" Overhaul the Overhauled Pattern Match Checker Overhaul the Overhauled Pattern Match Checker * 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). Hence, an example written with pattern guards is 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: Trac #11195, #11276, #11303, #11374, #11162 Test Plan: validate Reviewers: goldfire, bgamari, hvr, austin Subscribers: simonpj, thomie Differential Revision: https://phabricator.haskell.org/D1795 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11162#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11162: T783 regresses severely in allocations with new pattern match checker -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: closed Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Resolution: fixed | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: T783 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by thomie): * status: new => closed * resolution: => fixed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11162#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler