Re: [GHC] #8472: Primitive string literals prevent optimization

#8472: Primitive string literals prevent optimization -------------------------------------+------------------------------------- Reporter: akio | Owner: gridaphobe Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: fixed | Keywords: newcomer Operating System: Linux | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2554, Wiki Page: | Phab:D2605 -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"f5b275a239d2554c4da0b7621211642bf3b10650/ghc" f5b275a2/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="f5b275a239d2554c4da0b7621211642bf3b10650" Don't tick top-level string literals This fixes a regression due to D2605 (see #8472) wherein top-level primitive strings would fail to be noticed by CoreToStg as they were wrapped in a tick. This resulted in a panic in CoreToStg due to inconsistent CAF information (or a Core Lint failure, if enabled). Here we document the invariant that unlifted expressions can only sit at top-level if of the form `Lit (MachStr ...)` with no ticks or other embellishments. Moreover, we fix instance of this in `Simplify.prepareRhs` and `FloatOut.wrapTick` where this invariant was being broken. Test Plan: Validate with `-g`. Run testsuite with `WAY=ghci`. Reviewers: austin, simonpj Reviewed By: simonpj Subscribers: simonpj, akio, scpmw, thomie Differential Revision: https://phabricator.haskell.org/D3051 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8472#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler