Re: [GHC] #13338: New versions of time and Cabal are causing a Core Lint error on Windows

#13338: New versions of time and Cabal are causing a Core Lint error on Windows -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: (none) Type: bug | Status: patch Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | simplCore/should_compile/T13338 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3217 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"d0508ef001e9c93920f6eb066cab5e79041cb886/ghc" d0508ef/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="d0508ef001e9c93920f6eb066cab5e79041cb886" When floating, don't box an expression that's okay for speculation (#13338) Commit 432f952e (Float unboxed expressions by boxing) lets the float-out pass turn, for example, ... (-# (remInt# x# 100000#) i#) ... into let lvl :: Int lvl = case remInt# x# 100000# of v { __DEFAULT__ -> I# v } in ... (-# (case lvl of { I# v -> v }) i#) ... But when, as in the example above, the expression that was floated out was the argument of an application, the resulting application may no longer satisfy the let/app invariant, because exprOkForSpeculation doesn't look far enough inside the definition of lvl. Solution: When the expression we floated out was okay for speculation, don't bother boxing it. It will be evaluated earlier, and that's okay by assumption. Fixes the let/app invariant and is cheaper too. Test Plan: make slowtest TEST=T13338 Reviewers: austin, bgamari, simonpj Reviewed By: bgamari, simonpj Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D3217 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13338#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler