Re: [GHC] #16111: Inconsistent behavior of Data.Bits.shiftL with different optimization levels and -fllvm

#16111: Inconsistent behavior of Data.Bits.shiftL with different optimization levels and -fllvm -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: harpocrates Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | https://gitlab.haskell.org/ghc/ghc/merge_requests/113 -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"5341edf3635f2875271acc469570481c52000374/ghc" 5341edf/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="5341edf3635f2875271acc469570481c52000374" Error out of invalid Int/Word bit shifts Although the Haddock's for `shiftL` and `shiftR` do require the number of bits to be non-negative, we should still check this before calling out to primitives (which also have undefined behaviour for negative bit shifts). If a user _really_ wants to bypass checks that the number of bits is sensible, they already have the aptly-named `unsafeShiftL`/`unsafeShiftR` at their disposal. See #16111. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16111#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler