#13629: sqrt should use machine instruction on x86_64 -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.4.1 Component: Compiler (NCG) | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime | Test Case: performance bug | numeric/num009 Blocked By: | Blocking: Related Tickets: #13570 | Differential Rev(s): Phab:D3508 Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): I think I would prefer to make the C call cheaper (by, for instance, marking it as pure so that the sinker can better optimize code around it) than to bring x87 into the fold. x87's `fsin` is terribly imprecise (and consequently causes the `num009` test to fail on platforms where it is used). Moreover, as you point out, x87 performance varies widely between microarchitectures. Finally, x87's architecture is really a nuisance for the native codegen, requiring a number of hacks. It would be nice if some day we could do away with x87 support entirely (although this likely won't happen any time soon). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13629#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler