#2269: Word type to Double or Float conversions are slower than Int conversions -------------------------------------+------------------------------------- Reporter: dons | Owner: dons@… Type: feature | Status: new request | Milestone: 7.10.1 Priority: lowest | Version: 6.8.2 Component: Compiler | Keywords: rules, Resolution: | performance, double Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: Runtime | Blocked By: performance bug | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by thomie): Primops for word2Double and word2Float were added 2 years ago. commit 2e8c769422740c001e0a247bfec61d4f78598582 {{{ Author: Johan Tibell <> Date: Wed Dec 5 19:08:48 2012 -0800 Implement word2Float# and word2Double# }}} commit cd01e48fbc548ff8d81ab547108bfdde8a113cd7 {{{ Author: Johan Tibell <> Date: Thu Dec 13 12:03:40 2012 -0800 Add test for word2Double# and word2Float# }}} commit a18cf9cbdfec08732f5b7e0c886a5d899a6a5998 {{{ Author: Johan Tibell <> Date: Thu Dec 13 14:49:58 2012 -0800 Add fromIntegral/Word->Double and fromIntegral/Word-Float rules }}} commit 8cd4ced57dccc1f4f54d242982209ec61e145700 {{{ Author: Johan Tibell <> Date: Tue Dec 18 14:40:02 2012 +0100 perf test for Word->Float/Double conversion }}} commit 6d5f25f5e0b33173fb2e7983cab40808c723f220 {{{ Author: Geoffrey Mainland <> Date: Thu Jan 3 16:59:03 2013 +0000 Fix LLVM code generated for word2Float# and word2Double#. }}} commit 744035fdd4b882c17ef7c6e4439b9e7099e7ec3d {{{ Author: Johan Tibell <> Date: Mon Jan 7 21:35:07 2013 -0800 Fix Word2Float# test on 32-bit }}} The resulting core of the example from the description now looks the same for `Word->Double` as for `Int->Double`. {{{ $ cabal install vector $ cat test.hs {-# LANGUAGE CPP #-} import Data.Vector as V import Data.Word main = print . V.sum #ifdef WORD . V.map (fromIntegral::Word->Double) #else . V.map (fromIntegral::Int->Double) #endif $ V.enumFromTo 0 100000000 $ ghc -ddump-simpl -dsuppress-all -O2 -fforce-recomp -DWORD test.hs -o testWord ... main_$s$wfoldlM'_loop main_$s$wfoldlM'_loop = \ sc_s5G6 sc1_s5G7 -> case tagToEnum# (leWord# sc1_s5G7 (__word 100000000)) of _ { False -> sc_s5G6; True -> main_$s$wfoldlM'_loop (+## sc_s5G6 (word2Double# sc1_s5G7)) (plusWord# sc1_s5G7 (__word 1)) } ... $ ghc -ddump-simpl -dsuppress-all -O2 -fforce-recomp -DINT test.hs -o testInt ... main_$s$wfoldlM'_loop main_$s$wfoldlM'_loop = \ sc_s5GQ sc1_s5GR -> case tagToEnum# (<=# sc1_s5GR 100000000) of _ { False -> sc_s5GQ; True -> main_$s$wfoldlM'_loop (+## sc_s5GQ (int2Double# sc1_s5GR)) (+# sc1_s5GR 1) } }}} But `testWord` is still 3 times slower than `testInt`. {{{ $ time ./testWord 5.00000005e15 real 0m0.579s user 0m0.575s sys 0m0.003s $ time ./testInt 5.00000005e15 real 0m0.196s user 0m0.191s sys 0m0.004s }}} As I can not easily explain this difference, I'll leave this ticket open for now. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/2269#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler