#9342: Branchless arithmetic operations -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: feature request | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.8.3 (CodeGen) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by strake888): On my AMD FX-8320, branchless `abs` and `sgn` seem speedier but branchless `cmp` seems slower: {{{ $ ./bench 'abs ' benchmarking abs time 37.06 ms (36.60 ms .. 37.56 ms) 1.000 R² (0.999 R² .. 1.000 R²) mean 37.99 ms (37.68 ms .. 38.37 ms) std dev 676.9 μs (490.1 μs .. 926.6 μs) $ ./bench 'abs''' benchmarking abs' time 34.41 ms (33.97 ms .. 34.77 ms) 1.000 R² (0.999 R² .. 1.000 R²) mean 34.08 ms (33.95 ms .. 34.25 ms) std dev 307.3 μs (243.0 μs .. 418.2 μs) $ ./bench 'sgn ' benchmarking sgn time 36.70 ms (36.33 ms .. 37.10 ms) 1.000 R² (0.999 R² .. 1.000 R²) mean 36.93 ms (36.79 ms .. 37.03 ms) std dev 216.7 μs (127.8 μs .. 343.1 μs) $ ./bench 'sgn''' benchmarking sgn' time 34.60 ms (34.24 ms .. 34.92 ms) 1.000 R² (0.999 R² .. 1.000 R²) mean 34.18 ms (34.02 ms .. 34.36 ms) std dev 348.1 μs (263.4 μs .. 461.5 μs) $ ./bench 'cmp ' benchmarking cmp time 35.80 ms (35.04 ms .. 36.80 ms) 0.998 R² (0.996 R² .. 0.999 R²) mean 36.79 ms (36.32 ms .. 37.15 ms) std dev 875.3 μs (665.6 μs .. 1.178 ms) $ ./bench 'cmp''' benchmarking cmp' time 36.41 ms (35.72 ms .. 37.08 ms) 0.999 R² (0.998 R² .. 1.000 R²) mean 36.44 ms (35.96 ms .. 36.74 ms) std dev 726.9 μs (513.8 μs .. 1.044 ms) $ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9342#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler