#16122: `round :: Double -> Int64` much slower than `fromIntegral @Int @Int64 . round` -------------------------------------+------------------------------------- Reporter: Fuuzetsu | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by akio): Replying to [comment:4 simonpj]:
* Rules are applied to the RHS of other rules, if the phases allow; this seems reasonable. After all, that's what will happen whenever the rule is applied.
Hmm, this doesn't appear to be true in general. It looks like user-defined rules are never applied to the RHS of other rules. Only built-in rules are. I checked this by compiling the following module: {{{#!hs module Foo where import qualified GHC.List as List foo, bar:: Int foo = 0 bar = 0 baz :: [Int] baz = [] {-# RULES "foo" foo = 1 #-} {-# RULES "bar/foo" bar = foo #-} -- the "foo" rule doesn't fire {-# RULES "baz" baz = List.concat [] #-} -- the "concat" rule from GHC.List doesn't fire }}} Here is what I think is the relevant code https://gitlab.haskell.org/ghc/ghc/blob/9ea8dcea3e5ba96808ef91028e0efde9d31f.... The rule RHS is simplified under `rule_env`, which has the `sm_rules` field set to `False`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16122#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler