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| author | Giles Anderson <agander@gmail.com> | 2019-04-09 21:51:21 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-04-15 06:20:29 -0400 |
| commit | b024e2891d06a81b3fd824f33fc72fb805e03c8f (patch) | |
| tree | 912ae486aa530d33b2550e232cca4f6f08be3ea8 | |
| parent | 1825f50d1736401724ef644e4d481cc26e8f47e5 (diff) | |
| download | haskell-b024e2891d06a81b3fd824f33fc72fb805e03c8f.tar.gz | |
Document how -O3 is handled by GHC
-O2 is the highest value of optimization.
-O3 will be reverted to -O2.
| -rw-r--r-- | docs/users_guide/using-optimisation.rst | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/docs/users_guide/using-optimisation.rst b/docs/users_guide/using-optimisation.rst index 95adb22a11..990c3960af 100644 --- a/docs/users_guide/using-optimisation.rst +++ b/docs/users_guide/using-optimisation.rst @@ -88,6 +88,17 @@ So, for example, ``ghc -c Foo.hs`` runtime or space *worse* if you're unlucky. They are normally turned on or off individually. +.. ghc-flag:: -On + :shortdesc: Any -On where n > 2 is the same as -O2. + :type: dynamic + :reverse: -O0 + :category: optimization-levels + + .. index:: + single: optimise; aggressively + + Any -On where n > 2 is the same as -O2. + We don't use a ``-O*`` flag for day-to-day work. We use ``-O`` to get respectable speed; e.g., when we want to measure something. When we want to go for broke, we tend to use ``-O2`` (and we go for lots of coffee |