Commit b024e289 authored by Giles Anderson's avatar Giles Anderson Committed by Marge Bot
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Document how -O3 is handled by GHC

    -O2 is the highest value of optimization.
    -O3 will be reverted to -O2.
parent 1825f50d
......@@ -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
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