Add primops for copying/cloning an array in the new codegen

Daniel Peebles's benchmarks show that copying arrays using a indexArray#/writeArray# loop is much slower than using a (new) primop that calls memcpy. In addition, cloning arrays is slower than it need to be due to newArray# filling the array with a default element, just to have all the elements be overwritten by the contents of the array being cloned.

I suggest we add the following primops:

copyArray#        ::        Array# a -> Int# -> MutableArray# s a -> Int# -> Int# -> State# s -> State# s
copyMutableArray# :: MutableArray# a -> Int# -> MutableArray# s a -> Int# -> Int# -> State# s -> State# s

cloneArray#        ::        Array#   a -> Int# -> Int# -> State# s -> (# State# s, Array# a #)
cloneMutableArray# :: MutableArray# s a -> Int# -> Int# -> State# s -> (# State# s, MutableArray# s a #)

freezeArray# :: MutableArray# s a -> Int# -> Int# -> State# s -> (# State# s, Array# a #)
thawArray#   ::        Array#   a -> Int# -> Int# -> State# s -> (# State# s, MutableArray# s a #)

Note that ByteArray# versions can be created using FFI calls to memcpy and thus don't need to be primops.

Trac metadata

Trac field	Value
Version	7.0.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
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CC	johan.tibell@gmail.com, pumpkingod@gmail.com
Operating system
Architecture