Add stg_ap_pnnv and related call patterns

In the implementation of bytestring encoding and decoding libraries, the call patterns stg_ap_pnnv and stg_ap_nnv occur very often. These call patterns are required to avoid boxing the pointers denoting the start and end of the memory area to write to/read from. The first 'p' often stems from using continuation passing style or from a record of configuration paramters. For example, the type of a bytestring builder looks about as follows.

newtype Builder = Builder ((Addr# -> Addr# -> IO BuildSignal) -> Addr# -> Addr# -> IO BuildSignal)

The first Addr# is the pointer to the next free byte and the second Addr# is the pointer to the first byte after the buffer being filled. The current implementation of the bytestring builder in the bytestring-0.10. library however uses

newtype Builder = Builder ((Ptr Word8 -> Ptr Word8 -> IO BuildSignal) -> Ptr Word8 -> Ptr Word8 -> IO BuildSignal)

as the benchmarks demonstrated that the repeated boxing is cheaper than the unknown calls implemented through a series of stg_ap_p, stg_ap_n, stg_ap_n, stg_ap_v calls.

I therefore suggest adding the following call patterns

ppnnv, pnnv, nnv, and nv.

to allow more efficient implementations of bytestring and text decoding/encoding. Note that the 'ppnnv' is used for a constant environment, a continuation, and a range resulting in a side-effecting function.

Trac metadata

Trac field	Value
Version	7.4.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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