Compiling DynFlags is jolly slow

Compiling DynFlags really takes a long time these days.

Ian thinks that it's due to the Read and Show instances he has added (see attached W2.hs.

Simon M suggests: instead of using Read/Show, you could generate some code in mkDerivedConstants to use ReadP and Outputable, which should be much smaller and faster.

This ticket is

• To see if we can speed up compilation of DynFlags
• To check WHY it is so slow. Are there any lessons we can learn or ways to make it compile faster? Is it tickling some asymptotically-bad corner of the compiler?

Simon

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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Architecture