Bigger core size in ghc8 compared to ghc7

Generated core size (as reported by ghc -v) is much bigger in ghc 8.0.2 compared to ghc 7.10.1. Things are slightly better in ghc 8.2.0rc2, but not as good as in ghc7

I think that results in a slight runtime performance problem.

steps to reproduce:

ghc -O A.hs

Result size of CorePrep  = {terms: 5,016, types: 9,813, coercions: 1,443} -- ghc8
Result size of CorePrep  = {terms: 975, types: 2,375, coercions: 150} -- ghc7
Result size of CorePrep  = {terms: 1,342, types: 2,838, coercions: 320, joins: 0/66} -- ghc8.2

Trac metadata

Trac field	Value
Version	8.2.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture