integer-gmp2 uses a new 64bit-based primop
introduced in b62bd5ecf3be421778e4835010b6b334e95c5a56.
However, the returned values differ for exceptional IEEE values:
Previous (expected) semantics:
> decodeFloat (-1/0) (-4503599627370496,972) > decodeFloat (1/0) (4503599627370496,972) > decodeFloat (0/0) (-6755399441055744,972)
Currently (broken) semantics:
> decodeFloat (-1/0 :: Double) (-9223372036854775808,-53) > decodeFloat (1/0 :: Double) (-9223372036854775808,-53) > decodeFloat (0/0 :: Double) (-9223372036854775808,-53)
This patch reverts to the old expected semantics.
We'll revisit the implementation during GHC 7.11 development.
This should address Trac #9810