Fix APFloat mod (committing for simonbyrne)

The previous version was prone to intermediate rounding or overflow.

Differential Revision: https://reviews.llvm.org/D29346


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299256 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed