Revert "Revert "[builtins] Rounding mode support for addxf3/subxf3""

Test failure fixed.

This reverts commit e204d244badb2e9765a1020f41c773f63da208f4.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@371003 91177308-0d34-0410-b5e6-96231b3b80d8
14 files changed