- Download pdf
- Change FPCSR SPR permissions to allow for reading and writing from user space.
- Clarify that FPU underflow detection is done by detecting tininess before rounding.
- Authors Stafford Horne firstname.lastname@example.org
Details of Additions/Changes
2020-05-22 - Stafford Horne
While working on the glibc port for OpenRISC we found that pretty much every architecture allows reading and writing to the floating point control register (in OpenRISC FPCSR) in userland. This is used by userland to control the rounding mode and exception reading and controlling of the FPU.
2021-10-09 - Stafford Horne
The IEEE standard allows specifying how detecting of tininess occurs. Tininess detection is how underflow exceptions are triggered. There are two allowed methods for detecting tininess one is before rounding and the other being after rounding.