It has been been a few years since the release of OpenRISC version 1.2. But, it’s been a busy few years of getting GDB and GCC ports upstream. Now with the GCC port upstream we are able to make progress and this new architecture revision does just that bringing in a handful of new instructions:

  • New instruction lf.stod.d for converting floats from single precision to double prevision
  • New instruction lf.dtos.d for converting floats from double precision to single precision
  • New instruction l.adrp for constructing addresses
  • New instructions lf.sfun* to support unordered compares
  • New instruction l.lf to load floats with NaN boxing on 64-bit hardware
  • Remove instructions lf.rem.d and lf.rem.s used for calculating floating point remainder

Perhaps one of the biggest new features is the addition of support for performing double precision floating point operations using 32-bit hardware. The is by way of the new ORFPX64A32 instruction set extension.

With that said OpenRISC architecture specification version 1.3 has been released. Quite a few of the instructions and changes are already implemented in OpenRISC soft cores and toolchains so you should be able to use them right away.

See the full details on the release page.

Soft Core Support

Some soft cores already support the new instructions if you want to try them out you can find them here:

  • mor1kx - has support for lf.sfun* operations.
  • or1k_marocchino - has support for lf.sfun* operations as well as the ORFPX64A32 extension.

Software Upstreaming Effort

In order for the new features to be useful to most users they must be available in OpenRISC software. Stafford is working on submitting toolchain patches for the following components.

  • GCC - Patches, ready to go but depends on binutils being in first.
  • binutils - Working on adding test cases for the l.adrp instruction. Should send for upstream review in a few weeks.
  • cgen- Added unordered support to support binutils, patches submitted waiting for review.

Please feel free to contact us via the mailing list if you have any questions.


04 June 2019