On 5/15/23 05:49, juzhe.zh...@rivai.ai wrote:
From: Juzhe-Zhong <juzhe.zh...@rivai.ai>
This patch is adding rounding mode operand and FRM_REGNUM dependency
into floating-point instructions.
The floating-point instructions we added FRM and rounding mode operand:
1. vfadd/vfsub
2. vfwadd/vfwsub
3. vfmul
4. vfdiv
5. vfwmul
6. vfwmacc/vfwnmacc/vfwmsac/vfwnmsac
7. vfsqrt7/vfrec7
8. floating-point conversions.
9. floating-point reductions.
The floating-point instructions we did NOT add FRM and rounding mode operand:
1. vfsqrt/vfneg
Assuming vfsqrt is actually an estimator the best place to handle
rounding modes is at the last step(s) after N-R or Goldschmidt
refinement steps. I haven't paid too much attention to FP yet, but this
is an area I've got fairly extensive experience.
Sadly RISC-V's estimator is fairly poor and the single instance FMACs
are going to result in an implementation that may not actually be any
better than what glibc can do.
Jeff
