Oh, Craig says vfrsqrt7.v not have frm but vsqrt.v have frm, and checked spike that match that.
On Mon, May 15, 2023 at 9:55 PM 钟居哲 <juzhe.zh...@rivai.ai> wrote: > > I don't know why we should not add frm vfsqrt.v since I saw topper (LLVM > maintainer) said we should > not add frm into vsqrt.v. Maybe kito knows the reason ? > > https://github.com/riscv-non-isa/rvv-intrinsic-doc/pull/226 > > > > > juzhe.zh...@rivai.ai > > From: Jeff Law > Date: 2023-05-15 21:52 > To: juzhe.zhong; gcc-patches > CC: kito.cheng; kito.cheng; palmer; palmer; rdapp.gcc > Subject: Re: [PATCH] RISC-V: Add rounding mode operand for floating point > instructions > > > 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 >
