Re: [RFC v2 62/76] target/riscv: rvv-0.9: single-width floating-point re

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Re: [RFC v2 62/76] target/riscv: rvv-0.9: single-width floating-point re

From:	Richard Henderson
Subject:	Re: [RFC v2 62/76] target/riscv: rvv-0.9: single-width floating-point reduction
Date:	Fri, 31 Jul 2020 09:45:45 -0700
User-agent:	Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

On 7/22/20 2:16 AM, frank.chang@sifive.com wrote:
>  # Vector ordered and unordered reduction sum
> -vfredsum_vs     0000-1 . ..... ..... 001 ..... 1010111 @r_vm
> +vfredsum_vs     000001 . ..... ..... 001 ..... 1010111 @r_vm
> +vfredosum_vs    000011 . ..... ..... 001 ..... 1010111 @r_vm

"The vfredosum instruction is a valid implementation of the vfredsum 
instruction."

Which is exactly what we're doing here.

Why should we treat them differently?  There is no parallelism that we can
exploit in tcg, unlike in hardware.


r~

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[RFC v2 57/76] target/riscv: rvv-0.9: mask-register logical instructions, (continued)
- [RFC v2 57/76] target/riscv: rvv-0.9: mask-register logical instructions, frank . chang, 2020/07/22
- [RFC v2 58/76] target/riscv: rvv-0.9: slide instructions, frank . chang, 2020/07/22
  - Re: [RFC v2 58/76] target/riscv: rvv-0.9: slide instructions, Richard Henderson, 2020/07/31
- [RFC v2 59/76] target/riscv: rvv-0.9: floating-point slide instructions, frank . chang, 2020/07/22
  - Re: [RFC v2 59/76] target/riscv: rvv-0.9: floating-point slide instructions, Richard Henderson, 2020/07/31
- [RFC v2 60/76] target/riscv: rvv-0.9: narrowing fixed-point clip instructions, frank . chang, 2020/07/22
  - Re: [RFC v2 60/76] target/riscv: rvv-0.9: narrowing fixed-point clip instructions, Richard Henderson, 2020/07/31
- [RFC v2 61/76] target/riscv: rvv-0.9: floating-point/integer type-convert instructions, frank . chang, 2020/07/22
  - Re: [RFC v2 61/76] target/riscv: rvv-0.9: floating-point/integer type-convert instructions, Richard Henderson, 2020/07/31
- [RFC v2 62/76] target/riscv: rvv-0.9: single-width floating-point reduction, frank . chang, 2020/07/22
  - Re: [RFC v2 62/76] target/riscv: rvv-0.9: single-width floating-point reduction, Richard Henderson <=
- [RFC v2 63/76] target/riscv: rvv-0.9: widening floating-point reduction instructions, frank . chang, 2020/07/22
- [RFC v2 64/76] target/riscv: rvv-0.9: single-width scaling shift instructions, frank . chang, 2020/07/22
  - Re: [RFC v2 64/76] target/riscv: rvv-0.9: single-width scaling shift instructions, Richard Henderson, 2020/07/31
- [RFC v2 65/76] target/riscv: rvv-0.9: remove widening saturating scaled multiply-add, frank . chang, 2020/07/22
  - Re: [RFC v2 65/76] target/riscv: rvv-0.9: remove widening saturating scaled multiply-add, Richard Henderson, 2020/07/31
- [RFC v2 66/76] target/riscv: rvv-0.9: remove vmford.vv and vmford.vf, frank . chang, 2020/07/22
  - Re: [RFC v2 66/76] target/riscv: rvv-0.9: remove vmford.vv and vmford.vf, Richard Henderson, 2020/07/31
- [RFC v2 67/76] target/riscv: rvv-0.9: remove integer extract instruction, frank . chang, 2020/07/22
  - Re: [RFC v2 67/76] target/riscv: rvv-0.9: remove integer extract instruction, Richard Henderson, 2020/07/31
- [RFC v2 68/76] fpu: add api to handle alternative sNaN propagation, frank . chang, 2020/07/22

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