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Re: [RFC 01/15] target/riscv: reformat @sh format encoding for B-extensi
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From: |
Richard Henderson |
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Subject: |
Re: [RFC 01/15] target/riscv: reformat @sh format encoding for B-extension |
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Date: |
Thu, 19 Nov 2020 11:03:46 -0800 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 |
On 11/18/20 12:29 AM, frank.chang@sifive.com wrote:
> -slli 00.... ...... ..... 001 ..... 0010011 @sh
> -srli 00.... ...... ..... 101 ..... 0010011 @sh
> -srai 01.... ...... ..... 101 ..... 0010011 @sh
> +slli 000000 ...... ..... 001 ..... 0010011 @sh
> +srli 000000 ...... ..... 101 ..... 0010011 @sh
> +srai 010000 ...... ..... 101 ..... 0010011 @sh
We need at least 7 bits here for rv128, if we ever get around to it. The code
in trans_slli et al already eliminates numbers that are two large.
In the rvb draft, only 5 bits are used in the uppermost field. Let's leave it
at that.
r~
- [RFC 00/15] support subsets of bitmanip extension, frank . chang, 2020/11/18
- [RFC 01/15] target/riscv: reformat @sh format encoding for B-extension, frank . chang, 2020/11/18
- Re: [RFC 01/15] target/riscv: reformat @sh format encoding for B-extension,
Richard Henderson <=
- [RFC 02/15] target/riscv: rvb: count leading/trailing zeros, frank . chang, 2020/11/18
- [RFC 03/15] target/riscv: rvb: count bits set, frank . chang, 2020/11/18
- [RFC 04/15] target/riscv: rvb: logic-with-negate, frank . chang, 2020/11/18
- [RFC 05/15] target/riscv: rvb: pack two words into one register, frank . chang, 2020/11/18
- [RFC 06/15] target/riscv: rvb: min/max instructions, frank . chang, 2020/11/18