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Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instruct
From: |
Richard Henderson |
Subject: |
Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions |
Date: |
Tue, 13 Oct 2020 15:31:29 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 |
On 10/12/20 8:37 AM, Peter Maydell wrote:
> + nextlabel = gen_new_label();
> + tcg_gen_brcondi_i32(TCG_COND_NE, cpu_R[a->rn], 0, nextlabel);
> + gen_jmp(s, read_pc(s) + a->imm);
> +
> + gen_set_label(nextlabel);
> + tmp = load_reg(s, a->rn);
> + store_reg(s, 14, tmp);
> + gen_jmp(s, s->base.pc_next);
> + return true;
Oh, fwiw, with the tcg optimization patches just posted, this branch is better
inverted. That way the load of rn can be reused on the non-taken branch path.
Maybe sometime I'll try to propagate the data to the taken path, but that
automatically requires extra memory allocation, so it'll be difficult to do
that without a tcg slowdown.
r~
- [PATCH 05/10] target/arm: Don't allow BLX imm for M-profile, (continued)
- [PATCH 05/10] target/arm: Don't allow BLX imm for M-profile, Peter Maydell, 2020/10/12
- [PATCH 06/10] target/arm: Implement v8.1M branch-future insns (as NOPs), Peter Maydell, 2020/10/12
- [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions, Peter Maydell, 2020/10/12
- Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions, Peter Maydell, 2020/10/12
- Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions, Richard Henderson, 2020/10/13
- Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions, Peter Maydell, 2020/10/13
- Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions, Richard Henderson, 2020/10/13
- Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions, Peter Maydell, 2020/10/13
- Re: [PATCH 07/10] target/arm: Implement v8.1M low-overhead-loop instructions,
Richard Henderson <=
[PATCH 08/10] target/arm: Fix has_vfp/has_neon ID reg squashing for M-profile, Peter Maydell, 2020/10/12