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From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [PATCH v3 13/14] tcg/arm: Reserve a register for guest_base
Date: Fri, 20 Aug 2021 08:47:08 -1000	[thread overview]
Message-ID: <47d219b3-72fb-f9bf-d420-cd08bc781119@linaro.org> (raw)
In-Reply-To: <CAFEAcA81XmmHFtVfA9U307y5D41NzuHZNTFXgHe2-1Y+ZEhjSg@mail.gmail.com>

On 8/20/21 2:03 AM, Peter Maydell wrote:
>> -        } else if (datalo != addend) {
>> +        } else if (scratch_addend) {
>>               tcg_out_ld32_rwb(s, COND_AL, datalo, addend, addrlo);
>>               tcg_out_ld32_12(s, COND_AL, datahi, addend, 4);
>>           } else {
> 
> I don't understand this change. Yes, we can trash the addend
> register, but if it's the same as 'datalo' then the second load
> is not going to DTRT... Shouldn't this be
>    if (scratch_addend && datalo != addend)
> ?

Previously, addend was *always* a scratch register, TCG_REG_TMP or such.
Afterward, addend may be TCG_REG_GUEST_BASE, which should not be modified.
At no point is there overlap between addend and data{hi,lo}.

r~


  reply	other threads:[~2021-08-20 18:48 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 21:28 [PATCH v3 00/14] tcg/arm: Unaligned access and other cleanup Richard Henderson
2021-08-18 21:28 ` [PATCH v3 01/14] tcg/arm: Remove fallback definition of __ARM_ARCH Richard Henderson
2021-08-20 10:38   ` Peter Maydell
2021-08-18 21:29 ` [PATCH v3 02/14] tcg/arm: Standardize on tcg_out_<branch>_{reg,imm} Richard Henderson
2021-08-18 21:58   ` Philippe Mathieu-Daudé
2021-08-20 10:39   ` [PATCH v3 02/14] tcg/arm: Standardize on tcg_out_<branch>_{reg, imm} Peter Maydell
2021-08-18 21:29 ` [PATCH v3 03/14] tcg/arm: Simplify use_armvt5_instructions Richard Henderson
2021-08-20 10:59   ` Peter Maydell
2021-08-18 21:29 ` [PATCH v3 04/14] tcg/arm: Support armv4t in tcg_out_goto and tcg_out_call Richard Henderson
2021-08-20 10:50   ` Peter Maydell
2021-08-18 21:29 ` [PATCH v3 05/14] tcg/arm: Examine QEMU_TCG_DEBUG environment variable Richard Henderson
2021-08-20 11:01   ` Peter Maydell
2021-08-18 21:29 ` [PATCH v3 06/14] tcg/arm: Support unaligned access for softmmu Richard Henderson
2021-08-20 13:34   ` Peter Maydell
2021-08-20 17:19     ` Richard Henderson
2021-08-18 21:29 ` [PATCH v3 07/14] tcg/arm: Split out tcg_out_ldstm Richard Henderson
2021-08-20 11:45   ` Peter Maydell
2021-08-18 21:29 ` [PATCH v3 08/14] tcg/arm: Simplify usage of encode_imm Richard Henderson
2021-08-20 11:50   ` Peter Maydell
2021-08-18 21:29 ` [PATCH v3 09/14] tcg/arm: Drop inline markers Richard Henderson
2021-08-18 22:02   ` Philippe Mathieu-Daudé
2021-08-18 21:29 ` [PATCH v3 10/14] tcg/arm: Give enum arm_cond_code_e a typedef and use it Richard Henderson
2021-08-18 22:04   ` Philippe Mathieu-Daudé
2021-08-18 21:29 ` [PATCH v3 11/14] tcg/arm: More use of the ARMInsn enum Richard Henderson
2021-08-18 22:04   ` Philippe Mathieu-Daudé
2021-08-18 21:29 ` [PATCH v3 12/14] tcg/arm: More use of the TCGReg enum Richard Henderson
2021-08-18 22:05   ` Philippe Mathieu-Daudé
2021-08-18 21:29 ` [PATCH v3 13/14] tcg/arm: Reserve a register for guest_base Richard Henderson
2021-08-20 12:03   ` Peter Maydell
2021-08-20 18:47     ` Richard Henderson [this message]
2021-08-21 10:38       ` Peter Maydell
2021-08-18 21:29 ` [PATCH v3 14/14] tcg/arm: Support raising sigbus for user-only Richard Henderson
2021-08-20 13:56   ` Peter Maydell

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