Re: [PATCH v2 02/15] tcg/arm: Add host vector framework

[Richard Henderson]

On 2/8/21 10:28 AM, Peter Maydell wrote:
> On Mon, 8 Feb 2021 at 17:53, Peter Maydell <peter.maydell@linaro.org> wrote:
>> The AAPCS says that q4-q7 are preserved across calls.
> 
> Speaking of which, doesn't that mean we also need to
> save and restore q4-q7 in tcg_target_qemu_prologue()
> if we might be generating neon insns? (It doesn't look like
> aarch64's prologue does this, which seems like a bug.)

I just put them on the reserved list so that they don't get used.

>     tcg_regset_reset_reg(tcg_target_call_clobber_regs, TCG_REG_V8);
...
>     tcg_regset_reset_reg(tcg_target_call_clobber_regs, TCG_REG_V15);

We have way more vector registers than TCG will currently use, and we have to
assume all helpers can modify env->memory, so avoiding the call-saved ones is 
best.


r~