The t6-t8 are scratch registers and should not be allocatable.

Besides, add s0, s1, s2, s5 and s8 as allocatable registers.

Change-Id: I0805cc5273d0e0ec5040a0376bcbfba276202077
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3147315
Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76739}

Change-Id: I49276c44d4b457d65be0e5e922c7c473bb64071e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3124216
Auto-Submit: Yu Yin <xwafish@gmail.com>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76557}

Bug: v8:12008
Change-Id: I2e1d918a1370dae1e15919fbf02d69cbe48f63bf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3089095Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76308}