Reapply the following commit [1], which has been reverted by
the recent change [2] with no obvious reasons.
Also, add a comment block to explain the calculation.
[1]
```
commit 298c2e5e4fb46f5ffa7de7bbc5a32a9da0663768
Author: YAMAMOTO Takashi <yamamoto@midokura.com>
Date: Wed Jan 29 03:26:43 2020 +0900
sim: Fix stack alignment
The recent x86-64 convention requires 16-byte alignment before
(not after) calling a function.
This fixes snprintf crash I observed on macOS while saving XMM registers.
```
[2]
```
commit 2335b69120a3e36f1aa0cecc19c95208806cae54
Author: Xiang Xiao <xiaoxiang@xiaomi.com>
Date: Mon Apr 12 23:44:08 2021 +0800
arch: Allocate the space from the beginning in up_stack_frame
arch: Allocate the space from the beginning in up_stack_frame
and modify the affected portion:
1.Correct the stack dump and check
2.Allocate tls_info_s by up_stack_frame too
3.Move the stack fork allocation from arch to sched
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
```
7f307f9765