[Bug target/125736] GCC doesn't use implicit zero-extended register in address

[lh_mouse at 126 dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125736

--- Comment #1 from LIU Hao <lh_mouse at 126 dot com> ---
This looks like an issue specific in the address expression. If I change the
input constraint from `"Ts"` to `"r"`, then GCC does make use of implicit
zero-extension:

```
 lea    eax,[rax*8+0x1480]
 mov    eax,DWORD PTR gs:[rax]
```

but this produces two instructions instead of one.