[PATCH1/7][LoongArch] GDB support

[Paul Hua]

Hi Simon,

Thanks for the review.


>
> Please write a little commit message that gives a bit of background
> about that architecture, for those who don't know it.  Also, where to
> find documentation about it (about the instruction set, for example),
> should someone need to fix some bugs in it.

LoongArch has the typical characteristics of RISC. LoongArch
instructions are of fixed size and have regular instruction formats.
Most of the instructions have two source operands and one destination
operand. LoongArch is a load-store architecture; this means only the
load/store instructions can access memory the operands of the other
instructions are within the processor core or the immediate number in
the instruction opcode.
LoongArch is divided into two versions, the 32-bit version (LA32) and
the 64-bit version (LA64). LA64 applications are “application-level
backward binary compatibility” with LA32 applications. That means LA32
applications can run directly on the machine compatible with LA64, but
the behavior of system software (such as the kernel) on the machine
compatible with LA32 is not guaranteed to be the same as on the
machine compatible with LA64.
LoongArch is composed of a basic part (Loongson Base) and an expanded
part, as shown in the figure. The expansion part includes Loongson
Binary Translation (LBT), Loongson VirtualiZation (LVZ), Loongson SIMD
EXtension (LSX), and Loongson Advanced SIMD EXtension(LASX).

The LoongArch documents are on
https://loongson.github.io/LoongArch-Documentation/README-EN.html
ISA documents are on
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html


> Who are the authors of this code?  Are there multiple or it's just you?
> Are they all covered by a copyright assignment?  See:
>
>   https://sourceware.org/gdb/wiki/ContributionChecklist#FSF_copyright_Assignment
We (Loongson[1]) are the authors of this code, We (Loongson) have been
signed the FSF Copyright Assignment. All code cover by @loongson.cn
mail address.

[1] http://www.loongson.cn/


> Simon