[llvm] [LoongArch][ISel] Check the number of sign bits in `PatGprGpr_32` (PR #107432)

[Lu Weining via llvm-commits]

================
@@ -189,8 +189,6 @@ define signext i32 @sdiv_si32_ui32_ui32(i32 %a, i32 %b) {
 ;
 ; LA64-LABEL: sdiv_si32_ui32_ui32:
 ; LA64:       # %bb.0: # %entry
-; LA64-NEXT:    addi.w $a1, $a1, 0
----------------
SixWeining wrote:

The English version misses a description about {div,mod}.[wu] while the Chinese version has.
```
在 LoongArch64 位兼容的机器上,执行 DIV.W[U]和 MOD.W[U]指令时,如果通用寄存器 rj 或 rk 中的
数值超过了 32 位有符号数/无符号数的数值范围,则指令执行结果可以为无意义的任意值。
```
Note that "32位有符号数/无符号数" should be "32位有符号数".

This limitation means that we should ensure the input operands are signed extend 32-bits values.

What's more, LoongArch V1.10 introduced a CPUCFG bit indicating whether the above limitation exist or not. If this bit is `1`, we can omit the explict `addi.w $a1, $a1, 0`.

Chinese version: https://www.loongson.cn/download/index

https://github.com/llvm/llvm-project/pull/107432