[llvm] [MIPS] Sign-extend subwords when expanding atomic max/min (PR #89246)

[YunQiang Su via llvm-commits]

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@@ -1118,6 +1118,8 @@ define i16 @test_max_16(ptr nocapture %ptr, i16 signext %val) {
 ; MIPSEL-NEXT:    srav $7, $7, $10
 ; MIPSEL-NEXT:    seh $2, $2
 ; MIPSEL-NEXT:    seh $7, $7
+; MIPSEL-NEXT:    sllv $2, $2, $10
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wzssyqa wrote:

I see. Thanks.
While it seems there is another problem introduced by the previous patch (not your current):

if `ptr` is something like
```
struct xx {
    int16 a;
    int16 b;
}
```
our code will overwrite another halfword.

https://github.com/llvm/llvm-project/pull/89246