Merge 755b439694432d4f68e20e979b479cbc30602bb1 into 18.x

[brad0]

[Mips] Fix missing sign extension in expansion of sub-word
atomic max (#77072)

Add sign extension "SEB/SEH" before compare.

Fix #61881

[brad0]

/cherry-pick 755b439

[llvmbot]

@llvm/issue-subscribers-backend-mips

Author: Brad Smith (brad0)

[Mips] Fix missing sign extension in expansion of sub-word atomic max (#77072)

Add sign extension "SEB/SEH" before compare.

Fix #61881

[llvmbot]

/pull-request #84566