[llvm] [llvm][InstCombine] Fold signum(x) into scmp(x, 0) (PR #143445)

[Iris Shi via llvm-commits]

el-ev wrote:

> @el-ev I had added a test in scmp.ll- `scmp_x_0_from_gt_minus_1`

Could you please add additional test cases and pre-commit the tests?

Please check https://llvm.org/docs/InstCombineContributorGuide.html 

https://github.com/llvm/llvm-project/pull/143445