[llvm] [InstCombine] Fold usub_sat((sub nuw C1, A), C2) to usub_sat(C1 - C2, A) or 0 (PR #82280)

[Yingwei Zheng via llvm-commits]

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@@ -7,6 +7,77 @@
 declare void @use(i64)
 declare void @usei32(i32)
 declare void @usei1(i1)
+declare i32 @llvm.usub.sat.i32(i32, i32)
+declare i16 @llvm.usub.sat.i16(i16, i16)
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dtcxzyw wrote:

```suggestion
```

Explicit declarations of llvm intrinsics are not necessary.


https://github.com/llvm/llvm-project/pull/82280