[llvm] [IR] Add nowrap flags for trunc instruction (PR #85592)

[Nikita Popov via llvm-commits]

================
@@ -1021,3 +1021,37 @@ define i16 @PR44545(i32 %t0, i32 %data) {
   %sub = add nsw i16 %cast, -1
   ret i16 %sub
 }
+
+; Make sure that SimplifyDemandedBits the nowrap flags
----------------
nikic wrote:

```suggestion
; Make sure that SimplifyDemandedBits drops the nowrap flags.
```

https://github.com/llvm/llvm-project/pull/85592