[llvm] [IR] Add `samesign` flag to icmp instruction (PR #111419)

[Nikita Popov via llvm-commits]

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@@ -1224,6 +1224,17 @@ class ICmpInst: public CmpInst {
   /// Return the unsigned version of the predicate.
   static Predicate getUnsignedPredicate(Predicate pred);
 
+  /// An icmp instruction, which can be marked as "samesign", indicating that
+  /// the two operands have the same sign. This means that we can convert
+  /// "slt/ult" to "ult", which enables more optimizations.
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nikic wrote:

```suggestion
  /// "slt" to "ult" and vice versa, which enables more optimizations.
```
I'd also move this comment to hasSameSign(), which is the public API.

https://github.com/llvm/llvm-project/pull/111419