[llvm] [InstCombine] Fix saturated add canonicalization (PR #97973)

[Nikita Popov via llvm-commits]

================
@@ -996,6 +989,23 @@ static Value *canonicalizeSaturatedAdd(ICmpInst *Cmp, Value *TVal, Value *FVal,
   if (!match(TVal, m_AllOnes()))
     return nullptr;
 
+  if (Pred == ICmpInst::ICMP_UGE &&
+      match(FVal, m_Add(m_Value(X), m_APInt(C))) && X == Cmp0 &&
+      match(TVal, m_AllOnes()) && match(Cmp1, m_APInt(CmpC)) && *CmpC == ~*C) {
+    // (X u >= ~C) ? -1 : (X + C) --> uadd.sat(X, C)
----------------
nikic wrote:

```suggestion
    // (X u>= ~C) ? -1 : (X + C) --> uadd.sat(X, C)
```

https://github.com/llvm/llvm-project/pull/97973