[llvm] [SimplifyCFG] Fold switch over ucmp/scmp to icmp and br (PR #105636)

[Yingwei Zheng via llvm-commits]

================
@@ -7131,6 +7131,59 @@ static bool simplifySwitchOfPowersOfTwo(SwitchInst *SI, IRBuilder<> &Builder,
   return true;
 }
 
+/// Fold switch over ucmp/scmp intrinsic to br if two of the switch arms have
+/// the same destination.
+static bool simplifySwitchOfCmpIntrinsic(SwitchInst *SI,
+                                         IRBuilderBase &Builder) {
+  auto *Cmp = dyn_cast<CmpIntrinsic>(SI->getCondition());
+  if (!Cmp || !Cmp->hasOneUse() || SI->getNumCases() != 2)
----------------
dtcxzyw wrote:

We should handle the following case:
```
  switch i8 %cond, label %default.unreachable [
    i8 -1, label %bb1
    i8 0, label %bb1
    i8 1, label %bb2
  ]
```


https://github.com/llvm/llvm-project/pull/105636