[llvm] [SimplifyCFG] Add optimization for switches of powers of two (PR #70977)

[via llvm-commits]

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@@ -6839,6 +6837,66 @@ static bool ReduceSwitchRange(SwitchInst *SI, IRBuilder<> &Builder,
   return true;
 }
 
+static bool isSwitchOfPowersOfTwo(ArrayRef<int64_t> Values) {
+  for (auto &Value : Values) {
+    if (Value <= 0 || (Value & (Value - 1)) != 0)
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DKay7 wrote:

I found the `isPowerOf2` method in `APInt` class, so I used it instead.

https://github.com/llvm/llvm-project/pull/70977