[llvm] [InstCombine] Optimize powi(X, Y)/ (X * Z) with Ofast (PR #87047)

[Matt Arsenault via llvm-commits]

================
@@ -580,15 +580,21 @@ Instruction *InstCombinerImpl::foldFPSignBitOps(BinaryOperator &I) {
 
 Instruction *InstCombinerImpl::foldPowiReassoc(BinaryOperator &I) {
   auto createPowiExpr = [](BinaryOperator &I, InstCombinerImpl &IC, Value *X,
-                           Value *Y, Value *Z) {
+                           Value *Y, Value *Z, bool UpdateUsers = true) {
----------------
arsenm wrote:

Don't understand why UpdateUsers would be an option 

https://github.com/llvm/llvm-project/pull/87047