[llvm] [StructurizeCFG] Hoist and simplify zero-cost incoming else phi values (PR #139605)

[Matt Arsenault via llvm-commits]

================
@@ -279,7 +281,7 @@ class StructurizeCFG {
   ConstantInt *BoolTrue;
   ConstantInt *BoolFalse;
   Value *BoolPoison;
-
+  TargetTransformInfo *TTI;
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arsenm wrote:

```suggestion
  const TargetTransformInfo *TTI;
```

https://github.com/llvm/llvm-project/pull/139605