[llvm] [StructurizeCFG] Order IF Else block using Heuristics (PR #139605)

[Matt Arsenault via llvm-commits]

================
@@ -409,6 +411,31 @@ class StructurizeCFGLegacyPass : public RegionPass {
 
 } // end anonymous namespace
 
+/// Helper function for heuristics to order if else block
+/// Checks whether an instruction is potential vector copy instruction, if so,
+/// checks if the operands are from different BB. if so, returns True.
+// Then there's a possibility of coelescing without interference when ordered
----------------
arsenm wrote:

```suggestion
// Then there's a possibility of coalescing without interference when ordered
```

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