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

[Matt Arsenault via llvm-commits]

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@@ -419,6 +446,58 @@ INITIALIZE_PASS_DEPENDENCY(RegionInfoPass)
 INITIALIZE_PASS_END(StructurizeCFGLegacyPass, "structurizecfg",
                     "Structurize the CFG", false, false)
 
+/// Then and Else block order in SCC is arbitrary. But based on the
+/// order, after structurization there are cases where there might be extra
+/// VGPR copies due to interference during register coelescing.
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arsenm wrote:

```suggestion
/// VGPR copies due to interference during register coalescing.
```

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