[llvm] [GlobalISel] Combine [S,U]SUBO (PR #116489)

[Matt Arsenault via llvm-commits]

================
@@ -1901,6 +1907,13 @@ def cmp_combines: GICombineGroup<[
   redundant_binop_in_equality
 ]>;
 
+
+def artifact_combines: GICombineGroup<[
+  merge_combines,
+  match_addos,
+  match_subos
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arsenm wrote:

These names aren't great. match_subo_no_overflow? 

https://github.com/llvm/llvm-project/pull/116489