[llvm] update_test_checks: improve IR value name stability (PR #110940)

[Nicolai Hähnle via llvm-commits]

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@@ -1554,39 +1598,71 @@ def diffify_line(line, mapper):
                     else:
                         break
 
-                if rhs_value.name in local_commits:
+                if rhs_value.name in new_color.mapping:
                     # Same, but for a possible commit happening on the same line
-                    if local_commits[rhs_value.name] == lhs_value.name:
+                    if new_color.color[rhs_value.name] == lhs_value.name:
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nhaehnle wrote:

You're right, thanks. #111347 

https://github.com/llvm/llvm-project/pull/110940