[lld] [lld] check cache before real_path in loadDylib (PR #140791)

[Vincent Lee via llvm-commits]

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@@ -253,6 +265,7 @@ DylibFile *macho::loadDylib(MemoryBufferRef mbref, DylibFile *umbrella,
     }
     file =
         make<DylibFile>(**result, umbrella, isBundleLoader, explicitlyLinked);
+    realfile = file;
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thevinster wrote:

What if we just use `realfile` everywhere? In the case when the pointers are the same, everything works as expected. But when they are different, the first cache lookup is basically always a miss and will rely on the second resolved path lookup to find the result. In theory, it shouldn't be a huge hit, but it's still a minor regression from the current implementation. But, it makes things easier to reason about without needing to set both `file` and `realfile`? 

https://github.com/llvm/llvm-project/pull/140791