[clang] [llvm] [clang][deps] Cache `VFS::getRealPath()` (PR #68645)

[Ben Langmuir via cfe-commits]

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@@ -159,7 +159,37 @@ DependencyScanningFilesystemSharedCache::CacheShard::
     getOrInsertEntryForFilename(StringRef Filename,
                                 const CachedFileSystemEntry &Entry) {
   std::lock_guard<std::mutex> LockGuard(CacheLock);
-  return *EntriesByFilename.insert({Filename, &Entry}).first->getValue();
+  CacheByFilename[Filename].first = &Entry;
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benlangmuir wrote:

This is changing "get or insert" into "replace".

https://github.com/llvm/llvm-project/pull/68645