[clang] [clang][modules] Remove preloaded SLocEntries from PCM files (PR #66962)

[Ben Langmuir via cfe-commits]

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@@ -1986,13 +1984,15 @@ bool SourceManager::isInTheSameTranslationUnitImpl(
   if (isLoadedFileID(LOffs.first) != isLoadedFileID(ROffs.first))
     return false;
 
-  // If both are loaded from different AST files.
   if (isLoadedFileID(LOffs.first) && isLoadedFileID(ROffs.first)) {
-    auto FindTableSegment = [this](FileID FID) {
-      return llvm::upper_bound(LoadedSLocEntryTableSegments, -FID.ID - 2);
+    auto FindSLocEntryAlloc = [this](FileID FID) {
+      // FileIDs are negative, we store the beginning of each allocation (the
+      // lowest FileID), later allocations have lower FileIDs.
+      return llvm::upper_bound(LoadedSLocEntryAllocBegin, FID, std::greater{});
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benlangmuir wrote:

I would have expected lower_bound; is this related to -2 vs -1?

https://github.com/llvm/llvm-project/pull/66962