[clang] [llvm] [ThinLTO] Support dead RTTI data elimination under -fno-split-lto-unit (PR #126336)

[via cfe-commits]

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@@ -1920,6 +1924,18 @@ Error LTO::runThinLTO(AddStreamFn AddStream, FileCache Cache,
       ThinLTO.CombinedIndex, WholeProgramVisibilityEnabledInLTO,
       DynamicExportSymbols, VisibleToRegularObjSymbols);
 
+  Triple TT(getTargetTriple());
+  DeadRTTIElimIndex(ThinLTO.CombinedIndex, TT).run();
+
+  if (!ThinLTO.CombinedIndex.withGlobalValueDeadStripping())
+    computeDeadSymbolsWithConstProp(ThinLTO.CombinedIndex, GUIDPreservedSymbols,
+                                    IsPrevailing, Conf.OptLevel > 0);
+
+
+  if (Conf.CombinedIndexHook &&
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luxufan wrote:

Without this change, some existing test cases would fail. This is because the patch alters the position of the dead symbol analysis (moving it after DeadRTTIElimIndex). So this change makes the dumped index file still include information about dead symbols.

https://github.com/llvm/llvm-project/pull/126336