[PATCH] D18346: ThinLTO: special handling for LinkOnce functions

[Teresa Johnson via llvm-commits]

tejohnson added inline comments.

================
Comment at: lib/LTO/ThinLTOCodeGenerator.cpp:182
@@ +181,3 @@
+    if (!IsFirstDefinitionForLinker(*GVInfo, Index, ModulePath))
+      GV.setLinkage(GlobalValue::AvailableExternallyLinkage);
+    break;
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Thinking more about this - I don't think it is correct for WeakAny or LinkOnceAny to be converted to AvailableExternally. This could change the program result. The reason is that the selected copy is allowed to have different behavior than the unselected version. This is why WeakAny and LinkOnceAny return true from GlobalValue::mayBeOverridden(), which prevents optimizations such as inlining and therefore ensures that the linker-selected copy is executed. Changing their linkage to AvailableExternally enables the unselected versions to be inlined, and therefore the selected body is not executed at runtime, which can result in different program behavior.


http://reviews.llvm.org/D18346