From 37b80122bd1225eb8889d42b4fd5d7d383a329e7 Mon Sep 17 00:00:00 2001 From: Teresa Johnson Date: Fri, 10 May 2019 20:08:24 +0000 Subject: [ThinLTO] Auto-hide prevailing linkonce_odr only when all copies eligible Summary: We hit undefined references building with ThinLTO when one source file contained explicit instantiations of a template method (weak_odr) but there were also implicit instantiations in another file (linkonce_odr), and the latter was the prevailing copy. In this case the symbol was marked hidden when the prevailing linkonce_odr copy was promoted to weak_odr. It led to unsats when the resulting shared library was linked with other code that contained a reference (expecting to be resolved due to the explicit instantiation). Add a CanAutoHide flag to the GV summary to allow the thin link to identify when all copies are eligible for auto-hiding (because they were all originally linkonce_odr global unnamed addr), and only do the auto-hide in that case. Most of the changes here are due to plumbing the new flag through the bitcode and llvm assembly, and resulting test changes. I augmented the existing auto-hide test to check for this situation. Reviewers: pcc Subscribers: mehdi_amini, inglorion, eraman, dexonsmith, arphaman, dang, llvm-commits, steven_wu, wmi Tags: #llvm Differential Revision: https://reviews.llvm.org/D59709 llvm-svn: 360466 --- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 1 + 1 file changed, 1 insertion(+) (limited to 'llvm/lib/Bitcode/Writer/BitcodeWriter.cpp') diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp index c835976..63b0aab 100644 --- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp +++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp @@ -996,6 +996,7 @@ static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) { RawFlags |= Flags.NotEligibleToImport; // bool RawFlags |= (Flags.Live << 1); RawFlags |= (Flags.DSOLocal << 2); + RawFlags |= (Flags.CanAutoHide << 3); // Linkage don't need to be remapped at that time for the summary. Any future // change to the getEncodedLinkage() function will need to be taken into -- cgit v1.1