From 54fb3ca96e261f7107cb1b5778c34cb0e0808be6 Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Wed, 27 Jan 2021 10:43:51 -0800 Subject: [ThinLTO] Add Visibility bits to GlobalValueSummary::GVFlags Imported functions and variable get the visibility from the module supplying the definition. However, non-imported definitions do not get the visibility from (ELF) the most constraining visibility among all modules (Mach-O) the visibility of the prevailing definition. This patch * adds visibility bits to GlobalValueSummary::GVFlags * computes the result visibility and propagates it to all definitions Protected/hidden can imply dso_local which can enable some optimizations (this is stronger than GVFlags::DSOLocal because the implied dso_local can be leveraged for ELF -shared while default visibility dso_local has to be cleared for ELF -shared). Note: we don't have summaries for declarations, so for ELF if a declaration has the most constraining visibility, the result visibility may not be that one. Differential Revision: https://reviews.llvm.org/D92900 --- llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Bitcode/Reader/BitcodeReader.cpp') diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp index f280020..b33c6b7 100644 --- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp +++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp @@ -968,13 +968,17 @@ static FunctionSummary::FFlags getDecodedFFlags(uint64_t RawFlags) { return Flags; } -/// Decode the flags for GlobalValue in the summary. +// Decode the flags for GlobalValue in the summary. The bits for each attribute: +// +// linkage: [0,4), notEligibleToImport: 4, live: 5, local: 6, canAutoHide: 7, +// visibility: [8, 10). static GlobalValueSummary::GVFlags getDecodedGVSummaryFlags(uint64_t RawFlags, uint64_t Version) { // Summary were not emitted before LLVM 3.9, we don't need to upgrade Linkage // like getDecodedLinkage() above. Any future change to the linkage enum and // to getDecodedLinkage() will need to be taken into account here as above. auto Linkage = GlobalValue::LinkageTypes(RawFlags & 0xF); // 4 bits + auto Visibility = GlobalValue::VisibilityTypes((RawFlags >> 8) & 3); // 2 bits RawFlags = RawFlags >> 4; bool NotEligibleToImport = (RawFlags & 0x1) || Version < 3; // The Live flag wasn't introduced until version 3. For dead stripping @@ -984,7 +988,8 @@ static GlobalValueSummary::GVFlags getDecodedGVSummaryFlags(uint64_t RawFlags, bool Local = (RawFlags & 0x4); bool AutoHide = (RawFlags & 0x8); - return GlobalValueSummary::GVFlags(Linkage, NotEligibleToImport, Live, Local, AutoHide); + return GlobalValueSummary::GVFlags(Linkage, Visibility, NotEligibleToImport, + Live, Local, AutoHide); } // Decode the flags for GlobalVariable in the summary -- cgit v1.1