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/Writer/BitcodeWriter.cpp | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (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 37ecb99..19e7e18 100644 --- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp +++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp @@ -1044,7 +1044,8 @@ static uint64_t getEncodedFFlags(FunctionSummary::FFlags Flags) { return RawFlags; } -// Decode the flags for GlobalValue in the summary +// Decode the flags for GlobalValue in the summary. See getDecodedGVSummaryFlags +// in BitcodeReader.cpp. static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) { uint64_t RawFlags = 0; @@ -1058,6 +1059,8 @@ static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) { // account here as well. RawFlags = (RawFlags << 4) | Flags.Linkage; // 4 bits + RawFlags |= (Flags.Visibility << 8); // 2 bits + return RawFlags; } -- cgit v1.1