From 96efdd6107a06e762e2cd25eb41b053f946ac87a Mon Sep 17 00:00:00 2001 From: Peter Collingbourne Date: Tue, 14 Jun 2016 21:01:22 +0000 Subject: IR: Introduce local_unnamed_addr attribute. If a local_unnamed_addr attribute is attached to a global, the address is known to be insignificant within the module. It is distinct from the existing unnamed_addr attribute in that it only describes a local property of the module rather than a global property of the symbol. This attribute is intended to be used by the code generator and LTO to allow the linker to decide whether the global needs to be in the symbol table. It is possible to exclude a global from the symbol table if three things are true: - This attribute is present on every instance of the global (which means that the normal rule that the global must have a unique address can be broken without being observable by the program by performing comparisons against the global's address) - The global has linkonce_odr linkage (which means that each linkage unit must have its own copy of the global if it requires one, and the copy in each linkage unit must be the same) - It is a constant or a function (which means that the program cannot observe that the unique-address rule has been broken by writing to the global) Although this attribute could in principle be computed from the module contents, LTO clients (i.e. linkers) will normally need to be able to compute this property as part of symbol resolution, and it would be inefficient to materialize every module just to compute it. See: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/356401.html http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356738.html for earlier discussion. Part of the fix for PR27553. Differential Revision: http://reviews.llvm.org/D20348 llvm-svn: 272709 --- llvm/lib/Target/TargetLoweringObjectFile.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'llvm/lib/Target/TargetLoweringObjectFile.cpp') diff --git a/llvm/lib/Target/TargetLoweringObjectFile.cpp b/llvm/lib/Target/TargetLoweringObjectFile.cpp index b2b69025851..fd4936e1904 100644 --- a/llvm/lib/Target/TargetLoweringObjectFile.cpp +++ b/llvm/lib/Target/TargetLoweringObjectFile.cpp @@ -174,7 +174,7 @@ SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalValue *GV, // If the global is required to have a unique address, it can't be put // into a mergable section: just drop it into the general read-only // section instead. - if (!GVar->hasUnnamedAddr()) + if (!GVar->hasGlobalUnnamedAddr()) return SectionKind::getReadOnly(); // If initializer is a null-terminated string, put it in a "cstring" -- cgit v1.2.3