From bcb418e56f879a8df2428211e727e06f2b23b535 Mon Sep 17 00:00:00 2001 From: David Blaikie Date: Wed, 20 Nov 2013 18:40:16 +0000 Subject: [PATCH] CR feedback for r195166: Add comments regarding type unit mapping and type units disabling cross-CU sharing. Changes suggested by Manman Ren. llvm-svn: 195262 --- llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp | 9 +++++++-- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h | 6 +++++- 2 files changed, 12 insertions(+), 3 deletions(-) diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp index 2489002f7fde..688791e04ff6 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp @@ -112,8 +112,13 @@ int64_t CompileUnit::getDefaultLowerBound() const { /// Check whether the DIE for this MDNode can be shared across CUs. static bool isShareableAcrossCUs(DIDescriptor D) { - // When the MDNode can be part of the type system, the DIE can be - // shared across CUs. + // When the MDNode can be part of the type system, the DIE can be shared + // across CUs. + // Combining type units and cross-CU DIE sharing is lower value (since + // cross-CU DIE sharing is used in LTO and removes type redundancy at that + // level already) but may be implementable for some value in projects + // building multiple independent libraries with LTO and then linking those + // together. return (D.isType() || (D.isSubprogram() && !DISubprogram(D).isDefinition())) && !GenerateTypeUnits; diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h index c3b129973177..5ba7cbf9d73a 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h @@ -443,7 +443,11 @@ class DwarfDebug { ImportedEntityMap; ImportedEntityMap ScopesWithImportedEntities; - // Holder for types that are going to be extracted out into a type unit. + // Map from type MDNodes to a pair used as a union. If the pointer is + // non-null, proxy DIEs in CUs meant to reference this type should be stored + // in the vector. The hash will be added to these DIEs once it is computed. If + // the pointer is null, the hash is immediately available in the uint64_t and + // should be directly used for proxy DIEs. DenseMap* > > TypeUnits; // Whether to emit the pubnames/pubtypes sections.