From 5ccfdd8d215c7bf324a14523c71ed328325c2bc8 Mon Sep 17 00:00:00 2001 From: Anders Carlsson Date: Sun, 13 Jun 2010 17:49:16 +0000 Subject: [PATCH] Implement part of the EmptySubobjectMap optimization described in PR6998. We still need to do this for bases. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@105919 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/AST/RecordLayoutBuilder.cpp | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp index 7c0c8088e8..6b8d7cf22d 100644 --- a/lib/AST/RecordLayoutBuilder.cpp +++ b/lib/AST/RecordLayoutBuilder.cpp @@ -415,7 +415,14 @@ EmptySubobjectMap::CanPlaceFieldAtOffset(const FieldDecl *FD, uint64_t Offset) { void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD, const CXXRecordDecl *Class, uint64_t Offset) { - + // We know that the only empty subobjects that can conflict with empty + // field subobjects are subobjects empty bases that can be placed at offset + // zero. Because of this, we only need to keep track of empty field + // subobjects with offsets less than the size of the largest empty + // subobject for our class. + if (Offset >= SizeOfLargestEmptySubobject) + return; + AddSubobjectAtOffset(RD, Offset); const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); @@ -480,6 +487,14 @@ void EmptySubobjectMap::UpdateEmptyFieldSubobjects(const FieldDecl *FD, uint64_t ElementOffset = Offset; for (uint64_t I = 0; I != NumElements; ++I) { + // We know that the only empty subobjects that can conflict with empty + // field subobjects are subobjects empty bases that can be placed at + // offset zero. Because of this, we only need to keep track of empty field + // subobjects with offsets less than the size of the largest empty + // subobject for our class. + if (ElementOffset >= SizeOfLargestEmptySubobject) + return; + UpdateEmptyFieldSubobjects(RD, RD, ElementOffset); ElementOffset += Layout.getSize(); } -- 2.50.1