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[PDB] Serialize records into a stack-allocated buffer. 

We were using a std::vector<> and resizing to MaxRecordLength,
which is ~64KB.  We would then do this repeatedly often many
times in a tight loop, which was causing measurable performance
impact when linking PDBs.

Patch by Alex Telishev
Differential Revision: https://reviews.llvm.org/D36940

llvm-svn: 311375
This commit is contained in:
Zachary Turner 2017-08-21 20:17:19 +00:00
parent fb0994b37e
commit 5641c07d6b
2 changed files with 5 additions and 3 deletions
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5
llvm/include/llvm/DebugInfo/CodeView/SymbolSerializer.h
View File

@ -28,7 +28,10 @@ namespace codeview {
class SymbolSerializer : public SymbolVisitorCallbacks {
BumpPtrAllocator &Storage;
std::vector<uint8_t> RecordBuffer;
// Since this is a fixed size buffer, use a stack allocated buffer. This
// yields measurable performance increase over the repeated heap allocations
// when serializing many independent records via writeOneSymbol.
std::array<uint8_t, MaxRecordLength> RecordBuffer;
MutableBinaryByteStream Stream;
BinaryStreamWriter Writer;
SymbolRecordMapping Mapping;

3
llvm/lib/DebugInfo/CodeView/SymbolSerializer.cpp
View File

@ -21,8 +21,7 @@ using namespace llvm::codeview;
SymbolSerializer::SymbolSerializer(BumpPtrAllocator &Allocator,
CodeViewContainer Container)
: Storage(Allocator), RecordBuffer(MaxRecordLength),
Stream(RecordBuffer, support::little), Writer(Stream),
: Storage(Allocator), Stream(RecordBuffer, support::little), Writer(Stream),
Mapping(Writer, Container) {}
Error SymbolSerializer::visitSymbolBegin(CVSymbol &Record) {