6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-22 09:29:31 +00:00
Code Issues Projects Releases Wiki Activity

Fix quadratic performance during debug compression due to sections x symbols iteration.

Browse Source 
When fixing the symbols in each compressed section we were iterating
over all symbols for each compressed section. In extreme cases this
could snowball severely (5min uncompressed -> 35min compressed) due to
iterating over all symbols for each compressed section (large numbers of
compressed sections can be generated by DWARF type units).

To address this, build a map of the symbols in each section ahead of
time, and access that map if a section is being compressed. This brings
compile time for the aforementioned example down to ~6 minutes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207167 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Blaikie 2014-04-25 00:48:01 +00:00
parent 680311d2d2
commit 6715d6ec2e
1 changed files with 21 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
lib/MC/ELFObjectWriter.cpp
View File

@ -1250,20 +1250,21 @@ getCompressedFragment(MCAsmLayout &Layout,
return CompressedFragment;
}
static void UpdateSymbols(const MCAsmLayout &Layout, const MCSectionData &SD,
MCAssembler::symbol_range Symbols,
MCFragment *NewFragment) {
for (MCSymbolData &Data : Symbols) {
MCFragment *F = Data.getFragment();
if (F && F->getParent() == &SD) {
Data.setOffset(Data.getOffset() +
Layout.getFragmentOffset(Data.Fragment));
Data.setFragment(NewFragment);
}
typedef DenseMap<const MCSectionData *, std::vector<MCSymbolData *>>
DefiningSymbolMap;
static void UpdateSymbols(const MCAsmLayout &Layout,
const std::vector<MCSymbolData *> &Symbols,
MCFragment &NewFragment) {
for (MCSymbolData *Sym : Symbols) {
Sym->setOffset(Sym->getOffset() +
Layout.getFragmentOffset(Sym->getFragment()));
Sym->setFragment(&NewFragment);
}
}
static void CompressDebugSection(MCAssembler &Asm, MCAsmLayout &Layout,
const DefiningSymbolMap &DefiningSymbols,
const MCSectionELF &Section,
MCSectionData &SD) {
StringRef SectionName = Section.getSectionName();
@ -1278,7 +1279,9 @@ static void CompressDebugSection(MCAssembler &Asm, MCAsmLayout &Layout,
// Update the fragment+offsets of any symbols referring to fragments in this
// section to refer to the new fragment.
UpdateSymbols(Layout, SD, Asm.symbols(), CompressedFragment.get());
auto I = DefiningSymbols.find(&SD);
if (I != DefiningSymbols.end())
UpdateSymbols(Layout, I->second, *CompressedFragment);
// Invalidate the layout for the whole section since it will have new and
// different fragments now.
@ -1300,6 +1303,12 @@ void ELFObjectWriter::CompressDebugSections(MCAssembler &Asm,
if (!Asm.getContext().getAsmInfo()->compressDebugSections())
return;
DefiningSymbolMap DefiningSymbols;
for (MCSymbolData &SD : Asm.symbols())
if (MCFragment *F = SD.getFragment())
DefiningSymbols[F->getParent()].push_back(&SD);
for (MCSectionData &SD : Asm) {
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(SD.getSection());
@ -1311,7 +1320,7 @@ void ELFObjectWriter::CompressDebugSections(MCAssembler &Asm,
if (!SectionName.startswith(".debug_") || SectionName == ".debug_frame")
continue;
CompressDebugSection(Asm, Layout, Section, SD);
CompressDebugSection(Asm, Layout, DefiningSymbols, Section, SD);
}
}