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author | Fangrui Song <i@maskray.me> | 2022-02-01 10:10:22 -0800 |
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committer | Fangrui Song <i@maskray.me> | 2022-02-01 10:10:22 -0800 |
commit | 0c3704fdbd901e5f51acf11a85278bf9214ae7b2 (patch) | |
tree | 282687f9e8a3c9fc5d7028b28c628dc15bbbc3f1 /lld/ELF/SyntheticSections.cpp | |
parent | ceb9094a49134d21333150dd876fbb09a165eb3a (diff) | |
download | llvm-0c3704fdbd901e5f51acf11a85278bf9214ae7b2.zip llvm-0c3704fdbd901e5f51acf11a85278bf9214ae7b2.tar.gz llvm-0c3704fdbd901e5f51acf11a85278bf9214ae7b2.tar.bz2 |
[ELF] Deduplicate names of local symbols only with -O2
The deduplication requires a DenseMap of the same size of the local part of
.strtab . I optimized it in e20544543478b259eb09fa0a253d4fb1a5525d9e but it is
still quite slow.
For Release build of clang, deduplication makes .strtab 1.1% smaller and makes the link 3% slower.
For chrome, deduplication makes .strtab 0.1% smaller and makes the link 6% slower.
I suggest that we only perform the optimization with -O2 (default is -O1).
Not deduplicating local symbol names will simplify parallel symbol table write.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D118577
Diffstat (limited to 'lld/ELF/SyntheticSections.cpp')
-rw-r--r-- | lld/ELF/SyntheticSections.cpp | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp index 36a226c..986c130 100644 --- a/lld/ELF/SyntheticSections.cpp +++ b/lld/ELF/SyntheticSections.cpp @@ -1230,7 +1230,8 @@ StringTableSection::StringTableSection(StringRef name, bool dynamic) : SyntheticSection(dynamic ? (uint64_t)SHF_ALLOC : 0, SHT_STRTAB, 1, name), dynamic(dynamic) { // ELF string tables start with a NUL byte. - addString(""); + strings.push_back(""); + size = 1; } // Adds a string to the string table. If `hashIt` is true we hash and check for @@ -1243,6 +1244,8 @@ unsigned StringTableSection::addString(StringRef s, bool hashIt) { if (!r.second) return r.first->second; } + if (s.empty()) + return 0; unsigned ret = this->size; this->size = this->size + s.size() + 1; strings.push_back(s); @@ -2155,7 +2158,7 @@ void SymbolTableBaseSection::addSymbol(Symbol *b) { // Adding a local symbol to a .dynsym is a bug. assert(this->type != SHT_DYNSYM || !b->isLocal()); - bool hashIt = b->isLocal(); + bool hashIt = b->isLocal() && config->optimize >= 2; symbols.push_back({b, strTabSec.addString(b->getName(), hashIt)}); } |