[ELF] - Implemented --compress-debug-sections option.
Patch implements --compress-debug-sections=zlib.
In compare with D20211 (a year old patch, abandoned), it implementation
uses streaming and fully reimplemented, does not support zlib-gnu for
simplification.
This is PR32308.
Differential revision: https://reviews.llvm.org/D31941
llvm-svn: 300444
diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 93f8310..9fc6969 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -16,6 +16,7 @@
#include "SyntheticSections.h"
#include "Target.h"
#include "Threads.h"
+#include "llvm/Support/Compression.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/MathExtras.h"
@@ -83,6 +84,55 @@
return LA->OutSecOff < LB->OutSecOff;
}
+// Compressed sections has header which we create in this function.
+// Format is explaned here:
+// https://docs.oracle.com/cd/E53394_01/html/E54813/section_compression.html
+template <class ELFT>
+static std::vector<uint8_t> createHeader(size_t Size, uint32_t Alignment) {
+ const endianness E = ELFT::TargetEndianness;
+
+ std::vector<uint8_t> Ret(sizeof(typename ELFT::Chdr));
+ uint8_t *Buf = &Ret[0];
+ write32<E>(Buf, ELFCOMPRESS_ZLIB);
+ Buf += 4;
+
+ if (Config->Is64) {
+ Buf += sizeof(Elf64_Word); // Skip ch_reserved field.
+ write64<E>(Buf, Size);
+ Buf += sizeof(ELFT::Chdr::ch_size);
+ write64<E>(Buf, Alignment);
+ Buf += sizeof(ELFT::Chdr::ch_addralign);
+ } else {
+ write32<E>(Buf, Size);
+ Buf += sizeof(ELFT::Chdr::ch_size);
+ write32<E>(Buf, Alignment);
+ Buf += sizeof(ELFT::Chdr::ch_addralign);
+ }
+
+ return Ret;
+}
+
+template <class ELFT> void OutputSection::maybeCompress() {
+ // If -compress-debug-sections is specified, we compress output debug
+ // sections.
+ if (!Config->CompressDebugSections || !Name.startswith(".debug_") ||
+ (Flags & SHF_ALLOC))
+ return;
+
+ this->Flags |= SHF_COMPRESSED;
+ CompressedHeader = createHeader<ELFT>(this->Size, this->Alignment);
+
+ // Here we write relocated content of sections and compress it.
+ std::vector<uint8_t> Data(this->Size);
+ this->writeTo<ELFT>(&Data[0]);
+
+ if (Error E = zlib::compress(StringRef((char *)Data.data(), Data.size()),
+ CompressedData))
+ fatal("compress failed: " + llvm::toString(std::move(E)));
+
+ this->Size = this->CompressedHeader.size() + this->CompressedData.size();
+}
+
template <class ELFT> void OutputSection::finalize() {
if ((this->Flags & SHF_LINK_ORDER) && !this->Sections.empty()) {
std::sort(Sections.begin(), Sections.end(), compareByFilePosition);
@@ -245,6 +295,15 @@
template <class ELFT> void OutputSection::writeTo(uint8_t *Buf) {
Loc = Buf;
+ // We may have already rendered compressed content when using
+ // -compress-debug-sections option. Write it together with header.
+ if (!CompressedData.empty()) {
+ memcpy(Buf, CompressedHeader.data(), CompressedHeader.size());
+ Buf += CompressedHeader.size();
+ memcpy(Buf, CompressedData.data(), CompressedData.size());
+ return;
+ }
+
// Write leading padding.
uint32_t Filler = getFiller();
if (Filler)
@@ -422,6 +481,11 @@
template void OutputSection::finalize<ELF64LE>();
template void OutputSection::finalize<ELF64BE>();
+template void OutputSection::maybeCompress<ELF32LE>();
+template void OutputSection::maybeCompress<ELF32BE>();
+template void OutputSection::maybeCompress<ELF64LE>();
+template void OutputSection::maybeCompress<ELF64BE>();
+
template void OutputSection::writeTo<ELF32LE>(uint8_t *Buf);
template void OutputSection::writeTo<ELF32BE>(uint8_t *Buf);
template void OutputSection::writeTo<ELF64LE>(uint8_t *Buf);