diff options
| -rw-r--r-- | lld/ELF/OutputSections.cpp | 44 | ||||
| -rw-r--r-- | lld/ELF/OutputSections.h | 3 | ||||
| -rw-r--r-- | lld/test/ELF/mips-got-redundant.s | 15 |
3 files changed, 38 insertions, 24 deletions
diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp index 9421c4881fc..8ea9033e8d5 100644 --- a/lld/ELF/OutputSections.cpp +++ b/lld/ELF/OutputSections.cpp @@ -115,16 +115,30 @@ template <class ELFT> void GotSection<ELFT>::addEntry(SymbolBody &Sym) { // // See "Global Offset Table" in Chapter 5: // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf - // - // FIXME (simon): Now LLD allocates GOT entries for each - // "local symbol+addend" pair. That should be fixed to reduce size - // of generated GOT. - if (Sym.isPreemptible()) - Sym.MustBeInDynSym = true; - else { + if (Sym.isLocal()) { + // At this point we do not know final symbol value so to reduce number + // of allocated GOT entries do the following trick. Save all output + // sections referenced by GOT relocations. Then later in the `finalize` + // method calculate number of "pages" required to cover all saved output + // section and allocate appropriate number of GOT entries. + auto *OutSec = cast<DefinedRegular<ELFT>>(&Sym)->Section->OutSec; + MipsOutSections.insert(OutSec); + return; + } + if (!Sym.isPreemptible()) { + // In case of non-local symbols require an entry in the local part + // of MIPS GOT, we set GotIndex to 1 just to accent that this symbol + // has the GOT entry and escape creation more redundant GOT entries. + // FIXME (simon): We can try to store such symbols in the `Entries` + // container. But in that case we have to sort out that container + // and update GotIndex assigned to symbols. + Sym.GotIndex = 1; ++MipsLocalEntries; return; } + // All preemptible symbols with MIPS GOT entries should be represented + // in the dynamic symbols table. + Sym.MustBeInDynSym = true; } Sym.GotIndex = Entries.size(); Entries.push_back(&Sym); @@ -191,6 +205,14 @@ unsigned GotSection<ELFT>::getMipsLocalEntriesNum() const { } template <class ELFT> void GotSection<ELFT>::finalize() { + for (const OutputSectionBase<ELFT> *OutSec : MipsOutSections) { + // Calculate an upper bound of MIPS GOT entries required to store page + // addresses of local symbols. We assume the worst case - each 64kb + // page of the output section has at least one GOT relocation against it. + // Add 0x8000 to the section's size because the page address stored + // in the GOT entry is calculated as (value + 0x8000) & ~0xffff. + MipsLocalEntries += (OutSec->getSize() + 0x8000 + 0xfffe) / 0xffff; + } this->Header.sh_size = (Target->GotHeaderEntriesNum + MipsLocalEntries + Entries.size()) * sizeof(uintX_t); @@ -1348,8 +1370,12 @@ SymbolTableSection<ELFT>::SymbolTableSection( // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf static bool sortMipsSymbols(const std::pair<SymbolBody *, unsigned> &L, const std::pair<SymbolBody *, unsigned> &R) { - if (!L.first->isInGot() || !R.first->isInGot()) - return R.first->isInGot(); + // Sort entries related to non-local preemptible symbols by GOT indexes. + // All other entries go to the first part of GOT in arbitrary order. + bool LIsInLocalGot = !L.first->isInGot() || !L.first->isPreemptible(); + bool RIsInLocalGot = !R.first->isInGot() || !R.first->isPreemptible(); + if (LIsInLocalGot || RIsInLocalGot) + return !RIsInLocalGot; return L.first->GotIndex < R.first->GotIndex; } diff --git a/lld/ELF/OutputSections.h b/lld/ELF/OutputSections.h index 0b4edb9e355..a35fa1ef34f 100644 --- a/lld/ELF/OutputSections.h +++ b/lld/ELF/OutputSections.h @@ -13,6 +13,7 @@ #include "Config.h" #include "lld/Core/LLVM.h" +#include "llvm/ADT/SmallPtrSet.h" #include "llvm/MC/StringTableBuilder.h" #include "llvm/Object/ELF.h" @@ -124,6 +125,8 @@ private: std::vector<const SymbolBody *> Entries; uint32_t TlsIndexOff = -1; uint32_t MipsLocalEntries = 0; + // Output sections referenced by MIPS GOT relocations. + llvm::SmallPtrSet<const OutputSectionBase<ELFT> *, 10> MipsOutSections; llvm::DenseMap<uintX_t, size_t> MipsLocalGotPos; uintX_t getMipsLocalEntryAddr(uintX_t EntryValue); diff --git a/lld/test/ELF/mips-got-redundant.s b/lld/test/ELF/mips-got-redundant.s index 0526042e061..07c3c249f4f 100644 --- a/lld/test/ELF/mips-got-redundant.s +++ b/lld/test/ELF/mips-got-redundant.s @@ -25,21 +25,6 @@ # CHECK-NEXT: Initial: 0x40008 # ^-- glb1 # CHECK-NEXT: } -# CHECK-NEXT: Entry { -# CHECK-NEXT: Address: 0x20014 -# CHECK-NEXT: Access: -32732 -# CHECK-NEXT: Initial: 0x0 -# CHECK-NEXT: } -# CHECK-NEXT: Entry { -# CHECK-NEXT: Address: 0x20018 -# CHECK-NEXT: Access: -32728 -# CHECK-NEXT: Initial: 0x0 -# CHECK-NEXT: } -# CHECK-NEXT: Entry { -# CHECK-NEXT: Address: 0x2001C -# CHECK-NEXT: Access: -32724 -# CHECK-NEXT: Initial: 0x0 -# CHECK-NEXT: } # CHECK-NEXT: ] .text |
