Eliminate LayoutInputSection class
Previously we used LayoutInputSection class to correctly assign
symbols defined in linker script. This patch removes it and uses
pointer to preceding input section in SymbolAssignment class instead.
Differential revision: https://reviews.llvm.org/D23661
llvm-svn: 280348
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index b3a1c45..9afd5ba 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -133,54 +133,6 @@
return Ret;
}
-// You can define new symbols using linker scripts. For example,
-// ".text { abc.o(.text); foo = .; def.o(.text); }" defines symbol
-// foo just after abc.o's text section contents. This class is to
-// handle such symbol definitions.
-//
-// In order to handle scripts like the above one, we want to
-// keep symbol definitions in output sections. Because output sections
-// can contain only input sections, we wrap symbol definitions
-// with dummy input sections. This class serves that purpose.
-template <class ELFT>
-class elf::LayoutInputSection : public InputSectionBase<ELFT> {
-public:
- explicit LayoutInputSection(SymbolAssignment *Cmd);
- static bool classof(const InputSectionBase<ELFT> *S);
- SymbolAssignment *Cmd;
-
-private:
- typename ELFT::Shdr Hdr;
-};
-
-template <class ELFT>
-static InputSectionBase<ELFT> *
-getNonLayoutSection(std::vector<InputSectionBase<ELFT> *> &Vec) {
- for (InputSectionBase<ELFT> *S : Vec)
- if (!isa<LayoutInputSection<ELFT>>(S))
- return S;
- return nullptr;
-}
-
-template <class T> static T *zero(T *Val) {
- memset(Val, 0, sizeof(*Val));
- return Val;
-}
-
-template <class ELFT>
-LayoutInputSection<ELFT>::LayoutInputSection(SymbolAssignment *Cmd)
- : InputSectionBase<ELFT>(nullptr, zero(&Hdr),
- InputSectionBase<ELFT>::Layout),
- Cmd(Cmd) {
- this->Live = true;
- Hdr.sh_type = SHT_NOBITS;
-}
-
-template <class ELFT>
-bool LayoutInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
- return S->SectionKind == InputSectionBase<ELFT>::Layout;
-}
-
template <class ELFT>
static bool compareName(InputSectionBase<ELFT> *A, InputSectionBase<ELFT> *B) {
return A->getSectionName() < B->getSectionName();
@@ -236,12 +188,13 @@
std::vector<InputSectionBase<ELFT> *>
LinkerScript<ELFT>::createInputSectionList(OutputSectionCommand &OutCmd) {
std::vector<InputSectionBase<ELFT> *> Ret;
+ DenseSet<InputSectionBase<ELFT> *> SectionIndex;
for (const std::unique_ptr<BaseCommand> &Base : OutCmd.Commands) {
if (auto *OutCmd = dyn_cast<SymbolAssignment>(Base.get())) {
if (shouldDefine<ELFT>(OutCmd))
addSynthetic<ELFT>(OutCmd);
- Ret.push_back(new (LAlloc.Allocate()) LayoutInputSection<ELFT>(OutCmd));
+ OutCmd->GoesAfter = Ret.empty() ? nullptr : Ret.back();
continue;
}
@@ -253,7 +206,12 @@
std::stable_sort(V.begin(), V.end(), getComparator<ELFT>(Cmd->SortInner));
if (Cmd->SortOuter)
std::stable_sort(V.begin(), V.end(), getComparator<ELFT>(Cmd->SortOuter));
- Ret.insert(Ret.end(), V.begin(), V.end());
+
+ // Add all input sections corresponding to rule 'Cmd' to
+ // resulting vector. We do not add duplicate input sections.
+ for (InputSectionBase<ELFT> *S : V)
+ if (SectionIndex.insert(S).second)
+ Ret.push_back(S);
}
return Ret;
}
@@ -284,13 +242,12 @@
}
std::vector<InputSectionBase<ELFT> *> V = createInputSectionList(*Cmd);
- InputSectionBase<ELFT> *Head = getNonLayoutSection<ELFT>(V);
- if (!Head)
+ if (V.empty())
continue;
OutputSectionBase<ELFT> *OutSec;
bool IsNew;
- std::tie(OutSec, IsNew) = Factory.create(Head, Cmd->Name);
+ std::tie(OutSec, IsNew) = Factory.create(V.front(), Cmd->Name);
if (IsNew)
OutputSections->push_back(OutSec);
@@ -298,8 +255,7 @@
for (InputSectionBase<ELFT> *Sec : V) {
if (Subalign)
Sec->Alignment = Subalign;
- if (!Sec->OutSec)
- OutSec->addSection(Sec);
+ OutSec->addSection(Sec);
}
}
}
@@ -359,31 +315,49 @@
addStartEndSymbols(Cmd, Sec);
return;
}
-
typedef typename ELFT::uint uintX_t;
uintX_t Off = 0;
+ auto ItCmd = Cmd->Commands.begin();
- for (InputSection<ELFT> *I : OutSec->Sections) {
- if (auto *L = dyn_cast<LayoutInputSection<ELFT>>(I)) {
- uintX_t Value = L->Cmd->Expression(Sec->getVA() + Off) - Sec->getVA();
- if (L->Cmd->Name == ".") {
+ // Assigns values to all symbols following the given
+ // input section 'D' in output section 'Sec'. When symbols
+ // are in the beginning of output section the value of 'D'
+ // is nullptr.
+ auto AssignSuccessors = [&](InputSectionData *D) {
+ for (; ItCmd != Cmd->Commands.end(); ++ItCmd) {
+ auto *AssignCmd = dyn_cast<SymbolAssignment>(ItCmd->get());
+ if (!AssignCmd)
+ continue;
+ if (D != AssignCmd->GoesAfter)
+ break;
+
+ uintX_t Value = AssignCmd->Expression(Sec->getVA() + Off) - Sec->getVA();
+ if (AssignCmd->Name == ".") {
+ // Update to location counter means update to section size.
Off = Value;
- } else if (auto *Sym =
- cast_or_null<DefinedSynthetic<ELFT>>(L->Cmd->Sym)) {
- // shouldDefine could have returned false, so we need to check Sym,
- // for non-null value.
+ Sec->setSize(Off);
+ continue;
+ }
+
+ if (DefinedSynthetic<ELFT> *Sym =
+ cast_or_null<DefinedSynthetic<ELFT>>(AssignCmd->Sym)) {
Sym->Section = OutSec;
Sym->Value = Value;
}
- } else {
- Off = alignTo(Off, I->Alignment);
- I->OutSecOff = Off;
- Off += I->getSize();
}
+ };
+
+ AssignSuccessors(nullptr);
+ for (InputSection<ELFT> *I : OutSec->Sections) {
+ Off = alignTo(Off, I->Alignment);
+ I->OutSecOff = Off;
+ Off += I->getSize();
// Update section size inside for-loop, so that SIZEOF
// works correctly in the case below:
// .foo { *(.aaa) a = SIZEOF(.foo); *(.bbb) }
Sec->setSize(Off);
+ // Add symbols following current input section.
+ AssignSuccessors(I);
}
}