[PECOFF] Support yet another new type of weak symbol.
COMDAT_SELECT_LARGEST is a COMDAT type that make linker to choose the largest
definition from among all of the definition of a symbol. If the size is the
same, the choice is arbitrary.
Differential Revision: http://llvm-reviews.chandlerc.com/D3011
llvm-svn: 204172
diff --git a/lld/lib/Core/SymbolTable.cpp b/lld/lib/Core/SymbolTable.cpp
index add6628..9bacdad 100644
--- a/lld/lib/Core/SymbolTable.cpp
+++ b/lld/lib/Core/SymbolTable.cpp
@@ -102,13 +102,14 @@
MCR_Error
};
-static MergeResolution mergeCases[][5] = {
- // no tentative weak weakAddress sameNameAndSize
- {MCR_Error, MCR_First, MCR_First, MCR_First, MCR_SameSize}, // no
- {MCR_Second, MCR_Largest, MCR_Second, MCR_Second, MCR_SameSize}, // tentative
- {MCR_Second, MCR_First, MCR_First, MCR_Second, MCR_SameSize}, // weak
- {MCR_Second, MCR_First, MCR_First, MCR_First, MCR_SameSize}, // weakAddress
- {MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize}, // sameSize
+static MergeResolution mergeCases[][6] = {
+ // no tentative weak weakAddress sameNameAndSize largest
+ {MCR_Error, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // no
+ {MCR_Second, MCR_Largest, MCR_Second, MCR_Second, MCR_SameSize, MCR_Largest}, // tentative
+ {MCR_Second, MCR_First, MCR_First, MCR_Second, MCR_SameSize, MCR_Largest}, // weak
+ {MCR_Second, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // weakAddress
+ {MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize}, // sameSize
+ {MCR_Largest, MCR_Largest, MCR_Largest, MCR_Largest, MCR_SameSize, MCR_Largest}, // largest
};
static MergeResolution mergeSelect(DefinedAtom::Merge first,
@@ -118,6 +119,33 @@
return mergeCases[first][second];
}
+static uint64_t getSizeFollowReferences(const DefinedAtom *atom, uint32_t kind) {
+ uint64_t size = 0;
+redo:
+ while (atom) {
+ for (const Reference *r : *atom) {
+ if (r->kindNamespace() == Reference::KindNamespace::all &&
+ r->kindArch() == Reference::KindArch::all &&
+ r->kindValue() == kind) {
+ atom = cast<DefinedAtom>(r->target());
+ size += atom->size();
+ goto redo;
+ }
+ }
+ break;
+ }
+ return size;
+}
+
+// Returns the size of the section containing the given atom. Atoms in the same
+// section are connected by layout-before and layout-after edges, so this
+// function traverses them to get the total size of atoms in the same section.
+static uint64_t sectionSize(const DefinedAtom *atom) {
+ return atom->size()
+ + getSizeFollowReferences(atom, lld::Reference::kindLayoutBefore)
+ + getSizeFollowReferences(atom, lld::Reference::kindLayoutAfter);
+}
+
void SymbolTable::addByName(const Atom &newAtom) {
StringRef name = newAtom.name();
assert(!name.empty());
@@ -148,19 +176,22 @@
case MCR_Second:
useNew = true;
break;
- case MCR_Largest:
- useNew = true;
+ case MCR_Largest: {
+ uint64_t existingSize = sectionSize((DefinedAtom*)existing);
+ uint64_t newSize = sectionSize((DefinedAtom*)&newAtom);
+ useNew = (newSize >= existingSize);
break;
+ }
case MCR_SameSize: {
- uint64_t sa = ((DefinedAtom*)existing)->size();
- uint64_t sb = ((DefinedAtom*)&newAtom)->size();
- if (sa == sb) {
+ uint64_t existingSize = sectionSize((DefinedAtom*)existing);
+ uint64_t newSize = sectionSize((DefinedAtom*)&newAtom);
+ if (existingSize == newSize) {
useNew = true;
break;
}
llvm::errs() << "Size mismatch: "
- << existing->name() << " (" << sa << ") "
- << newAtom.name() << " (" << sb << ")\n";
+ << existing->name() << " (" << existingSize << ") "
+ << newAtom.name() << " (" << newSize << ")\n";
// fallthrough
}
case MCR_Error: