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[LLD][COFF] Introduce Symbol::getDefined helper. (NFC) #151253

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Merged
merged 1 commit into from
Jul 31, 2025
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[LLD][COFF] Introduce Symbol::getDefined helper. (NFC) #151253

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12 changes: 2 additions & 10 deletions lld/COFF/Driver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1318,13 +1318,9 @@ void LinkerDriver::convertResources() {
}

void LinkerDriver::maybeCreateECExportThunk(StringRef name, Symbol *&sym) {
Defined *def;
if (!sym)
return;
if (auto undef = dyn_cast<Undefined>(sym))
def = undef->getDefinedWeakAlias();
else
def = dyn_cast<Defined>(sym);
Defined *def = sym->getDefined();
if (!def)
return;

Expand Down Expand Up @@ -1356,11 +1352,7 @@ void LinkerDriver::createECExportThunks() {
Symbol *sym = ctx.symtab.find(targetName);
if (!sym)
continue;
Defined *targetSym;
if (auto undef = dyn_cast<Undefined>(sym))
targetSym = undef->getDefinedWeakAlias();
else
targetSym = dyn_cast<Defined>(sym);
Defined *targetSym = sym->getDefined();
if (!targetSym)
continue;

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8 changes: 8 additions & 0 deletions lld/COFF/Symbols.cpp
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Expand Up @@ -91,6 +91,14 @@ bool Symbol::isLive() const {
return true;
}

Defined *Symbol::getDefined() {
if (auto d = dyn_cast<Defined>(this))
return d;
if (auto u = dyn_cast<Undefined>(this))
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This (very) vaguely changes the logic from before - previously we tested dyn_cast<Undefined> before, while we now test them in different order. (In theory this could have a performance aspect, but that's not relevant.) What I wanted to say here, is that as long as only one of dyn_cast<Defined> and dyn_cast<Undefined> can succeed, i.e. they are mutually exclusive, then this should be fine - and this mildly rewritten form looks ok.

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Yes, I believe the assumption that only one of them can succeed is safe. I wrote it in this order because I’d expect Defined to be more common, but as you said, the performance impact is not really relevant.

return u->getDefinedWeakAlias();
return nullptr;
}

void Symbol::replaceKeepingName(Symbol *other, size_t size) {
StringRef origName = getName();
memcpy(this, other, size);
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4 changes: 4 additions & 0 deletions lld/COFF/Symbols.h
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Expand Up @@ -95,6 +95,10 @@ class Symbol {
symbolKind == LazyDLLSymbolKind;
}

// Get the Defined symbol associated with this symbol, either itself or its
// weak alias.
Defined *getDefined();

private:
void computeName();

Expand Down