Symbols from LTO objects don't contain Wasm signatures, but we need a
signature when we create undefined/stub functions for missing weakly
undefined symbols.
Luckily, after LTO, we know that symbols that are not referenced by a
regular object file must not be needed in the final output so there
is no need to generate undefined/stub function for them.
Differential Revision: https://reviews.llvm.org/D126554
declare extern_weak i32 @foo()
+declare extern_weak i32 @bar()
+
+; The reference to bar here will exist in the LTO file, but the LTO process will
+; remove it, so it will never be referenced by an normal object file, and
+; therefore never have a signature.
+define void @unused_function() #0 {
+entry:
+ %call2 = call i32 @bar()
+ ret void
+}
+
define void @_start() #0 {
entry:
%call2 = call i32 @foo()
// the call instruction that passes Wasm validation.
void SymbolTable::handleWeakUndefines() {
for (Symbol *sym : getSymbols()) {
- if (sym->isUndefWeak()) {
+ if (sym->isUndefWeak() && sym->isUsedInRegularObj) {
if (sym->getSignature()) {
replaceWithUndefined(sym);
} else {