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[lld][WebAssembly] Process stub libraries in a loop
When stub libraries trigger the fetching of new object files we can potentially introduce new undefined symbols so process the stub in loop until no new objects are pulled in. Differential Revision: https://reviews.llvm.org/D153466
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3 files changed

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‎lld/test/wasm/Inputs/libstub.so

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Original file line numberDiff line numberDiff line change
@@ -3,3 +3,4 @@
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foo: foodep1,foodep2
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# This symbols as no dependencies
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bar
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baz: bazdep

‎lld/test/wasm/stub-library-archive.s

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# RUN: split-file %s %t
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# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %t/main.s
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# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t/foodeps.o %t/foodeps.s
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# RUN: rm -f %t/libfoodeps.a
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# RUN: llvm-ar rcs %t/libfoodeps.a %t/foodeps.o
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# RUN: wasm-ld %t.o %p/Inputs/libstub.so %t/libfoodeps.a -o %t.wasm
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# RUN: obj2yaml %t.wasm | FileCheck %s
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#--- main.s
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# The function foo is defined in libstub.so but depends on foodep1 and foodep2
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# foodep1 and foodep2 a defined libfoodeps.a(foodeps.o) but this function
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# depeds on baz which is also defined in libstub.so.
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.functype foo () -> ()
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.globl _start
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_start:
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.functype _start () -> ()
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call foo
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end_function
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.globl bazdep
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bazdep:
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.functype bazdep () -> ()
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end_function
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#--- foodeps.s
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.functype baz () -> ()
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.globl foodep1
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foodep1:
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.functype foodep1 () -> ()
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call baz
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end_function
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.globl foodep2
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foodep2:
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.functype foodep2 () -> ()
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end_function
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# CHECK: - Type: EXPORT
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# CHECK-NEXT: Exports:
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# CHECK-NEXT: - Name: memory
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# CHECK-NEXT: Kind: MEMORY
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# CHECK-NEXT: Index: 0
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# CHECK-NEXT: - Name: _start
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# CHECK-NEXT: Kind: FUNCTION
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# CHECK-NEXT: Index: 2
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# CHECK-NEXT: - Name: bazdep
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# CHECK-NEXT: Kind: FUNCTION
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# CHECK-NEXT: Index: 3
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# CHECK-NEXT: - Name: foodep1
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# CHECK-NEXT: Kind: FUNCTION
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# CHECK-NEXT: Index: 4
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# CHECK-NEXT: - Name: foodep2
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# CHECK-NEXT: Kind: FUNCTION
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# CHECK-NEXT: Index: 5

‎lld/wasm/Driver.cpp

Lines changed: 50 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -898,52 +898,61 @@ static void processStubLibrariesPreLTO() {
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static void processStubLibraries() {
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log("-- processStubLibraries");
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for (auto &stub_file : symtab->stubFiles) {
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LLVM_DEBUG(llvm::dbgs()
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<< "processing stub file: " << stub_file->getName() << "\n");
904-
for (auto [name, deps]: stub_file->symbolDependencies) {
905-
auto* sym = symtab->find(name);
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if (!sym || !sym->isUndefined()) {
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LLVM_DEBUG(llvm::dbgs() << "stub symbol not needed: " << name << "\n");
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continue;
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}
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// The first stub library to define a given symbol sets this and
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// definitions in later stub libraries are ignored.
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if (sym->forceImport)
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continue; // Already handled
914-
sym->forceImport = true;
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if (sym->traced)
916-
message(toString(stub_file) + ": importing " + name);
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else
918-
LLVM_DEBUG(llvm::dbgs()
919-
<< toString(stub_file) << ": importing " << name << "\n");
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for (const auto dep : deps) {
921-
auto* needed = symtab->find(dep);
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if (!needed) {
923-
error(toString(stub_file) + ": undefined symbol: " + dep +
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". Required by " + toString(*sym));
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} else if (needed->isUndefined()) {
926-
error(toString(stub_file) +
927-
": undefined symbol: " + toString(*needed) +
928-
". Required by " + toString(*sym));
929-
} else {
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if (needed->traced)
931-
message(toString(stub_file) + ": exported " + toString(*needed) +
932-
" due to import of " + name);
901+
bool depsAdded = false;
902+
do {
903+
depsAdded = false;
904+
for (auto &stub_file : symtab->stubFiles) {
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LLVM_DEBUG(llvm::dbgs()
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<< "processing stub file: " << stub_file->getName() << "\n");
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for (auto [name, deps]: stub_file->symbolDependencies) {
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auto* sym = symtab->find(name);
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if (!sym || !sym->isUndefined()) {
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if (sym && sym->traced)
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message(toString(stub_file) + ": stub symbol not needed: " + name);
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else
934-
LLVM_DEBUG(llvm::dbgs()
935-
<< "force export: " << toString(*needed) << "\n");
936-
needed->forceExport = true;
937-
if (auto *lazy = dyn_cast<LazySymbol>(needed)) {
938-
lazy->fetch();
939-
if (!config->whyExtract.empty())
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config->whyExtractRecords.emplace_back(stub_file->getName(),
941-
sym->getFile(), *sym);
913+
LLVM_DEBUG(llvm::dbgs() << "stub symbol not needed: `" << name << "`\n");
914+
continue;
915+
}
916+
// The first stub library to define a given symbol sets this and
917+
// definitions in later stub libraries are ignored.
918+
if (sym->forceImport)
919+
continue; // Already handled
920+
sym->forceImport = true;
921+
if (sym->traced)
922+
message(toString(stub_file) + ": importing " + name);
923+
else
924+
LLVM_DEBUG(llvm::dbgs()
925+
<< toString(stub_file) << ": importing " << name << "\n");
926+
for (const auto dep : deps) {
927+
auto* needed = symtab->find(dep);
928+
if (!needed) {
929+
error(toString(stub_file) + ": undefined symbol: " + dep +
930+
". Required by " + toString(*sym));
931+
} else if (needed->isUndefined()) {
932+
error(toString(stub_file) +
933+
": undefined symbol: " + toString(*needed) +
934+
". Required by " + toString(*sym));
935+
} else {
936+
if (needed->traced)
937+
message(toString(stub_file) + ": exported " + toString(*needed) +
938+
" due to import of " + name);
939+
else
940+
LLVM_DEBUG(llvm::dbgs()
941+
<< "force export: " << toString(*needed) << "\n");
942+
needed->forceExport = true;
943+
if (auto *lazy = dyn_cast<LazySymbol>(needed)) {
944+
depsAdded = true;
945+
lazy->fetch();
946+
if (!config->whyExtract.empty())
947+
config->whyExtractRecords.emplace_back(stub_file->getName(),
948+
sym->getFile(), *sym);
949+
}
942950
}
943951
}
944952
}
945953
}
946-
}
954+
} while (depsAdded);
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947956
log("-- done processStubLibraries");
948957
}
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