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[lld][WebAssembly] Allow --export of optional start/stop symbols

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This moves the error checking until after all optional
symbols (including the section start/end symbols) have
been created.

Differential Revision: https://reviews.llvm.org/D96318
This commit is contained in:
Sam Clegg
2021-02-08 17:16:15 -08:00
parent eec04092d6
commit 34d033ca12
3 changed files with 44 additions and 5 deletions
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31
lld/test/wasm/export-optional.s Normal file
View File

@@ -0,0 +1,31 @@
# Test the --export of optional linker-synthetic symbols works.
# Specifically the __start_xxx and __end_xx symbols.
# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %s -o %t.o
# RUN: wasm-ld --export=__start_foo %t.o -o %t.wasm
# RUN: obj2yaml %t.wasm | FileCheck %s
.globl _start
_start:
.functype _start () -> ()
i32.load foo
drop
end_function
.globl foo
.section foo,"",@
foo:
.int32 42
.size foo, 4
# CHECK: - Type: EXPORT
# CHECK-NEXT: Exports:
# CHECK-NEXT: - Name: memory
# CHECK-NEXT: Kind: MEMORY
# CHECK-NEXT: Index: 0
# CHECK-NEXT: - Name: _start
# CHECK-NEXT: Kind: FUNCTION
# CHECK-NEXT: Index: 0
# CHECK-NEXT: - Name: __start_foo
# CHECK-NEXT: Kind: GLOBAL
# CHECK-NEXT: Index: 1

5
lld/wasm/Driver.cpp
View File

@@ -1015,11 +1015,6 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
Symbol *sym = symtab->find(arg->getValue());
if (sym && sym->isDefined())
sym->forceExport = true;
else if (config->unresolvedSymbols == UnresolvedPolicy::ReportError)
error(Twine("symbol exported via --export not found: ") +
arg->getValue());
else if (config->unresolvedSymbols == UnresolvedPolicy::Warn)
warn(Twine("symbol exported via --export not found: ") + arg->getValue());
}
if (!config->relocatable && !config->isPic) {

13
lld/wasm/Writer.cpp
View File

@@ -1350,6 +1350,19 @@ void Writer::run() {
addStartStopSymbols(seg);
}
// Delay reporting error about explict exports until after addStartStopSymbols
// which can create optional symbols.
for (auto &entry : config->exportedSymbols) {
StringRef name = entry.first();
Symbol *sym = symtab->find(name);
if (sym && sym->isDefined())
sym->forceExport = true;
else if (config->unresolvedSymbols == UnresolvedPolicy::ReportError)
error(Twine("symbol exported via --export not found: ") + name);
else if (config->unresolvedSymbols == UnresolvedPolicy::Warn)
warn(Twine("symbol exported via --export not found: ") + name);
}
log("-- scanRelocations");
scanRelocations();
log("-- finalizeIndirectFunctionTable");