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[ThinLTO] Fix nondeterministic exit on error. 

In the multi-threaded case, if a thread hits an error, we mimick
LLVMContext's behavior of reporting the error and exit-ing. However,
this doesn't cleanly join the other threads, so depending on how fast
the process exits, other threads may report 'terminate called without an
active exception'.

To avoid this non-determinsim, and without introducing a more complicated
design, we just report the error, but not exit early. We do track whether
we hit errors and exit(1) after joining.

Differential Revision: https://reviews.llvm.org/D115574
This commit is contained in:
Mircea Trofin 2021-12-10 20:59:24 -08:00
parent fe1b5b56c6
commit 4fed39ddee
1 changed files with 19 additions and 9 deletions
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28
llvm/tools/llvm-lto2/llvm-lto2.cpp
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@ -29,6 +29,7 @@
#include "llvm/Support/PluginLoader.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/Threading.h"
#include <atomic>
using namespace llvm;
using namespace lto;
@ -236,13 +237,6 @@ static int run(int argc, char **argv) {
std::vector<std::unique_ptr<MemoryBuffer>> MBs;
Config Conf;
Conf.DiagHandler = [](const DiagnosticInfo &DI) {
DiagnosticPrinterRawOStream DP(errs());
DI.print(DP);
errs() << '\n';
if (DI.getSeverity() == DS_Error)
exit(1);
};
Conf.CPU = codegen::getMCPU();
Conf.Options = codegen::InitTargetOptionsFromCodeGenFlags(Triple());
@ -314,9 +308,25 @@ static int run(int argc, char **argv) {
else
Backend = createInProcessThinBackend(
llvm::heavyweight_hardware_concurrency(Threads));
// Track whether we hit an error; in particular, in the multi-threaded case,
// we can't exit() early because the rest of the threads wouldn't have had a
// change to be join-ed, and that would result in a "terminate called without
// an active exception". Altogether, this results in nondeterministic
// behavior. Instead, we don't exit in the multi-threaded case, but we make
// sure to report the error and then at the end (after joining cleanly)
// exit(1).
std::atomic<bool> HasErrors;
std::atomic_init(&HasErrors, false);
Conf.DiagHandler = [&](const DiagnosticInfo &DI) {
DiagnosticPrinterRawOStream DP(errs());
DI.print(DP);
errs() << '\n';
if (DI.getSeverity() == DS_Error)
HasErrors = true;
};
LTO Lto(std::move(Conf), std::move(Backend));
bool HasErrors = false;
for (std::string F : InputFilenames) {
std::unique_ptr<MemoryBuffer> MB = check(MemoryBuffer::getFile(F), F);
std::unique_ptr<InputFile> Input =
@ -381,7 +391,7 @@ static int run(int argc, char **argv) {
"failed to create cache");
check(Lto.run(AddStream, Cache), "LTO::run failed");
return 0;
return static_cast<int>(HasErrors);
}
static int dumpSymtab(int argc, char **argv) {