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Weaken definitions of typeinfos and vtables

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Introduce a backend pass that changes the linkage of external symbols
starting with "_ZT" (ie. typeinfo names, typeinfos, and vtables) to
weak symbols. This avoids duplicate symbol errors with the new JIT
linker.

FIXME: This is a hack, we should teach the frontend to emit these
only once, or mark all duplicates as available_externally (if that
improves performance due to optimizations).
This commit is contained in:
Jonas Hahnfeld 2022-05-31 17:57:29 +02:00 committed by jenkins
parent e338773863
commit f63fdda04e
1 changed files with 40 additions and 0 deletions
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40
lib/Interpreter/BackendPasses.cpp
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@ -86,6 +86,45 @@ namespace {
char KeepLocalGVPass::ID = 0;
namespace {
class WeakTypeinfoVTablePass: public ModulePass {
static char ID;
bool runOnGlobalVariable(GlobalVariable& GV) {
// Only need to consider symbols with external linkage because only
// these could be reported as duplicate.
if (GV.getLinkage() != llvm::GlobalValue::ExternalLinkage)
return false;
if (GV.getName().startswith("_ZT")) {
// Currently, if Cling sees the "key function" of a virtual class, it
// emits typeinfo and vtable variables in every transaction llvm::Module
// that reference them. Turn them into weak linkage to avoid duplicate
// symbol errors from the JIT linker.
// FIXME: This is a hack, we should teach the frontend to emit these
// only once, or mark all duplicates as available_externally (if that
// improves performance due to optimizations).
GV.setLinkage(llvm::GlobalValue::WeakAnyLinkage);
return true; // a change!
}
return false;
}
public:
WeakTypeinfoVTablePass() : ModulePass(ID) {}
bool runOnModule(Module &M) override {
bool ret = false;
for (auto &&GV : M.globals())
ret |= runOnGlobalVariable(GV);
return ret;
}
};
}
char WeakTypeinfoVTablePass::ID = 0;
namespace {
// Add a suffix to the CUDA module ctor/dtor to generate a unique name.
@ -270,6 +309,7 @@ void BackendPasses::CreatePasses(llvm::Module& M, int OptLevel)
m_MPM[OptLevel].reset(new legacy::PassManager());
m_MPM[OptLevel]->add(new KeepLocalGVPass());
m_MPM[OptLevel]->add(new WeakTypeinfoVTablePass());
m_MPM[OptLevel]->add(new ReuseExistingWeakSymbols(m_JIT));
// The function __cuda_module_ctor and __cuda_module_dtor will just generated,