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//===--- GoAnnotation.cpp -------------------------------------------------===//
//
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//
//===----------------------------------------------------------------------===//
//
// LLVM backend pass to attach auxiliary information to the
// exception table, for the use of Go stack maps.
//
//===----------------------------------------------------------------------===//
#include "GoStackMap.h"
#include "GollvmPasses.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/PassRegistry.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
namespace {
class GoAnnotation : public MachineFunctionPass {
public:
static char ID;
GoAnnotation() : MachineFunctionPass(ID) {
initializeGoAnnotationPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
bool runOnMachineFunction(MachineFunction &MF) override;
private:
};
} // namespace
char GoAnnotation::ID = 0;
INITIALIZE_PASS(GoAnnotation, "go-annotation",
"Add annotations for Go code", false,
false)
FunctionPass *llvm::createGoAnnotationPass() { return new GoAnnotation(); }
bool
GoAnnotation::runOnMachineFunction(MachineFunction &MF) {
// Create a dummy landing pad entry at the function entry PC,
// with a sentinel value, to mark this as a Go function.
MCContext &Context = MF.getContext();
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
MachineBasicBlock &EntryBB = MF.front();
auto MBBI = EntryBB.begin();
DebugLoc DL = EntryBB.findDebugLoc(MBBI);
MCSymbol *EntryLabel = Context.createTempSymbol();
BuildMI(EntryBB, MBBI, DL, TII->get(TargetOpcode::EH_LABEL)).addSym(EntryLabel);
// Besides begin/end labels and typeID, other fields of LPI
// does not really matter. We set fields that are required
// to make EHStreamer happy.
LandingPadInfo &LPI = MF.getOrCreateLandingPadInfo(&EntryBB);
LPI.BeginLabels.push_back(EntryLabel);
LPI.EndLabels.push_back(EntryLabel); // 0 size, so it doesn't capture any exception.
LPI.LandingPadLabel = EntryLabel;
const Function &F = MF.getFunction();
const Module *M = F.getParent();
GlobalValue *X = M->getGlobalVariable(GO_FUNC_SYM,
/* AllowInternal */ true);
assert(X);
unsigned TypeID = MF.getTypeIDFor(X);
LPI.TypeIds.push_back(TypeID);
return true;
}