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//===------------ RISCVLandingPadSetup.cpp ---------------------------------==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This is a RISC-V pass to setup landing pad labels for indirect jumps.
// Currently this pass only supports fixed labels.
//
//===----------------------------------------------------------------------===//
#include "RISCV.h"
#include "RISCVInstrInfo.h"
#include "RISCVSubtarget.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
using namespace llvm;
#define DEBUG_TYPE "riscv-lpad-setup"
#define PASS_NAME "RISC-V Landing Pad Setup"
extern cl::opt<uint32_t> PreferredLandingPadLabel;
namespace {
class RISCVLandingPadSetup : public MachineFunctionPass {
public:
static char ID;
RISCVLandingPadSetup() : MachineFunctionPass(ID) {}
bool runOnMachineFunction(MachineFunction &F) override;
StringRef getPassName() const override { return PASS_NAME; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
};
} // end anonymous namespace
bool RISCVLandingPadSetup::runOnMachineFunction(MachineFunction &MF) {
const auto &STI = MF.getSubtarget<RISCVSubtarget>();
const RISCVInstrInfo &TII = *STI.getInstrInfo();
if (!STI.hasStdExtZicfilp())
return false;
uint32_t Label = 0;
if (PreferredLandingPadLabel.getNumOccurrences() > 0) {
if (!isUInt<20>(PreferredLandingPadLabel))
report_fatal_error("riscv-landing-pad-label=<val>, <val> needs to fit in "
"unsigned 20-bits");
Label = PreferredLandingPadLabel;
}
// Zicfilp does not check X7 if landing pad label is zero.
if (Label == 0)
return false;
bool Changed = false;
for (MachineBasicBlock &MBB : MF)
for (MachineInstr &MI : llvm::make_early_inc_range(MBB)) {
if (MI.getOpcode() != RISCV::PseudoBRINDNonX7 &&
MI.getOpcode() != RISCV::PseudoCALLIndirectNonX7 &&
MI.getOpcode() != RISCV::PseudoTAILIndirectNonX7)
continue;
BuildMI(MBB, MI, MI.getDebugLoc(), TII.get(RISCV::LUI), RISCV::X7)
.addImm(Label);
MachineInstrBuilder(MF, &MI).addUse(RISCV::X7, RegState::ImplicitKill);
Changed = true;
}
return Changed;
}
INITIALIZE_PASS(RISCVLandingPadSetup, DEBUG_TYPE, PASS_NAME, false, false)
char RISCVLandingPadSetup::ID = 0;
FunctionPass *llvm::createRISCVLandingPadSetupPass() {
return new RISCVLandingPadSetup();
}
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