llvm/llvm/lib/Target/NVPTX/NVPTXProxyRegErasure.cpp

//===- NVPTXProxyRegErasure.cpp - NVPTX Proxy Register Instruction Erasure -==//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// The pass is needed to remove ProxyReg instructions and restore related
// registers. The instructions were needed at instruction selection stage to
// make sure that callseq_end nodes won't be removed as "dead nodes". This can
// happen when we expand instructions into libcalls and the call site doesn't
// care about the libcall chain. Call site cares about data flow only, and the
// latest data flow node happens to be before callseq_end. Therefore the node
// becomes dangling and "dead". The ProxyReg acts like an additional data flow
// node *after* the callseq_end in the chain and ensures that everything will be
// preserved.
//
//===----------------------------------------------------------------------===//

#include "NVPTX.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"

usingnamespacellvm;

namespace llvm {
void initializeNVPTXProxyRegErasurePass(PassRegistry &);
}

namespace {

struct NVPTXProxyRegErasure : public MachineFunctionPass { … };

} // namespace

char NVPTXProxyRegErasure::ID = …;

INITIALIZE_PASS(…)

bool NVPTXProxyRegErasure::runOnMachineFunction(MachineFunction &MF) { … }

MachineFunctionPass *llvm::createNVPTXProxyRegErasurePass() { … }