llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp

//===-- WebAssemblyFrameLowering.cpp - WebAssembly Frame Lowering ----------==//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file contains the WebAssembly implementation of
/// TargetFrameLowering class.
///
/// On WebAssembly, there aren't a lot of things to do here. There are no
/// callee-saved registers to save, and no spill slots.
///
/// The stack grows downward.
///
//===----------------------------------------------------------------------===//

#include "WebAssemblyFrameLowering.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssemblyInstrInfo.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "WebAssemblyTargetMachine.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/Debug.h"
using namespace llvm;

#define DEBUG_TYPE "wasm-frame-info"

// TODO: Implement a red zone?

/// Return true if the specified function should have a dedicated frame pointer
/// register.
bool WebAssemblyFrameLowering::hasFP(const MachineFunction &MF) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  const auto *RegInfo =
      MF.getSubtarget<WebAssemblySubtarget>().getRegisterInfo();
  return MFI->hasCalls() || MFI->hasVarSizedObjects() ||
         MFI->isFrameAddressTaken() || MFI->hasStackMap() ||
         MFI->hasPatchPoint() || RegInfo->needsStackRealignment(MF);
}

/// Under normal circumstances, when a frame pointer is not required, we reserve
/// argument space for call sites in the function immediately on entry to the
/// current function. This eliminates the need for add/sub sp brackets around
/// call sites. Returns true if the call frame is included as part of the stack
/// frame.
bool WebAssemblyFrameLowering::hasReservedCallFrame(
    const MachineFunction &MF) const {
  return !MF.getFrameInfo()->hasVarSizedObjects();
}

void WebAssemblyFrameLowering::eliminateCallFramePseudoInstr(
    MachineFunction & /*MF*/, MachineBasicBlock & /*MBB*/,
    MachineBasicBlock::iterator /*I*/) const {
  llvm_unreachable("TODO: implement eliminateCallFramePseudoInstr");
}

void WebAssemblyFrameLowering::emitPrologue(MachineFunction & /*MF*/,
                                            MachineBasicBlock & /*MBB*/) const {
  llvm_unreachable("TODO: implement emitPrologue");
}

void WebAssemblyFrameLowering::emitEpilogue(MachineFunction & /*MF*/,
                                            MachineBasicBlock & /*MBB*/) const {
  llvm_unreachable("TODO: implement emitEpilogue");
}