294 lines
10 KiB
C++
294 lines
10 KiB
C++
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//===-- MSP430FrameLowering.cpp - MSP430 Frame Information ----------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains the MSP430 implementation of TargetFrameLowering class.
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//
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//===----------------------------------------------------------------------===//
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#include "MSP430FrameLowering.h"
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#include "MSP430InstrInfo.h"
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#include "MSP430MachineFunctionInfo.h"
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#include "MSP430Subtarget.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Function.h"
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#include "llvm/Target/TargetOptions.h"
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using namespace llvm;
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bool MSP430FrameLowering::hasFP(const MachineFunction &MF) const {
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const MachineFrameInfo &MFI = MF.getFrameInfo();
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return (MF.getTarget().Options.DisableFramePointerElim(MF) ||
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MF.getFrameInfo().hasVarSizedObjects() ||
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MFI.isFrameAddressTaken());
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}
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bool MSP430FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
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return !MF.getFrameInfo().hasVarSizedObjects();
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}
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void MSP430FrameLowering::emitPrologue(MachineFunction &MF,
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MachineBasicBlock &MBB) const {
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assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
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MachineFrameInfo &MFI = MF.getFrameInfo();
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MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
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const MSP430InstrInfo &TII =
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*static_cast<const MSP430InstrInfo *>(MF.getSubtarget().getInstrInfo());
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MachineBasicBlock::iterator MBBI = MBB.begin();
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DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
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// Get the number of bytes to allocate from the FrameInfo.
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uint64_t StackSize = MFI.getStackSize();
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uint64_t NumBytes = 0;
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if (hasFP(MF)) {
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// Calculate required stack adjustment
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uint64_t FrameSize = StackSize - 2;
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NumBytes = FrameSize - MSP430FI->getCalleeSavedFrameSize();
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// Get the offset of the stack slot for the EBP register... which is
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// guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
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// Update the frame offset adjustment.
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MFI.setOffsetAdjustment(-NumBytes);
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// Save FP into the appropriate stack slot...
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BuildMI(MBB, MBBI, DL, TII.get(MSP430::PUSH16r))
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.addReg(MSP430::R4, RegState::Kill);
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// Update FP with the new base value...
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BuildMI(MBB, MBBI, DL, TII.get(MSP430::MOV16rr), MSP430::R4)
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.addReg(MSP430::SP);
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// Mark the FramePtr as live-in in every block except the entry.
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for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
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I != E; ++I)
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I->addLiveIn(MSP430::R4);
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} else
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NumBytes = StackSize - MSP430FI->getCalleeSavedFrameSize();
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// Skip the callee-saved push instructions.
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while (MBBI != MBB.end() && (MBBI->getOpcode() == MSP430::PUSH16r))
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++MBBI;
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if (MBBI != MBB.end())
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DL = MBBI->getDebugLoc();
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if (NumBytes) { // adjust stack pointer: SP -= numbytes
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// If there is an SUB16ri of SP immediately before this instruction, merge
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// the two.
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//NumBytes -= mergeSPUpdates(MBB, MBBI, true);
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// If there is an ADD16ri or SUB16ri of SP immediately after this
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// instruction, merge the two instructions.
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// mergeSPUpdatesDown(MBB, MBBI, &NumBytes);
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if (NumBytes) {
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MachineInstr *MI =
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BuildMI(MBB, MBBI, DL, TII.get(MSP430::SUB16ri), MSP430::SP)
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.addReg(MSP430::SP).addImm(NumBytes);
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// The SRW implicit def is dead.
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MI->getOperand(3).setIsDead();
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}
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}
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}
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void MSP430FrameLowering::emitEpilogue(MachineFunction &MF,
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MachineBasicBlock &MBB) const {
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const MachineFrameInfo &MFI = MF.getFrameInfo();
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MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
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const MSP430InstrInfo &TII =
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*static_cast<const MSP430InstrInfo *>(MF.getSubtarget().getInstrInfo());
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MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
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unsigned RetOpcode = MBBI->getOpcode();
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DebugLoc DL = MBBI->getDebugLoc();
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switch (RetOpcode) {
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case MSP430::RET:
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case MSP430::RETI: break; // These are ok
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default:
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llvm_unreachable("Can only insert epilog into returning blocks");
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}
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// Get the number of bytes to allocate from the FrameInfo
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uint64_t StackSize = MFI.getStackSize();
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unsigned CSSize = MSP430FI->getCalleeSavedFrameSize();
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uint64_t NumBytes = 0;
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if (hasFP(MF)) {
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// Calculate required stack adjustment
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uint64_t FrameSize = StackSize - 2;
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NumBytes = FrameSize - CSSize;
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// pop FP.
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BuildMI(MBB, MBBI, DL, TII.get(MSP430::POP16r), MSP430::R4);
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} else
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NumBytes = StackSize - CSSize;
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// Skip the callee-saved pop instructions.
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while (MBBI != MBB.begin()) {
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MachineBasicBlock::iterator PI = std::prev(MBBI);
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unsigned Opc = PI->getOpcode();
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if (Opc != MSP430::POP16r && !PI->isTerminator())
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break;
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--MBBI;
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}
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DL = MBBI->getDebugLoc();
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// If there is an ADD16ri or SUB16ri of SP immediately before this
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// instruction, merge the two instructions.
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//if (NumBytes || MFI.hasVarSizedObjects())
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// mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);
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if (MFI.hasVarSizedObjects()) {
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BuildMI(MBB, MBBI, DL,
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TII.get(MSP430::MOV16rr), MSP430::SP).addReg(MSP430::R4);
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if (CSSize) {
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MachineInstr *MI =
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BuildMI(MBB, MBBI, DL,
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TII.get(MSP430::SUB16ri), MSP430::SP)
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.addReg(MSP430::SP).addImm(CSSize);
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// The SRW implicit def is dead.
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MI->getOperand(3).setIsDead();
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}
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} else {
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// adjust stack pointer back: SP += numbytes
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if (NumBytes) {
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MachineInstr *MI =
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BuildMI(MBB, MBBI, DL, TII.get(MSP430::ADD16ri), MSP430::SP)
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.addReg(MSP430::SP).addImm(NumBytes);
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// The SRW implicit def is dead.
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MI->getOperand(3).setIsDead();
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}
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}
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}
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// FIXME: Can we eleminate these in favour of generic code?
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bool MSP430FrameLowering::spillCalleeSavedRegisters(
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MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
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ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
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if (CSI.empty())
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return false;
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DebugLoc DL;
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if (MI != MBB.end()) DL = MI->getDebugLoc();
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MachineFunction &MF = *MBB.getParent();
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const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
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MSP430MachineFunctionInfo *MFI = MF.getInfo<MSP430MachineFunctionInfo>();
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MFI->setCalleeSavedFrameSize(CSI.size() * 2);
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for (unsigned i = CSI.size(); i != 0; --i) {
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unsigned Reg = CSI[i-1].getReg();
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// Add the callee-saved register as live-in. It's killed at the spill.
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MBB.addLiveIn(Reg);
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BuildMI(MBB, MI, DL, TII.get(MSP430::PUSH16r))
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.addReg(Reg, RegState::Kill);
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}
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return true;
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}
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bool MSP430FrameLowering::restoreCalleeSavedRegisters(
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MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
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MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
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if (CSI.empty())
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return false;
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DebugLoc DL;
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if (MI != MBB.end()) DL = MI->getDebugLoc();
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MachineFunction &MF = *MBB.getParent();
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const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
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for (unsigned i = 0, e = CSI.size(); i != e; ++i)
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BuildMI(MBB, MI, DL, TII.get(MSP430::POP16r), CSI[i].getReg());
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return true;
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}
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MachineBasicBlock::iterator MSP430FrameLowering::eliminateCallFramePseudoInstr(
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MachineFunction &MF, MachineBasicBlock &MBB,
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MachineBasicBlock::iterator I) const {
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const MSP430InstrInfo &TII =
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*static_cast<const MSP430InstrInfo *>(MF.getSubtarget().getInstrInfo());
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if (!hasReservedCallFrame(MF)) {
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// If the stack pointer can be changed after prologue, turn the
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// adjcallstackup instruction into a 'sub SP, <amt>' and the
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// adjcallstackdown instruction into 'add SP, <amt>'
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// TODO: consider using push / pop instead of sub + store / add
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MachineInstr &Old = *I;
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uint64_t Amount = TII.getFrameSize(Old);
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if (Amount != 0) {
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// We need to keep the stack aligned properly. To do this, we round the
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// amount of space needed for the outgoing arguments up to the next
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// alignment boundary.
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Amount = alignTo(Amount, getStackAlign());
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MachineInstr *New = nullptr;
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if (Old.getOpcode() == TII.getCallFrameSetupOpcode()) {
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New =
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BuildMI(MF, Old.getDebugLoc(), TII.get(MSP430::SUB16ri), MSP430::SP)
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.addReg(MSP430::SP)
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.addImm(Amount);
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} else {
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assert(Old.getOpcode() == TII.getCallFrameDestroyOpcode());
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// factor out the amount the callee already popped.
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Amount -= TII.getFramePoppedByCallee(Old);
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if (Amount)
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New = BuildMI(MF, Old.getDebugLoc(), TII.get(MSP430::ADD16ri),
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MSP430::SP)
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.addReg(MSP430::SP)
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.addImm(Amount);
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}
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if (New) {
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// The SRW implicit def is dead.
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New->getOperand(3).setIsDead();
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// Replace the pseudo instruction with a new instruction...
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MBB.insert(I, New);
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}
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}
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} else if (I->getOpcode() == TII.getCallFrameDestroyOpcode()) {
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// If we are performing frame pointer elimination and if the callee pops
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// something off the stack pointer, add it back.
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if (uint64_t CalleeAmt = TII.getFramePoppedByCallee(*I)) {
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MachineInstr &Old = *I;
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MachineInstr *New =
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BuildMI(MF, Old.getDebugLoc(), TII.get(MSP430::SUB16ri), MSP430::SP)
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.addReg(MSP430::SP)
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.addImm(CalleeAmt);
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// The SRW implicit def is dead.
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New->getOperand(3).setIsDead();
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MBB.insert(I, New);
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}
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}
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return MBB.erase(I);
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}
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void
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MSP430FrameLowering::processFunctionBeforeFrameFinalized(MachineFunction &MF,
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RegScavenger *) const {
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// Create a frame entry for the FP register that must be saved.
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if (hasFP(MF)) {
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int FrameIdx = MF.getFrameInfo().CreateFixedObject(2, -4, true);
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(void)FrameIdx;
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assert(FrameIdx == MF.getFrameInfo().getObjectIndexBegin() &&
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"Slot for FP register must be last in order to be found!");
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}
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}
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