//===-- MSP430FrameLowering.cpp - MSP430 Frame Information ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the MSP430 implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "MSP430FrameLowering.h"
#include "MSP430InstrInfo.h"
#include "MSP430MachineFunctionInfo.h"
#include "MSP430Subtarget.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/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
bool MSP430FrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
return (MF.getTarget().Options.DisableFramePointerElim(MF) ||
MF.getFrameInfo()->hasVarSizedObjects() ||
MFI->isFrameAddressTaken());
}
bool MSP430FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
return !MF.getFrameInfo()->hasVarSizedObjects();
}
void MSP430FrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB
MachineFrameInfo *MFI = MF.getFrameInfo();
MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
const MSP430InstrInfo &TII =
*static_cast<const MSP430InstrInfo *>(MF.getSubtarget().getInstrInfo());
MachineBasicBlock::iterator MBBI = MBB.begin();
DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
// Get the number of bytes to allocate from the FrameInfo.
uint64_t StackSize = MFI->getStackSize();
uint64_t NumBytes = 0;
if (hasFP(MF)) {
// Calculate required stack adjustment
uint64_t FrameSize = StackSize - 2;
NumBytes = FrameSize - MSP430FI->getCalleeSavedFrameSize();
// Get the offset of the stack slot for the EBP register... which is
// guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
// Update the frame offset adjustment.
MFI->setOffsetAdjustment(-NumBytes);
// Save FP into the appropriate stack slot...
BuildMI(MBB, MBBI, DL, TII.get(MSP430::PUSH16r))
.addReg(MSP430::FP, RegState::Kill);
// Update FP with the new base value...
BuildMI(MBB, MBBI, DL, TII.get(MSP430::MOV16rr), MSP430::FP)
.addReg(MSP430::SP);
// Mark the FramePtr as live-in in every block except the entry.
for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
I != E; ++I)
I->addLiveIn(MSP430::FP);
} else
NumBytes = StackSize - MSP430FI->getCalleeSavedFrameSize();
// Skip the callee-saved push instructions.
while (MBBI != MBB.end() && (MBBI->getOpcode() == MSP430::PUSH16r))
++MBBI;
if (MBBI != MBB.end())
DL = MBBI->getDebugLoc();
if (NumBytes) { // adjust stack pointer: SP -= numbytes
// If there is an SUB16ri of SP immediately before this instruction, merge
// the two.
//NumBytes -= mergeSPUpdates(MBB, MBBI, true);
// If there is an ADD16ri or SUB16ri of SP immediately after this
// instruction, merge the two instructions.
// mergeSPUpdatesDown(MBB, MBBI, &NumBytes);
if (NumBytes) {
MachineInstr *MI =
BuildMI(MBB, MBBI, DL, TII.get(MSP430::SUB16ri), MSP430::SP)
.addReg(MSP430::SP).addImm(NumBytes);
// The SRW implicit def is dead.
MI->getOperand(3).setIsDead();
}
}
}
void MSP430FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
const MSP430InstrInfo &TII =
*static_cast<const MSP430InstrInfo *>(MF.getSubtarget().getInstrInfo());
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
unsigned RetOpcode = MBBI->getOpcode();
DebugLoc DL = MBBI->getDebugLoc();
switch (RetOpcode) {
case MSP430::RET:
case MSP430::RETI: break; // These are ok
default:
llvm_unreachable("Can only insert epilog into returning blocks");
}
// Get the number of bytes to allocate from the FrameInfo
uint64_t StackSize = MFI->getStackSize();
unsigned CSSize = MSP430FI->getCalleeSavedFrameSize();
uint64_t NumBytes = 0;
if (hasFP(MF)) {
// Calculate required stack adjustment
uint64_t FrameSize = StackSize - 2;
NumBytes = FrameSize - CSSize;
// pop FP.
BuildMI(MBB, MBBI, DL, TII.get(MSP430::POP16r), MSP430::FP);
} else
NumBytes = StackSize - CSSize;
// Skip the callee-saved pop instructions.
while (MBBI != MBB.begin()) {
MachineBasicBlock::iterator PI = std::prev(MBBI);
unsigned Opc = PI->getOpcode();
if (Opc != MSP430::POP16r && !PI->isTerminator())
break;
--MBBI;
}
DL = MBBI->getDebugLoc();
// If there is an ADD16ri or SUB16ri of SP immediately before this
// instruction, merge the two instructions.
//if (NumBytes || MFI->hasVarSizedObjects())
// mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);
if (MFI->hasVarSizedObjects()) {
BuildMI(MBB, MBBI, DL,
TII.get(MSP430::MOV16rr), MSP430::SP).addReg(MSP430::FP);
if (CSSize) {
MachineInstr *MI =
BuildMI(MBB, MBBI, DL,
TII.get(MSP430::SUB16ri), MSP430::SP)
.addReg(MSP430::SP).addImm(CSSize);
// The SRW implicit def is dead.
MI->getOperand(3).setIsDead();
}
} else {
// adjust stack pointer back: SP += numbytes
if (NumBytes) {
MachineInstr *MI =
BuildMI(MBB, MBBI, DL, TII.get(MSP430::ADD16ri), MSP430::SP)
.addReg(MSP430::SP).addImm(NumBytes);
// The SRW implicit def is dead.
MI->getOperand(3).setIsDead();
}
}
}
// FIXME: Can we eleminate these in favour of generic code?
bool
MSP430FrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
DebugLoc DL;
if (MI != MBB.end()) DL = MI->getDebugLoc();
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
MSP430MachineFunctionInfo *MFI = MF.getInfo<MSP430MachineFunctionInfo>();
MFI->setCalleeSavedFrameSize(CSI.size() * 2);
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
// Add the callee-saved register as live-in. It's killed at the spill.
MBB.addLiveIn(Reg);
BuildMI(MBB, MI, DL, TII.get(MSP430::PUSH16r))
.addReg(Reg, RegState::Kill);
}
return true;
}
bool
MSP430FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
DebugLoc DL;
if (MI != MBB.end()) DL = MI->getDebugLoc();
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
for (unsigned i = 0, e = CSI.size(); i != e; ++i)
BuildMI(MBB, MI, DL, TII.get(MSP430::POP16r), CSI[i].getReg());
return true;
}
void MSP430FrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const MSP430InstrInfo &TII =
*static_cast<const MSP430InstrInfo *>(MF.getSubtarget().getInstrInfo());
unsigned StackAlign = getStackAlignment();
if (!hasReservedCallFrame(MF)) {
// If the stack pointer can be changed after prologue, turn the
// adjcallstackup instruction into a 'sub SP, <amt>' and the
// adjcallstackdown instruction into 'add SP, <amt>'
// TODO: consider using push / pop instead of sub + store / add
MachineInstr *Old = I;
uint64_t Amount = Old->getOperand(0).getImm();
if (Amount != 0) {
// We need to keep the stack aligned properly. To do this, we round the
// amount of space needed for the outgoing arguments up to the next
// alignment boundary.
Amount = (Amount+StackAlign-1)/StackAlign*StackAlign;
MachineInstr *New = nullptr;
if (Old->getOpcode() == TII.getCallFrameSetupOpcode()) {
New = BuildMI(MF, Old->getDebugLoc(),
TII.get(MSP430::SUB16ri), MSP430::SP)
.addReg(MSP430::SP).addImm(Amount);
} else {
assert(Old->getOpcode() == TII.getCallFrameDestroyOpcode());
// factor out the amount the callee already popped.
uint64_t CalleeAmt = Old->getOperand(1).getImm();
Amount -= CalleeAmt;
if (Amount)
New = BuildMI(MF, Old->getDebugLoc(),
TII.get(MSP430::ADD16ri), MSP430::SP)
.addReg(MSP430::SP).addImm(Amount);
}
if (New) {
// The SRW implicit def is dead.
New->getOperand(3).setIsDead();
// Replace the pseudo instruction with a new instruction...
MBB.insert(I, New);
}
}
} else if (I->getOpcode() == TII.getCallFrameDestroyOpcode()) {
// If we are performing frame pointer elimination and if the callee pops
// something off the stack pointer, add it back.
if (uint64_t CalleeAmt = I->getOperand(1).getImm()) {
MachineInstr *Old = I;
MachineInstr *New =
BuildMI(MF, Old->getDebugLoc(), TII.get(MSP430::SUB16ri),
MSP430::SP).addReg(MSP430::SP).addImm(CalleeAmt);
// The SRW implicit def is dead.
New->getOperand(3).setIsDead();
MBB.insert(I, New);
}
}
MBB.erase(I);
}
void
MSP430FrameLowering::processFunctionBeforeFrameFinalized(MachineFunction &MF,
RegScavenger *) const {
// Create a frame entry for the FP register that must be saved.
if (hasFP(MF)) {
int FrameIdx = MF.getFrameInfo()->CreateFixedObject(2, -4, true);
(void)FrameIdx;
assert(FrameIdx == MF.getFrameInfo()->getObjectIndexBegin() &&
"Slot for FP register must be last in order to be found!");
}
}