#include "Thumb1FrameLowering.h"
#include "ARMMachineFunctionInfo.h"
+#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
void Thumb1FrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
- assert(&MBB == &MF.front() && "Shrink-wrapping not yet implemented");
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
}
}
-
// Adjust FP so it point to the stack slot that contains the previous FP.
if (HasFP) {
- FramePtrOffsetInBlock += MFI->getObjectOffset(FramePtrSpillFI)
- + GPRCS1Size + ArgRegsSaveSize;
+ FramePtrOffsetInBlock +=
+ MFI->getObjectOffset(FramePtrSpillFI) + GPRCS1Size + ArgRegsSaveSize;
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr)
.addReg(ARM::SP).addImm(FramePtrOffsetInBlock / 4)
.setMIFlags(MachineInstr::FrameSetup));
void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
- MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
- assert((MBBI->getOpcode() == ARM::tBX_RET ||
- MBBI->getOpcode() == ARM::tPOP_RET) &&
- "Can only insert epilog into returning blocks");
- DebugLoc dl = MBBI->getDebugLoc();
+ MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
+ DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const ThumbRegisterInfo *RegInfo =
// frame pointer stack slot, the target is ELF and the function has FP, or
// the target uses var sized objects.
if (NumBytes) {
- assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
+ assert(!MFI->getPristineRegs(MF).test(ARM::R4) &&
"No scratch register to restore SP from FP!");
emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
TII, *RegInfo);
ARM::SP)
.addReg(FramePtr));
} else {
- if (MBBI->getOpcode() == ARM::tBX_RET &&
- &MBB.front() != MBBI &&
- std::prev(MBBI)->getOpcode() == ARM::tPOP) {
+ if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tBX_RET &&
+ &MBB.front() != MBBI && std::prev(MBBI)->getOpcode() == ARM::tPOP) {
MachineBasicBlock::iterator PMBBI = std::prev(MBBI);
if (!tryFoldSPUpdateIntoPushPop(STI, MF, PMBBI, NumBytes))
emitSPUpdate(MBB, PMBBI, TII, dl, *RegInfo, NumBytes);
}
}
+ if (needPopSpecialFixUp(MF)) {
+ bool Done = emitPopSpecialFixUp(MBB, /* DoIt */ true);
+ (void)Done;
+ assert(Done && "Emission of the special fixup failed!?");
+ }
+}
+
+bool Thumb1FrameLowering::canUseAsEpilogue(const MachineBasicBlock &MBB) const {
+ if (!needPopSpecialFixUp(*MBB.getParent()))
+ return true;
+
+ MachineBasicBlock *TmpMBB = const_cast<MachineBasicBlock *>(&MBB);
+ return emitPopSpecialFixUp(*TmpMBB, /* DoIt */ false);
+}
+
+bool Thumb1FrameLowering::needPopSpecialFixUp(const MachineFunction &MF) const {
+ ARMFunctionInfo *AFI =
+ const_cast<MachineFunction *>(&MF)->getInfo<ARMFunctionInfo>();
+ if (AFI->getArgRegsSaveSize())
+ return true;
+
bool IsV4PopReturn = false;
- for (const CalleeSavedInfo &CSI : MFI->getCalleeSavedInfo())
+ for (const CalleeSavedInfo &CSI : MF.getFrameInfo()->getCalleeSavedInfo())
if (CSI.getReg() == ARM::LR)
IsV4PopReturn = true;
- IsV4PopReturn &= STI.hasV4TOps() && !STI.hasV5TOps();
-
- // Unlike T2 and ARM mode, the T1 pop instruction cannot restore
- // to LR, and we can't pop the value directly to the PC since
- // we need to update the SP after popping the value. So instead
- // we have to emit:
- // POP {r3}
- // ADD sp, #offset
- // BX r3
- // If this would clobber a return value, then generate this sequence instead:
- // MOV ip, r3
- // POP {r3}
- // ADD sp, #offset
- // MOV lr, r3
- // MOV r3, ip
- // BX lr
- if (ArgRegsSaveSize || IsV4PopReturn) {
- // Get the last instruction, tBX_RET
- MBBI = MBB.getLastNonDebugInstr();
- assert (MBBI->getOpcode() == ARM::tBX_RET);
- DebugLoc dl = MBBI->getDebugLoc();
-
- if (AFI->getReturnRegsCount() <= 3) {
- // Epilogue: pop saved LR to R3 and branch off it.
- AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
- .addReg(ARM::R3, RegState::Define);
-
- emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize);
-
- MachineInstrBuilder MIB =
- BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX))
- .addReg(ARM::R3, RegState::Kill);
- AddDefaultPred(MIB);
- MIB.copyImplicitOps(&*MBBI);
- // erase the old tBX_RET instruction
- MBB.erase(MBBI);
- } else {
- AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
- .addReg(ARM::R12, RegState::Define)
- .addReg(ARM::R3, RegState::Kill));
+ return IsV4PopReturn && STI.hasV4TOps() && !STI.hasV5TOps();
+}
- AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
- .addReg(ARM::R3, RegState::Define);
+bool Thumb1FrameLowering::emitPopSpecialFixUp(MachineBasicBlock &MBB,
+ bool DoIt) const {
+ MachineFunction &MF = *MBB.getParent();
+ ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
+ unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize();
+ const TargetInstrInfo &TII = *STI.getInstrInfo();
+ const ThumbRegisterInfo *RegInfo =
+ static_cast<const ThumbRegisterInfo *>(STI.getRegisterInfo());
- emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize);
+ // If MBBI is a return instruction, we may be able to directly restore
+ // LR in the PC.
+ // This is possible if we do not need to emit any SP update.
+ // Otherwise, we need a temporary register to pop the value
+ // and copy that value into LR.
+ auto MBBI = MBB.getFirstTerminator();
+ if (!ArgRegsSaveSize && MBBI != MBB.end() &&
+ MBBI->getOpcode() == ARM::tBX_RET) {
+ if (!DoIt)
+ return true;
+ MachineInstrBuilder MIB =
+ AddDefaultPred(
+ BuildMI(MBB, MBBI, MBBI->getDebugLoc(), TII.get(ARM::tPOP_RET)))
+ .addReg(ARM::PC, RegState::Define);
+ MIB.copyImplicitOps(&*MBBI);
+ // erase the old tBX_RET instruction
+ MBB.erase(MBBI);
+ return true;
+ }
- AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
- .addReg(ARM::LR, RegState::Define)
- .addReg(ARM::R3, RegState::Kill));
+ // Look for a temporary register to use.
+ // First, compute the liveness information.
+ LivePhysRegs UsedRegs(STI.getRegisterInfo());
+ UsedRegs.addLiveOuts(&MBB, /*AddPristines*/ true);
+ // The semantic of pristines changed recently and now,
+ // the callee-saved registers that are touched in the function
+ // are not part of the pristines set anymore.
+ // Add those callee-saved now.
+ const TargetRegisterInfo *TRI = STI.getRegisterInfo();
+ const MCPhysReg *CSRegs = TRI->getCalleeSavedRegs(&MF);
+ for (unsigned i = 0; CSRegs[i]; ++i)
+ UsedRegs.addReg(CSRegs[i]);
+
+ DebugLoc dl = DebugLoc();
+ if (MBBI != MBB.end()) {
+ dl = MBBI->getDebugLoc();
+ auto InstUpToMBBI = MBB.end();
+ // The post-decrement is on purpose here.
+ // We want to have the liveness right before MBBI.
+ while (InstUpToMBBI-- != MBBI)
+ UsedRegs.stepBackward(*InstUpToMBBI);
+ }
- AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
- .addReg(ARM::R3, RegState::Define)
- .addReg(ARM::R12, RegState::Kill));
- // Keep the tBX_RET instruction
+ // Look for a register that can be directly use in the POP.
+ unsigned PopReg = 0;
+ // And some temporary register, just in case.
+ unsigned TemporaryReg = 0;
+ BitVector PopFriendly =
+ TRI->getAllocatableSet(MF, TRI->getRegClass(ARM::tGPRRegClassID));
+ assert(PopFriendly.any() && "No allocatable pop-friendly register?!");
+ // Rebuild the GPRs from the high registers because they are removed
+ // form the GPR reg class for thumb1.
+ BitVector GPRsNoLRSP =
+ TRI->getAllocatableSet(MF, TRI->getRegClass(ARM::hGPRRegClassID));
+ GPRsNoLRSP |= PopFriendly;
+ GPRsNoLRSP.reset(ARM::LR);
+ GPRsNoLRSP.reset(ARM::SP);
+ GPRsNoLRSP.reset(ARM::PC);
+ for (int Register = GPRsNoLRSP.find_first(); Register != -1;
+ Register = GPRsNoLRSP.find_next(Register)) {
+ if (!UsedRegs.contains(Register)) {
+ // Remember the first pop-friendly register and exit.
+ if (PopFriendly.test(Register)) {
+ PopReg = Register;
+ TemporaryReg = 0;
+ break;
+ }
+ // Otherwise, remember that the register will be available to
+ // save a pop-friendly register.
+ TemporaryReg = Register;
}
}
+
+ if (!DoIt && !PopReg && !TemporaryReg)
+ return false;
+
+ assert((PopReg || TemporaryReg) && "Cannot get LR");
+
+ if (TemporaryReg) {
+ assert(!PopReg && "Unnecessary MOV is about to be inserted");
+ PopReg = PopFriendly.find_first();
+ AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
+ .addReg(TemporaryReg, RegState::Define)
+ .addReg(PopReg, RegState::Kill));
+ }
+
+ assert(PopReg && "Do not know how to get LR");
+ AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
+ .addReg(PopReg, RegState::Define);
+
+ emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize);
+
+ if (!TemporaryReg && MBBI != MBB.end() && MBBI->getOpcode() == ARM::tBX_RET) {
+ MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX))
+ .addReg(PopReg, RegState::Kill);
+ AddDefaultPred(MIB);
+ MIB.copyImplicitOps(&*MBBI);
+ // erase the old tBX_RET instruction
+ MBB.erase(MBBI);
+ return true;
+ }
+
+ AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
+ .addReg(ARM::LR, RegState::Define)
+ .addReg(PopReg, RegState::Kill));
+
+ if (TemporaryReg) {
+ AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
+ .addReg(PopReg, RegState::Define)
+ .addReg(TemporaryReg, RegState::Kill));
+ }
+
+ return true;
}
bool Thumb1FrameLowering::
const TargetInstrInfo &TII = *STI.getInstrInfo();
bool isVarArg = AFI->getArgRegsSaveSize() > 0;
- DebugLoc DL = MI->getDebugLoc();
+ DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
MachineInstrBuilder MIB = BuildMI(MF, DL, TII.get(ARM::tPOP));
AddDefaultPred(MIB);
bool NumRegs = false;
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
- if (Reg == ARM::LR) {
+ if (Reg == ARM::LR && MBB.succ_empty()) {
// Special epilogue for vararg functions. See emitEpilogue
if (isVarArg)
continue;
continue;
Reg = ARM::PC;
(*MIB).setDesc(TII.get(ARM::tPOP_RET));
- MIB.copyImplicitOps(&*MI);
+ if (MI != MBB.end())
+ MIB.copyImplicitOps(&*MI);
MI = MBB.erase(MI);
}
MIB.addReg(Reg, getDefRegState(true));
projects / oota-llvm.git / blobdiff