void findUsesOfImpDef(SmallVectorImpl<MachineOperand *> &UsesOfImpDefs,
const MemOpQueue &MemOps, unsigned DefReg,
unsigned RangeBegin, unsigned RangeEnd);
+ void UpdateBaseRegUses(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator MBBI,
+ DebugLoc dl, unsigned Base, unsigned WordOffset,
+ ARMCC::CondCodes Pred, unsigned PredReg);
bool MergeOps(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
int Offset, unsigned Base, bool BaseKill, int Opcode,
ARMCC::CondCodes Pred, unsigned PredReg, unsigned Scratch,
char ARMLoadStoreOpt::ID = 0;
}
+static bool definesCPSR(const MachineInstr *MI) {
+ for (const auto &MO : MI->operands()) {
+ if (!MO.isReg())
+ continue;
+ if (MO.isDef() && MO.getReg() == ARM::CPSR && !MO.isDead())
+ // If the instruction has live CPSR def, then it's not safe to fold it
+ // into load / store.
+ return true;
+ }
+
+ return false;
+}
+
+static int getMemoryOpOffset(const MachineInstr *MI) {
+ int Opcode = MI->getOpcode();
+ bool isAM3 = Opcode == ARM::LDRD || Opcode == ARM::STRD;
+ unsigned NumOperands = MI->getDesc().getNumOperands();
+ unsigned OffField = MI->getOperand(NumOperands-3).getImm();
+
+ if (Opcode == ARM::t2LDRi12 || Opcode == ARM::t2LDRi8 ||
+ Opcode == ARM::t2STRi12 || Opcode == ARM::t2STRi8 ||
+ Opcode == ARM::t2LDRDi8 || Opcode == ARM::t2STRDi8 ||
+ Opcode == ARM::LDRi12 || Opcode == ARM::STRi12)
+ return OffField;
+
+ // Thumb1 immediate offsets are scaled by 4
+ if (Opcode == ARM::tLDRi || Opcode == ARM::tSTRi)
+ return OffField * 4;
+
+ int Offset = isAM3 ? ARM_AM::getAM3Offset(OffField)
+ : ARM_AM::getAM5Offset(OffField) * 4;
+ ARM_AM::AddrOpc Op = isAM3 ? ARM_AM::getAM3Op(OffField)
+ : ARM_AM::getAM5Op(OffField);
+
+ if (Op == ARM_AM::sub)
+ return -Offset;
+
+ return Offset;
+}
+
static int getLoadStoreMultipleOpcode(int Opcode, ARM_AM::AMSubMode Mode) {
switch (Opcode) {
default: llvm_unreachable("Unhandled opcode!");
return Opc == ARM::STRi12 || isT1i32Store(Opc) || isT2i32Store(Opc);
}
+static unsigned getImmScale(unsigned Opc) {
+ switch (Opc) {
+ default: llvm_unreachable("Unhandled opcode!");
+ case ARM::tLDRi:
+ case ARM::tSTRi:
+ return 1;
+ case ARM::tLDRHi:
+ case ARM::tSTRHi:
+ return 2;
+ case ARM::tLDRBi:
+ case ARM::tSTRBi:
+ return 4;
+ }
+}
+
+/// Update future uses of the base register with the offset introduced
+/// due to writeback. This function only works on Thumb1.
+void
+ARMLoadStoreOpt::UpdateBaseRegUses(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator MBBI,
+ DebugLoc dl, unsigned Base,
+ unsigned WordOffset,
+ ARMCC::CondCodes Pred, unsigned PredReg) {
+ assert(isThumb1 && "Can only update base register uses for Thumb1!");
+ // Start updating any instructions with immediate offsets. Insert a SUB before
+ // the first non-updateable instruction (if any).
+ for (; MBBI != MBB.end(); ++MBBI) {
+ bool InsertSub = false;
+ unsigned Opc = MBBI->getOpcode();
+
+ if (MBBI->readsRegister(Base)) {
+ int Offset;
+ bool IsLoad =
+ Opc == ARM::tLDRi || Opc == ARM::tLDRHi || Opc == ARM::tLDRBi;
+ bool IsStore =
+ Opc == ARM::tSTRi || Opc == ARM::tSTRHi || Opc == ARM::tSTRBi;
+
+ if (IsLoad || IsStore) {
+ // Loads and stores with immediate offsets can be updated, but only if
+ // the new offset isn't negative.
+ // The MachineOperand containing the offset immediate is the last one
+ // before predicates.
+ MachineOperand &MO =
+ MBBI->getOperand(MBBI->getDesc().getNumOperands() - 3);
+ // The offsets are scaled by 1, 2 or 4 depending on the Opcode.
+ Offset = MO.getImm() - WordOffset * getImmScale(Opc);
+
+ // If storing the base register, it needs to be reset first.
+ unsigned InstrSrcReg = MBBI->getOperand(0).getReg();
+
+ if (Offset >= 0 && !(IsStore && InstrSrcReg == Base))
+ MO.setImm(Offset);
+ else
+ InsertSub = true;
+
+ } else if ((Opc == ARM::tSUBi8 || Opc == ARM::tADDi8) &&
+ !definesCPSR(MBBI)) {
+ // SUBS/ADDS using this register, with a dead def of the CPSR.
+ // Merge it with the update; if the merged offset is too large,
+ // insert a new sub instead.
+ MachineOperand &MO =
+ MBBI->getOperand(MBBI->getDesc().getNumOperands() - 3);
+ Offset = (Opc == ARM::tSUBi8) ?
+ MO.getImm() + WordOffset * 4 :
+ MO.getImm() - WordOffset * 4 ;
+ if (Offset >= 0 && TL->isLegalAddImmediate(Offset)) {
+ // FIXME: Swap ADDS<->SUBS if Offset < 0, erase instruction if
+ // Offset == 0.
+ MO.setImm(Offset);
+ // The base register has now been reset, so exit early.
+ return;
+ } else {
+ InsertSub = true;
+ }
+
+ } else {
+ // Can't update the instruction.
+ InsertSub = true;
+ }
+
+ } else if (definesCPSR(MBBI) || MBBI->isCall() || MBBI->isBranch()) {
+ // Since SUBS sets the condition flags, we can't place the base reset
+ // after an instruction that has a live CPSR def.
+ // The base register might also contain an argument for a function call.
+ InsertSub = true;
+ }
+
+ if (InsertSub) {
+ // An instruction above couldn't be updated, so insert a sub.
+ AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII->get(ARM::tSUBi8), Base), true)
+ .addReg(Base, getKillRegState(false)).addImm(WordOffset * 4)
+ .addImm(Pred).addReg(PredReg);
+ return;
+ }
+
+ if (MBBI->killsRegister(Base))
+ // Register got killed. Stop updating.
+ return;
+ }
+
+ // End of block was reached.
+ if (MBB.succ_size() > 0) {
+ // FIXME: Because of a bug, live registers are sometimes missing from
+ // the successor blocks' live-in sets. This means we can't trust that
+ // information and *always* have to reset at the end of a block.
+ // See PR21029.
+ if (MBBI != MBB.end()) --MBBI;
+ AddDefaultT1CC(
+ BuildMI(MBB, MBBI, dl, TII->get(ARM::tSUBi8), Base), true)
+ .addReg(Base, getKillRegState(false)).addImm(WordOffset * 4)
+ .addImm(Pred).addReg(PredReg);
+ }
+}
+
/// MergeOps - Create and insert a LDM or STM with Base as base register and
/// registers in Regs as the register operands that would be loaded / stored.
/// It returns true if the transformation is done.
(MBB.computeRegisterLiveness(TRI, ARM::CPSR, std::prev(MBBI), 15) ==
MachineBasicBlock::LQR_Dead);
+ bool Writeback = isThumb1; // Thumb1 LDM/STM have base reg writeback.
+
+ // Exception: If the base register is in the input reglist, Thumb1 LDM is
+ // non-writeback.
+ // It's also not possible to merge an STR of the base register in Thumb1.
+ if (isThumb1)
+ for (unsigned I = 0; I < NumRegs; ++I)
+ if (Base == Regs[I].first) {
+ if (Opcode == ARM::tLDRi) {
+ Writeback = false;
+ break;
+ } else if (Opcode == ARM::tSTRi) {
+ return false;
+ }
+ }
+
ARM_AM::AMSubMode Mode = ARM_AM::ia;
// VFP and Thumb2 do not support IB or DA modes. Thumb1 only supports IA.
bool isNotVFP = isi32Load(Opcode) || isi32Store(Opcode);
Opcode = getLoadStoreMultipleOpcode(Opcode, Mode);
if (!Opcode) return false;
- bool Writeback = isThumb1; // Thumb1 LDM/STM have base reg writeback.
-
- // Exception: If the base register is in the input reglist, Thumb1 LDM is
- // non-writeback. Check for this.
- if (Opcode == ARM::tLDMIA && isThumb1)
- for (unsigned I = 0; I < NumRegs; ++I)
- if (Base == Regs[I].first) {
- Writeback = false;
- break;
- }
-
- // If the merged instruction has writeback and the base register is not killed
- // it's not safe to do the merge on Thumb1. This is because resetting the base
- // register writeback by inserting a SUBS sets the condition flags.
- // FIXME: Try something clever here to see if resetting the base register can
- // be avoided, e.g. by updating a later ADD/SUB of the base register with the
- // writeback.
- if (isThumb1 && Writeback && !BaseKill) return false;
+ // Check if a Thumb1 LDM/STM merge is safe. This is the case if:
+ // - There is no writeback (LDM of base register),
+ // - the base register is killed by the merged instruction,
+ // - or it's safe to overwrite the condition flags, i.e. to insert a SUBS
+ // to reset the base register.
+ // Otherwise, don't merge.
+ // It's safe to return here since the code to materialize a new base register
+ // above is also conditional on SafeToClobberCPSR.
+ if (isThumb1 && !SafeToClobberCPSR && Writeback && !BaseKill)
+ return false;
MachineInstrBuilder MIB;
// Thumb1: we might need to set base writeback when building the MI.
MIB.addReg(Base, getDefRegState(true))
.addReg(Base, getKillRegState(BaseKill));
+
+ // The base isn't dead after a merged instruction with writeback.
+ // Insert a sub instruction after the newly formed instruction to reset.
+ if (!BaseKill)
+ UpdateBaseRegUses(MBB, MBBI, dl, Base, NumRegs, Pred, PredReg);
+
} else {
// No writeback, simply build the MachineInstr.
MIB = BuildMI(MBB, MBBI, dl, TII->get(Opcode));
memOps[i].MBBI = Merges.back();
memOps[i].Position = insertPos;
}
+
+ // Update memOps offsets, since they may have been modified by MergeOps.
+ for (auto &MemOp : memOps) {
+ MemOp.Offset = getMemoryOpOffset(MemOp.MBBI);
+ }
}
/// MergeLDR_STR - Merge a number of load / store instructions into one or more
Base, BaseKill, Opcode, Pred, PredReg, Scratch, dl, Merges);
}
-static bool definesCPSR(MachineInstr *MI) {
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg())
- continue;
- if (MO.isDef() && MO.getReg() == ARM::CPSR && !MO.isDead())
- // If the instruction has live CPSR def, then it's not safe to fold it
- // into load / store.
- return true;
- }
-
- return false;
-}
-
static bool isMatchingDecrement(MachineInstr *MI, unsigned Base,
unsigned Bytes, unsigned Limit,
ARMCC::CondCodes Pred, unsigned PredReg) {
RS->forward(std::prev(Loc));
}
-static int getMemoryOpOffset(const MachineInstr *MI) {
- int Opcode = MI->getOpcode();
- bool isAM3 = Opcode == ARM::LDRD || Opcode == ARM::STRD;
- unsigned NumOperands = MI->getDesc().getNumOperands();
- unsigned OffField = MI->getOperand(NumOperands-3).getImm();
-
- if (Opcode == ARM::t2LDRi12 || Opcode == ARM::t2LDRi8 ||
- Opcode == ARM::t2STRi12 || Opcode == ARM::t2STRi8 ||
- Opcode == ARM::t2LDRDi8 || Opcode == ARM::t2STRDi8 ||
- Opcode == ARM::LDRi12 || Opcode == ARM::STRi12)
- return OffField;
-
- // Thumb1 immediate offsets are scaled by 4
- if (Opcode == ARM::tLDRi || Opcode == ARM::tSTRi)
- return OffField * 4;
-
- int Offset = isAM3 ? ARM_AM::getAM3Offset(OffField)
- : ARM_AM::getAM5Offset(OffField) * 4;
- if (isAM3) {
- if (ARM_AM::getAM3Op(OffField) == ARM_AM::sub)
- Offset = -Offset;
- } else {
- if (ARM_AM::getAM5Op(OffField) == ARM_AM::sub)
- Offset = -Offset;
- }
- return Offset;
-}
-
static void InsertLDR_STR(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
int Offset, bool isDef,
projects / oota-llvm.git / commitdiff