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+//===-- PPCCTRLoops.cpp - Identify and generate CTR loops -----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass identifies loops where we can generate the PPC branch instructions
+// that decrement and test the count register (CTR) (bdnz and friends).
+// This pass is based on the HexagonHardwareLoops pass.
+//
+// The pattern that defines the induction variable can changed depending on
+// prior optimizations. For example, the IndVarSimplify phase run by 'opt'
+// normalizes induction variables, and the Loop Strength Reduction pass
+// run by 'llc' may also make changes to the induction variable.
+// The pattern detected by this phase is due to running Strength Reduction.
+//
+// Criteria for CTR loops:
+// - Countable loops (w/ ind. var for a trip count)
+// - Assumes loops are normalized by IndVarSimplify
+// - Try inner-most loops first
+// - No nested CTR loops.
+// - No function calls in loops.
+//
+// Note: As with unconverted loops, PPCBranchSelector must be run after this
+// pass in order to convert long-displacement jumps into jump pairs.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "ctrloops"
+#include "PPC.h"
+#include "PPCTargetMachine.h"
+#include "llvm/Constants.h"
+#include "llvm/PassSupport.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include <algorithm>
+
+using namespace llvm;
+
+STATISTIC(NumCTRLoops, "Number of loops converted to CTR loops");
+
+namespace {
+ class CountValue;
+ struct PPCCTRLoops : public MachineFunctionPass {
+ MachineLoopInfo *MLI;
+ MachineRegisterInfo *MRI;
+ const TargetInstrInfo *TII;
+
+ public:
+ static char ID; // Pass identification, replacement for typeid
+
+ PPCCTRLoops() : MachineFunctionPass(ID) {}
+
+ virtual bool runOnMachineFunction(MachineFunction &MF);
+
+ const char *getPassName() const { return "PPC CTR Loops"; }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ AU.addRequired<MachineDominatorTree>();
+ AU.addPreserved<MachineDominatorTree>();
+ AU.addRequired<MachineLoopInfo>();
+ AU.addPreserved<MachineLoopInfo>();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+
+ private:
+ /// getCanonicalInductionVariable - Check to see if the loop has a canonical
+ /// induction variable.
+ /// Should be defined in MachineLoop. Based upon version in class Loop.
+ MachineInstr *getCanonicalInductionVariable(MachineLoop *L,
+ MachineInstr *&IOp) const;
+
+ /// getTripCount - Return a loop-invariant LLVM register indicating the
+ /// number of times the loop will be executed. If the trip-count cannot
+ /// be determined, this return null.
+ CountValue *getTripCount(MachineLoop *L, bool &WordCmp,
+ SmallVector<MachineInstr *, 2> &OldInsts) const;
+
+ /// isInductionOperation - Return true if the instruction matches the
+ /// pattern for an opertion that defines an induction variable.
+ bool isInductionOperation(const MachineInstr *MI, unsigned IVReg) const;
+
+ /// isInvalidOperation - Return true if the instruction is not valid within
+ /// a CTR loop.
+ bool isInvalidLoopOperation(const MachineInstr *MI) const;
+
+ /// containsInavlidInstruction - Return true if the loop contains an
+ /// instruction that inhibits using the CTR loop.
+ bool containsInvalidInstruction(MachineLoop *L) const;
+
+ /// converToCTRLoop - Given a loop, check if we can convert it to a
+ /// CTR loop. If so, then perform the conversion and return true.
+ bool convertToCTRLoop(MachineLoop *L);
+
+ /// isDead - Return true if the instruction is now dead.
+ bool isDead(const MachineInstr *MI,
+ SmallVector<MachineInstr *, 1> &DeadPhis) const;
+
+ /// removeIfDead - Remove the instruction if it is now dead.
+ void removeIfDead(MachineInstr *MI);
+ };
+
+ char PPCCTRLoops::ID = 0;
+
+
+ // CountValue class - Abstraction for a trip count of a loop. A
+ // smaller vesrsion of the MachineOperand class without the concerns
+ // of changing the operand representation.
+ class CountValue {
+ public:
+ enum CountValueType {
+ CV_Register,
+ CV_Immediate
+ };
+ private:
+ CountValueType Kind;
+ union Values {
+ unsigned RegNum;
+ int64_t ImmVal;
+ Values(unsigned r) : RegNum(r) {}
+ Values(int64_t i) : ImmVal(i) {}
+ } Contents;
+ bool isNegative;
+
+ public:
+ CountValue(unsigned r, bool neg) : Kind(CV_Register), Contents(r),
+ isNegative(neg) {}
+ explicit CountValue(int64_t i) : Kind(CV_Immediate), Contents(i),
+ isNegative(i < 0) {}
+ CountValueType getType() const { return Kind; }
+ bool isReg() const { return Kind == CV_Register; }
+ bool isImm() const { return Kind == CV_Immediate; }
+ bool isNeg() const { return isNegative; }
+
+ unsigned getReg() const {
+ assert(isReg() && "Wrong CountValue accessor");
+ return Contents.RegNum;
+ }
+ void setReg(unsigned Val) {
+ Contents.RegNum = Val;
+ }
+ int64_t getImm() const {
+ assert(isImm() && "Wrong CountValue accessor");
+ if (isNegative) {
+ return -Contents.ImmVal;
+ }
+ return Contents.ImmVal;
+ }
+ void setImm(int64_t Val) {
+ Contents.ImmVal = Val;
+ }
+
+ void print(raw_ostream &OS, const TargetMachine *TM = 0) const {
+ if (isReg()) { OS << PrintReg(getReg()); }
+ if (isImm()) { OS << getImm(); }
+ }
+ };
+} // end anonymous namespace
+
+
+/// isCompareEquals - Returns true if the instruction is a compare equals
+/// instruction with an immediate operand.
+static bool isCompareEqualsImm(const MachineInstr *MI, bool &WordCmp) {
+ if (MI->getOpcode() == PPC::CMPWI || MI->getOpcode() == PPC::CMPLWI) {
+ WordCmp = true;
+ return true;
+ } else if (MI->getOpcode() == PPC::CMPDI || MI->getOpcode() == PPC::CMPLDI) {
+ WordCmp = false;
+ return true;
+ }
+
+ return false;
+}
+
+
+/// createPPCCTRLoops - Factory for creating
+/// the CTR loop phase.
+FunctionPass *llvm::createPPCCTRLoops() {
+ return new PPCCTRLoops();
+}
+
+
+bool PPCCTRLoops::runOnMachineFunction(MachineFunction &MF) {
+ DEBUG(dbgs() << "********* PPC CTR Loops *********\n");
+
+ bool Changed = false;
+
+ // get the loop information
+ MLI = &getAnalysis<MachineLoopInfo>();
+ // get the register information
+ MRI = &MF.getRegInfo();
+ // the target specific instructio info.
+ TII = MF.getTarget().getInstrInfo();
+
+ for (MachineLoopInfo::iterator I = MLI->begin(), E = MLI->end();
+ I != E; ++I) {
+ MachineLoop *L = *I;
+ if (!L->getParentLoop()) {
+ Changed |= convertToCTRLoop(L);
+ }
+ }
+
+ return Changed;
+}
+
+/// getCanonicalInductionVariable - Check to see if the loop has a canonical
+/// induction variable. We check for a simple recurrence pattern - an
+/// integer recurrence that decrements by one each time through the loop and
+/// ends at zero. If so, return the phi node that corresponds to it.
+///
+/// Based upon the similar code in LoopInfo except this code is specific to
+/// the machine.
+/// This method assumes that the IndVarSimplify pass has been run by 'opt'.
+///
+MachineInstr
+*PPCCTRLoops::getCanonicalInductionVariable(MachineLoop *L,
+ MachineInstr *&IOp) const {
+ MachineBasicBlock *TopMBB = L->getTopBlock();
+ MachineBasicBlock::pred_iterator PI = TopMBB->pred_begin();
+ assert(PI != TopMBB->pred_end() &&
+ "Loop must have more than one incoming edge!");
+ MachineBasicBlock *Backedge = *PI++;
+ if (PI == TopMBB->pred_end()) return 0; // dead loop
+ MachineBasicBlock *Incoming = *PI++;
+ if (PI != TopMBB->pred_end()) return 0; // multiple backedges?
+
+ // make sure there is one incoming and one backedge and determine which
+ // is which.
+ if (L->contains(Incoming)) {
+ if (L->contains(Backedge))
+ return 0;
+ std::swap(Incoming, Backedge);
+ } else if (!L->contains(Backedge))
+ return 0;
+
+ // Loop over all of the PHI nodes, looking for a canonical induction variable:
+ // - The PHI node is "reg1 = PHI reg2, BB1, reg3, BB2".
+ // - The recurrence comes from the backedge.
+ // - the definition is an induction operatio.n
+ for (MachineBasicBlock::iterator I = TopMBB->begin(), E = TopMBB->end();
+ I != E && I->isPHI(); ++I) {
+ MachineInstr *MPhi = &*I;
+ unsigned DefReg = MPhi->getOperand(0).getReg();
+ for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2) {
+ // Check each operand for the value from the backedge.
+ MachineBasicBlock *MBB = MPhi->getOperand(i+1).getMBB();
+ if (L->contains(MBB)) { // operands comes from the backedge
+ // Check if the definition is an induction operation.
+ MachineInstr *DI = MRI->getVRegDef(MPhi->getOperand(i).getReg());
+ if (isInductionOperation(DI, DefReg)) {
+ IOp = DI;
+ return MPhi;
+ }
+ }
+ }
+ }
+ return 0;
+}
+
+/// getTripCount - Return a loop-invariant LLVM value indicating the
+/// number of times the loop will be executed. The trip count can
+/// be either a register or a constant value. If the trip-count
+/// cannot be determined, this returns null.
+///
+/// We find the trip count from the phi instruction that defines the
+/// induction variable. We follow the links to the CMP instruction
+/// to get the trip count.
+///
+/// Based upon getTripCount in LoopInfo.
+///
+CountValue *PPCCTRLoops::getTripCount(MachineLoop *L, bool &WordCmp,
+ SmallVector<MachineInstr *, 2> &OldInsts) const {
+ // Check that the loop has a induction variable.
+ MachineInstr *IOp;
+ MachineInstr *IV_Inst = getCanonicalInductionVariable(L, IOp);
+ if (IV_Inst == 0) return 0;
+
+ // Canonical loops will end with a 'cmpwi/cmpdi cr, IV, Imm',
+ // if Imm is 0, get the count from the PHI opnd
+ // if Imm is -M, than M is the count
+ // Otherwise, Imm is the count
+ MachineOperand *IV_Opnd;
+ const MachineOperand *InitialValue;
+ if (!L->contains(IV_Inst->getOperand(2).getMBB())) {
+ InitialValue = &IV_Inst->getOperand(1);
+ IV_Opnd = &IV_Inst->getOperand(3);
+ } else {
+ InitialValue = &IV_Inst->getOperand(3);
+ IV_Opnd = &IV_Inst->getOperand(1);
+ }
+
+ // Look for the cmp instruction to determine if we
+ // can get a useful trip count. The trip count can
+ // be either a register or an immediate. The location
+ // of the value depends upon the type (reg or imm).
+ while ((IV_Opnd = IV_Opnd->getNextOperandForReg())) {
+ MachineInstr *MI = IV_Opnd->getParent();
+ if (L->contains(MI) && isCompareEqualsImm(MI, WordCmp)) {
+ OldInsts.push_back(MI);
+ OldInsts.push_back(IOp);
+
+ const MachineOperand &MO = MI->getOperand(2);
+ assert(MO.isImm() && "IV Cmp Operand should be an immediate");
+ int64_t ImmVal = MO.getImm();
+
+ const MachineInstr *IV_DefInstr = MRI->getVRegDef(IV_Opnd->getReg());
+ assert(L->contains(IV_DefInstr->getParent()) &&
+ "IV definition should occurs in loop");
+ int64_t iv_value = IV_DefInstr->getOperand(2).getImm();
+
+ if (ImmVal == 0) {
+ // Make sure the induction variable changes by one on each iteration.
+ if (iv_value != 1 && iv_value != -1) {
+ return 0;
+ }
+ return new CountValue(InitialValue->getReg(), iv_value > 0);
+ } else {
+ assert(InitialValue->isReg() && "Expecting register for init value");
+ const MachineInstr *DefInstr = MRI->getVRegDef(InitialValue->getReg());
+
+ // Here we need to look for an immediate load (an li or lis/ori pair).
+ if (DefInstr && (DefInstr->getOpcode() == PPC::ORI8 ||
+ DefInstr->getOpcode() == PPC::ORI)) {
+ int64_t start = DefInstr->getOperand(2).getImm();
+ const MachineInstr *DefInstr2 =
+ MRI->getVRegDef(DefInstr->getOperand(0).getReg());
+ if (DefInstr2 && (DefInstr2->getOpcode() == PPC::LIS8 ||
+ DefInstr2->getOpcode() == PPC::LIS)) {
+ start |= DefInstr2->getOperand(1).getImm() << 16;
+
+ int64_t count = ImmVal - start;
+ if ((count % iv_value) != 0) {
+ return 0;
+ }
+ return new CountValue(count/iv_value);
+ }
+ } else if (DefInstr && (DefInstr->getOpcode() == PPC::LI8 ||
+ DefInstr->getOpcode() == PPC::LI)) {
+ int64_t count = ImmVal - DefInstr->getOperand(1).getImm();
+ if ((count % iv_value) != 0) {
+ return 0;
+ }
+ return new CountValue(count/iv_value);
+ }
+ }
+ }
+ }
+ return 0;
+}
+
+/// isInductionOperation - return true if the operation is matches the
+/// pattern that defines an induction variable:
+/// addi iv, c
+///
+bool
+PPCCTRLoops::isInductionOperation(const MachineInstr *MI,
+ unsigned IVReg) const {
+ return ((MI->getOpcode() == PPC::ADDI || MI->getOpcode() == PPC::ADDI8) &&
+ MI->getOperand(1).getReg() == IVReg);
+}
+
+/// isInvalidOperation - Return true if the operation is invalid within
+/// CTR loop.
+bool
+PPCCTRLoops::isInvalidLoopOperation(const MachineInstr *MI) const {
+
+ // call is not allowed because the callee may use a CTR loop
+ if (MI->getDesc().isCall()) {
+ return true;
+ }
+ // check if the instruction defines a CTR loop register
+ // (this will also catch nested CTR loops)
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (MO.isReg() && MO.isDef() &&
+ (MO.getReg() == PPC::CTR || MO.getReg() == PPC::CTR8)) {
+ return true;
+ }
+ }
+ return false;
+}
+
+/// containsInvalidInstruction - Return true if the loop contains
+/// an instruction that inhibits the use of the CTR loop function.
+///
+bool PPCCTRLoops::containsInvalidInstruction(MachineLoop *L) const {
+ const std::vector<MachineBasicBlock*> Blocks = L->getBlocks();
+ for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
+ MachineBasicBlock *MBB = Blocks[i];
+ for (MachineBasicBlock::iterator
+ MII = MBB->begin(), E = MBB->end(); MII != E; ++MII) {
+ const MachineInstr *MI = &*MII;
+ if (isInvalidLoopOperation(MI)) {
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
+/// isDead returns true if the instruction is dead
+/// (this was essentially copied from DeadMachineInstructionElim::isDead, but
+/// with special cases for inline asm, physical registers and instructions with
+/// side effects removed)
+bool PPCCTRLoops::isDead(const MachineInstr *MI,
+ SmallVector<MachineInstr *, 1> &DeadPhis) const {
+ // Examine each operand.
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (MO.isReg() && MO.isDef()) {
+ unsigned Reg = MO.getReg();
+ if (!MRI->use_nodbg_empty(Reg)) {
+ // This instruction has users, but if the only user is the phi node for the
+ // parent block, and the only use of that phi node is this instruction, then
+ // this instruction is dead: both it (and the phi node) can be removed.
+ MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg);
+ if (llvm::next(I) == MRI->use_end() &&
+ I.getOperand().getParent()->isPHI()) {
+ MachineInstr *OnePhi = I.getOperand().getParent();
+
+ for (unsigned j = 0, f = OnePhi->getNumOperands(); j != f; ++j) {
+ const MachineOperand &OPO = OnePhi->getOperand(j);
+ if (OPO.isReg() && OPO.isDef()) {
+ unsigned OPReg = OPO.getReg();
+
+ MachineRegisterInfo::use_iterator nextJ;
+ for (MachineRegisterInfo::use_iterator J = MRI->use_begin(OPReg),
+ E = MRI->use_end(); J!=E; J=nextJ) {
+ nextJ = llvm::next(J);
+ MachineOperand& Use = J.getOperand();
+ MachineInstr *UseMI = Use.getParent();
+
+ if (MI != UseMI) {
+ // The phi node has a user that is not MI, bail...
+ return false;
+ }
+ }
+ }
+ }
+
+ DeadPhis.push_back(OnePhi);
+ } else {
+ // This def has a non-debug use. Don't delete the instruction!
+ return false;
+ }
+ }
+ }
+ }
+
+ // If there are no defs with uses, the instruction is dead.
+ return true;
+}
+
+void PPCCTRLoops::removeIfDead(MachineInstr *MI) {
+ // This procedure was essentially copied from DeadMachineInstructionElim
+
+ SmallVector<MachineInstr *, 1> DeadPhis;
+ if (isDead(MI, DeadPhis)) {
+ DEBUG(dbgs() << "CTR looping will remove: " << *MI);
+
+ // It is possible that some DBG_VALUE instructions refer to this
+ // instruction. Examine each def operand for such references;
+ // if found, mark the DBG_VALUE as undef (but don't delete it).
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isDef())
+ continue;
+ unsigned Reg = MO.getReg();
+ MachineRegisterInfo::use_iterator nextI;
+ for (MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg),
+ E = MRI->use_end(); I!=E; I=nextI) {
+ nextI = llvm::next(I); // I is invalidated by the setReg
+ MachineOperand& Use = I.getOperand();
+ MachineInstr *UseMI = Use.getParent();
+ if (UseMI==MI)
+ continue;
+ if (Use.isDebug()) // this might also be a instr -> phi -> instr case
+ // which can also be removed.
+ UseMI->getOperand(0).setReg(0U);
+ }
+ }
+
+ MI->eraseFromParent();
+ for (unsigned i = 0; i < DeadPhis.size(); ++i) {
+ DeadPhis[i]->eraseFromParent();
+ }
+ }
+}
+
+/// converToCTRLoop - check if the loop is a candidate for
+/// converting to a CTR loop. If so, then perform the
+/// transformation.
+///
+/// This function works on innermost loops first. A loop can
+/// be converted if it is a counting loop; either a register
+/// value or an immediate.
+///
+/// The code makes several assumptions about the representation
+/// of the loop in llvm.
+bool PPCCTRLoops::convertToCTRLoop(MachineLoop *L) {
+ bool Changed = false;
+ // Process nested loops first.
+ for (MachineLoop::iterator I = L->begin(), E = L->end(); I != E; ++I) {
+ Changed |= convertToCTRLoop(*I);
+ }
+ // If a nested loop has been converted, then we can't convert this loop.
+ if (Changed) {
+ return Changed;
+ }
+
+ bool WordCmp;
+ SmallVector<MachineInstr *, 2> OldInsts;
+ // Are we able to determine the trip count for the loop?
+ CountValue *TripCount = getTripCount(L, WordCmp, OldInsts);
+ if (TripCount == 0) {
+ DEBUG(dbgs() << "failed to get trip count!\n");
+ return false;
+ }
+ // Does the loop contain any invalid instructions?
+ if (containsInvalidInstruction(L)) {
+ return false;
+ }
+ MachineBasicBlock *Preheader = L->getLoopPreheader();
+ // No preheader means there's not place for the loop instr.
+ if (Preheader == 0) {
+ return false;
+ }
+ MachineBasicBlock::iterator InsertPos = Preheader->getFirstTerminator();
+
+ DebugLoc dl;
+ if (InsertPos != Preheader->end())
+ dl = InsertPos->getDebugLoc();
+
+ MachineBasicBlock *LastMBB = L->getExitingBlock();
+ // Don't generate CTR loop if the loop has more than one exit.
+ if (LastMBB == 0) {
+ return false;
+ }
+ MachineBasicBlock::iterator LastI = LastMBB->getFirstTerminator();
+
+ // Determine the loop start.
+ MachineBasicBlock *LoopStart = L->getTopBlock();
+ if (L->getLoopLatch() != LastMBB) {
+ // When the exit and latch are not the same, use the latch block as the
+ // start.
+ // The loop start address is used only after the 1st iteration, and the loop
+ // latch may contains instrs. that need to be executed after the 1st iter.
+ LoopStart = L->getLoopLatch();
+ // Make sure the latch is a successor of the exit, otherwise it won't work.
+ if (!LastMBB->isSuccessor(LoopStart)) {
+ return false;
+ }
+ }
+
+ // Convert the loop to a CTR loop
+ DEBUG(dbgs() << "Change to CTR loop at "; L->dump());
+
+ MachineFunction *MF = LastMBB->getParent();
+ const PPCSubtarget &Subtarget = MF->getTarget().getSubtarget<PPCSubtarget>();
+ bool isPPC64 = Subtarget.isPPC64();
+
+ unsigned CountReg;
+ if (TripCount->isReg()) {
+ // Create a copy of the loop count register.
+ const TargetRegisterClass *RC =
+ MF->getRegInfo().getRegClass(TripCount->getReg());
+ CountReg = MF->getRegInfo().createVirtualRegister(RC);
+ BuildMI(*Preheader, InsertPos, dl,
+ TII->get(TargetOpcode::COPY), CountReg).addReg(TripCount->getReg());
+ if (TripCount->isNeg()) {
+ unsigned CountReg1 = CountReg;
+ CountReg = MF->getRegInfo().createVirtualRegister(RC);
+ BuildMI(*Preheader, InsertPos, dl,
+ TII->get(isPPC64 ? PPC::NEG8 : PPC::NEG),
+ CountReg).addReg(CountReg1);
+ }
+
+ // On a 64-bit system, if the original comparison was only 32-bit, then
+ // mask out the higher-order part of the count.
+ if (isPPC64 && WordCmp) {
+ unsigned CountReg1 = CountReg;
+ CountReg = MF->getRegInfo().createVirtualRegister(RC);
+ BuildMI(*Preheader, InsertPos, dl,
+ TII->get(PPC::RLDICL), CountReg).addReg(CountReg1
+ ).addImm(0).addImm(32);
+ }
+ } else {
+ assert(TripCount->isImm() && "Expecting immedate vaule for trip count");
+ // Put the trip count in a register for transfer into the count register.
+ const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
+ const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
+ const TargetRegisterClass *RC = isPPC64 ? G8RC : GPRC;
+
+ int64_t CountImm = TripCount->getImm();
+ if (TripCount->isNeg())
+ CountImm = -CountImm;
+
+ CountReg = MF->getRegInfo().createVirtualRegister(RC);
+ if (CountImm > 0xFFFF) {
+ BuildMI(*Preheader, InsertPos, dl,
+ TII->get(isPPC64 ? PPC::LIS8 : PPC::LIS),
+ CountReg).addImm(CountImm >> 16);
+ unsigned CountReg1 = CountReg;
+ CountReg = MF->getRegInfo().createVirtualRegister(RC);
+ BuildMI(*Preheader, InsertPos, dl,
+ TII->get(isPPC64 ? PPC::ORI8 : PPC::ORI),
+ CountReg).addReg(CountReg1).addImm(CountImm & 0xFFFF);
+ } else {
+ BuildMI(*Preheader, InsertPos, dl,
+ TII->get(isPPC64 ? PPC::LI8 : PPC::LI),
+ CountReg).addImm(CountImm);
+ }
+ }
+
+ // Add the mtctr instruction to the beginning of the loop.
+ BuildMI(*Preheader, InsertPos, dl,
+ TII->get(isPPC64 ? PPC::MTCTR8 : PPC::MTCTR)).addReg(CountReg,
+ TripCount->isImm() ? RegState::Kill : 0);
+
+ // Make sure the loop start always has a reference in the CFG. We need to
+ // create a BlockAddress operand to get this mechanism to work both the
+ // MachineBasicBlock and BasicBlock objects need the flag set.
+ LoopStart->setHasAddressTaken();
+ // This line is needed to set the hasAddressTaken flag on the BasicBlock
+ // object
+ BlockAddress::get(const_cast<BasicBlock *>(LoopStart->getBasicBlock()));
+
+ // Replace the loop branch with a bdnz instruction.
+ dl = LastI->getDebugLoc();
+ const std::vector<MachineBasicBlock*> Blocks = L->getBlocks();
+ for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
+ MachineBasicBlock *MBB = Blocks[i];
+ if (MBB != Preheader)
+ MBB->addLiveIn(isPPC64 ? PPC::CTR8 : PPC::CTR);
+ }
+
+ // The loop ends with either:
+ // - a conditional branch followed by an unconditional branch, or
+ // - a conditional branch to the loop start.
+ assert(LastI->getOpcode() == PPC::BCC &&
+ "loop end must start with a BCC instruction");
+ // Either the BCC branches to the beginning of the loop, or it
+ // branches out of the loop and there is an unconditional branch
+ // to the start of the loop.
+ MachineBasicBlock *BranchTarget = LastI->getOperand(2).getMBB();
+ BuildMI(*LastMBB, LastI, dl,
+ TII->get((BranchTarget == LoopStart) ?
+ (isPPC64 ? PPC::BDNZ8 : PPC::BDNZ) :
+ (isPPC64 ? PPC::BDZ8 : PPC::BDZ))).addMBB(BranchTarget);
+
+ // Conditional branch; just delete it.
+ LastMBB->erase(LastI);
+
+ delete TripCount;
+
+ // The induction operation (add) and the comparison (cmpwi) may now be
+ // unneeded. If these are unneeded, then remove them.
+ for (unsigned i = 0; i < OldInsts.size(); ++i)
+ removeIfDead(OldInsts[i]);
+
+ ++NumCTRLoops;
+ return true;
+}
+
generated by cgit v1.1 at 2025-02-02 18:25:24 +0000