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llvm-project/llvm/lib/Target/Hexagon/HexagonExpandCondsets.cpp

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//===--- HexagonExpandCondsets.cpp ----------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Replace mux instructions with the corresponding legal instructions.
// It is meant to work post-SSA, but still on virtual registers. It was
// originally placed between register coalescing and machine instruction
// scheduler.
// In this place in the optimization sequence, live interval analysis had
// been performed, and the live intervals should be preserved. A large part
// of the code deals with preserving the liveness information.
//
// Liveness tracking aside, the main functionality of this pass is divided
// into two steps. The first step is to replace an instruction
// vreg0 = C2_mux vreg0, vreg1, vreg2
// with a pair of conditional transfers
// vreg0 = A2_tfrt vreg0, vreg1
// vreg0 = A2_tfrf vreg0, vreg2
// It is the intention that the execution of this pass could be terminated
// after this step, and the code generated would be functionally correct.
//
// If the uses of the source values vreg1 and vreg2 are kills, and their
// definitions are predicable, then in the second step, the conditional
// transfers will then be rewritten as predicated instructions. E.g.
// vreg0 = A2_or vreg1, vreg2
// vreg3 = A2_tfrt vreg99, vreg0<kill>
// will be rewritten as
// vreg3 = A2_port vreg99, vreg1, vreg2
//
// This replacement has two variants: "up" and "down". Consider this case:
// vreg0 = A2_or vreg1, vreg2
// ... [intervening instructions] ...
// vreg3 = A2_tfrt vreg99, vreg0<kill>
// variant "up":
// vreg3 = A2_port vreg99, vreg1, vreg2
// ... [intervening instructions, vreg0->vreg3] ...
// [deleted]
// variant "down":
// [deleted]
// ... [intervening instructions] ...
// vreg3 = A2_port vreg99, vreg1, vreg2
//
// Both, one or none of these variants may be valid, and checks are made
// to rule out inapplicable variants.
//
// As an additional optimization, before either of the two steps above is
// executed, the pass attempts to coalesce the target register with one of
// the source registers, e.g. given an instruction
// vreg3 = C2_mux vreg0, vreg1, vreg2
// vreg3 will be coalesced with either vreg1 or vreg2. If this succeeds,
// the instruction would then be (for example)
// vreg3 = C2_mux vreg0, vreg3, vreg2
// and, under certain circumstances, this could result in only one predicated
// instruction:
// vreg3 = A2_tfrf vreg0, vreg2
//
#define DEBUG_TYPE "expand-condsets"
#include "HexagonTargetMachine.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
static cl::opt<unsigned> OptTfrLimit("expand-condsets-tfr-limit",
cl::init(~0U), cl::Hidden, cl::desc("Max number of mux expansions"));
static cl::opt<unsigned> OptCoaLimit("expand-condsets-coa-limit",
cl::init(~0U), cl::Hidden, cl::desc("Max number of segment coalescings"));
namespace llvm {
void initializeHexagonExpandCondsetsPass(PassRegistry&);
FunctionPass *createHexagonExpandCondsets();
}
namespace {
class HexagonExpandCondsets : public MachineFunctionPass {
public:
static char ID;
HexagonExpandCondsets() :
MachineFunctionPass(ID), HII(0), TRI(0), MRI(0),
LIS(0), CoaLimitActive(false),
TfrLimitActive(false), CoaCounter(0), TfrCounter(0) {
if (OptCoaLimit.getPosition())
CoaLimitActive = true, CoaLimit = OptCoaLimit;
if (OptTfrLimit.getPosition())
TfrLimitActive = true, TfrLimit = OptTfrLimit;
initializeHexagonExpandCondsetsPass(*PassRegistry::getPassRegistry());
}
virtual const char *getPassName() const {
return "Hexagon Expand Condsets";
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveIntervals>();
AU.addPreserved<LiveIntervals>();
AU.addPreserved<SlotIndexes>();
MachineFunctionPass::getAnalysisUsage(AU);
}
virtual bool runOnMachineFunction(MachineFunction &MF);
private:
const HexagonInstrInfo *HII;
const TargetRegisterInfo *TRI;
MachineRegisterInfo *MRI;
LiveIntervals *LIS;
bool CoaLimitActive, TfrLimitActive;
unsigned CoaLimit, TfrLimit, CoaCounter, TfrCounter;
struct RegisterRef {
RegisterRef(const MachineOperand &Op) : Reg(Op.getReg()),
Sub(Op.getSubReg()) {}
RegisterRef(unsigned R = 0, unsigned S = 0) : Reg(R), Sub(S) {}
bool operator== (RegisterRef RR) const {
return Reg == RR.Reg && Sub == RR.Sub;
}
bool operator!= (RegisterRef RR) const { return !operator==(RR); }
unsigned Reg, Sub;
};
typedef DenseMap<unsigned,unsigned> ReferenceMap;
enum { Sub_Low = 0x1, Sub_High = 0x2, Sub_None = (Sub_Low | Sub_High) };
enum { Exec_Then = 0x10, Exec_Else = 0x20 };
unsigned getMaskForSub(unsigned Sub);
bool isCondset(const MachineInstr *MI);
void addRefToMap(RegisterRef RR, ReferenceMap &Map, unsigned Exec);
bool isRefInMap(RegisterRef, ReferenceMap &Map, unsigned Exec);
LiveInterval::iterator nextSegment(LiveInterval &LI, SlotIndex S);
LiveInterval::iterator prevSegment(LiveInterval &LI, SlotIndex S);
void makeDefined(unsigned Reg, SlotIndex S, bool SetDef);
void makeUndead(unsigned Reg, SlotIndex S);
void shrinkToUses(unsigned Reg, LiveInterval &LI);
void updateKillFlags(unsigned Reg, LiveInterval &LI);
void terminateSegment(LiveInterval::iterator LT, SlotIndex S,
LiveInterval &LI);
void addInstrToLiveness(MachineInstr *MI);
void removeInstrFromLiveness(MachineInstr *MI);
unsigned getCondTfrOpcode(const MachineOperand &SO, bool Cond);
MachineInstr *genTfrFor(MachineOperand &SrcOp, unsigned DstR,
unsigned DstSR, const MachineOperand &PredOp, bool Cond);
bool split(MachineInstr *MI);
bool splitInBlock(MachineBasicBlock &B);
bool isPredicable(MachineInstr *MI);
MachineInstr *getReachingDefForPred(RegisterRef RD,
MachineBasicBlock::iterator UseIt, unsigned PredR, bool Cond);
bool canMoveOver(MachineInstr *MI, ReferenceMap &Defs, ReferenceMap &Uses);
bool canMoveMemTo(MachineInstr *MI, MachineInstr *ToI, bool IsDown);
void predicateAt(RegisterRef RD, MachineInstr *MI,
MachineBasicBlock::iterator Where, unsigned PredR, bool Cond);
void renameInRange(RegisterRef RO, RegisterRef RN, unsigned PredR,
bool Cond, MachineBasicBlock::iterator First,
MachineBasicBlock::iterator Last);
bool predicate(MachineInstr *TfrI, bool Cond);
bool predicateInBlock(MachineBasicBlock &B);
void postprocessUndefImplicitUses(MachineBasicBlock &B);
void removeImplicitUses(MachineInstr *MI);
void removeImplicitUses(MachineBasicBlock &B);
bool isIntReg(RegisterRef RR, unsigned &BW);
bool isIntraBlocks(LiveInterval &LI);
bool coalesceRegisters(RegisterRef R1, RegisterRef R2);
bool coalesceSegments(MachineFunction &MF);
};
}
char HexagonExpandCondsets::ID = 0;
unsigned HexagonExpandCondsets::getMaskForSub(unsigned Sub) {
switch (Sub) {
case Hexagon::subreg_loreg:
return Sub_Low;
case Hexagon::subreg_hireg:
return Sub_High;
case Hexagon::NoSubRegister:
return Sub_None;
}
llvm_unreachable("Invalid subregister");
}
bool HexagonExpandCondsets::isCondset(const MachineInstr *MI) {
unsigned Opc = MI->getOpcode();
switch (Opc) {
case Hexagon::C2_mux:
case Hexagon::C2_muxii:
case Hexagon::C2_muxir:
case Hexagon::C2_muxri:
case Hexagon::MUX64_rr:
return true;
break;
}
return false;
}
void HexagonExpandCondsets::addRefToMap(RegisterRef RR, ReferenceMap &Map,
unsigned Exec) {
unsigned Mask = getMaskForSub(RR.Sub) | Exec;
ReferenceMap::iterator F = Map.find(RR.Reg);
if (F == Map.end())
Map.insert(std::make_pair(RR.Reg, Mask));
else
F->second |= Mask;
}
bool HexagonExpandCondsets::isRefInMap(RegisterRef RR, ReferenceMap &Map,
unsigned Exec) {
ReferenceMap::iterator F = Map.find(RR.Reg);
if (F == Map.end())
return false;
unsigned Mask = getMaskForSub(RR.Sub) | Exec;
if (Mask & F->second)
return true;
return false;
}
LiveInterval::iterator HexagonExpandCondsets::nextSegment(LiveInterval &LI,
SlotIndex S) {
for (LiveInterval::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
if (I->start >= S)
return I;
}
return LI.end();
}
LiveInterval::iterator HexagonExpandCondsets::prevSegment(LiveInterval &LI,
SlotIndex S) {
LiveInterval::iterator P = LI.end();
for (LiveInterval::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
if (I->end > S)
return P;
P = I;
}
return P;
}
/// Find the implicit use of register Reg in slot index S, and make sure
/// that the "defined" flag is set to SetDef. While the mux expansion is
/// going on, predicated instructions will have implicit uses of the
/// registers that are being defined. This is to keep any preceding
/// definitions live. If there is no preceding definition, the implicit
/// use will be marked as "undef", otherwise it will be "defined". This
/// function is used to update the flag.
void HexagonExpandCondsets::makeDefined(unsigned Reg, SlotIndex S,
bool SetDef) {
if (!S.isRegister())
return;
MachineInstr *MI = LIS->getInstructionFromIndex(S);
assert(MI && "Expecting instruction");
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isUse() || Op.getReg() != Reg)
continue;
bool IsDef = !Op.isUndef();
if (Op.isImplicit() && IsDef != SetDef)
Op.setIsUndef(!SetDef);
}
}
void HexagonExpandCondsets::makeUndead(unsigned Reg, SlotIndex S) {
// If S is a block boundary, then there can still be a dead def reaching
// this point. Instead of traversing the CFG, queue start points of all
// live segments that begin with a register, and end at a block boundary.
// This may "resurrect" some truly dead definitions, but doing so is
// harmless.
SmallVector<MachineInstr*,8> Defs;
if (S.isBlock()) {
LiveInterval &LI = LIS->getInterval(Reg);
for (LiveInterval::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
if (!I->start.isRegister() || !I->end.isBlock())
continue;
MachineInstr *MI = LIS->getInstructionFromIndex(I->start);
Defs.push_back(MI);
}
} else if (S.isRegister()) {
MachineInstr *MI = LIS->getInstructionFromIndex(S);
Defs.push_back(MI);
}
for (unsigned i = 0, n = Defs.size(); i < n; ++i) {
MachineInstr *MI = Defs[i];
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isDef() || Op.getReg() != Reg)
continue;
Op.setIsDead(false);
}
}
}
/// Shrink the segments in the live interval for a given register to the last
/// use before each subsequent def. Unlike LiveIntervals::shrinkToUses, this
/// function will not mark any definitions of Reg as dead. The reason for this
/// is that this function is used while a MUX instruction is being expanded,
/// or while a conditional copy is undergoing predication. During these
/// processes, there may be defs present in the instruction sequence that have
/// not yet been removed, or there may be missing uses that have not yet been
/// added. We want to utilize LiveIntervals::shrinkToUses as much as possible,
/// but since it does not extend any intervals that are too short, we need to
/// pre-emptively extend them here in anticipation of further changes.
void HexagonExpandCondsets::shrinkToUses(unsigned Reg, LiveInterval &LI) {
SmallVector<MachineInstr*,4> Deads;
LIS->shrinkToUses(&LI, &Deads);
// Need to undo the deadification made by "shrinkToUses". It's easier to
// do it here, since we have a list of all instructions that were just
// marked as dead.
for (unsigned i = 0, n = Deads.size(); i < n; ++i) {
MachineInstr *MI = Deads[i];
// Clear the "dead" flag.
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isDef() || Op.getReg() != Reg)
continue;
Op.setIsDead(false);
}
// Extend the live segment to the beginning of the next one.
LiveInterval::iterator End = LI.end();
SlotIndex S = LIS->getInstructionIndex(*MI).getRegSlot();
LiveInterval::iterator T = LI.FindSegmentContaining(S);
assert(T != End);
LiveInterval::iterator N = std::next(T);
if (N != End)
T->end = N->start;
else
T->end = LIS->getMBBEndIdx(MI->getParent());
}
updateKillFlags(Reg, LI);
}
/// Given an updated live interval LI for register Reg, update the kill flags
/// in instructions using Reg to reflect the liveness changes.
void HexagonExpandCondsets::updateKillFlags(unsigned Reg, LiveInterval &LI) {
MRI->clearKillFlags(Reg);
for (LiveInterval::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
SlotIndex EX = I->end;
if (!EX.isRegister())
continue;
MachineInstr *MI = LIS->getInstructionFromIndex(EX);
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isUse() || Op.getReg() != Reg)
continue;
// Only set the kill flag on the first encountered use of Reg in this
// instruction.
Op.setIsKill(true);
break;
}
}
}
/// When adding a new instruction to liveness, the newly added definition
/// will start a new live segment. This may happen at a position that falls
/// within an existing live segment. In such case that live segment needs to
/// be truncated to make room for the new segment. Ultimately, the truncation
/// will occur at the last use, but for now the segment can be terminated
/// right at the place where the new segment will start. The segments will be
/// shrunk-to-uses later.
void HexagonExpandCondsets::terminateSegment(LiveInterval::iterator LT,
SlotIndex S, LiveInterval &LI) {
// Terminate the live segment pointed to by LT within a live interval LI.
if (LT == LI.end())
return;
VNInfo *OldVN = LT->valno;
SlotIndex EX = LT->end;
LT->end = S;
// If LT does not end at a block boundary, the termination is done.
if (!EX.isBlock())
return;
// If LT ended at a block boundary, it's possible that its value number
// is picked up at the beginning other blocks. Create a new value number
// and change such blocks to use it instead.
VNInfo *NewVN = 0;
for (LiveInterval::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
if (!I->start.isBlock() || I->valno != OldVN)
continue;
// Generate on-demand a new value number that is defined by the
// block beginning (i.e. -phi).
if (!NewVN)
NewVN = LI.getNextValue(I->start, LIS->getVNInfoAllocator());
I->valno = NewVN;
}
}
/// Add the specified instruction to live intervals. This function is used
/// to update the live intervals while the program code is being changed.
/// Neither the expansion of a MUX, nor the predication are atomic, and this
/// function is used to update the live intervals while these transformations
/// are being done.
void HexagonExpandCondsets::addInstrToLiveness(MachineInstr *MI) {
SlotIndex MX = LIS->isNotInMIMap(*MI) ? LIS->InsertMachineInstrInMaps(*MI)
: LIS->getInstructionIndex(*MI);
DEBUG(dbgs() << "adding liveness info for instr\n " << MX << " " << *MI);
MX = MX.getRegSlot();
bool Predicated = HII->isPredicated(*MI);
MachineBasicBlock *MB = MI->getParent();
// Strip all implicit uses from predicated instructions. They will be
// added again, according to the updated information.
if (Predicated)
removeImplicitUses(MI);
// For each def in MI we need to insert a new live segment starting at MX
// into the interval. If there already exists a live segment in the interval
// that contains MX, we need to terminate it at MX.
SmallVector<RegisterRef,2> Defs;
for (auto &Op : MI->operands())
if (Op.isReg() && Op.isDef())
Defs.push_back(RegisterRef(Op));
for (unsigned i = 0, n = Defs.size(); i < n; ++i) {
unsigned DefR = Defs[i].Reg;
LiveInterval &LID = LIS->getInterval(DefR);
DEBUG(dbgs() << "adding def " << PrintReg(DefR, TRI)
<< " with interval\n " << LID << "\n");
// If MX falls inside of an existing live segment, terminate it.
LiveInterval::iterator LT = LID.FindSegmentContaining(MX);
if (LT != LID.end())
terminateSegment(LT, MX, LID);
DEBUG(dbgs() << "after terminating segment\n " << LID << "\n");
// Create a new segment starting from MX.
LiveInterval::iterator P = prevSegment(LID, MX), N = nextSegment(LID, MX);
SlotIndex EX;
VNInfo *VN = LID.getNextValue(MX, LIS->getVNInfoAllocator());
if (N == LID.end()) {
// There is no live segment after MX. End this segment at the end of
// the block.
EX = LIS->getMBBEndIdx(MB);
} else {
// If the next segment starts at the block boundary, end the new segment
// at the boundary of the preceding block (i.e. the previous index).
// Otherwise, end the segment at the beginning of the next segment. In
// either case it will be "shrunk-to-uses" later.
EX = N->start.isBlock() ? N->start.getPrevIndex() : N->start;
}
if (Predicated) {
// Predicated instruction will have an implicit use of the defined
// register. This is necessary so that this definition will not make
// any previous definitions dead. If there are no previous live
// segments, still add the implicit use, but make it "undef".
// Because of the implicit use, the preceding definition is not
// dead. Mark is as such (if necessary).
MachineOperand ImpUse = MachineOperand::CreateReg(DefR, false, true);
ImpUse.setSubReg(Defs[i].Sub);
bool Undef = false;
if (P == LID.end())
Undef = true;
else {
// If the previous segment extends to the end of the previous block,
// the end index may actually be the beginning of this block. If
// the previous segment ends at a block boundary, move it back by one,
// to get the proper block for it.
SlotIndex PE = P->end.isBlock() ? P->end.getPrevIndex() : P->end;
MachineBasicBlock *PB = LIS->getMBBFromIndex(PE);
if (PB != MB && !LIS->isLiveInToMBB(LID, MB))
Undef = true;
}
if (!Undef) {
makeUndead(DefR, P->valno->def);
// We are adding a live use, so extend the previous segment to
// include it.
P->end = MX;
} else {
ImpUse.setIsUndef(true);
}
if (!MI->readsRegister(DefR))
MI->addOperand(ImpUse);
if (N != LID.end())
makeDefined(DefR, N->start, true);
}
LiveRange::Segment NR = LiveRange::Segment(MX, EX, VN);
LID.addSegment(NR);
DEBUG(dbgs() << "added a new segment " << NR << "\n " << LID << "\n");
shrinkToUses(DefR, LID);
DEBUG(dbgs() << "updated imp-uses: " << *MI);
LID.verify();
}
// For each use in MI:
// - If there is no live segment that contains MX for the used register,
// extend the previous one. Ignore implicit uses.
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isUse() || Op.isImplicit() || Op.isUndef())
continue;
unsigned UseR = Op.getReg();
LiveInterval &LIU = LIS->getInterval(UseR);
// Find the last segment P that starts before MX.
LiveInterval::iterator P = LIU.FindSegmentContaining(MX);
if (P == LIU.end())
P = prevSegment(LIU, MX);
assert(P != LIU.end() && "MI uses undefined register?");
SlotIndex EX = P->end;
// If P contains MX, there is not much to do.
if (EX > MX) {
Op.setIsKill(false);
continue;
}
// Otherwise, extend P to "next(MX)".
P->end = MX.getNextIndex();
Op.setIsKill(true);
// Get the old "kill" instruction, and remove the kill flag.
if (MachineInstr *KI = LIS->getInstructionFromIndex(MX))
KI->clearRegisterKills(UseR, nullptr);
shrinkToUses(UseR, LIU);
LIU.verify();
}
}
/// Update the live interval information to reflect the removal of the given
/// instruction from the program. As with "addInstrToLiveness", this function
/// is called while the program code is being changed.
void HexagonExpandCondsets::removeInstrFromLiveness(MachineInstr *MI) {
SlotIndex MX = LIS->getInstructionIndex(*MI).getRegSlot();
DEBUG(dbgs() << "removing instr\n " << MX << " " << *MI);
// For each def in MI:
// If MI starts a live segment, merge this segment with the previous segment.
//
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isDef())
continue;
unsigned DefR = Op.getReg();
LiveInterval &LID = LIS->getInterval(DefR);
LiveInterval::iterator LT = LID.FindSegmentContaining(MX);
assert(LT != LID.end() && "Expecting live segments");
DEBUG(dbgs() << "removing def at " << MX << " of " << PrintReg(DefR, TRI)
<< " with interval\n " << LID << "\n");
if (LT->start != MX)
continue;
VNInfo *MVN = LT->valno;
if (LT != LID.begin()) {
// If the current live segment is not the first, the task is easy. If
// the previous segment continues into the current block, extend it to
// the end of the current one, and merge the value numbers.
// Otherwise, remove the current segment, and make the end of it "undef".
LiveInterval::iterator P = std::prev(LT);
SlotIndex PE = P->end.isBlock() ? P->end.getPrevIndex() : P->end;
MachineBasicBlock *MB = MI->getParent();
MachineBasicBlock *PB = LIS->getMBBFromIndex(PE);
if (PB != MB && !LIS->isLiveInToMBB(LID, MB)) {
makeDefined(DefR, LT->end, false);
LID.removeSegment(*LT);
} else {
// Make the segments adjacent, so that merge-vn can also merge the
// segments.
P->end = LT->start;
makeUndead(DefR, P->valno->def);
LID.MergeValueNumberInto(MVN, P->valno);
}
} else {
LiveInterval::iterator N = std::next(LT);
LiveInterval::iterator RmB = LT, RmE = N;
while (N != LID.end()) {
// Iterate until the first register-based definition is found
// (i.e. skip all block-boundary entries).
LiveInterval::iterator Next = std::next(N);
if (N->start.isRegister()) {
makeDefined(DefR, N->start, false);
break;
}
if (N->end.isRegister()) {
makeDefined(DefR, N->end, false);
RmE = Next;
break;
}
RmE = Next;
N = Next;
}
// Erase the segments in one shot to avoid invalidating iterators.
LID.segments.erase(RmB, RmE);
}
bool VNUsed = false;
for (LiveInterval::iterator I = LID.begin(), E = LID.end(); I != E; ++I) {
if (I->valno != MVN)
continue;
VNUsed = true;
break;
}
if (!VNUsed)
MVN->markUnused();
DEBUG(dbgs() << "new interval: ");
if (!LID.empty()) {
DEBUG(dbgs() << LID << "\n");
LID.verify();
} else {
DEBUG(dbgs() << "<empty>\n");
LIS->removeInterval(DefR);
}
}
// For uses there is nothing to do. The intervals will be updated via
// shrinkToUses.
SmallVector<unsigned,4> Uses;
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isUse())
continue;
unsigned R = Op.getReg();
if (!TargetRegisterInfo::isVirtualRegister(R))
continue;
Uses.push_back(R);
}
LIS->RemoveMachineInstrFromMaps(*MI);
MI->eraseFromParent();
for (unsigned i = 0, n = Uses.size(); i < n; ++i) {
LiveInterval &LI = LIS->getInterval(Uses[i]);
shrinkToUses(Uses[i], LI);
}
}
/// Get the opcode for a conditional transfer of the value in SO (source
/// operand). The condition (true/false) is given in Cond.
unsigned HexagonExpandCondsets::getCondTfrOpcode(const MachineOperand &SO,
bool Cond) {
using namespace Hexagon;
if (SO.isReg()) {
unsigned PhysR;
RegisterRef RS = SO;
if (TargetRegisterInfo::isVirtualRegister(RS.Reg)) {
const TargetRegisterClass *VC = MRI->getRegClass(RS.Reg);
assert(VC->begin() != VC->end() && "Empty register class");
PhysR = *VC->begin();
} else {
assert(TargetRegisterInfo::isPhysicalRegister(RS.Reg));
PhysR = RS.Reg;
}
unsigned PhysS = (RS.Sub == 0) ? PhysR : TRI->getSubReg(PhysR, RS.Sub);
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(PhysS);
switch (RC->getSize()) {
case 4:
return Cond ? A2_tfrt : A2_tfrf;
case 8:
return Cond ? A2_tfrpt : A2_tfrpf;
}
llvm_unreachable("Invalid register operand");
}
if (SO.isImm() || SO.isFPImm())
return Cond ? C2_cmoveit : C2_cmoveif;
llvm_unreachable("Unexpected source operand");
}
/// Generate a conditional transfer, copying the value SrcOp to the
/// destination register DstR:DstSR, and using the predicate register from
/// PredOp. The Cond argument specifies whether the predicate is to be
/// if(PredOp), or if(!PredOp).
MachineInstr *HexagonExpandCondsets::genTfrFor(MachineOperand &SrcOp,
unsigned DstR, unsigned DstSR, const MachineOperand &PredOp, bool Cond) {
MachineInstr *MI = SrcOp.getParent();
MachineBasicBlock &B = *MI->getParent();
MachineBasicBlock::iterator At = MI;
DebugLoc DL = MI->getDebugLoc();
// Don't avoid identity copies here (i.e. if the source and the destination
// are the same registers). It is actually better to generate them here,
// since this would cause the copy to potentially be predicated in the next
// step. The predication will remove such a copy if it is unable to
/// predicate.
unsigned Opc = getCondTfrOpcode(SrcOp, Cond);
MachineInstr *TfrI = BuildMI(B, At, DL, HII->get(Opc))
.addReg(DstR, RegState::Define, DstSR)
.addOperand(PredOp)
.addOperand(SrcOp);
// We don't want any kills yet.
TfrI->clearKillInfo();
DEBUG(dbgs() << "created an initial copy: " << *TfrI);
return TfrI;
}
/// Replace a MUX instruction MI with a pair A2_tfrt/A2_tfrf. This function
/// performs all necessary changes to complete the replacement.
bool HexagonExpandCondsets::split(MachineInstr *MI) {
if (TfrLimitActive) {
if (TfrCounter >= TfrLimit)
return false;
TfrCounter++;
}
DEBUG(dbgs() << "\nsplitting BB#" << MI->getParent()->getNumber()
<< ": " << *MI);
MachineOperand &MD = MI->getOperand(0); // Definition
MachineOperand &MP = MI->getOperand(1); // Predicate register
assert(MD.isDef());
unsigned DR = MD.getReg(), DSR = MD.getSubReg();
// First, create the two invididual conditional transfers, and add each
// of them to the live intervals information. Do that first and then remove
// the old instruction from live intervals.
if (MachineInstr *TfrT = genTfrFor(MI->getOperand(2), DR, DSR, MP, true))
addInstrToLiveness(TfrT);
if (MachineInstr *TfrF = genTfrFor(MI->getOperand(3), DR, DSR, MP, false))
addInstrToLiveness(TfrF);
removeInstrFromLiveness(MI);
return true;
}
/// Split all MUX instructions in the given block into pairs of contitional
/// transfers.
bool HexagonExpandCondsets::splitInBlock(MachineBasicBlock &B) {
bool Changed = false;
MachineBasicBlock::iterator I, E, NextI;
for (I = B.begin(), E = B.end(); I != E; I = NextI) {
NextI = std::next(I);
if (isCondset(I))
Changed |= split(I);
}
return Changed;
}
bool HexagonExpandCondsets::isPredicable(MachineInstr *MI) {
if (HII->isPredicated(*MI) || !HII->isPredicable(*MI))
return false;
if (MI->hasUnmodeledSideEffects() || MI->mayStore())
return false;
// Reject instructions with multiple defs (e.g. post-increment loads).
bool HasDef = false;
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isDef())
continue;
if (HasDef)
return false;
HasDef = true;
}
for (auto &Mo : MI->memoperands())
if (Mo->isVolatile())
return false;
return true;
}
/// Find the reaching definition for a predicated use of RD. The RD is used
/// under the conditions given by PredR and Cond, and this function will ignore
/// definitions that set RD under the opposite conditions.
MachineInstr *HexagonExpandCondsets::getReachingDefForPred(RegisterRef RD,
MachineBasicBlock::iterator UseIt, unsigned PredR, bool Cond) {
MachineBasicBlock &B = *UseIt->getParent();
MachineBasicBlock::iterator I = UseIt, S = B.begin();
if (I == S)
return 0;
bool PredValid = true;
do {
--I;
MachineInstr *MI = &*I;
// Check if this instruction can be ignored, i.e. if it is predicated
// on the complementary condition.
if (PredValid && HII->isPredicated(*MI)) {
if (MI->readsRegister(PredR) && (Cond != HII->isPredicatedTrue(*MI)))
continue;
}
// Check the defs. If the PredR is defined, invalidate it. If RD is
// defined, return the instruction or 0, depending on the circumstances.
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isDef())
continue;
RegisterRef RR = Op;
if (RR.Reg == PredR) {
PredValid = false;
continue;
}
if (RR.Reg != RD.Reg)
continue;
// If the "Reg" part agrees, there is still the subregister to check.
// If we are looking for vreg1:loreg, we can skip vreg1:hireg, but
// not vreg1 (w/o subregisters).
if (RR.Sub == RD.Sub)
return MI;
if (RR.Sub == 0 || RD.Sub == 0)
return 0;
// We have different subregisters, so we can continue looking.
}
} while (I != S);
return 0;
}
/// Check if the instruction MI can be safely moved over a set of instructions
/// whose side-effects (in terms of register defs and uses) are expressed in
/// the maps Defs and Uses. These maps reflect the conditional defs and uses
/// that depend on the same predicate register to allow moving instructions
/// over instructions predicated on the opposite condition.
bool HexagonExpandCondsets::canMoveOver(MachineInstr *MI, ReferenceMap &Defs,
ReferenceMap &Uses) {
// In order to be able to safely move MI over instructions that define
// "Defs" and use "Uses", no def operand from MI can be defined or used
// and no use operand can be defined.
for (auto &Op : MI->operands()) {
if (!Op.isReg())
continue;
RegisterRef RR = Op;
// For physical register we would need to check register aliases, etc.
// and we don't want to bother with that. It would be of little value
// before the actual register rewriting (from virtual to physical).
if (!TargetRegisterInfo::isVirtualRegister(RR.Reg))
return false;
// No redefs for any operand.
if (isRefInMap(RR, Defs, Exec_Then))
return false;
// For defs, there cannot be uses.
if (Op.isDef() && isRefInMap(RR, Uses, Exec_Then))
return false;
}
return true;
}
/// Check if the instruction accessing memory (TheI) can be moved to the
/// location ToI.
bool HexagonExpandCondsets::canMoveMemTo(MachineInstr *TheI, MachineInstr *ToI,
bool IsDown) {
bool IsLoad = TheI->mayLoad(), IsStore = TheI->mayStore();
if (!IsLoad && !IsStore)
return true;
if (HII->areMemAccessesTriviallyDisjoint(TheI, ToI))
return true;
if (TheI->hasUnmodeledSideEffects())
return false;
MachineBasicBlock::iterator StartI = IsDown ? TheI : ToI;
MachineBasicBlock::iterator EndI = IsDown ? ToI : TheI;
bool Ordered = TheI->hasOrderedMemoryRef();
// Search for aliased memory reference in (StartI, EndI).
for (MachineBasicBlock::iterator I = std::next(StartI); I != EndI; ++I) {
MachineInstr *MI = &*I;
if (MI->hasUnmodeledSideEffects())
return false;
bool L = MI->mayLoad(), S = MI->mayStore();
if (!L && !S)
continue;
if (Ordered && MI->hasOrderedMemoryRef())
return false;
bool Conflict = (L && IsStore) || S;
if (Conflict)
return false;
}
return true;
}
/// Generate a predicated version of MI (where the condition is given via
/// PredR and Cond) at the point indicated by Where.
void HexagonExpandCondsets::predicateAt(RegisterRef RD, MachineInstr *MI,
MachineBasicBlock::iterator Where, unsigned PredR, bool Cond) {
// The problem with updating live intervals is that we can move one def
// past another def. In particular, this can happen when moving an A2_tfrt
// over an A2_tfrf defining the same register. From the point of view of
// live intervals, these two instructions are two separate definitions,
// and each one starts another live segment. LiveIntervals's "handleMove"
// does not allow such moves, so we need to handle it ourselves. To avoid
// invalidating liveness data while we are using it, the move will be
// implemented in 4 steps: (1) add a clone of the instruction MI at the
// target location, (2) update liveness, (3) delete the old instruction,
// and (4) update liveness again.
MachineBasicBlock &B = *MI->getParent();
DebugLoc DL = Where->getDebugLoc(); // "Where" points to an instruction.
unsigned Opc = MI->getOpcode();
unsigned PredOpc = HII->getCondOpcode(Opc, !Cond);
MachineInstrBuilder MB = BuildMI(B, Where, DL, HII->get(PredOpc));
unsigned Ox = 0, NP = MI->getNumOperands();
// Skip all defs from MI first.
while (Ox < NP) {
MachineOperand &MO = MI->getOperand(Ox);
if (!MO.isReg() || !MO.isDef())
break;
Ox++;
}
// Add the new def, then the predicate register, then the rest of the
// operands.
MB.addReg(RD.Reg, RegState::Define, RD.Sub);
MB.addReg(PredR);
while (Ox < NP) {
MachineOperand &MO = MI->getOperand(Ox);
if (!MO.isReg() || !MO.isImplicit())
MB.addOperand(MO);
Ox++;
}
MachineFunction &MF = *B.getParent();
MachineInstr::mmo_iterator I = MI->memoperands_begin();
unsigned NR = std::distance(I, MI->memoperands_end());
MachineInstr::mmo_iterator MemRefs = MF.allocateMemRefsArray(NR);
for (unsigned i = 0; i < NR; ++i)
MemRefs[i] = *I++;
MB.setMemRefs(MemRefs, MemRefs+NR);
MachineInstr *NewI = MB;
NewI->clearKillInfo();
addInstrToLiveness(NewI);
}
/// In the range [First, Last], rename all references to the "old" register RO
/// to the "new" register RN, but only in instructions predicated on the given
/// condition.
void HexagonExpandCondsets::renameInRange(RegisterRef RO, RegisterRef RN,
unsigned PredR, bool Cond, MachineBasicBlock::iterator First,
MachineBasicBlock::iterator Last) {
MachineBasicBlock::iterator End = std::next(Last);
for (MachineBasicBlock::iterator I = First; I != End; ++I) {
MachineInstr *MI = &*I;
// Do not touch instructions that are not predicated, or are predicated
// on the opposite condition.
if (!HII->isPredicated(*MI))
continue;
if (!MI->readsRegister(PredR) || (Cond != HII->isPredicatedTrue(*MI)))
continue;
for (auto &Op : MI->operands()) {
if (!Op.isReg() || RO != RegisterRef(Op))
continue;
Op.setReg(RN.Reg);
Op.setSubReg(RN.Sub);
// In practice, this isn't supposed to see any defs.
assert(!Op.isDef() && "Not expecting a def");
}
}
}
/// For a given conditional copy, predicate the definition of the source of
/// the copy under the given condition (using the same predicate register as
/// the copy).
bool HexagonExpandCondsets::predicate(MachineInstr *TfrI, bool Cond) {
// TfrI - A2_tfr[tf] Instruction (not A2_tfrsi).
unsigned Opc = TfrI->getOpcode();
(void)Opc;
assert(Opc == Hexagon::A2_tfrt || Opc == Hexagon::A2_tfrf);
DEBUG(dbgs() << "\nattempt to predicate if-" << (Cond ? "true" : "false")
<< ": " << *TfrI);
MachineOperand &MD = TfrI->getOperand(0);
MachineOperand &MP = TfrI->getOperand(1);
MachineOperand &MS = TfrI->getOperand(2);
// The source operand should be a <kill>. This is not strictly necessary,
// but it makes things a lot simpler. Otherwise, we would need to rename
// some registers, which would complicate the transformation considerably.
if (!MS.isKill())
return false;
RegisterRef RT(MS);
unsigned PredR = MP.getReg();
MachineInstr *DefI = getReachingDefForPred(RT, TfrI, PredR, Cond);
if (!DefI || !isPredicable(DefI))
return false;
DEBUG(dbgs() << "Source def: " << *DefI);
// Collect the information about registers defined and used between the
// DefI and the TfrI.
// Map: reg -> bitmask of subregs
ReferenceMap Uses, Defs;
MachineBasicBlock::iterator DefIt = DefI, TfrIt = TfrI;
// Check if the predicate register is valid between DefI and TfrI.
// If it is, we can then ignore instructions predicated on the negated
// conditions when collecting def and use information.
bool PredValid = true;
for (MachineBasicBlock::iterator I = std::next(DefIt); I != TfrIt; ++I) {
if (!I->modifiesRegister(PredR, 0))
continue;
PredValid = false;
break;
}
for (MachineBasicBlock::iterator I = std::next(DefIt); I != TfrIt; ++I) {
MachineInstr *MI = &*I;
// If this instruction is predicated on the same register, it could
// potentially be ignored.
// By default assume that the instruction executes on the same condition
// as TfrI (Exec_Then), and also on the opposite one (Exec_Else).
unsigned Exec = Exec_Then | Exec_Else;
if (PredValid && HII->isPredicated(*MI) && MI->readsRegister(PredR))
Exec = (Cond == HII->isPredicatedTrue(*MI)) ? Exec_Then : Exec_Else;
for (auto &Op : MI->operands()) {
if (!Op.isReg())
continue;
// We don't want to deal with physical registers. The reason is that
// they can be aliased with other physical registers. Aliased virtual
// registers must share the same register number, and can only differ
// in the subregisters, which we are keeping track of. Physical
// registers ters no longer have subregisters---their super- and
// subregisters are other physical registers, and we are not checking
// that.
RegisterRef RR = Op;
if (!TargetRegisterInfo::isVirtualRegister(RR.Reg))
return false;
ReferenceMap &Map = Op.isDef() ? Defs : Uses;
addRefToMap(RR, Map, Exec);
}
}
// The situation:
// RT = DefI
// ...
// RD = TfrI ..., RT
// If the register-in-the-middle (RT) is used or redefined between
// DefI and TfrI, we may not be able proceed with this transformation.
// We can ignore a def that will not execute together with TfrI, and a
// use that will. If there is such a use (that does execute together with
// TfrI), we will not be able to move DefI down. If there is a use that
// executed if TfrI's condition is false, then RT must be available
// unconditionally (cannot be predicated).
// Essentially, we need to be able to rename RT to RD in this segment.
if (isRefInMap(RT, Defs, Exec_Then) || isRefInMap(RT, Uses, Exec_Else))
return false;
RegisterRef RD = MD;
// If the predicate register is defined between DefI and TfrI, the only
// potential thing to do would be to move the DefI down to TfrI, and then
// predicate. The reaching def (DefI) must be movable down to the location
// of the TfrI.
// If the target register of the TfrI (RD) is not used or defined between
// DefI and TfrI, consider moving TfrI up to DefI.
bool CanUp = canMoveOver(TfrI, Defs, Uses);
bool CanDown = canMoveOver(DefI, Defs, Uses);
// The TfrI does not access memory, but DefI could. Check if it's safe
// to move DefI down to TfrI.
if (DefI->mayLoad() || DefI->mayStore())
if (!canMoveMemTo(DefI, TfrI, true))
CanDown = false;
DEBUG(dbgs() << "Can move up: " << (CanUp ? "yes" : "no")
<< ", can move down: " << (CanDown ? "yes\n" : "no\n"));
MachineBasicBlock::iterator PastDefIt = std::next(DefIt);
if (CanUp)
predicateAt(RD, DefI, PastDefIt, PredR, Cond);
else if (CanDown)
predicateAt(RD, DefI, TfrIt, PredR, Cond);
else
return false;
if (RT != RD)
renameInRange(RT, RD, PredR, Cond, PastDefIt, TfrIt);
// Delete the user of RT first (it should work either way, but this order
// of deleting is more natural).
removeInstrFromLiveness(TfrI);
removeInstrFromLiveness(DefI);
return true;
}
/// Predicate all cases of conditional copies in the specified block.
bool HexagonExpandCondsets::predicateInBlock(MachineBasicBlock &B) {
bool Changed = false;
MachineBasicBlock::iterator I, E, NextI;
for (I = B.begin(), E = B.end(); I != E; I = NextI) {
NextI = std::next(I);
unsigned Opc = I->getOpcode();
if (Opc == Hexagon::A2_tfrt || Opc == Hexagon::A2_tfrf) {
bool Done = predicate(I, (Opc == Hexagon::A2_tfrt));
if (!Done) {
// If we didn't predicate I, we may need to remove it in case it is
// an "identity" copy, e.g. vreg1 = A2_tfrt vreg2, vreg1.
if (RegisterRef(I->getOperand(0)) == RegisterRef(I->getOperand(2)))
removeInstrFromLiveness(I);
}
Changed |= Done;
}
}
return Changed;
}
void HexagonExpandCondsets::removeImplicitUses(MachineInstr *MI) {
for (unsigned i = MI->getNumOperands(); i > 0; --i) {
MachineOperand &MO = MI->getOperand(i-1);
if (MO.isReg() && MO.isUse() && MO.isImplicit())
MI->RemoveOperand(i-1);
}
}
void HexagonExpandCondsets::removeImplicitUses(MachineBasicBlock &B) {
for (MachineInstr &MI : B)
if (HII->isPredicated(MI))
removeImplicitUses(&MI);
}
void HexagonExpandCondsets::postprocessUndefImplicitUses(MachineBasicBlock &B) {
// Implicit uses that are "undef" are only meaningful (outside of the
// internals of this pass) when the instruction defines a subregister,
// and the implicit-undef use applies to the defined register. In such
// cases, the proper way to record the information in the IR is to mark
// the definition as "undef", which will be interpreted as "read-undef".
typedef SmallSet<unsigned,2> RegisterSet;
for (MachineBasicBlock::iterator I = B.begin(), E = B.end(); I != E; ++I) {
MachineInstr *MI = &*I;
RegisterSet Undefs;
for (unsigned i = MI->getNumOperands(); i > 0; --i) {
MachineOperand &MO = MI->getOperand(i-1);
if (MO.isReg() && MO.isUse() && MO.isImplicit() && MO.isUndef()) {
MI->RemoveOperand(i-1);
Undefs.insert(MO.getReg());
}
}
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isDef() || !Op.getSubReg())
continue;
if (Undefs.count(Op.getReg()))
Op.setIsUndef(true);
}
}
}
bool HexagonExpandCondsets::isIntReg(RegisterRef RR, unsigned &BW) {
if (!TargetRegisterInfo::isVirtualRegister(RR.Reg))
return false;
const TargetRegisterClass *RC = MRI->getRegClass(RR.Reg);
if (RC == &Hexagon::IntRegsRegClass) {
BW = 32;
return true;
}
if (RC == &Hexagon::DoubleRegsRegClass) {
BW = (RR.Sub != 0) ? 32 : 64;
return true;
}
return false;
}
bool HexagonExpandCondsets::isIntraBlocks(LiveInterval &LI) {
for (LiveInterval::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
LiveRange::Segment &LR = *I;
// Range must start at a register...
if (!LR.start.isRegister())
return false;
// ...and end in a register or in a dead slot.
if (!LR.end.isRegister() && !LR.end.isDead())
return false;
}
return true;
}
bool HexagonExpandCondsets::coalesceRegisters(RegisterRef R1, RegisterRef R2) {
if (CoaLimitActive) {
if (CoaCounter >= CoaLimit)
return false;
CoaCounter++;
}
unsigned BW1, BW2;
if (!isIntReg(R1, BW1) || !isIntReg(R2, BW2) || BW1 != BW2)
return false;
if (MRI->isLiveIn(R1.Reg))
return false;
if (MRI->isLiveIn(R2.Reg))
return false;
LiveInterval &L1 = LIS->getInterval(R1.Reg);
LiveInterval &L2 = LIS->getInterval(R2.Reg);
bool Overlap = L1.overlaps(L2);
DEBUG(dbgs() << "compatible registers: ("
<< (Overlap ? "overlap" : "disjoint") << ")\n "
<< PrintReg(R1.Reg, TRI, R1.Sub) << " " << L1 << "\n "
<< PrintReg(R2.Reg, TRI, R2.Sub) << " " << L2 << "\n");
if (R1.Sub || R2.Sub)
return false;
if (Overlap)
return false;
// Coalescing could have a negative impact on scheduling, so try to limit
// to some reasonable extent. Only consider coalescing segments, when one
// of them does not cross basic block boundaries.
if (!isIntraBlocks(L1) && !isIntraBlocks(L2))
return false;
MRI->replaceRegWith(R2.Reg, R1.Reg);
// Move all live segments from L2 to L1.
typedef DenseMap<VNInfo*,VNInfo*> ValueInfoMap;
ValueInfoMap VM;
for (LiveInterval::iterator I = L2.begin(), E = L2.end(); I != E; ++I) {
VNInfo *NewVN, *OldVN = I->valno;
ValueInfoMap::iterator F = VM.find(OldVN);
if (F == VM.end()) {
NewVN = L1.getNextValue(I->valno->def, LIS->getVNInfoAllocator());
VM.insert(std::make_pair(OldVN, NewVN));
} else {
NewVN = F->second;
}
L1.addSegment(LiveRange::Segment(I->start, I->end, NewVN));
}
while (L2.begin() != L2.end())
L2.removeSegment(*L2.begin());
updateKillFlags(R1.Reg, L1);
DEBUG(dbgs() << "coalesced: " << L1 << "\n");
L1.verify();
return true;
}
/// Attempt to coalesce one of the source registers to a MUX intruction with
/// the destination register. This could lead to having only one predicated
/// instruction in the end instead of two.
bool HexagonExpandCondsets::coalesceSegments(MachineFunction &MF) {
SmallVector<MachineInstr*,16> Condsets;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock &B = *I;
for (MachineBasicBlock::iterator J = B.begin(), F = B.end(); J != F; ++J) {
MachineInstr *MI = &*J;
if (!isCondset(MI))
continue;
MachineOperand &S1 = MI->getOperand(2), &S2 = MI->getOperand(3);
if (!S1.isReg() && !S2.isReg())
continue;
Condsets.push_back(MI);
}
}
bool Changed = false;
for (unsigned i = 0, n = Condsets.size(); i < n; ++i) {
MachineInstr *CI = Condsets[i];
RegisterRef RD = CI->getOperand(0);
RegisterRef RP = CI->getOperand(1);
MachineOperand &S1 = CI->getOperand(2), &S2 = CI->getOperand(3);
bool Done = false;
// Consider this case:
// vreg1 = instr1 ...
// vreg2 = instr2 ...
// vreg0 = C2_mux ..., vreg1, vreg2
// If vreg0 was coalesced with vreg1, we could end up with the following
// code:
// vreg0 = instr1 ...
// vreg2 = instr2 ...
// vreg0 = A2_tfrf ..., vreg2
// which will later become:
// vreg0 = instr1 ...
// vreg0 = instr2_cNotPt ...
// i.e. there will be an unconditional definition (instr1) of vreg0
// followed by a conditional one. The output dependency was there before
// and it unavoidable, but if instr1 is predicable, we will no longer be
// able to predicate it here.
// To avoid this scenario, don't coalesce the destination register with
// a source register that is defined by a predicable instruction.
if (S1.isReg()) {
RegisterRef RS = S1;
MachineInstr *RDef = getReachingDefForPred(RS, CI, RP.Reg, true);
if (!RDef || !HII->isPredicable(*RDef))
Done = coalesceRegisters(RD, RegisterRef(S1));
}
if (!Done && S2.isReg()) {
RegisterRef RS = S2;
MachineInstr *RDef = getReachingDefForPred(RS, CI, RP.Reg, false);
if (!RDef || !HII->isPredicable(*RDef))
Done = coalesceRegisters(RD, RegisterRef(S2));
}
Changed |= Done;
}
return Changed;
}
bool HexagonExpandCondsets::runOnMachineFunction(MachineFunction &MF) {
HII = static_cast<const HexagonInstrInfo*>(MF.getSubtarget().getInstrInfo());
TRI = MF.getSubtarget().getRegisterInfo();
LIS = &getAnalysis<LiveIntervals>();
MRI = &MF.getRegInfo();
bool Changed = false;
// Try to coalesce the target of a mux with one of its sources.
// This could eliminate a register copy in some circumstances.
Changed |= coalesceSegments(MF);
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
// First, simply split all muxes into a pair of conditional transfers
// and update the live intervals to reflect the new arrangement.
// This is done mainly to make the live interval update simpler, than it
// would be while trying to predicate instructions at the same time.
Changed |= splitInBlock(*I);
// Traverse all blocks and collapse predicable instructions feeding
// conditional transfers into predicated instructions.
// Walk over all the instructions again, so we may catch pre-existing
// cases that were not created in the previous step.
Changed |= predicateInBlock(*I);
}
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
postprocessUndefImplicitUses(*I);
return Changed;
}
//===----------------------------------------------------------------------===//
// Public Constructor Functions
//===----------------------------------------------------------------------===//
static void initializePassOnce(PassRegistry &Registry) {
const char *Name = "Hexagon Expand Condsets";
PassInfo *PI = new PassInfo(Name, "expand-condsets",
&HexagonExpandCondsets::ID, 0, false, false);
Registry.registerPass(*PI, true);
}
void llvm::initializeHexagonExpandCondsetsPass(PassRegistry &Registry) {
CALL_ONCE_INITIALIZATION(initializePassOnce)
}
FunctionPass *llvm::createHexagonExpandCondsets() {
return new HexagonExpandCondsets();
}
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