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llvm-project/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp

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//===-- SimpleRegisterCoalescing.cpp - Register Coalescing ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a simple register coalescing pass that attempts to
// aggressively coalesce every register copy that it can.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regcoalescing"
#include "SimpleRegisterCoalescing.h"
#include "VirtRegMap.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/Value.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegisterCoalescer.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
#include <cmath>
using namespace llvm;
STATISTIC(numJoins , "Number of interval joins performed");
STATISTIC(numSubJoins , "Number of subclass joins performed");
STATISTIC(numCommutes , "Number of instruction commuting performed");
STATISTIC(numExtends , "Number of copies extended");
STATISTIC(NumReMats , "Number of instructions re-materialized");
STATISTIC(numPeep , "Number of identity moves eliminated after coalescing");
STATISTIC(numAborts , "Number of times interval joining aborted");
char SimpleRegisterCoalescing::ID = 0;
static cl::opt<bool>
EnableJoining("join-liveintervals",
cl::desc("Coalesce copies (default=true)"),
cl::init(true));
static cl::opt<bool>
NewHeuristic("new-coalescer-heuristic",
cl::desc("Use new coalescer heuristic"),
cl::init(false), cl::Hidden);
static cl::opt<bool>
CrossClassJoin("join-subclass-copies",
cl::desc("Coalesce copies to sub- register class"),
cl::init(false), cl::Hidden);
static RegisterPass<SimpleRegisterCoalescing>
X("simple-register-coalescing", "Simple Register Coalescing");
// Declare that we implement the RegisterCoalescer interface
static RegisterAnalysisGroup<RegisterCoalescer, true/*The Default*/> V(X);
const PassInfo *const llvm::SimpleRegisterCoalescingID = &X;
void SimpleRegisterCoalescing::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<LiveIntervals>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreservedID(MachineDominatorsID);
AU.addPreservedID(PHIEliminationID);
AU.addPreservedID(TwoAddressInstructionPassID);
AU.addRequired<LiveIntervals>();
AU.addRequired<MachineLoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy with IntA
/// being the source and IntB being the dest, thus this defines a value number
/// in IntB. If the source value number (in IntA) is defined by a copy from B,
/// see if we can merge these two pieces of B into a single value number,
/// eliminating a copy. For example:
///
/// A3 = B0
/// ...
/// B1 = A3 <- this copy
///
/// In this case, B0 can be extended to where the B1 copy lives, allowing the B1
/// value number to be replaced with B0 (which simplifies the B liveinterval).
///
/// This returns true if an interval was modified.
///
bool SimpleRegisterCoalescing::AdjustCopiesBackFrom(LiveInterval &IntA,
LiveInterval &IntB,
MachineInstr *CopyMI) {
unsigned CopyIdx = li_->getDefIndex(li_->getInstructionIndex(CopyMI));
// BValNo is a value number in B that is defined by a copy from A. 'B3' in
// the example above.
LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);
if (BLR == IntB.end()) // Should never happen!
return false;
VNInfo *BValNo = BLR->valno;
// Get the location that B is defined at. Two options: either this value has
// an unknown definition point or it is defined at CopyIdx. If unknown, we
// can't process it.
if (!BValNo->copy) return false;
assert(BValNo->def == CopyIdx && "Copy doesn't define the value?");
// AValNo is the value number in A that defines the copy, A3 in the example.
LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyIdx-1);
if (ALR == IntA.end()) // Should never happen!
return false;
VNInfo *AValNo = ALR->valno;
// If AValNo is defined as a copy from IntB, we can potentially process this.
// Get the instruction that defines this value number.
unsigned SrcReg = li_->getVNInfoSourceReg(AValNo);
if (!SrcReg) return false; // Not defined by a copy.
// If the value number is not defined by a copy instruction, ignore it.
// If the source register comes from an interval other than IntB, we can't
// handle this.
if (SrcReg != IntB.reg) return false;
// Get the LiveRange in IntB that this value number starts with.
LiveInterval::iterator ValLR = IntB.FindLiveRangeContaining(AValNo->def-1);
if (ValLR == IntB.end()) // Should never happen!
return false;
// Make sure that the end of the live range is inside the same block as
// CopyMI.
MachineInstr *ValLREndInst = li_->getInstructionFromIndex(ValLR->end-1);
if (!ValLREndInst ||
ValLREndInst->getParent() != CopyMI->getParent()) return false;
// Okay, we now know that ValLR ends in the same block that the CopyMI
// live-range starts. If there are no intervening live ranges between them in
// IntB, we can merge them.
if (ValLR+1 != BLR) return false;
// If a live interval is a physical register, conservatively check if any
// of its sub-registers is overlapping the live interval of the virtual
// register. If so, do not coalesce.
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg) &&
*tri_->getSubRegisters(IntB.reg)) {
for (const unsigned* SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR)
if (li_->hasInterval(*SR) && IntA.overlaps(li_->getInterval(*SR))) {
DOUT << "Interfere with sub-register ";
DEBUG(li_->getInterval(*SR).print(DOUT, tri_));
return false;
}
}
DOUT << "\nExtending: "; IntB.print(DOUT, tri_);
unsigned FillerStart = ValLR->end, FillerEnd = BLR->start;
// We are about to delete CopyMI, so need to remove it as the 'instruction
// that defines this value #'. Update the the valnum with the new defining
// instruction #.
BValNo->def = FillerStart;
BValNo->copy = NULL;
// Okay, we can merge them. We need to insert a new liverange:
// [ValLR.end, BLR.begin) of either value number, then we merge the
// two value numbers.
IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo));
// If the IntB live range is assigned to a physical register, and if that
// physreg has aliases,
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
// Update the liveintervals of sub-registers.
for (const unsigned *AS = tri_->getSubRegisters(IntB.reg); *AS; ++AS) {
LiveInterval &AliasLI = li_->getInterval(*AS);
AliasLI.addRange(LiveRange(FillerStart, FillerEnd,
AliasLI.getNextValue(FillerStart, 0, li_->getVNInfoAllocator())));
}
}
// Okay, merge "B1" into the same value number as "B0".
if (BValNo != ValLR->valno)
IntB.MergeValueNumberInto(BValNo, ValLR->valno);
DOUT << " result = "; IntB.print(DOUT, tri_);
DOUT << "\n";
// If the source instruction was killing the source register before the
// merge, unset the isKill marker given the live range has been extended.
int UIdx = ValLREndInst->findRegisterUseOperandIdx(IntB.reg, true);
if (UIdx != -1)
ValLREndInst->getOperand(UIdx).setIsKill(false);
++numExtends;
return true;
}
/// HasOtherReachingDefs - Return true if there are definitions of IntB
/// other than BValNo val# that can reach uses of AValno val# of IntA.
bool SimpleRegisterCoalescing::HasOtherReachingDefs(LiveInterval &IntA,
LiveInterval &IntB,
VNInfo *AValNo,
VNInfo *BValNo) {
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
AI != AE; ++AI) {
if (AI->valno != AValNo) continue;
LiveInterval::Ranges::iterator BI =
std::upper_bound(IntB.ranges.begin(), IntB.ranges.end(), AI->start);
if (BI != IntB.ranges.begin())
--BI;
for (; BI != IntB.ranges.end() && AI->end >= BI->start; ++BI) {
if (BI->valno == BValNo)
continue;
if (BI->start <= AI->start && BI->end > AI->start)
return true;
if (BI->start > AI->start && BI->start < AI->end)
return true;
}
}
return false;
}
/// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy with IntA
/// being the source and IntB being the dest, thus this defines a value number
/// in IntB. If the source value number (in IntA) is defined by a commutable
/// instruction and its other operand is coalesced to the copy dest register,
/// see if we can transform the copy into a noop by commuting the definition. For
/// example,
///
/// A3 = op A2 B0<kill>
/// ...
/// B1 = A3 <- this copy
/// ...
/// = op A3 <- more uses
///
/// ==>
///
/// B2 = op B0 A2<kill>
/// ...
/// B1 = B2 <- now an identify copy
/// ...
/// = op B2 <- more uses
///
/// This returns true if an interval was modified.
///
bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
LiveInterval &IntB,
MachineInstr *CopyMI) {
unsigned CopyIdx = li_->getDefIndex(li_->getInstructionIndex(CopyMI));
// FIXME: For now, only eliminate the copy by commuting its def when the
// source register is a virtual register. We want to guard against cases
// where the copy is a back edge copy and commuting the def lengthen the
// live interval of the source register to the entire loop.
if (TargetRegisterInfo::isPhysicalRegister(IntA.reg))
return false;
// BValNo is a value number in B that is defined by a copy from A. 'B3' in
// the example above.
LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);
if (BLR == IntB.end()) // Should never happen!
return false;
VNInfo *BValNo = BLR->valno;
// Get the location that B is defined at. Two options: either this value has
// an unknown definition point or it is defined at CopyIdx. If unknown, we
// can't process it.
if (!BValNo->copy) return false;
assert(BValNo->def == CopyIdx && "Copy doesn't define the value?");
// AValNo is the value number in A that defines the copy, A3 in the example.
LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyIdx-1);
if (ALR == IntA.end()) // Should never happen!
return false;
VNInfo *AValNo = ALR->valno;
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization.
if (AValNo->def == ~0U || AValNo->def == ~1U || AValNo->hasPHIKill)
return false;
MachineInstr *DefMI = li_->getInstructionFromIndex(AValNo->def);
const TargetInstrDesc &TID = DefMI->getDesc();
unsigned NewDstIdx;
if (!TID.isCommutable() ||
!tii_->CommuteChangesDestination(DefMI, NewDstIdx))
return false;
MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
unsigned NewReg = NewDstMO.getReg();
if (NewReg != IntB.reg || !NewDstMO.isKill())
return false;
// Make sure there are no other definitions of IntB that would reach the
// uses which the new definition can reach.
if (HasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
return false;
// If some of the uses of IntA.reg is already coalesced away, return false.
// It's not possible to determine whether it's safe to perform the coalescing.
for (MachineRegisterInfo::use_iterator UI = mri_->use_begin(IntA.reg),
UE = mri_->use_end(); UI != UE; ++UI) {
MachineInstr *UseMI = &*UI;
unsigned UseIdx = li_->getInstructionIndex(UseMI);
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR == IntA.end())
continue;
if (ULR->valno == AValNo && JoinedCopies.count(UseMI))
return false;
}
// At this point we have decided that it is legal to do this
// transformation. Start by commuting the instruction.
MachineBasicBlock *MBB = DefMI->getParent();
MachineInstr *NewMI = tii_->commuteInstruction(DefMI);
if (!NewMI)
return false;
if (NewMI != DefMI) {
li_->ReplaceMachineInstrInMaps(DefMI, NewMI);
MBB->insert(DefMI, NewMI);
MBB->erase(DefMI);
}
unsigned OpIdx = NewMI->findRegisterUseOperandIdx(IntA.reg, false);
NewMI->getOperand(OpIdx).setIsKill();
bool BHasPHIKill = BValNo->hasPHIKill;
SmallVector<VNInfo*, 4> BDeadValNos;
SmallVector<unsigned, 4> BKills;
std::map<unsigned, unsigned> BExtend;
// If ALR and BLR overlaps and end of BLR extends beyond end of ALR, e.g.
// A = or A, B
// ...
// B = A
// ...
// C = A<kill>
// ...
// = B
//
// then do not add kills of A to the newly created B interval.
bool Extended = BLR->end > ALR->end && ALR->end != ALR->start;
if (Extended)
BExtend[ALR->end] = BLR->end;
// Update uses of IntA of the specific Val# with IntB.
for (MachineRegisterInfo::use_iterator UI = mri_->use_begin(IntA.reg),
UE = mri_->use_end(); UI != UE;) {
MachineOperand &UseMO = UI.getOperand();
MachineInstr *UseMI = &*UI;
++UI;
if (JoinedCopies.count(UseMI))
continue;
unsigned UseIdx = li_->getInstructionIndex(UseMI);
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR == IntA.end() || ULR->valno != AValNo)
continue;
UseMO.setReg(NewReg);
if (UseMI == CopyMI)
continue;
if (UseMO.isKill()) {
if (Extended)
UseMO.setIsKill(false);
else
BKills.push_back(li_->getUseIndex(UseIdx)+1);
}
unsigned SrcReg, DstReg;
if (!tii_->isMoveInstr(*UseMI, SrcReg, DstReg))
continue;
if (DstReg == IntB.reg) {
// This copy will become a noop. If it's defining a new val#,
// remove that val# as well. However this live range is being
// extended to the end of the existing live range defined by the copy.
unsigned DefIdx = li_->getDefIndex(UseIdx);
const LiveRange *DLR = IntB.getLiveRangeContaining(DefIdx);
BHasPHIKill |= DLR->valno->hasPHIKill;
assert(DLR->valno->def == DefIdx);
BDeadValNos.push_back(DLR->valno);
BExtend[DLR->start] = DLR->end;
JoinedCopies.insert(UseMI);
// If this is a kill but it's going to be removed, the last use
// of the same val# is the new kill.
if (UseMO.isKill())
BKills.pop_back();
}
}
// We need to insert a new liverange: [ALR.start, LastUse). It may be we can
// simply extend BLR if CopyMI doesn't end the range.
DOUT << "\nExtending: "; IntB.print(DOUT, tri_);
// Remove val#'s defined by copies that will be coalesced away.
for (unsigned i = 0, e = BDeadValNos.size(); i != e; ++i)
IntB.removeValNo(BDeadValNos[i]);
// Extend BValNo by merging in IntA live ranges of AValNo. Val# definition
// is updated. Kills are also updated.
VNInfo *ValNo = BValNo;
ValNo->def = AValNo->def;
ValNo->copy = NULL;
for (unsigned j = 0, ee = ValNo->kills.size(); j != ee; ++j) {
unsigned Kill = ValNo->kills[j];
if (Kill != BLR->end)
BKills.push_back(Kill);
}
ValNo->kills.clear();
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
AI != AE; ++AI) {
if (AI->valno != AValNo) continue;
unsigned End = AI->end;
std::map<unsigned, unsigned>::iterator EI = BExtend.find(End);
if (EI != BExtend.end())
End = EI->second;
IntB.addRange(LiveRange(AI->start, End, ValNo));
}
IntB.addKills(ValNo, BKills);
ValNo->hasPHIKill = BHasPHIKill;
DOUT << " result = "; IntB.print(DOUT, tri_);
DOUT << "\n";
DOUT << "\nShortening: "; IntA.print(DOUT, tri_);
IntA.removeValNo(AValNo);
DOUT << " result = "; IntA.print(DOUT, tri_);
DOUT << "\n";
++numCommutes;
return true;
}
/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
/// computation, replace the copy by rematerialize the definition.
bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
unsigned DstReg,
MachineInstr *CopyMI) {
unsigned CopyIdx = li_->getUseIndex(li_->getInstructionIndex(CopyMI));
LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
if (SrcLR == SrcInt.end()) // Should never happen!
return false;
VNInfo *ValNo = SrcLR->valno;
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization.
if (ValNo->def == ~0U || ValNo->def == ~1U || ValNo->hasPHIKill)
return false;
MachineInstr *DefMI = li_->getInstructionFromIndex(ValNo->def);
const TargetInstrDesc &TID = DefMI->getDesc();
if (!TID.isAsCheapAsAMove())
return false;
bool SawStore = false;
if (!DefMI->isSafeToMove(tii_, SawStore))
return false;
unsigned DefIdx = li_->getDefIndex(CopyIdx);
const LiveRange *DLR= li_->getInterval(DstReg).getLiveRangeContaining(DefIdx);
DLR->valno->copy = NULL;
MachineBasicBlock::iterator MII = CopyMI;
MachineBasicBlock *MBB = CopyMI->getParent();
tii_->reMaterialize(*MBB, MII, DstReg, DefMI);
MachineInstr *NewMI = prior(MII);
// CopyMI may have implicit instructions, transfer them over to the newly
// rematerialized instruction. And update implicit def interval valnos.
for (unsigned i = CopyMI->getDesc().getNumOperands(),
e = CopyMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = CopyMI->getOperand(i);
if (MO.isReg() && MO.isImplicit())
NewMI->addOperand(MO);
if (MO.isDef() && li_->hasInterval(MO.getReg())) {
unsigned Reg = MO.getReg();
DLR = li_->getInterval(Reg).getLiveRangeContaining(DefIdx);
if (DLR && DLR->valno->copy == CopyMI)
DLR->valno->copy = NULL;
}
}
li_->ReplaceMachineInstrInMaps(CopyMI, NewMI);
CopyMI->eraseFromParent();
ReMatCopies.insert(CopyMI);
++NumReMats;
return true;
}
/// isBackEdgeCopy - Returns true if CopyMI is a back edge copy.
///
bool SimpleRegisterCoalescing::isBackEdgeCopy(MachineInstr *CopyMI,
unsigned DstReg) const {
MachineBasicBlock *MBB = CopyMI->getParent();
const MachineLoop *L = loopInfo->getLoopFor(MBB);
if (!L)
return false;
if (MBB != L->getLoopLatch())
return false;
LiveInterval &LI = li_->getInterval(DstReg);
unsigned DefIdx = li_->getInstructionIndex(CopyMI);
LiveInterval::const_iterator DstLR =
LI.FindLiveRangeContaining(li_->getDefIndex(DefIdx));
if (DstLR == LI.end())
return false;
unsigned KillIdx = li_->getMBBEndIdx(MBB) + 1;
if (DstLR->valno->kills.size() == 1 &&
DstLR->valno->kills[0] == KillIdx && DstLR->valno->hasPHIKill)
return true;
return false;
}
/// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
/// update the subregister number if it is not zero. If DstReg is a
/// physical register and the existing subregister number of the def / use
/// being updated is not zero, make sure to set it to the correct physical
/// subregister.
void
SimpleRegisterCoalescing::UpdateRegDefsUses(unsigned SrcReg, unsigned DstReg,
unsigned SubIdx) {
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
if (DstIsPhys && SubIdx) {
// Figure out the real physical register we are updating with.
DstReg = tri_->getSubReg(DstReg, SubIdx);
SubIdx = 0;
}
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(SrcReg),
E = mri_->reg_end(); I != E; ) {
MachineOperand &O = I.getOperand();
MachineInstr *UseMI = &*I;
++I;
unsigned OldSubIdx = O.getSubReg();
if (DstIsPhys) {
unsigned UseDstReg = DstReg;
if (OldSubIdx)
UseDstReg = tri_->getSubReg(DstReg, OldSubIdx);
unsigned CopySrcReg, CopyDstReg;
if (tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg) &&
CopySrcReg != CopyDstReg &&
CopySrcReg == SrcReg && CopyDstReg != UseDstReg) {
// If the use is a copy and it won't be coalesced away, and its source
// is defined by a trivial computation, try to rematerialize it instead.
if (ReMaterializeTrivialDef(li_->getInterval(SrcReg), CopyDstReg,UseMI))
continue;
}
O.setReg(UseDstReg);
O.setSubReg(0);
} else {
// Sub-register indexes goes from small to large. e.g.
// RAX: 1 -> AL, 2 -> AX, 3 -> EAX
// EAX: 1 -> AL, 2 -> AX
// So RAX's sub-register 2 is AX, RAX's sub-regsiter 3 is EAX, whose
// sub-register 2 is also AX.
if (SubIdx && OldSubIdx && SubIdx != OldSubIdx)
assert(OldSubIdx < SubIdx && "Conflicting sub-register index!");
else if (SubIdx)
O.setSubReg(SubIdx);
// Remove would-be duplicated kill marker.
if (O.isKill() && UseMI->killsRegister(DstReg))
O.setIsKill(false);
O.setReg(DstReg);
}
}
}
/// RemoveDeadImpDef - Remove implicit_def instructions which are "re-defining"
/// registers due to insert_subreg coalescing. e.g.
/// r1024 = op
/// r1025 = implicit_def
/// r1025 = insert_subreg r1025, r1024
/// = op r1025
/// =>
/// r1025 = op
/// r1025 = implicit_def
/// r1025 = insert_subreg r1025, r1025
/// = op r1025
void
SimpleRegisterCoalescing::RemoveDeadImpDef(unsigned Reg, LiveInterval &LI) {
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(Reg),
E = mri_->reg_end(); I != E; ) {
MachineOperand &O = I.getOperand();
MachineInstr *DefMI = &*I;
++I;
if (!O.isDef())
continue;
if (DefMI->getOpcode() != TargetInstrInfo::IMPLICIT_DEF)
continue;
if (!LI.liveBeforeAndAt(li_->getInstructionIndex(DefMI)))
continue;
li_->RemoveMachineInstrFromMaps(DefMI);
DefMI->eraseFromParent();
}
}
/// RemoveUnnecessaryKills - Remove kill markers that are no longer accurate
/// due to live range lengthening as the result of coalescing.
void SimpleRegisterCoalescing::RemoveUnnecessaryKills(unsigned Reg,
LiveInterval &LI) {
for (MachineRegisterInfo::use_iterator UI = mri_->use_begin(Reg),
UE = mri_->use_end(); UI != UE; ++UI) {
MachineOperand &UseMO = UI.getOperand();
if (UseMO.isKill()) {
MachineInstr *UseMI = UseMO.getParent();
unsigned UseIdx = li_->getUseIndex(li_->getInstructionIndex(UseMI));
if (JoinedCopies.count(UseMI))
continue;
const LiveRange *UI = LI.getLiveRangeContaining(UseIdx);
if (!UI || !LI.isKill(UI->valno, UseIdx+1))
UseMO.setIsKill(false);
}
}
}
/// removeRange - Wrapper for LiveInterval::removeRange. This removes a range
/// from a physical register live interval as well as from the live intervals
/// of its sub-registers.
static void removeRange(LiveInterval &li, unsigned Start, unsigned End,
LiveIntervals *li_, const TargetRegisterInfo *tri_) {
li.removeRange(Start, End, true);
if (TargetRegisterInfo::isPhysicalRegister(li.reg)) {
for (const unsigned* SR = tri_->getSubRegisters(li.reg); *SR; ++SR) {
if (!li_->hasInterval(*SR))
continue;
LiveInterval &sli = li_->getInterval(*SR);
unsigned RemoveEnd = Start;
while (RemoveEnd != End) {
LiveInterval::iterator LR = sli.FindLiveRangeContaining(Start);
if (LR == sli.end())
break;
RemoveEnd = (LR->end < End) ? LR->end : End;
sli.removeRange(Start, RemoveEnd, true);
Start = RemoveEnd;
}
}
}
}
/// removeIntervalIfEmpty - Check if the live interval of a physical register
/// is empty, if so remove it and also remove the empty intervals of its
/// sub-registers. Return true if live interval is removed.
static bool removeIntervalIfEmpty(LiveInterval &li, LiveIntervals *li_,
const TargetRegisterInfo *tri_) {
if (li.empty()) {
if (TargetRegisterInfo::isPhysicalRegister(li.reg))
for (const unsigned* SR = tri_->getSubRegisters(li.reg); *SR; ++SR) {
if (!li_->hasInterval(*SR))
continue;
LiveInterval &sli = li_->getInterval(*SR);
if (sli.empty())
li_->removeInterval(*SR);
}
li_->removeInterval(li.reg);
return true;
}
return false;
}
/// ShortenDeadCopyLiveRange - Shorten a live range defined by a dead copy.
/// Return true if live interval is removed.
bool SimpleRegisterCoalescing::ShortenDeadCopyLiveRange(LiveInterval &li,
MachineInstr *CopyMI) {
unsigned CopyIdx = li_->getInstructionIndex(CopyMI);
LiveInterval::iterator MLR =
li.FindLiveRangeContaining(li_->getDefIndex(CopyIdx));
if (MLR == li.end())
return false; // Already removed by ShortenDeadCopySrcLiveRange.
unsigned RemoveStart = MLR->start;
unsigned RemoveEnd = MLR->end;
// Remove the liverange that's defined by this.
if (RemoveEnd == li_->getDefIndex(CopyIdx)+1) {
removeRange(li, RemoveStart, RemoveEnd, li_, tri_);
return removeIntervalIfEmpty(li, li_, tri_);
}
return false;
}
/// PropagateDeadness - Propagate the dead marker to the instruction which
/// defines the val#.
static void PropagateDeadness(LiveInterval &li, MachineInstr *CopyMI,
unsigned &LRStart, LiveIntervals *li_,
const TargetRegisterInfo* tri_) {
MachineInstr *DefMI =
li_->getInstructionFromIndex(li_->getDefIndex(LRStart));
if (DefMI && DefMI != CopyMI) {
int DeadIdx = DefMI->findRegisterDefOperandIdx(li.reg, false, tri_);
if (DeadIdx != -1) {
DefMI->getOperand(DeadIdx).setIsDead();
// A dead def should have a single cycle interval.
++LRStart;
}
}
}
/// isSameOrFallThroughBB - Return true if MBB == SuccMBB or MBB simply
/// fallthoughs to SuccMBB.
static bool isSameOrFallThroughBB(MachineBasicBlock *MBB,
MachineBasicBlock *SuccMBB,
const TargetInstrInfo *tii_) {
if (MBB == SuccMBB)
return true;
MachineBasicBlock *TBB = 0, *FBB = 0;
SmallVector<MachineOperand, 4> Cond;
return !tii_->AnalyzeBranch(*MBB, TBB, FBB, Cond) && !TBB && !FBB &&
MBB->isSuccessor(SuccMBB);
}
/// ShortenDeadCopySrcLiveRange - Shorten a live range as it's artificially
/// extended by a dead copy. Mark the last use (if any) of the val# as kill as
/// ends the live range there. If there isn't another use, then this live range
/// is dead. Return true if live interval is removed.
bool
SimpleRegisterCoalescing::ShortenDeadCopySrcLiveRange(LiveInterval &li,
MachineInstr *CopyMI) {
unsigned CopyIdx = li_->getInstructionIndex(CopyMI);
if (CopyIdx == 0) {
// FIXME: special case: function live in. It can be a general case if the
// first instruction index starts at > 0 value.
assert(TargetRegisterInfo::isPhysicalRegister(li.reg));
// Live-in to the function but dead. Remove it from entry live-in set.
if (mf_->begin()->isLiveIn(li.reg))
mf_->begin()->removeLiveIn(li.reg);
const LiveRange *LR = li.getLiveRangeContaining(CopyIdx);
removeRange(li, LR->start, LR->end, li_, tri_);
return removeIntervalIfEmpty(li, li_, tri_);
}
LiveInterval::iterator LR = li.FindLiveRangeContaining(CopyIdx-1);
if (LR == li.end())
// Livein but defined by a phi.
return false;
unsigned RemoveStart = LR->start;
unsigned RemoveEnd = li_->getDefIndex(CopyIdx)+1;
if (LR->end > RemoveEnd)
// More uses past this copy? Nothing to do.
return false;
MachineBasicBlock *CopyMBB = CopyMI->getParent();
unsigned MBBStart = li_->getMBBStartIdx(CopyMBB);
unsigned LastUseIdx;
MachineOperand *LastUse = lastRegisterUse(LR->start, CopyIdx-1, li.reg,
LastUseIdx);
if (LastUse) {
MachineInstr *LastUseMI = LastUse->getParent();
if (!isSameOrFallThroughBB(LastUseMI->getParent(), CopyMBB, tii_)) {
// r1024 = op
// ...
// BB1:
// = r1024
//
// BB2:
// r1025<dead> = r1024<kill>
if (MBBStart < LR->end)
removeRange(li, MBBStart, LR->end, li_, tri_);
return false;
}
// There are uses before the copy, just shorten the live range to the end
// of last use.
LastUse->setIsKill();
removeRange(li, li_->getDefIndex(LastUseIdx), LR->end, li_, tri_);
unsigned SrcReg, DstReg;
if (tii_->isMoveInstr(*LastUseMI, SrcReg, DstReg) &&
DstReg == li.reg) {
// Last use is itself an identity code.
int DeadIdx = LastUseMI->findRegisterDefOperandIdx(li.reg, false, tri_);
LastUseMI->getOperand(DeadIdx).setIsDead();
}
return false;
}
// Is it livein?
if (LR->start <= MBBStart && LR->end > MBBStart) {
if (LR->start == 0) {
assert(TargetRegisterInfo::isPhysicalRegister(li.reg));
// Live-in to the function but dead. Remove it from entry live-in set.
mf_->begin()->removeLiveIn(li.reg);
}
// FIXME: Shorten intervals in BBs that reaches this BB.
}
if (LR->valno->def == RemoveStart)
// If the def MI defines the val#, propagate the dead marker.
PropagateDeadness(li, CopyMI, RemoveStart, li_, tri_);
removeRange(li, RemoveStart, LR->end, li_, tri_);
return removeIntervalIfEmpty(li, li_, tri_);
}
/// CanCoalesceWithImpDef - Returns true if the specified copy instruction
/// from an implicit def to another register can be coalesced away.
bool SimpleRegisterCoalescing::CanCoalesceWithImpDef(MachineInstr *CopyMI,
LiveInterval &li,
LiveInterval &ImpLi) const{
if (!CopyMI->killsRegister(ImpLi.reg))
return false;
unsigned CopyIdx = li_->getDefIndex(li_->getInstructionIndex(CopyMI));
LiveInterval::iterator LR = li.FindLiveRangeContaining(CopyIdx);
if (LR == li.end())
return false;
if (LR->valno->hasPHIKill)
return false;
if (LR->valno->def != CopyIdx)
return false;
// Make sure all of val# uses are copies.
for (MachineRegisterInfo::use_iterator UI = mri_->use_begin(li.reg),
UE = mri_->use_end(); UI != UE;) {
MachineInstr *UseMI = &*UI;
++UI;
if (JoinedCopies.count(UseMI))
continue;
unsigned UseIdx = li_->getUseIndex(li_->getInstructionIndex(UseMI));
LiveInterval::iterator ULR = li.FindLiveRangeContaining(UseIdx);
if (ULR == li.end() || ULR->valno != LR->valno)
continue;
// If the use is not a use, then it's not safe to coalesce the move.
unsigned SrcReg, DstReg;
if (!tii_->isMoveInstr(*UseMI, SrcReg, DstReg)) {
if (UseMI->getOpcode() == TargetInstrInfo::INSERT_SUBREG &&
UseMI->getOperand(1).getReg() == li.reg)
continue;
return false;
}
}
return true;
}
/// RemoveCopiesFromValNo - The specified value# is defined by an implicit
/// def and it is being removed. Turn all copies from this value# into
/// identity copies so they will be removed.
void SimpleRegisterCoalescing::RemoveCopiesFromValNo(LiveInterval &li,
VNInfo *VNI) {
SmallVector<MachineInstr*, 4> ImpDefs;
MachineOperand *LastUse = NULL;
unsigned LastUseIdx = li_->getUseIndex(VNI->def);
for (MachineRegisterInfo::reg_iterator RI = mri_->reg_begin(li.reg),
RE = mri_->reg_end(); RI != RE;) {
MachineOperand *MO = &RI.getOperand();
MachineInstr *MI = &*RI;
++RI;
if (MO->isDef()) {
if (MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) {
ImpDefs.push_back(MI);
}
continue;
}
if (JoinedCopies.count(MI))
continue;
unsigned UseIdx = li_->getUseIndex(li_->getInstructionIndex(MI));
LiveInterval::iterator ULR = li.FindLiveRangeContaining(UseIdx);
if (ULR == li.end() || ULR->valno != VNI)
continue;
// If the use is a copy, turn it into an identity copy.
unsigned SrcReg, DstReg;
if (tii_->isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == li.reg) {
// Each use MI may have multiple uses of this register. Change them all.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.getReg() == li.reg)
MO.setReg(DstReg);
}
JoinedCopies.insert(MI);
} else if (UseIdx > LastUseIdx) {
LastUseIdx = UseIdx;
LastUse = MO;
}
}
if (LastUse)
LastUse->setIsKill();
else {
// Remove dead implicit_def's.
while (!ImpDefs.empty()) {
MachineInstr *ImpDef = ImpDefs.back();
ImpDefs.pop_back();
li_->RemoveMachineInstrFromMaps(ImpDef);
ImpDef->eraseFromParent();
}
}
}
static unsigned getMatchingSuperReg(unsigned Reg, unsigned SubIdx,
const TargetRegisterClass *RC,
const TargetRegisterInfo* TRI) {
for (const unsigned *SRs = TRI->getSuperRegisters(Reg);
unsigned SR = *SRs; ++SRs)
if (Reg == TRI->getSubReg(SR, SubIdx) && RC->contains(SR))
return SR;
return 0;
}
/// isProfitableToCoalesceToSubRC - Given that register class of DstReg is
/// a subset of the register class of SrcReg, return true if it's profitable
/// to coalesce the two registers.
bool
SimpleRegisterCoalescing::isProfitableToCoalesceToSubRC(unsigned SrcReg,
unsigned DstReg,
MachineBasicBlock *MBB){
if (!CrossClassJoin)
return false;
// First let's make sure all uses are in the same MBB.
for (MachineRegisterInfo::reg_iterator RI = mri_->reg_begin(SrcReg),
RE = mri_->reg_end(); RI != RE; ++RI) {
MachineInstr &MI = *RI;
if (MI.getParent() != MBB)
return false;
}
for (MachineRegisterInfo::reg_iterator RI = mri_->reg_begin(DstReg),
RE = mri_->reg_end(); RI != RE; ++RI) {
MachineInstr &MI = *RI;
if (MI.getParent() != MBB)
return false;
}
// Then make sure the intervals are *short*.
LiveInterval &SrcInt = li_->getInterval(SrcReg);
LiveInterval &DstInt = li_->getInterval(DstReg);
unsigned SrcSize = li_->getApproximateInstructionCount(SrcInt);
unsigned DstSize = li_->getApproximateInstructionCount(DstInt);
const TargetRegisterClass *RC = mri_->getRegClass(DstReg);
unsigned Threshold = allocatableRCRegs_[RC].count() * 2;
return (SrcSize + DstSize) <= Threshold;
}
/// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
/// which are the src/dst of the copy instruction CopyMI. This returns true
/// if the copy was successfully coalesced away. If it is not currently
/// possible to coalesce this interval, but it may be possible if other
/// things get coalesced, then it returns true by reference in 'Again'.
bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
MachineInstr *CopyMI = TheCopy.MI;
Again = false;
if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
return false; // Already done.
DOUT << li_->getInstructionIndex(CopyMI) << '\t' << *CopyMI;
unsigned SrcReg;
unsigned DstReg;
bool isExtSubReg = CopyMI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG;
bool isInsSubReg = CopyMI->getOpcode() == TargetInstrInfo::INSERT_SUBREG;
unsigned SubIdx = 0;
if (isExtSubReg) {
DstReg = CopyMI->getOperand(0).getReg();
SrcReg = CopyMI->getOperand(1).getReg();
} else if (isInsSubReg) {
if (CopyMI->getOperand(2).getSubReg()) {
DOUT << "\tSource of insert_subreg is already coalesced "
<< "to another register.\n";
return false; // Not coalescable.
}
DstReg = CopyMI->getOperand(0).getReg();
SrcReg = CopyMI->getOperand(2).getReg();
} else if (!tii_->isMoveInstr(*CopyMI, SrcReg, DstReg)) {
assert(0 && "Unrecognized copy instruction!");
return false;
}
// If they are already joined we continue.
if (SrcReg == DstReg) {
DOUT << "\tCopy already coalesced.\n";
return false; // Not coalescable.
}
bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
// If they are both physical registers, we cannot join them.
if (SrcIsPhys && DstIsPhys) {
DOUT << "\tCan not coalesce physregs.\n";
return false; // Not coalescable.
}
// We only join virtual registers with allocatable physical registers.
if (SrcIsPhys && !allocatableRegs_[SrcReg]) {
DOUT << "\tSrc reg is unallocatable physreg.\n";
return false; // Not coalescable.
}
if (DstIsPhys && !allocatableRegs_[DstReg]) {
DOUT << "\tDst reg is unallocatable physreg.\n";
return false; // Not coalescable.
}
// Should be non-null only when coalescing to a sub-register class.
const TargetRegisterClass *SubRC = NULL;
MachineBasicBlock *CopyMBB = CopyMI->getParent();
unsigned RealDstReg = 0;
unsigned RealSrcReg = 0;
if (isExtSubReg || isInsSubReg) {
SubIdx = CopyMI->getOperand(isExtSubReg ? 2 : 3).getImm();
if (SrcIsPhys && isExtSubReg) {
// r1024 = EXTRACT_SUBREG EAX, 0 then r1024 is really going to be
// coalesced with AX.
unsigned DstSubIdx = CopyMI->getOperand(0).getSubReg();
if (DstSubIdx) {
// r1024<2> = EXTRACT_SUBREG EAX, 2. Then r1024 has already been
// coalesced to a larger register so the subreg indices cancel out.
if (DstSubIdx != SubIdx) {
DOUT << "\t Sub-register indices mismatch.\n";
return false; // Not coalescable.
}
} else
SrcReg = tri_->getSubReg(SrcReg, SubIdx);
SubIdx = 0;
} else if (DstIsPhys && isInsSubReg) {
// EAX = INSERT_SUBREG EAX, r1024, 0
unsigned SrcSubIdx = CopyMI->getOperand(2).getSubReg();
if (SrcSubIdx) {
// EAX = INSERT_SUBREG EAX, r1024<2>, 2 Then r1024 has already been
// coalesced to a larger register so the subreg indices cancel out.
if (SrcSubIdx != SubIdx) {
DOUT << "\t Sub-register indices mismatch.\n";
return false; // Not coalescable.
}
} else
DstReg = tri_->getSubReg(DstReg, SubIdx);
SubIdx = 0;
} else if ((DstIsPhys && isExtSubReg) || (SrcIsPhys && isInsSubReg)) {
// If this is a extract_subreg where dst is a physical register, e.g.
// cl = EXTRACT_SUBREG reg1024, 1
// then create and update the actual physical register allocated to RHS.
// Ditto for
// reg1024 = INSERT_SUBREG r1024, cl, 1
if (CopyMI->getOperand(1).getSubReg()) {
DOUT << "\tSrc of extract_ / insert_subreg already coalesced with reg"
<< " of a super-class.\n";
return false; // Not coalescable.
}
const TargetRegisterClass *RC =
mri_->getRegClass(isExtSubReg ? SrcReg : DstReg);
if (isExtSubReg) {
RealDstReg = getMatchingSuperReg(DstReg, SubIdx, RC, tri_);
assert(RealDstReg && "Invalid extract_subreg instruction!");
} else {
RealSrcReg = getMatchingSuperReg(SrcReg, SubIdx, RC, tri_);
assert(RealSrcReg && "Invalid extract_subreg instruction!");
}
// For this type of EXTRACT_SUBREG, conservatively
// check if the live interval of the source register interfere with the
// actual super physical register we are trying to coalesce with.
unsigned PhysReg = isExtSubReg ? RealDstReg : RealSrcReg;
LiveInterval &RHS = li_->getInterval(isExtSubReg ? SrcReg : DstReg);
if (li_->hasInterval(PhysReg) &&
RHS.overlaps(li_->getInterval(PhysReg))) {
DOUT << "Interfere with register ";
DEBUG(li_->getInterval(PhysReg).print(DOUT, tri_));
return false; // Not coalescable
}
for (const unsigned* SR = tri_->getSubRegisters(PhysReg); *SR; ++SR)
if (li_->hasInterval(*SR) && RHS.overlaps(li_->getInterval(*SR))) {
DOUT << "Interfere with sub-register ";
DEBUG(li_->getInterval(*SR).print(DOUT, tri_));
return false; // Not coalescable
}
SubIdx = 0;
} else {
unsigned OldSubIdx = isExtSubReg ? CopyMI->getOperand(0).getSubReg()
: CopyMI->getOperand(2).getSubReg();
if (OldSubIdx) {
if (OldSubIdx == SubIdx &&
!differingRegisterClasses(SrcReg, DstReg, SubRC))
// r1024<2> = EXTRACT_SUBREG r1025, 2. Then r1024 has already been
// coalesced to a larger register so the subreg indices cancel out.
// Also check if the other larger register is of the same register
// class as the would be resulting register.
SubIdx = 0;
else {
DOUT << "\t Sub-register indices mismatch.\n";
return false; // Not coalescable.
}
}
if (SubIdx) {
unsigned LargeReg = isExtSubReg ? SrcReg : DstReg;
unsigned SmallReg = isExtSubReg ? DstReg : SrcReg;
unsigned LargeRegSize =
li_->getApproximateInstructionCount(li_->getInterval(LargeReg));
unsigned SmallRegSize =
li_->getApproximateInstructionCount(li_->getInterval(SmallReg));
const TargetRegisterClass *RC = mri_->getRegClass(SmallReg);
unsigned Threshold = allocatableRCRegs_[RC].count();
// Be conservative. If both sides are virtual registers, do not coalesce
// if this will cause a high use density interval to target a smaller
// set of registers.
if (SmallRegSize > Threshold || LargeRegSize > Threshold) {
if ((float)std::distance(mri_->use_begin(SmallReg),
mri_->use_end()) / SmallRegSize <
(float)std::distance(mri_->use_begin(LargeReg),
mri_->use_end()) / LargeRegSize) {
Again = true; // May be possible to coalesce later.
return false;
}
}
}
}
} else if (differingRegisterClasses(SrcReg, DstReg, SubRC)) {
// FIXME: What if the resul of a EXTRACT_SUBREG is then coalesced
// with another? If it's the resulting destination register, then
// the subidx must be propagated to uses (but only those defined
// by the EXTRACT_SUBREG). If it's being coalesced into another
// register, it should be safe because register is assumed to have
// the register class of the super-register.
if (!SubRC || !isProfitableToCoalesceToSubRC(SrcReg, DstReg, CopyMBB)) {
// If they are not of the same register class, we cannot join them.
DOUT << "\tSrc/Dest are different register classes.\n";
// Allow the coalescer to try again in case either side gets coalesced to
// a physical register that's compatible with the other side. e.g.
// r1024 = MOV32to32_ r1025
// but later r1024 is assigned EAX then r1025 may be coalesced with EAX.
Again = true; // May be possible to coalesce later.
return false;
}
}
LiveInterval &SrcInt = li_->getInterval(SrcReg);
LiveInterval &DstInt = li_->getInterval(DstReg);
assert(SrcInt.reg == SrcReg && DstInt.reg == DstReg &&
"Register mapping is horribly broken!");
DOUT << "\t\tInspecting "; SrcInt.print(DOUT, tri_);
DOUT << " and "; DstInt.print(DOUT, tri_);
DOUT << ": ";
// Check if it is necessary to propagate "isDead" property.
if (!isExtSubReg && !isInsSubReg) {
MachineOperand *mopd = CopyMI->findRegisterDefOperand(DstReg, false);
bool isDead = mopd->isDead();
// We need to be careful about coalescing a source physical register with a
// virtual register. Once the coalescing is done, it cannot be broken and
// these are not spillable! If the destination interval uses are far away,
// think twice about coalescing them!
if (!isDead && (SrcIsPhys || DstIsPhys)) {
LiveInterval &JoinVInt = SrcIsPhys ? DstInt : SrcInt;
unsigned JoinVReg = SrcIsPhys ? DstReg : SrcReg;
unsigned JoinPReg = SrcIsPhys ? SrcReg : DstReg;
const TargetRegisterClass *RC = mri_->getRegClass(JoinVReg);
unsigned Threshold = allocatableRCRegs_[RC].count() * 2;
if (TheCopy.isBackEdge)
Threshold *= 2; // Favors back edge copies.
// If the virtual register live interval is long but it has low use desity,
// do not join them, instead mark the physical register as its allocation
// preference.
unsigned Length = li_->getApproximateInstructionCount(JoinVInt);
if (Length > Threshold &&
(((float)std::distance(mri_->use_begin(JoinVReg),
mri_->use_end()) / Length) < (1.0 / Threshold))) {
JoinVInt.preference = JoinPReg;
++numAborts;
DOUT << "\tMay tie down a physical register, abort!\n";
Again = true; // May be possible to coalesce later.
return false;
}
}
}
// Okay, attempt to join these two intervals. On failure, this returns false.
// Otherwise, if one of the intervals being joined is a physreg, this method
// always canonicalizes DstInt to be it. The output "SrcInt" will not have
// been modified, so we can use this information below to update aliases.
bool Swapped = false;
// If SrcInt is implicitly defined, it's safe to coalesce.
bool isEmpty = SrcInt.empty();
if (isEmpty && !CanCoalesceWithImpDef(CopyMI, DstInt, SrcInt)) {
// Only coalesce an empty interval (defined by implicit_def) with
// another interval which has a valno defined by the CopyMI and the CopyMI
// is a kill of the implicit def.
DOUT << "Not profitable!\n";
return false;
}
if (!isEmpty && !JoinIntervals(DstInt, SrcInt, Swapped)) {
// Coalescing failed.
// If definition of source is defined by trivial computation, try
// rematerializing it.
if (!isExtSubReg && !isInsSubReg &&
ReMaterializeTrivialDef(SrcInt, DstInt.reg, CopyMI))
return true;
// If we can eliminate the copy without merging the live ranges, do so now.
if (!isExtSubReg && !isInsSubReg &&
(AdjustCopiesBackFrom(SrcInt, DstInt, CopyMI) ||
RemoveCopyByCommutingDef(SrcInt, DstInt, CopyMI))) {
JoinedCopies.insert(CopyMI);
return true;
}
// Otherwise, we are unable to join the intervals.
DOUT << "Interference!\n";
Again = true; // May be possible to coalesce later.
return false;
}
LiveInterval *ResSrcInt = &SrcInt;
LiveInterval *ResDstInt = &DstInt;
if (Swapped) {
std::swap(SrcReg, DstReg);
std::swap(ResSrcInt, ResDstInt);
}
assert(TargetRegisterInfo::isVirtualRegister(SrcReg) &&
"LiveInterval::join didn't work right!");
// If we're about to merge live ranges into a physical register live range,
// we have to update any aliased register's live ranges to indicate that they
// have clobbered values for this range.
if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
// If this is a extract_subreg where dst is a physical register, e.g.
// cl = EXTRACT_SUBREG reg1024, 1
// then create and update the actual physical register allocated to RHS.
if (RealDstReg || RealSrcReg) {
LiveInterval &RealInt =
li_->getOrCreateInterval(RealDstReg ? RealDstReg : RealSrcReg);
SmallSet<const VNInfo*, 4> CopiedValNos;
for (LiveInterval::Ranges::const_iterator I = ResSrcInt->ranges.begin(),
E = ResSrcInt->ranges.end(); I != E; ++I) {
const LiveRange *DstLR = ResDstInt->getLiveRangeContaining(I->start);
assert(DstLR && "Invalid joined interval!");
const VNInfo *DstValNo = DstLR->valno;
if (CopiedValNos.insert(DstValNo)) {
VNInfo *ValNo = RealInt.getNextValue(DstValNo->def, DstValNo->copy,
li_->getVNInfoAllocator());
ValNo->hasPHIKill = DstValNo->hasPHIKill;
RealInt.addKills(ValNo, DstValNo->kills);
RealInt.MergeValueInAsValue(*ResDstInt, DstValNo, ValNo);
}
}
DstReg = RealDstReg ? RealDstReg : RealSrcReg;
}
// Update the liveintervals of sub-registers.
for (const unsigned *AS = tri_->getSubRegisters(DstReg); *AS; ++AS)
li_->getOrCreateInterval(*AS).MergeInClobberRanges(*ResSrcInt,
li_->getVNInfoAllocator());
}
// If this is a EXTRACT_SUBREG, make sure the result of coalescing is the
// larger super-register.
if ((isExtSubReg || isInsSubReg) && !SrcIsPhys && !DstIsPhys) {
if ((isExtSubReg && !Swapped) || (isInsSubReg && Swapped)) {
ResSrcInt->Copy(*ResDstInt, li_->getVNInfoAllocator());
std::swap(SrcReg, DstReg);
std::swap(ResSrcInt, ResDstInt);
}
}
// Coalescing to a virtual register that is of a sub-register class of the
// other. Make sure the resulting register is set to the right register class.
if (SubRC) {
mri_->setRegClass(DstReg, SubRC);
++numSubJoins;
}
if (NewHeuristic) {
// Add all copies that define val# in the source interval into the queue.
for (LiveInterval::const_vni_iterator i = ResSrcInt->vni_begin(),
e = ResSrcInt->vni_end(); i != e; ++i) {
const VNInfo *vni = *i;
if (!vni->def || vni->def == ~1U || vni->def == ~0U)
continue;
MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def);
unsigned NewSrcReg, NewDstReg;
if (CopyMI &&
JoinedCopies.count(CopyMI) == 0 &&
tii_->isMoveInstr(*CopyMI, NewSrcReg, NewDstReg)) {
unsigned LoopDepth = loopInfo->getLoopDepth(CopyMBB);
JoinQueue->push(CopyRec(CopyMI, LoopDepth,
isBackEdgeCopy(CopyMI, DstReg)));
}
}
}
// Remember to delete the copy instruction.
JoinedCopies.insert(CopyMI);
// Some live range has been lengthened due to colaescing, eliminate the
// unnecessary kills.
RemoveUnnecessaryKills(SrcReg, *ResDstInt);
if (TargetRegisterInfo::isVirtualRegister(DstReg))
RemoveUnnecessaryKills(DstReg, *ResDstInt);
if (isInsSubReg)
// Avoid:
// r1024 = op
// r1024 = implicit_def
// ...
// = r1024
RemoveDeadImpDef(DstReg, *ResDstInt);
UpdateRegDefsUses(SrcReg, DstReg, SubIdx);
// SrcReg is guarateed to be the register whose live interval that is
// being merged.
li_->removeInterval(SrcReg);
if (isEmpty) {
// Now the copy is being coalesced away, the val# previously defined
// by the copy is being defined by an IMPLICIT_DEF which defines a zero
// length interval. Remove the val#.
unsigned CopyIdx = li_->getDefIndex(li_->getInstructionIndex(CopyMI));
const LiveRange *LR = ResDstInt->getLiveRangeContaining(CopyIdx);
VNInfo *ImpVal = LR->valno;
assert(ImpVal->def == CopyIdx);
unsigned NextDef = LR->end;
RemoveCopiesFromValNo(*ResDstInt, ImpVal);
ResDstInt->removeValNo(ImpVal);
LR = ResDstInt->FindLiveRangeContaining(NextDef);
if (LR != ResDstInt->end() && LR->valno->def == NextDef) {
// Special case: vr1024 = implicit_def
// vr1024 = insert_subreg vr1024, vr1025, c
// The insert_subreg becomes a "copy" that defines a val# which can itself
// be coalesced away.
MachineInstr *DefMI = li_->getInstructionFromIndex(NextDef);
if (DefMI->getOpcode() == TargetInstrInfo::INSERT_SUBREG)
LR->valno->copy = DefMI;
}
}
// If resulting interval has a preference that no longer fits because of subreg
// coalescing, just clear the preference.
if (ResDstInt->preference && (isExtSubReg || isInsSubReg) &&
TargetRegisterInfo::isVirtualRegister(ResDstInt->reg)) {
const TargetRegisterClass *RC = mri_->getRegClass(ResDstInt->reg);
if (!RC->contains(ResDstInt->preference))
ResDstInt->preference = 0;
}
DOUT << "\n\t\tJoined. Result = "; ResDstInt->print(DOUT, tri_);
DOUT << "\n";
++numJoins;
return true;
}
/// ComputeUltimateVN - Assuming we are going to join two live intervals,
/// compute what the resultant value numbers for each value in the input two
/// ranges will be. This is complicated by copies between the two which can
/// and will commonly cause multiple value numbers to be merged into one.
///
/// VN is the value number that we're trying to resolve. InstDefiningValue
/// keeps track of the new InstDefiningValue assignment for the result
/// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
/// whether a value in this or other is a copy from the opposite set.
/// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
/// already been assigned.
///
/// ThisFromOther[x] - If x is defined as a copy from the other interval, this
/// contains the value number the copy is from.
///
static unsigned ComputeUltimateVN(VNInfo *VNI,
SmallVector<VNInfo*, 16> &NewVNInfo,
DenseMap<VNInfo*, VNInfo*> &ThisFromOther,
DenseMap<VNInfo*, VNInfo*> &OtherFromThis,
SmallVector<int, 16> &ThisValNoAssignments,
SmallVector<int, 16> &OtherValNoAssignments) {
unsigned VN = VNI->id;
// If the VN has already been computed, just return it.
if (ThisValNoAssignments[VN] >= 0)
return ThisValNoAssignments[VN];
// assert(ThisValNoAssignments[VN] != -2 && "Cyclic case?");
// If this val is not a copy from the other val, then it must be a new value
// number in the destination.
DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI);
if (I == ThisFromOther.end()) {
NewVNInfo.push_back(VNI);
return ThisValNoAssignments[VN] = NewVNInfo.size()-1;
}
VNInfo *OtherValNo = I->second;
// Otherwise, this *is* a copy from the RHS. If the other side has already
// been computed, return it.
if (OtherValNoAssignments[OtherValNo->id] >= 0)
return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id];
// Mark this value number as currently being computed, then ask what the
// ultimate value # of the other value is.
ThisValNoAssignments[VN] = -2;
unsigned UltimateVN =
ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther,
OtherValNoAssignments, ThisValNoAssignments);
return ThisValNoAssignments[VN] = UltimateVN;
}
static bool InVector(VNInfo *Val, const SmallVector<VNInfo*, 8> &V) {
return std::find(V.begin(), V.end(), Val) != V.end();
}
/// RangeIsDefinedByCopyFromReg - Return true if the specified live range of
/// the specified live interval is defined by a copy from the specified
/// register.
bool SimpleRegisterCoalescing::RangeIsDefinedByCopyFromReg(LiveInterval &li,
LiveRange *LR,
unsigned Reg) {
unsigned SrcReg = li_->getVNInfoSourceReg(LR->valno);
if (SrcReg == Reg)
return true;
if (LR->valno->def == ~0U &&
TargetRegisterInfo::isPhysicalRegister(li.reg) &&
*tri_->getSuperRegisters(li.reg)) {
// It's a sub-register live interval, we may not have precise information.
// Re-compute it.
MachineInstr *DefMI = li_->getInstructionFromIndex(LR->start);
unsigned SrcReg, DstReg;
if (DefMI && tii_->isMoveInstr(*DefMI, SrcReg, DstReg) &&
DstReg == li.reg && SrcReg == Reg) {
// Cache computed info.
LR->valno->def = LR->start;
LR->valno->copy = DefMI;
return true;
}
}
return false;
}
/// SimpleJoin - Attempt to joint the specified interval into this one. The
/// caller of this method must guarantee that the RHS only contains a single
/// value number and that the RHS is not defined by a copy from this
/// interval. This returns false if the intervals are not joinable, or it
/// joins them and returns true.
bool SimpleRegisterCoalescing::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS){
assert(RHS.containsOneValue());
// Some number (potentially more than one) value numbers in the current
// interval may be defined as copies from the RHS. Scan the overlapping
// portions of the LHS and RHS, keeping track of this and looking for
// overlapping live ranges that are NOT defined as copies. If these exist, we
// cannot coalesce.
LiveInterval::iterator LHSIt = LHS.begin(), LHSEnd = LHS.end();
LiveInterval::iterator RHSIt = RHS.begin(), RHSEnd = RHS.end();
if (LHSIt->start < RHSIt->start) {
LHSIt = std::upper_bound(LHSIt, LHSEnd, RHSIt->start);
if (LHSIt != LHS.begin()) --LHSIt;
} else if (RHSIt->start < LHSIt->start) {
RHSIt = std::upper_bound(RHSIt, RHSEnd, LHSIt->start);
if (RHSIt != RHS.begin()) --RHSIt;
}
SmallVector<VNInfo*, 8> EliminatedLHSVals;
while (1) {
// Determine if these live intervals overlap.
bool Overlaps = false;
if (LHSIt->start <= RHSIt->start)
Overlaps = LHSIt->end > RHSIt->start;
else
Overlaps = RHSIt->end > LHSIt->start;
// If the live intervals overlap, there are two interesting cases: if the
// LHS interval is defined by a copy from the RHS, it's ok and we record
// that the LHS value # is the same as the RHS. If it's not, then we cannot
// coalesce these live ranges and we bail out.
if (Overlaps) {
// If we haven't already recorded that this value # is safe, check it.
if (!InVector(LHSIt->valno, EliminatedLHSVals)) {
// Copy from the RHS?
if (!RangeIsDefinedByCopyFromReg(LHS, LHSIt, RHS.reg))
return false; // Nope, bail out.
if (LHSIt->contains(RHSIt->valno->def))
// Here is an interesting situation:
// BB1:
// vr1025 = copy vr1024
// ..
// BB2:
// vr1024 = op
// = vr1025
// Even though vr1025 is copied from vr1024, it's not safe to
// coalesced them since live range of vr1025 intersects the
// def of vr1024. This happens because vr1025 is assigned the
// value of the previous iteration of vr1024.
return false;
EliminatedLHSVals.push_back(LHSIt->valno);
}
// We know this entire LHS live range is okay, so skip it now.
if (++LHSIt == LHSEnd) break;
continue;
}
if (LHSIt->end < RHSIt->end) {
if (++LHSIt == LHSEnd) break;
} else {
// One interesting case to check here. It's possible that we have
// something like "X3 = Y" which defines a new value number in the LHS,
// and is the last use of this liverange of the RHS. In this case, we
// want to notice this copy (so that it gets coalesced away) even though
// the live ranges don't actually overlap.
if (LHSIt->start == RHSIt->end) {
if (InVector(LHSIt->valno, EliminatedLHSVals)) {
// We already know that this value number is going to be merged in
// if coalescing succeeds. Just skip the liverange.
if (++LHSIt == LHSEnd) break;
} else {
// Otherwise, if this is a copy from the RHS, mark it as being merged
// in.
if (RangeIsDefinedByCopyFromReg(LHS, LHSIt, RHS.reg)) {
if (LHSIt->contains(RHSIt->valno->def))
// Here is an interesting situation:
// BB1:
// vr1025 = copy vr1024
// ..
// BB2:
// vr1024 = op
// = vr1025
// Even though vr1025 is copied from vr1024, it's not safe to
// coalesced them since live range of vr1025 intersects the
// def of vr1024. This happens because vr1025 is assigned the
// value of the previous iteration of vr1024.
return false;
EliminatedLHSVals.push_back(LHSIt->valno);
// We know this entire LHS live range is okay, so skip it now.
if (++LHSIt == LHSEnd) break;
}
}
}
if (++RHSIt == RHSEnd) break;
}
}
// If we got here, we know that the coalescing will be successful and that
// the value numbers in EliminatedLHSVals will all be merged together. Since
// the most common case is that EliminatedLHSVals has a single number, we
// optimize for it: if there is more than one value, we merge them all into
// the lowest numbered one, then handle the interval as if we were merging
// with one value number.
VNInfo *LHSValNo;
if (EliminatedLHSVals.size() > 1) {
// Loop through all the equal value numbers merging them into the smallest
// one.
VNInfo *Smallest = EliminatedLHSVals[0];
for (unsigned i = 1, e = EliminatedLHSVals.size(); i != e; ++i) {
if (EliminatedLHSVals[i]->id < Smallest->id) {
// Merge the current notion of the smallest into the smaller one.
LHS.MergeValueNumberInto(Smallest, EliminatedLHSVals[i]);
Smallest = EliminatedLHSVals[i];
} else {
// Merge into the smallest.
LHS.MergeValueNumberInto(EliminatedLHSVals[i], Smallest);
}
}
LHSValNo = Smallest;
} else if (EliminatedLHSVals.empty()) {
if (TargetRegisterInfo::isPhysicalRegister(LHS.reg) &&
*tri_->getSuperRegisters(LHS.reg))
// Imprecise sub-register information. Can't handle it.
return false;
assert(0 && "No copies from the RHS?");
} else {
LHSValNo = EliminatedLHSVals[0];
}
// Okay, now that there is a single LHS value number that we're merging the
// RHS into, update the value number info for the LHS to indicate that the
// value number is defined where the RHS value number was.
const VNInfo *VNI = RHS.getValNumInfo(0);
LHSValNo->def = VNI->def;
LHSValNo->copy = VNI->copy;
// Okay, the final step is to loop over the RHS live intervals, adding them to
// the LHS.
LHSValNo->hasPHIKill |= VNI->hasPHIKill;
LHS.addKills(LHSValNo, VNI->kills);
LHS.MergeRangesInAsValue(RHS, LHSValNo);
LHS.weight += RHS.weight;
if (RHS.preference && !LHS.preference)
LHS.preference = RHS.preference;
return true;
}
/// JoinIntervals - Attempt to join these two intervals. On failure, this
/// returns false. Otherwise, if one of the intervals being joined is a
/// physreg, this method always canonicalizes LHS to be it. The output
/// "RHS" will not have been modified, so we can use this information
/// below to update aliases.
bool SimpleRegisterCoalescing::JoinIntervals(LiveInterval &LHS,
LiveInterval &RHS, bool &Swapped) {
// Compute the final value assignment, assuming that the live ranges can be
// coalesced.
SmallVector<int, 16> LHSValNoAssignments;
SmallVector<int, 16> RHSValNoAssignments;
DenseMap<VNInfo*, VNInfo*> LHSValsDefinedFromRHS;
DenseMap<VNInfo*, VNInfo*> RHSValsDefinedFromLHS;
SmallVector<VNInfo*, 16> NewVNInfo;
// If a live interval is a physical register, conservatively check if any
// of its sub-registers is overlapping the live interval of the virtual
// register. If so, do not coalesce.
if (TargetRegisterInfo::isPhysicalRegister(LHS.reg) &&
*tri_->getSubRegisters(LHS.reg)) {
for (const unsigned* SR = tri_->getSubRegisters(LHS.reg); *SR; ++SR)
if (li_->hasInterval(*SR) && RHS.overlaps(li_->getInterval(*SR))) {
DOUT << "Interfere with sub-register ";
DEBUG(li_->getInterval(*SR).print(DOUT, tri_));
return false;
}
} else if (TargetRegisterInfo::isPhysicalRegister(RHS.reg) &&
*tri_->getSubRegisters(RHS.reg)) {
for (const unsigned* SR = tri_->getSubRegisters(RHS.reg); *SR; ++SR)
if (li_->hasInterval(*SR) && LHS.overlaps(li_->getInterval(*SR))) {
DOUT << "Interfere with sub-register ";
DEBUG(li_->getInterval(*SR).print(DOUT, tri_));
return false;
}
}
// Compute ultimate value numbers for the LHS and RHS values.
if (RHS.containsOneValue()) {
// Copies from a liveinterval with a single value are simple to handle and
// very common, handle the special case here. This is important, because
// often RHS is small and LHS is large (e.g. a physreg).
// Find out if the RHS is defined as a copy from some value in the LHS.
int RHSVal0DefinedFromLHS = -1;
int RHSValID = -1;
VNInfo *RHSValNoInfo = NULL;
VNInfo *RHSValNoInfo0 = RHS.getValNumInfo(0);
unsigned RHSSrcReg = li_->getVNInfoSourceReg(RHSValNoInfo0);
if ((RHSSrcReg == 0 || RHSSrcReg != LHS.reg)) {
// If RHS is not defined as a copy from the LHS, we can use simpler and
// faster checks to see if the live ranges are coalescable. This joiner
// can't swap the LHS/RHS intervals though.
if (!TargetRegisterInfo::isPhysicalRegister(RHS.reg)) {
return SimpleJoin(LHS, RHS);
} else {
RHSValNoInfo = RHSValNoInfo0;
}
} else {
// It was defined as a copy from the LHS, find out what value # it is.
RHSValNoInfo = LHS.getLiveRangeContaining(RHSValNoInfo0->def-1)->valno;
RHSValID = RHSValNoInfo->id;
RHSVal0DefinedFromLHS = RHSValID;
}
LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
NewVNInfo.resize(LHS.getNumValNums(), NULL);
// Okay, *all* of the values in LHS that are defined as a copy from RHS
// should now get updated.
for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
i != e; ++i) {
VNInfo *VNI = *i;
unsigned VN = VNI->id;
if (unsigned LHSSrcReg = li_->getVNInfoSourceReg(VNI)) {
if (LHSSrcReg != RHS.reg) {
// If this is not a copy from the RHS, its value number will be
// unmodified by the coalescing.
NewVNInfo[VN] = VNI;
LHSValNoAssignments[VN] = VN;
} else if (RHSValID == -1) {
// Otherwise, it is a copy from the RHS, and we don't already have a
// value# for it. Keep the current value number, but remember it.
LHSValNoAssignments[VN] = RHSValID = VN;
NewVNInfo[VN] = RHSValNoInfo;
LHSValsDefinedFromRHS[VNI] = RHSValNoInfo0;
} else {
// Otherwise, use the specified value #.
LHSValNoAssignments[VN] = RHSValID;
if (VN == (unsigned)RHSValID) { // Else this val# is dead.
NewVNInfo[VN] = RHSValNoInfo;
LHSValsDefinedFromRHS[VNI] = RHSValNoInfo0;
}
}
} else {
NewVNInfo[VN] = VNI;
LHSValNoAssignments[VN] = VN;
}
}
assert(RHSValID != -1 && "Didn't find value #?");
RHSValNoAssignments[0] = RHSValID;
if (RHSVal0DefinedFromLHS != -1) {
// This path doesn't go through ComputeUltimateVN so just set
// it to anything.
RHSValsDefinedFromLHS[RHSValNoInfo0] = (VNInfo*)1;
}
} else {
// Loop over the value numbers of the LHS, seeing if any are defined from
// the RHS.
for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
i != e; ++i) {
VNInfo *VNI = *i;
if (VNI->def == ~1U || VNI->copy == 0) // Src not defined by a copy?
continue;
// DstReg is known to be a register in the LHS interval. If the src is
// from the RHS interval, we can use its value #.
if (li_->getVNInfoSourceReg(VNI) != RHS.reg)
continue;
// Figure out the value # from the RHS.
LHSValsDefinedFromRHS[VNI]=RHS.getLiveRangeContaining(VNI->def-1)->valno;
}
// Loop over the value numbers of the RHS, seeing if any are defined from
// the LHS.
for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
i != e; ++i) {
VNInfo *VNI = *i;
if (VNI->def == ~1U || VNI->copy == 0) // Src not defined by a copy?
continue;
// DstReg is known to be a register in the RHS interval. If the src is
// from the LHS interval, we can use its value #.
if (li_->getVNInfoSourceReg(VNI) != LHS.reg)
continue;
// Figure out the value # from the LHS.
RHSValsDefinedFromLHS[VNI]=LHS.getLiveRangeContaining(VNI->def-1)->valno;
}
LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
i != e; ++i) {
VNInfo *VNI = *i;
unsigned VN = VNI->id;
if (LHSValNoAssignments[VN] >= 0 || VNI->def == ~1U)
continue;
ComputeUltimateVN(VNI, NewVNInfo,
LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
LHSValNoAssignments, RHSValNoAssignments);
}
for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
i != e; ++i) {
VNInfo *VNI = *i;
unsigned VN = VNI->id;
if (RHSValNoAssignments[VN] >= 0 || VNI->def == ~1U)
continue;
// If this value number isn't a copy from the LHS, it's a new number.
if (RHSValsDefinedFromLHS.find(VNI) == RHSValsDefinedFromLHS.end()) {
NewVNInfo.push_back(VNI);
RHSValNoAssignments[VN] = NewVNInfo.size()-1;
continue;
}
ComputeUltimateVN(VNI, NewVNInfo,
RHSValsDefinedFromLHS, LHSValsDefinedFromRHS,
RHSValNoAssignments, LHSValNoAssignments);
}
}
// Armed with the mappings of LHS/RHS values to ultimate values, walk the
// interval lists to see if these intervals are coalescable.
LiveInterval::const_iterator I = LHS.begin();
LiveInterval::const_iterator IE = LHS.end();
LiveInterval::const_iterator J = RHS.begin();
LiveInterval::const_iterator JE = RHS.end();
// Skip ahead until the first place of potential sharing.
if (I->start < J->start) {
I = std::upper_bound(I, IE, J->start);
if (I != LHS.begin()) --I;
} else if (J->start < I->start) {
J = std::upper_bound(J, JE, I->start);
if (J != RHS.begin()) --J;
}
while (1) {
// Determine if these two live ranges overlap.
bool Overlaps;
if (I->start < J->start) {
Overlaps = I->end > J->start;
} else {
Overlaps = J->end > I->start;
}
// If so, check value # info to determine if they are really different.
if (Overlaps) {
// If the live range overlap will map to the same value number in the
// result liverange, we can still coalesce them. If not, we can't.
if (LHSValNoAssignments[I->valno->id] !=
RHSValNoAssignments[J->valno->id])
return false;
}
if (I->end < J->end) {
++I;
if (I == IE) break;
} else {
++J;
if (J == JE) break;
}
}
// Update kill info. Some live ranges are extended due to copy coalescing.
for (DenseMap<VNInfo*, VNInfo*>::iterator I = LHSValsDefinedFromRHS.begin(),
E = LHSValsDefinedFromRHS.end(); I != E; ++I) {
VNInfo *VNI = I->first;
unsigned LHSValID = LHSValNoAssignments[VNI->id];
LiveInterval::removeKill(NewVNInfo[LHSValID], VNI->def);
NewVNInfo[LHSValID]->hasPHIKill |= VNI->hasPHIKill;
RHS.addKills(NewVNInfo[LHSValID], VNI->kills);
}
// Update kill info. Some live ranges are extended due to copy coalescing.
for (DenseMap<VNInfo*, VNInfo*>::iterator I = RHSValsDefinedFromLHS.begin(),
E = RHSValsDefinedFromLHS.end(); I != E; ++I) {
VNInfo *VNI = I->first;
unsigned RHSValID = RHSValNoAssignments[VNI->id];
LiveInterval::removeKill(NewVNInfo[RHSValID], VNI->def);
NewVNInfo[RHSValID]->hasPHIKill |= VNI->hasPHIKill;
LHS.addKills(NewVNInfo[RHSValID], VNI->kills);
}
// If we get here, we know that we can coalesce the live ranges. Ask the
// intervals to coalesce themselves now.
if ((RHS.ranges.size() > LHS.ranges.size() &&
TargetRegisterInfo::isVirtualRegister(LHS.reg)) ||
TargetRegisterInfo::isPhysicalRegister(RHS.reg)) {
RHS.join(LHS, &RHSValNoAssignments[0], &LHSValNoAssignments[0], NewVNInfo);
Swapped = true;
} else {
LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo);
Swapped = false;
}
return true;
}
namespace {
// DepthMBBCompare - Comparison predicate that sort first based on the loop
// depth of the basic block (the unsigned), and then on the MBB number.
struct DepthMBBCompare {
typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair;
bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const {
if (LHS.first > RHS.first) return true; // Deeper loops first
return LHS.first == RHS.first &&
LHS.second->getNumber() < RHS.second->getNumber();
}
};
}
/// getRepIntervalSize - Returns the size of the interval that represents the
/// specified register.
template<class SF>
unsigned JoinPriorityQueue<SF>::getRepIntervalSize(unsigned Reg) {
return Rc->getRepIntervalSize(Reg);
}
/// CopyRecSort::operator - Join priority queue sorting function.
///
bool CopyRecSort::operator()(CopyRec left, CopyRec right) const {
// Inner loops first.
if (left.LoopDepth > right.LoopDepth)
return false;
else if (left.LoopDepth == right.LoopDepth)
if (left.isBackEdge && !right.isBackEdge)
return false;
return true;
}
void SimpleRegisterCoalescing::CopyCoalesceInMBB(MachineBasicBlock *MBB,
std::vector<CopyRec> &TryAgain) {
DOUT << ((Value*)MBB->getBasicBlock())->getName() << ":\n";
std::vector<CopyRec> VirtCopies;
std::vector<CopyRec> PhysCopies;
std::vector<CopyRec> ImpDefCopies;
unsigned LoopDepth = loopInfo->getLoopDepth(MBB);
for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
MII != E;) {
MachineInstr *Inst = MII++;
// If this isn't a copy nor a extract_subreg, we can't join intervals.
unsigned SrcReg, DstReg;
if (Inst->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
DstReg = Inst->getOperand(0).getReg();
SrcReg = Inst->getOperand(1).getReg();
} else if (Inst->getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
DstReg = Inst->getOperand(0).getReg();
SrcReg = Inst->getOperand(2).getReg();
} else if (!tii_->isMoveInstr(*Inst, SrcReg, DstReg))
continue;
bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
if (NewHeuristic) {
JoinQueue->push(CopyRec(Inst, LoopDepth, isBackEdgeCopy(Inst, DstReg)));
} else {
if (li_->hasInterval(SrcReg) && li_->getInterval(SrcReg).empty())
ImpDefCopies.push_back(CopyRec(Inst, 0, false));
else if (SrcIsPhys || DstIsPhys)
PhysCopies.push_back(CopyRec(Inst, 0, false));
else
VirtCopies.push_back(CopyRec(Inst, 0, false));
}
}
if (NewHeuristic)
return;
// Try coalescing implicit copies first, followed by copies to / from
// physical registers, then finally copies from virtual registers to
// virtual registers.
for (unsigned i = 0, e = ImpDefCopies.size(); i != e; ++i) {
CopyRec &TheCopy = ImpDefCopies[i];
bool Again = false;
if (!JoinCopy(TheCopy, Again))
if (Again)
TryAgain.push_back(TheCopy);
}
for (unsigned i = 0, e = PhysCopies.size(); i != e; ++i) {
CopyRec &TheCopy = PhysCopies[i];
bool Again = false;
if (!JoinCopy(TheCopy, Again))
if (Again)
TryAgain.push_back(TheCopy);
}
for (unsigned i = 0, e = VirtCopies.size(); i != e; ++i) {
CopyRec &TheCopy = VirtCopies[i];
bool Again = false;
if (!JoinCopy(TheCopy, Again))
if (Again)
TryAgain.push_back(TheCopy);
}
}
void SimpleRegisterCoalescing::joinIntervals() {
DOUT << "********** JOINING INTERVALS ***********\n";
if (NewHeuristic)
JoinQueue = new JoinPriorityQueue<CopyRecSort>(this);
std::vector<CopyRec> TryAgainList;
if (loopInfo->empty()) {
// If there are no loops in the function, join intervals in function order.
for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
I != E; ++I)
CopyCoalesceInMBB(I, TryAgainList);
} else {
// Otherwise, join intervals in inner loops before other intervals.
// Unfortunately we can't just iterate over loop hierarchy here because
// there may be more MBB's than BB's. Collect MBB's for sorting.
// Join intervals in the function prolog first. We want to join physical
// registers with virtual registers before the intervals got too long.
std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs;
for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();I != E;++I){
MachineBasicBlock *MBB = I;
MBBs.push_back(std::make_pair(loopInfo->getLoopDepth(MBB), I));
}
// Sort by loop depth.
std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare());
// Finally, join intervals in loop nest order.
for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
CopyCoalesceInMBB(MBBs[i].second, TryAgainList);
}
// Joining intervals can allow other intervals to be joined. Iteratively join
// until we make no progress.
if (NewHeuristic) {
SmallVector<CopyRec, 16> TryAgain;
bool ProgressMade = true;
while (ProgressMade) {
ProgressMade = false;
while (!JoinQueue->empty()) {
CopyRec R = JoinQueue->pop();
bool Again = false;
bool Success = JoinCopy(R, Again);
if (Success)
ProgressMade = true;
else if (Again)
TryAgain.push_back(R);
}
if (ProgressMade) {
while (!TryAgain.empty()) {
JoinQueue->push(TryAgain.back());
TryAgain.pop_back();
}
}
}
} else {
bool ProgressMade = true;
while (ProgressMade) {
ProgressMade = false;
for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) {
CopyRec &TheCopy = TryAgainList[i];
if (TheCopy.MI) {
bool Again = false;
bool Success = JoinCopy(TheCopy, Again);
if (Success || !Again) {
TheCopy.MI = 0; // Mark this one as done.
ProgressMade = true;
}
}
}
}
}
if (NewHeuristic)
delete JoinQueue;
}
/// Return true if the two specified registers belong to different register
/// classes. The registers may be either phys or virt regs. In the
/// case where both registers are virtual registers, it would also returns
/// true by reference the RegB register class in SubRC if it is a subset of
/// RegA's register class.
bool
SimpleRegisterCoalescing::differingRegisterClasses(unsigned RegA, unsigned RegB,
const TargetRegisterClass *&SubRC) const {
// Get the register classes for the first reg.
if (TargetRegisterInfo::isPhysicalRegister(RegA)) {
assert(TargetRegisterInfo::isVirtualRegister(RegB) &&
"Shouldn't consider two physregs!");
return !mri_->getRegClass(RegB)->contains(RegA);
}
// Compare against the regclass for the second reg.
const TargetRegisterClass *RegClassA = mri_->getRegClass(RegA);
if (TargetRegisterInfo::isVirtualRegister(RegB)) {
const TargetRegisterClass *RegClassB = mri_->getRegClass(RegB);
if (RegClassA == RegClassB)
return false;
SubRC = (RegClassA->hasSubClass(RegClassB)) ? RegClassB : NULL;
return true;
}
return !RegClassA->contains(RegB);
}
/// lastRegisterUse - Returns the last use of the specific register between
/// cycles Start and End or NULL if there are no uses.
MachineOperand *
SimpleRegisterCoalescing::lastRegisterUse(unsigned Start, unsigned End,
unsigned Reg, unsigned &UseIdx) const{
UseIdx = 0;
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
MachineOperand *LastUse = NULL;
for (MachineRegisterInfo::use_iterator I = mri_->use_begin(Reg),
E = mri_->use_end(); I != E; ++I) {
MachineOperand &Use = I.getOperand();
MachineInstr *UseMI = Use.getParent();
unsigned SrcReg, DstReg;
if (tii_->isMoveInstr(*UseMI, SrcReg, DstReg) && SrcReg == DstReg)
// Ignore identity copies.
continue;
unsigned Idx = li_->getInstructionIndex(UseMI);
if (Idx >= Start && Idx < End && Idx >= UseIdx) {
LastUse = &Use;
UseIdx = Idx;
}
}
return LastUse;
}
int e = (End-1) / InstrSlots::NUM * InstrSlots::NUM;
int s = Start;
while (e >= s) {
// Skip deleted instructions
MachineInstr *MI = li_->getInstructionFromIndex(e);
while ((e - InstrSlots::NUM) >= s && !MI) {
e -= InstrSlots::NUM;
MI = li_->getInstructionFromIndex(e);
}
if (e < s || MI == NULL)
return NULL;
// Ignore identity copies.
unsigned SrcReg, DstReg;
if (!(tii_->isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg))
for (unsigned i = 0, NumOps = MI->getNumOperands(); i != NumOps; ++i) {
MachineOperand &Use = MI->getOperand(i);
if (Use.isRegister() && Use.isUse() && Use.getReg() &&
tri_->regsOverlap(Use.getReg(), Reg)) {
UseIdx = e;
return &Use;
}
}
e -= InstrSlots::NUM;
}
return NULL;
}
void SimpleRegisterCoalescing::printRegName(unsigned reg) const {
if (TargetRegisterInfo::isPhysicalRegister(reg))
cerr << tri_->getName(reg);
else
cerr << "%reg" << reg;
}
void SimpleRegisterCoalescing::releaseMemory() {
JoinedCopies.clear();
ReMatCopies.clear();
}
static bool isZeroLengthInterval(LiveInterval *li) {
for (LiveInterval::Ranges::const_iterator
i = li->ranges.begin(), e = li->ranges.end(); i != e; ++i)
if (i->end - i->start > LiveIntervals::InstrSlots::NUM)
return false;
return true;
}
/// TurnCopyIntoImpDef - If source of the specified copy is an implicit def,
/// turn the copy into an implicit def.
bool
SimpleRegisterCoalescing::TurnCopyIntoImpDef(MachineBasicBlock::iterator &I,
MachineBasicBlock *MBB,
unsigned DstReg, unsigned SrcReg) {
MachineInstr *CopyMI = &*I;
unsigned CopyIdx = li_->getDefIndex(li_->getInstructionIndex(CopyMI));
if (!li_->hasInterval(SrcReg))
return false;
LiveInterval &SrcInt = li_->getInterval(SrcReg);
if (!SrcInt.empty())
return false;
if (!li_->hasInterval(DstReg))
return false;
LiveInterval &DstInt = li_->getInterval(DstReg);
const LiveRange *DstLR = DstInt.getLiveRangeContaining(CopyIdx);
DstInt.removeValNo(DstLR->valno);
CopyMI->setDesc(tii_->get(TargetInstrInfo::IMPLICIT_DEF));
for (int i = CopyMI->getNumOperands() - 1, e = 0; i > e; --i)
CopyMI->RemoveOperand(i);
bool NoUse = mri_->use_empty(SrcReg);
if (NoUse) {
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(SrcReg),
E = mri_->reg_end(); I != E; ) {
assert(I.getOperand().isDef());
MachineInstr *DefMI = &*I;
++I;
// The implicit_def source has no other uses, delete it.
assert(DefMI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF);
li_->RemoveMachineInstrFromMaps(DefMI);
DefMI->eraseFromParent();
}
}
++I;
return true;
}
bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
mri_ = &fn.getRegInfo();
tm_ = &fn.getTarget();
tri_ = tm_->getRegisterInfo();
tii_ = tm_->getInstrInfo();
li_ = &getAnalysis<LiveIntervals>();
loopInfo = &getAnalysis<MachineLoopInfo>();
DOUT << "********** SIMPLE REGISTER COALESCING **********\n"
<< "********** Function: "
<< ((Value*)mf_->getFunction())->getName() << '\n';
allocatableRegs_ = tri_->getAllocatableSet(fn);
for (TargetRegisterInfo::regclass_iterator I = tri_->regclass_begin(),
E = tri_->regclass_end(); I != E; ++I)
allocatableRCRegs_.insert(std::make_pair(*I,
tri_->getAllocatableSet(fn, *I)));
// Join (coalesce) intervals if requested.
if (EnableJoining) {
joinIntervals();
DOUT << "********** INTERVALS POST JOINING **********\n";
for (LiveIntervals::iterator I = li_->begin(), E = li_->end(); I != E; ++I){
I->second->print(DOUT, tri_);
DOUT << "\n";
}
}
// Perform a final pass over the instructions and compute spill weights
// and remove identity moves.
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
MachineBasicBlock* mbb = mbbi;
unsigned loopDepth = loopInfo->getLoopDepth(mbb);
for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
mii != mie; ) {
MachineInstr *MI = mii;
unsigned SrcReg, DstReg;
if (JoinedCopies.count(MI)) {
// Delete all coalesced copies.
if (!tii_->isMoveInstr(*MI, SrcReg, DstReg)) {
assert((MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG ||
MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG) &&
"Unrecognized copy instruction");
DstReg = MI->getOperand(0).getReg();
}
if (MI->registerDefIsDead(DstReg)) {
LiveInterval &li = li_->getInterval(DstReg);
if (!ShortenDeadCopySrcLiveRange(li, MI))
ShortenDeadCopyLiveRange(li, MI);
}
li_->RemoveMachineInstrFromMaps(MI);
mii = mbbi->erase(mii);
++numPeep;
continue;
}
// If the move will be an identity move delete it
bool isMove = tii_->isMoveInstr(*mii, SrcReg, DstReg);
if (isMove && SrcReg == DstReg) {
if (li_->hasInterval(SrcReg)) {
LiveInterval &RegInt = li_->getInterval(SrcReg);
// If def of this move instruction is dead, remove its live range
// from the dstination register's live interval.
if (mii->registerDefIsDead(DstReg)) {
if (!ShortenDeadCopySrcLiveRange(RegInt, mii))
ShortenDeadCopyLiveRange(RegInt, mii);
}
}
li_->RemoveMachineInstrFromMaps(mii);
mii = mbbi->erase(mii);
++numPeep;
} else if (!isMove || !TurnCopyIntoImpDef(mii, mbb, DstReg, SrcReg)) {
SmallSet<unsigned, 4> UniqueUses;
for (unsigned i = 0, e = mii->getNumOperands(); i != e; ++i) {
const MachineOperand &mop = mii->getOperand(i);
if (mop.isRegister() && mop.getReg() &&
TargetRegisterInfo::isVirtualRegister(mop.getReg())) {
unsigned reg = mop.getReg();
// Multiple uses of reg by the same instruction. It should not
// contribute to spill weight again.
if (UniqueUses.count(reg) != 0)
continue;
LiveInterval &RegInt = li_->getInterval(reg);
RegInt.weight +=
li_->getSpillWeight(mop.isDef(), mop.isUse(), loopDepth);
UniqueUses.insert(reg);
}
}
++mii;
}
}
}
for (LiveIntervals::iterator I = li_->begin(), E = li_->end(); I != E; ++I) {
LiveInterval &LI = *I->second;
if (TargetRegisterInfo::isVirtualRegister(LI.reg)) {
// If the live interval length is essentially zero, i.e. in every live
// range the use follows def immediately, it doesn't make sense to spill
// it and hope it will be easier to allocate for this li.
if (isZeroLengthInterval(&LI))
LI.weight = HUGE_VALF;
else {
bool isLoad = false;
if (li_->isReMaterializable(LI, isLoad)) {
// If all of the definitions of the interval are re-materializable,
// it is a preferred candidate for spilling. If non of the defs are
// loads, then it's potentially very cheap to re-materialize.
// FIXME: this gets much more complicated once we support non-trivial
// re-materialization.
if (isLoad)
LI.weight *= 0.9F;
else
LI.weight *= 0.5F;
}
}
// Slightly prefer live interval that has been assigned a preferred reg.
if (LI.preference)
LI.weight *= 1.01F;
// Divide the weight of the interval by its size. This encourages
// spilling of intervals that are large and have few uses, and
// discourages spilling of small intervals with many uses.
LI.weight /= li_->getApproximateInstructionCount(LI) * InstrSlots::NUM;
}
}
DEBUG(dump());
return true;
}
/// print - Implement the dump method.
void SimpleRegisterCoalescing::print(std::ostream &O, const Module* m) const {
li_->print(O, m);
}
RegisterCoalescer* llvm::createSimpleRegisterCoalescer() {
return new SimpleRegisterCoalescing();
}
// Make sure that anything that uses RegisterCoalescer pulls in this file...
DEFINING_FILE_FOR(SimpleRegisterCoalescing)
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