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llvm-mirror/lib/CodeGen/SimpleRegisterCoalescing.cpp
Evan Cheng 07d521ed99 Fix a pasto. Also simplify for Bill's benefit. 
llvm-svn: 82505
2009-09-22 01:48:19 +00:00

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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/Target/TargetOptions.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.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(numCrossRCs , "Number of cross class 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");
STATISTIC(numDeadValNo, "Number of valno def marked dead");
char SimpleRegisterCoalescing::ID = 0;
static cl::opt<bool>
EnableJoining("join-liveintervals",
cl::desc("Coalesce copies (default=true)"),
cl::init(true));
static cl::opt<bool>
DisableCrossClassJoin("disable-cross-class-join",
cl::desc("Avoid coalescing cross register class copies"),
cl::init(false), cl::Hidden);
static cl::opt<bool>
PhysJoinTweak("tweak-phys-join-heuristics",
cl::desc("Tweak heuristics for joining phys reg with vr"),
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.setPreservesCFG();
AU.addRequired<LiveIntervals>();
AU.addPreserved<LiveIntervals>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreservedID(MachineDominatorsID);
if (StrongPHIElim)
AU.addPreservedID(StrongPHIEliminationID);
else
AU.addPreservedID(PHIEliminationID);
AU.addPreservedID(TwoAddressInstructionPassID);
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) {
MachineInstrIndex 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);
assert(BLR != IntB.end() && "Live range not found!");
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->getCopy()) 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.
MachineInstrIndex CopyUseIdx = li_->getUseIndex(CopyIdx);
LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyUseIdx);
assert(ALR != IntA.end() && "Live range not found!");
VNInfo *AValNo = ALR->valno;
// If it's re-defined by an early clobber somewhere in the live range, then
// it's not safe to eliminate the copy. FIXME: This is a temporary workaround.
// See PR3149:
// 172 %ECX<def> = MOV32rr %reg1039<kill>
// 180 INLINEASM <es:subl $5,$1
// sbbl $3,$0>, 10, %EAX<def>, 14, %ECX<earlyclobber,def>, 9, %EAX<kill>,
// 36, <fi#0>, 1, %reg0, 0, 9, %ECX<kill>, 36, <fi#1>, 1, %reg0, 0
// 188 %EAX<def> = MOV32rr %EAX<kill>
// 196 %ECX<def> = MOV32rr %ECX<kill>
// 204 %ECX<def> = MOV32rr %ECX<kill>
// 212 %EAX<def> = MOV32rr %EAX<kill>
// 220 %EAX<def> = MOV32rr %EAX
// 228 %reg1039<def> = MOV32rr %ECX<kill>
// The early clobber operand ties ECX input to the ECX def.
//
// The live interval of ECX is represented as this:
// %reg20,inf = [46,47:1)[174,230:0) 0@174-(230) 1@46-(47)
// The coalescer has no idea there was a def in the middle of [174,230].
if (AValNo->hasRedefByEC())
return false;
// 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(li_->getPrevSlot(AValNo->def));
assert(ValLR != IntB.end() && "Live range not found!");
// Make sure that the end of the live range is inside the same block as
// CopyMI.
MachineInstr *ValLREndInst =
li_->getInstructionFromIndex(li_->getPrevSlot(ValLR->end));
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))) {
DEBUG({
errs() << "Interfere with sub-register ";
li_->getInterval(*SR).print(errs(), tri_);
});
return false;
}
}
DEBUG({
errs() << "\nExtending: ";
IntB.print(errs(), tri_);
});
MachineInstrIndex 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->setCopy(0);
// 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 sub-registers, update their live intervals as well.
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) {
LiveInterval &SRLI = li_->getInterval(*SR);
SRLI.addRange(LiveRange(FillerStart, FillerEnd,
SRLI.getNextValue(FillerStart, 0, true,
li_->getVNInfoAllocator())));
}
}
// Okay, merge "B1" into the same value number as "B0".
if (BValNo != ValLR->valno) {
IntB.addKills(ValLR->valno, BValNo->kills);
IntB.MergeValueNumberInto(BValNo, ValLR->valno);
}
DEBUG({
errs() << " result = ";
IntB.print(errs(), tri_);
errs() << "\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);
ValLR->valno->removeKill(FillerStart);
}
// If the copy instruction was killing the destination register before the
// merge, find the last use and trim the live range. That will also add the
// isKill marker.
if (CopyMI->killsRegister(IntA.reg))
TrimLiveIntervalToLastUse(CopyUseIdx, CopyMI->getParent(), IntA, ALR);
++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) {
MachineInstrIndex 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);
assert(BLR != IntB.end() && "Live range not found!");
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->getCopy()) 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(li_->getPrevSlot(CopyIdx));
assert(ALR != IntA.end() && "Live range not found!");
VNInfo *AValNo = ALR->valno;
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization. FIXME: Do isPHIDef and isDefAccurate both need to be
// tested?
if (AValNo->isPHIDef() || !AValNo->isDefAccurate() ||
AValNo->isUnused() || AValNo->hasPHIKill())
return false;
MachineInstr *DefMI = li_->getInstructionFromIndex(AValNo->def);
const TargetInstrDesc &TID = DefMI->getDesc();
if (!TID.isCommutable())
return false;
// If DefMI is a two-address instruction then commuting it will change the
// destination register.
int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg);
assert(DefIdx != -1);
unsigned UseOpIdx;
if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx))
return false;
unsigned Op1, Op2, NewDstIdx;
if (!tii_->findCommutedOpIndices(DefMI, Op1, Op2))
return false;
if (Op1 == UseOpIdx)
NewDstIdx = Op2;
else if (Op2 == UseOpIdx)
NewDstIdx = Op1;
else
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;
MachineInstrIndex 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;
VNInfo::KillSet BKills;
std::map<MachineInstrIndex, MachineInstrIndex> 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.
bool BHasSubRegs = false;
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg))
BHasSubRegs = *tri_->getSubRegisters(IntB.reg);
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;
MachineInstrIndex 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_->getNextSlot(li_->getUseIndex(UseIdx)));
}
unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
if (!tii_->isMoveInstr(*UseMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx))
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.
MachineInstrIndex 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.
DEBUG({
errs() << "\nExtending: ";
IntB.print(errs(), tri_);
});
// Remove val#'s defined by copies that will be coalesced away.
for (unsigned i = 0, e = BDeadValNos.size(); i != e; ++i) {
VNInfo *DeadVNI = BDeadValNos[i];
if (BHasSubRegs) {
for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) {
LiveInterval &SRLI = li_->getInterval(*SR);
const LiveRange *SRLR = SRLI.getLiveRangeContaining(DeadVNI->def);
SRLI.removeValNo(SRLR->valno);
}
}
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->setCopy(0);
for (unsigned j = 0, ee = ValNo->kills.size(); j != ee; ++j) {
if (ValNo->kills[j] != BLR->end)
BKills.push_back(ValNo->kills[j]);
}
ValNo->kills.clear();
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
AI != AE; ++AI) {
if (AI->valno != AValNo) continue;
MachineInstrIndex End = AI->end;
std::map<MachineInstrIndex, MachineInstrIndex>::iterator
EI = BExtend.find(End);
if (EI != BExtend.end())
End = EI->second;
IntB.addRange(LiveRange(AI->start, End, ValNo));
// If the IntB live range is assigned to a physical register, and if that
// physreg has sub-registers, update their live intervals as well.
if (BHasSubRegs) {
for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) {
LiveInterval &SRLI = li_->getInterval(*SR);
SRLI.MergeInClobberRange(AI->start, End, li_->getVNInfoAllocator());
}
}
}
IntB.addKills(ValNo, BKills);
ValNo->setHasPHIKill(BHasPHIKill);
DEBUG({
errs() << " result = ";
IntB.print(errs(), tri_);
errs() << '\n';
errs() << "\nShortening: ";
IntA.print(errs(), tri_);
});
IntA.removeValNo(AValNo);
DEBUG({
errs() << " result = ";
IntA.print(errs(), tri_);
errs() << '\n';
});
++numCommutes;
return true;
}
/// 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);
}
/// 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,
MachineInstrIndex Start, MachineInstrIndex 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);
MachineInstrIndex RemoveStart = Start;
MachineInstrIndex RemoveEnd = Start;
while (RemoveEnd != End) {
LiveInterval::iterator LR = sli.FindLiveRangeContaining(RemoveStart);
if (LR == sli.end())
break;
RemoveEnd = (LR->end < End) ? LR->end : End;
sli.removeRange(RemoveStart, RemoveEnd, true);
RemoveStart = RemoveEnd;
}
}
}
}
/// TrimLiveIntervalToLastUse - If there is a last use in the same basic block
/// as the copy instruction, trim the live interval to the last use and return
/// true.
bool
SimpleRegisterCoalescing::TrimLiveIntervalToLastUse(MachineInstrIndex CopyIdx,
MachineBasicBlock *CopyMBB,
LiveInterval &li,
const LiveRange *LR) {
MachineInstrIndex MBBStart = li_->getMBBStartIdx(CopyMBB);
MachineInstrIndex LastUseIdx;
MachineOperand *LastUse =
lastRegisterUse(LR->start, li_->getPrevSlot(CopyIdx), 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 true;
}
// 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_);
LR->valno->addKill(li_->getNextSlot(LastUseIdx));
unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
if (tii_->isMoveInstr(*LastUseMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) &&
DstReg == li.reg) {
// Last use is itself an identity code.
int DeadIdx = LastUseMI->findRegisterDefOperandIdx(li.reg, false, tri_);
LastUseMI->getOperand(DeadIdx).setIsDead();
}
return true;
}
// Is it livein?
if (LR->start <= MBBStart && LR->end > MBBStart) {
if (LR->start == MachineInstrIndex()) {
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.
}
return false;
}
/// 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,
unsigned DstSubIdx,
MachineInstr *CopyMI) {
MachineInstrIndex CopyIdx = li_->getUseIndex(li_->getInstructionIndex(CopyMI));
LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
assert(SrcLR != SrcInt.end() && "Live range not found!");
VNInfo *ValNo = SrcLR->valno;
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization. FIXME: Do isPHIDef and isDefAccurate both need to be
// tested?
if (ValNo->isPHIDef() || !ValNo->isDefAccurate() ||
ValNo->isUnused() || ValNo->hasPHIKill())
return false;
MachineInstr *DefMI = li_->getInstructionFromIndex(ValNo->def);
const TargetInstrDesc &TID = DefMI->getDesc();
if (!TID.isAsCheapAsAMove())
return false;
if (!DefMI->getDesc().isRematerializable() ||
!tii_->isTriviallyReMaterializable(DefMI))
return false;
bool SawStore = false;
if (!DefMI->isSafeToMove(tii_, SawStore))
return false;
if (TID.getNumDefs() != 1)
return false;
if (DefMI->getOpcode() != TargetInstrInfo::IMPLICIT_DEF) {
// Make sure the copy destination register class fits the instruction
// definition register class. The mismatch can happen as a result of earlier
// extract_subreg, insert_subreg, subreg_to_reg coalescing.
const TargetRegisterClass *RC = TID.OpInfo[0].getRegClass(tri_);
if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
if (mri_->getRegClass(DstReg) != RC)
return false;
} else if (!RC->contains(DstReg))
return false;
}
// If destination register has a sub-register index on it, make sure it mtches
// the instruction register class.
if (DstSubIdx) {
const TargetInstrDesc &TID = DefMI->getDesc();
if (TID.getNumDefs() != 1)
return false;
const TargetRegisterClass *DstRC = mri_->getRegClass(DstReg);
const TargetRegisterClass *DstSubRC =
DstRC->getSubRegisterRegClass(DstSubIdx);
const TargetRegisterClass *DefRC = TID.OpInfo[0].getRegClass(tri_);
if (DefRC == DstRC)
DstSubIdx = 0;
else if (DefRC != DstSubRC)
return false;
}
MachineInstrIndex DefIdx = li_->getDefIndex(CopyIdx);
const LiveRange *DLR= li_->getInterval(DstReg).getLiveRangeContaining(DefIdx);
DLR->valno->setCopy(0);
// Don't forget to update sub-register intervals.
if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
for (const unsigned* SR = tri_->getSubRegisters(DstReg); *SR; ++SR) {
if (!li_->hasInterval(*SR))
continue;
DLR = li_->getInterval(*SR).getLiveRangeContaining(DefIdx);
if (DLR && DLR->valno->getCopy() == CopyMI)
DLR->valno->setCopy(0);
}
}
// If copy kills the source register, find the last use and propagate
// kill.
bool checkForDeadDef = false;
MachineBasicBlock *MBB = CopyMI->getParent();
if (CopyMI->killsRegister(SrcInt.reg))
if (!TrimLiveIntervalToLastUse(CopyIdx, MBB, SrcInt, SrcLR)) {
checkForDeadDef = true;
}
MachineBasicBlock::iterator MII = next(MachineBasicBlock::iterator(CopyMI));
tii_->reMaterialize(*MBB, MII, DstReg, DstSubIdx, DefMI);
MachineInstr *NewMI = prior(MII);
if (checkForDeadDef) {
// PR4090 fix: Trim interval failed because there was no use of the
// source interval in this MBB. If the def is in this MBB too then we
// should mark it dead:
if (DefMI->getParent() == MBB) {
DefMI->addRegisterDead(SrcInt.reg, tri_);
SrcLR->end = li_->getNextSlot(SrcLR->start);
}
}
// CopyMI may have implicit operands, 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->getCopy() == CopyMI)
DLR->valno->setCopy(0);
}
}
li_->ReplaceMachineInstrInMaps(CopyMI, NewMI);
CopyMI->eraseFromParent();
ReMatCopies.insert(CopyMI);
ReMatDefs.insert(DefMI);
++NumReMats;
return true;
}
/// 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, CopySrcSubIdx, CopyDstSubIdx;
if (tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg,
CopySrcSubIdx, CopyDstSubIdx) &&
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,
CopyDstSubIdx, UseMI))
continue;
}
O.setReg(UseDstReg);
O.setSubReg(0);
continue;
}
// 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);
// After updating the operand, check if the machine instruction has
// become a copy. If so, update its val# information.
if (JoinedCopies.count(UseMI))
continue;
const TargetInstrDesc &TID = UseMI->getDesc();
unsigned CopySrcReg, CopyDstReg, CopySrcSubIdx, CopyDstSubIdx;
if (TID.getNumDefs() == 1 && TID.getNumOperands() > 2 &&
tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg,
CopySrcSubIdx, CopyDstSubIdx) &&
CopySrcReg != CopyDstReg &&
(TargetRegisterInfo::isVirtualRegister(CopyDstReg) ||
allocatableRegs_[CopyDstReg])) {
LiveInterval &LI = li_->getInterval(CopyDstReg);
MachineInstrIndex DefIdx =
li_->getDefIndex(li_->getInstructionIndex(UseMI));
if (const LiveRange *DLR = LI.getLiveRangeContaining(DefIdx)) {
if (DLR->valno->def == DefIdx)
DLR->valno->setCopy(UseMI);
}
}
}
}
/// 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())
continue;
MachineInstr *UseMI = UseMO.getParent();
MachineInstrIndex UseIdx =
li_->getUseIndex(li_->getInstructionIndex(UseMI));
const LiveRange *LR = LI.getLiveRangeContaining(UseIdx);
if (!LR || !LR->valno->isKill(li_->getNextSlot(UseIdx))) {
if (LR->valno->def != li_->getNextSlot(UseIdx)) {
// Interesting problem. After coalescing reg1027's def and kill are both
// at the same point: %reg1027,0.000000e+00 = [56,814:0) 0@70-(814)
//
// bb5:
// 60 %reg1027<def> = t2MOVr %reg1027, 14, %reg0, %reg0
// 68 %reg1027<def> = t2LDRi12 %reg1027<kill>, 8, 14, %reg0
// 76 t2CMPzri %reg1038<kill,undef>, 0, 14, %reg0, %CPSR<imp-def>
// 84 %reg1027<def> = t2MOVr %reg1027, 14, %reg0, %reg0
// 96 t2Bcc mbb<bb5,0x2030910>, 1, %CPSR<kill>
//
// Do not remove the kill marker on t2LDRi12.
UseMO.setIsKill(false);
}
}
}
}
/// 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) {
MachineInstrIndex CopyIdx = li_->getInstructionIndex(CopyMI);
LiveInterval::iterator MLR =
li.FindLiveRangeContaining(li_->getDefIndex(CopyIdx));
if (MLR == li.end())
return false; // Already removed by ShortenDeadCopySrcLiveRange.
MachineInstrIndex RemoveStart = MLR->start;
MachineInstrIndex RemoveEnd = MLR->end;
MachineInstrIndex DefIdx = li_->getDefIndex(CopyIdx);
// Remove the liverange that's defined by this.
if (RemoveStart == DefIdx && RemoveEnd == li_->getNextSlot(DefIdx)) {
removeRange(li, RemoveStart, RemoveEnd, li_, tri_);
return removeIntervalIfEmpty(li, li_, tri_);
}
return false;
}
/// RemoveDeadDef - If a def of a live interval is now determined dead, remove
/// the val# it defines. If the live interval becomes empty, remove it as well.
bool SimpleRegisterCoalescing::RemoveDeadDef(LiveInterval &li,
MachineInstr *DefMI) {
MachineInstrIndex DefIdx = li_->getDefIndex(li_->getInstructionIndex(DefMI));
LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx);
if (DefIdx != MLR->valno->def)
return false;
li.removeValNo(MLR->valno);
return removeIntervalIfEmpty(li, li_, tri_);
}
/// PropagateDeadness - Propagate the dead marker to the instruction which
/// defines the val#.
static void PropagateDeadness(LiveInterval &li, MachineInstr *CopyMI,
MachineInstrIndex &LRStart, LiveIntervals *li_,
const TargetRegisterInfo* tri_) {
MachineInstr *DefMI =
li_->getInstructionFromIndex(li_->getDefIndex(LRStart));
if (DefMI && DefMI != CopyMI) {
int DeadIdx = DefMI->findRegisterDefOperandIdx(li.reg, false);
if (DeadIdx != -1)
DefMI->getOperand(DeadIdx).setIsDead();
else
DefMI->addOperand(MachineOperand::CreateReg(li.reg,
true, true, false, true));
LRStart = li_->getNextSlot(LRStart);
}
}
/// 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) {
MachineInstrIndex CopyIdx = li_->getInstructionIndex(CopyMI);
if (CopyIdx == MachineInstrIndex()) {
// 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(li_->getPrevSlot(CopyIdx));
if (LR == li.end())
// Livein but defined by a phi.
return false;
MachineInstrIndex RemoveStart = LR->start;
MachineInstrIndex RemoveEnd = li_->getNextSlot(li_->getDefIndex(CopyIdx));
if (LR->end > RemoveEnd)
// More uses past this copy? Nothing to do.
return false;
// If there is a last use in the same bb, we can't remove the live range.
// Shorten the live interval and return.
MachineBasicBlock *CopyMBB = CopyMI->getParent();
if (TrimLiveIntervalToLastUse(CopyIdx, CopyMBB, li, LR))
return false;
// There are other kills of the val#. Nothing to do.
if (!li.isOnlyLROfValNo(LR))
return false;
MachineBasicBlock *StartMBB = li_->getMBBFromIndex(RemoveStart);
if (!isSameOrFallThroughBB(StartMBB, CopyMBB, tii_))
// If the live range starts in another mbb and the copy mbb is not a fall
// through mbb, then we can only cut the range from the beginning of the
// copy mbb.
RemoveStart = li_->getNextSlot(li_->getMBBStartIdx(CopyMBB));
if (LR->valno->def == RemoveStart) {
// If the def MI defines the val# and this copy is the only kill of the
// val#, then propagate the dead marker.
PropagateDeadness(li, CopyMI, RemoveStart, li_, tri_);
++numDeadValNo;
if (LR->valno->isKill(RemoveEnd))
LR->valno->removeKill(RemoveEnd);
}
removeRange(li, RemoveStart, RemoveEnd, 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;
// Make sure this is the only use.
for (MachineRegisterInfo::use_iterator UI = mri_->use_begin(ImpLi.reg),
UE = mri_->use_end(); UI != UE;) {
MachineInstr *UseMI = &*UI;
++UI;
if (CopyMI == UseMI || JoinedCopies.count(UseMI))
continue;
return false;
}
return true;
}
/// isWinToJoinVRWithSrcPhysReg - Return true if it's worth while to join a
/// a virtual destination register with physical source register.
bool
SimpleRegisterCoalescing::isWinToJoinVRWithSrcPhysReg(MachineInstr *CopyMI,
MachineBasicBlock *CopyMBB,
LiveInterval &DstInt,
LiveInterval &SrcInt) {
// 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.
const TargetRegisterClass *RC = mri_->getRegClass(DstInt.reg);
unsigned Threshold = allocatableRCRegs_[RC].count() * 2;
unsigned Length = li_->getApproximateInstructionCount(DstInt);
if (Length > Threshold &&
(((float)std::distance(mri_->use_begin(DstInt.reg),
mri_->use_end()) / Length) < (1.0 / Threshold)))
return false;
// If the virtual register live interval extends into a loop, turn down
// aggressiveness.
MachineInstrIndex CopyIdx =
li_->getDefIndex(li_->getInstructionIndex(CopyMI));
const MachineLoop *L = loopInfo->getLoopFor(CopyMBB);
if (!L) {
// Let's see if the virtual register live interval extends into the loop.
LiveInterval::iterator DLR = DstInt.FindLiveRangeContaining(CopyIdx);
assert(DLR != DstInt.end() && "Live range not found!");
DLR = DstInt.FindLiveRangeContaining(li_->getNextSlot(DLR->end));
if (DLR != DstInt.end()) {
CopyMBB = li_->getMBBFromIndex(DLR->start);
L = loopInfo->getLoopFor(CopyMBB);
}
}
if (!L || Length <= Threshold)
return true;
MachineInstrIndex UseIdx = li_->getUseIndex(CopyIdx);
LiveInterval::iterator SLR = SrcInt.FindLiveRangeContaining(UseIdx);
MachineBasicBlock *SMBB = li_->getMBBFromIndex(SLR->start);
if (loopInfo->getLoopFor(SMBB) != L) {
if (!loopInfo->isLoopHeader(CopyMBB))
return false;
// If vr's live interval extends pass the loop header, do not join.
for (MachineBasicBlock::succ_iterator SI = CopyMBB->succ_begin(),
SE = CopyMBB->succ_end(); SI != SE; ++SI) {
MachineBasicBlock *SuccMBB = *SI;
if (SuccMBB == CopyMBB)
continue;
if (DstInt.overlaps(li_->getMBBStartIdx(SuccMBB),
li_->getNextSlot(li_->getMBBEndIdx(SuccMBB))))
return false;
}
}
return true;
}
/// isWinToJoinVRWithDstPhysReg - Return true if it's worth while to join a
/// copy from a virtual source register to a physical destination register.
bool
SimpleRegisterCoalescing::isWinToJoinVRWithDstPhysReg(MachineInstr *CopyMI,
MachineBasicBlock *CopyMBB,
LiveInterval &DstInt,
LiveInterval &SrcInt) {
// 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.
const TargetRegisterClass *RC = mri_->getRegClass(SrcInt.reg);
unsigned Threshold = allocatableRCRegs_[RC].count() * 2;
unsigned Length = li_->getApproximateInstructionCount(SrcInt);
if (Length > Threshold &&
(((float)std::distance(mri_->use_begin(SrcInt.reg),
mri_->use_end()) / Length) < (1.0 / Threshold)))
return false;
if (SrcInt.empty())
// Must be implicit_def.
return false;
// If the virtual register live interval is defined or cross a loop, turn
// down aggressiveness.
MachineInstrIndex CopyIdx =
li_->getDefIndex(li_->getInstructionIndex(CopyMI));
MachineInstrIndex UseIdx = li_->getUseIndex(CopyIdx);
LiveInterval::iterator SLR = SrcInt.FindLiveRangeContaining(UseIdx);
assert(SLR != SrcInt.end() && "Live range not found!");
SLR = SrcInt.FindLiveRangeContaining(li_->getPrevSlot(SLR->start));
if (SLR == SrcInt.end())
return true;
MachineBasicBlock *SMBB = li_->getMBBFromIndex(SLR->start);
const MachineLoop *L = loopInfo->getLoopFor(SMBB);
if (!L || Length <= Threshold)
return true;
if (loopInfo->getLoopFor(CopyMBB) != L) {
if (SMBB != L->getLoopLatch())
return false;
// If vr's live interval is extended from before the loop latch, do not
// join.
for (MachineBasicBlock::pred_iterator PI = SMBB->pred_begin(),
PE = SMBB->pred_end(); PI != PE; ++PI) {
MachineBasicBlock *PredMBB = *PI;
if (PredMBB == SMBB)
continue;
if (SrcInt.overlaps(li_->getMBBStartIdx(PredMBB),
li_->getNextSlot(li_->getMBBEndIdx(PredMBB))))
return false;
}
}
return true;
}
/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
/// two virtual registers from different register classes.
bool
SimpleRegisterCoalescing::isWinToJoinCrossClass(unsigned LargeReg,
unsigned SmallReg,
unsigned Threshold) {
// Then make sure the intervals are *short*.
LiveInterval &LargeInt = li_->getInterval(LargeReg);
LiveInterval &SmallInt = li_->getInterval(SmallReg);
unsigned LargeSize = li_->getApproximateInstructionCount(LargeInt);
unsigned SmallSize = li_->getApproximateInstructionCount(SmallInt);
if (SmallSize > Threshold || LargeSize > Threshold)
if ((float)std::distance(mri_->use_begin(SmallReg),
mri_->use_end()) / SmallSize <
(float)std::distance(mri_->use_begin(LargeReg),
mri_->use_end()) / LargeSize)
return false;
return true;
}
/// HasIncompatibleSubRegDefUse - If we are trying to coalesce a virtual
/// register with a physical register, check if any of the virtual register
/// operand is a sub-register use or def. If so, make sure it won't result
/// in an illegal extract_subreg or insert_subreg instruction. e.g.
/// vr1024 = extract_subreg vr1025, 1
/// ...
/// vr1024 = mov8rr AH
/// If vr1024 is coalesced with AH, the extract_subreg is now illegal since
/// AH does not have a super-reg whose sub-register 1 is AH.
bool
SimpleRegisterCoalescing::HasIncompatibleSubRegDefUse(MachineInstr *CopyMI,
unsigned VirtReg,
unsigned PhysReg) {
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(VirtReg),
E = mri_->reg_end(); I != E; ++I) {
MachineOperand &O = I.getOperand();
MachineInstr *MI = &*I;
if (MI == CopyMI || JoinedCopies.count(MI))
continue;
unsigned SubIdx = O.getSubReg();
if (SubIdx && !tri_->getSubReg(PhysReg, SubIdx))
return true;
if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
SubIdx = MI->getOperand(2).getImm();
if (O.isUse() && !tri_->getSubReg(PhysReg, SubIdx))
return true;
if (O.isDef()) {
unsigned SrcReg = MI->getOperand(1).getReg();
const TargetRegisterClass *RC =
TargetRegisterInfo::isPhysicalRegister(SrcReg)
? tri_->getPhysicalRegisterRegClass(SrcReg)
: mri_->getRegClass(SrcReg);
if (!tri_->getMatchingSuperReg(PhysReg, SubIdx, RC))
return true;
}
}
if (MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) {
SubIdx = MI->getOperand(3).getImm();
if (VirtReg == MI->getOperand(0).getReg()) {
if (!tri_->getSubReg(PhysReg, SubIdx))
return true;
} else {
unsigned DstReg = MI->getOperand(0).getReg();
const TargetRegisterClass *RC =
TargetRegisterInfo::isPhysicalRegister(DstReg)
? tri_->getPhysicalRegisterRegClass(DstReg)
: mri_->getRegClass(DstReg);
if (!tri_->getMatchingSuperReg(PhysReg, SubIdx, RC))
return true;
}
}
}
return false;
}
/// CanJoinExtractSubRegToPhysReg - Return true if it's possible to coalesce
/// an extract_subreg where dst is a physical register, e.g.
/// cl = EXTRACT_SUBREG reg1024, 1
bool
SimpleRegisterCoalescing::CanJoinExtractSubRegToPhysReg(unsigned DstReg,
unsigned SrcReg, unsigned SubIdx,
unsigned &RealDstReg) {
const TargetRegisterClass *RC = mri_->getRegClass(SrcReg);
RealDstReg = tri_->getMatchingSuperReg(DstReg, SubIdx, RC);
assert(RealDstReg && "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.
LiveInterval &RHS = li_->getInterval(SrcReg);
if (li_->hasInterval(RealDstReg) &&
RHS.overlaps(li_->getInterval(RealDstReg))) {
DEBUG({
errs() << "Interfere with register ";
li_->getInterval(RealDstReg).print(errs(), tri_);
});
return false; // Not coalescable
}
for (const unsigned* SR = tri_->getSubRegisters(RealDstReg); *SR; ++SR)
if (li_->hasInterval(*SR) && RHS.overlaps(li_->getInterval(*SR))) {
DEBUG({
errs() << "Interfere with sub-register ";
li_->getInterval(*SR).print(errs(), tri_);
});
return false; // Not coalescable
}
return true;
}
/// CanJoinInsertSubRegToPhysReg - Return true if it's possible to coalesce
/// an insert_subreg where src is a physical register, e.g.
/// reg1024 = INSERT_SUBREG reg1024, c1, 0
bool
SimpleRegisterCoalescing::CanJoinInsertSubRegToPhysReg(unsigned DstReg,
unsigned SrcReg, unsigned SubIdx,
unsigned &RealSrcReg) {
const TargetRegisterClass *RC = mri_->getRegClass(DstReg);
RealSrcReg = tri_->getMatchingSuperReg(SrcReg, SubIdx, RC);
assert(RealSrcReg && "Invalid extract_subreg instruction!");
LiveInterval &RHS = li_->getInterval(DstReg);
if (li_->hasInterval(RealSrcReg) &&
RHS.overlaps(li_->getInterval(RealSrcReg))) {
DEBUG({
errs() << "Interfere with register ";
li_->getInterval(RealSrcReg).print(errs(), tri_);
});
return false; // Not coalescable
}
for (const unsigned* SR = tri_->getSubRegisters(RealSrcReg); *SR; ++SR)
if (li_->hasInterval(*SR) && RHS.overlaps(li_->getInterval(*SR))) {
DEBUG({
errs() << "Interfere with sub-register ";
li_->getInterval(*SR).print(errs(), tri_);
});
return false; // Not coalescable
}
return true;
}
/// getRegAllocPreference - Return register allocation preference register.
///
static unsigned getRegAllocPreference(unsigned Reg, MachineFunction &MF,
MachineRegisterInfo *MRI,
const TargetRegisterInfo *TRI) {
if (TargetRegisterInfo::isPhysicalRegister(Reg))
return 0;
std::pair<unsigned, unsigned> Hint = MRI->getRegAllocationHint(Reg);
return TRI->ResolveRegAllocHint(Hint.first, Hint.second, MF);
}
/// 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.
DEBUG(errs() << li_->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
unsigned SrcReg, DstReg, SrcSubIdx = 0, DstSubIdx = 0;
bool isExtSubReg = CopyMI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG;
bool isInsSubReg = CopyMI->getOpcode() == TargetInstrInfo::INSERT_SUBREG;
bool isSubRegToReg = CopyMI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG;
unsigned SubIdx = 0;
if (isExtSubReg) {
DstReg = CopyMI->getOperand(0).getReg();
DstSubIdx = CopyMI->getOperand(0).getSubReg();
SrcReg = CopyMI->getOperand(1).getReg();
SrcSubIdx = CopyMI->getOperand(2).getImm();
} else if (isInsSubReg || isSubRegToReg) {
DstReg = CopyMI->getOperand(0).getReg();
DstSubIdx = CopyMI->getOperand(3).getImm();
SrcReg = CopyMI->getOperand(2).getReg();
SrcSubIdx = CopyMI->getOperand(2).getSubReg();
if (SrcSubIdx && SrcSubIdx != DstSubIdx) {
// r1025 = INSERT_SUBREG r1025, r1024<2>, 2 Then r1024 has already been
// coalesced to a larger register so the subreg indices cancel out.
DEBUG(errs() << "\tSource of insert_subreg or subreg_to_reg is already "
"coalesced to another register.\n");
return false; // Not coalescable.
}
} else if (!tii_->isMoveInstr(*CopyMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)){
llvm_unreachable("Unrecognized copy instruction!");
}
// If they are already joined we continue.
if (SrcReg == DstReg) {
DEBUG(errs() << "\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) {
DEBUG(errs() << "\tCan not coalesce physregs.\n");
return false; // Not coalescable.
}
// We only join virtual registers with allocatable physical registers.
if (SrcIsPhys && !allocatableRegs_[SrcReg]) {
DEBUG(errs() << "\tSrc reg is unallocatable physreg.\n");
return false; // Not coalescable.
}
if (DstIsPhys && !allocatableRegs_[DstReg]) {
DEBUG(errs() << "\tDst reg is unallocatable physreg.\n");
return false; // Not coalescable.
}
// Check that a physical source register is compatible with dst regclass
if (SrcIsPhys) {
unsigned SrcSubReg = SrcSubIdx ?
tri_->getSubReg(SrcReg, SrcSubIdx) : SrcReg;
const TargetRegisterClass *DstRC = mri_->getRegClass(DstReg);
const TargetRegisterClass *DstSubRC = DstRC;
if (DstSubIdx)
DstSubRC = DstRC->getSubRegisterRegClass(DstSubIdx);
assert(DstSubRC && "Illegal subregister index");
if (!DstSubRC->contains(SrcSubReg)) {
DEBUG(errs() << "\tIncompatible destination regclass: "
<< tri_->getName(SrcSubReg) << " not in "
<< DstSubRC->getName() << ".\n");
return false; // Not coalescable.
}
}
// Check that a physical dst register is compatible with source regclass
if (DstIsPhys) {
unsigned DstSubReg = DstSubIdx ?
tri_->getSubReg(DstReg, DstSubIdx) : DstReg;
const TargetRegisterClass *SrcRC = mri_->getRegClass(SrcReg);
const TargetRegisterClass *SrcSubRC = SrcRC;
if (SrcSubIdx)
SrcSubRC = SrcRC->getSubRegisterRegClass(SrcSubIdx);
assert(SrcSubRC && "Illegal subregister index");
if (!SrcSubRC->contains(DstReg)) {
DEBUG(errs() << "\tIncompatible source regclass: "
<< tri_->getName(DstSubReg) << " not in "
<< SrcSubRC->getName() << ".\n");
(void)DstSubReg;
return false; // Not coalescable.
}
}
// Should be non-null only when coalescing to a sub-register class.
bool CrossRC = false;
const TargetRegisterClass *SrcRC= SrcIsPhys ? 0 : mri_->getRegClass(SrcReg);
const TargetRegisterClass *DstRC= DstIsPhys ? 0 : mri_->getRegClass(DstReg);
const TargetRegisterClass *NewRC = NULL;
MachineBasicBlock *CopyMBB = CopyMI->getParent();
unsigned RealDstReg = 0;
unsigned RealSrcReg = 0;
if (isExtSubReg || isInsSubReg || isSubRegToReg) {
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) {
DEBUG(errs() << "\t Sub-register indices mismatch.\n");
return false; // Not coalescable.
}
} else
SrcReg = tri_->getSubReg(SrcReg, SubIdx);
SubIdx = 0;
} else if (DstIsPhys && (isInsSubReg || isSubRegToReg)) {
// 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) {
DEBUG(errs() << "\t Sub-register indices mismatch.\n");
return false; // Not coalescable.
}
} else
DstReg = tri_->getSubReg(DstReg, SubIdx);
SubIdx = 0;
} else if ((DstIsPhys && isExtSubReg) ||
(SrcIsPhys && (isInsSubReg || isSubRegToReg))) {
if (!isSubRegToReg && CopyMI->getOperand(1).getSubReg()) {
DEBUG(errs() << "\tSrc of extract_subreg already coalesced with reg"
<< " of a super-class.\n");
return false; // Not coalescable.
}
if (isExtSubReg) {
if (!CanJoinExtractSubRegToPhysReg(DstReg, SrcReg, SubIdx, RealDstReg))
return false; // Not coalescable
} else {
if (!CanJoinInsertSubRegToPhysReg(DstReg, SrcReg, SubIdx, RealSrcReg))
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))
// 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 {
DEBUG(errs() << "\t Sub-register indices mismatch.\n");
return false; // Not coalescable.
}
}
if (SubIdx) {
if (!DstIsPhys && !SrcIsPhys) {
if (isInsSubReg || isSubRegToReg) {
NewRC = tri_->getMatchingSuperRegClass(DstRC, SrcRC, SubIdx);
} else // extract_subreg {
NewRC = tri_->getMatchingSuperRegClass(SrcRC, DstRC, SubIdx);
}
if (!NewRC) {
DEBUG(errs() << "\t Conflicting sub-register indices.\n");
return false; // Not coalescable
}
unsigned LargeReg = isExtSubReg ? SrcReg : DstReg;
unsigned SmallReg = isExtSubReg ? DstReg : SrcReg;
unsigned Limit= allocatableRCRegs_[mri_->getRegClass(SmallReg)].count();
if (!isWinToJoinCrossClass(LargeReg, SmallReg, Limit)) {
Again = true; // May be possible to coalesce later.
return false;
}
}
}
} else if (differingRegisterClasses(SrcReg, DstReg)) {
if (DisableCrossClassJoin)
return false;
CrossRC = true;
// FIXME: What if the result 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.
// Process moves where one of the registers have a sub-register index.
MachineOperand *DstMO = CopyMI->findRegisterDefOperand(DstReg);
MachineOperand *SrcMO = CopyMI->findRegisterUseOperand(SrcReg);
SubIdx = DstMO->getSubReg();
if (SubIdx) {
if (SrcMO->getSubReg())
// FIXME: can we handle this?
return false;
// This is not an insert_subreg but it looks like one.
// e.g. %reg1024:4 = MOV32rr %EAX
isInsSubReg = true;
if (SrcIsPhys) {
if (!CanJoinInsertSubRegToPhysReg(DstReg, SrcReg, SubIdx, RealSrcReg))
return false; // Not coalescable
SubIdx = 0;
}
} else {
SubIdx = SrcMO->getSubReg();
if (SubIdx) {
// This is not a extract_subreg but it looks like one.
// e.g. %cl = MOV16rr %reg1024:1
isExtSubReg = true;
if (DstIsPhys) {
if (!CanJoinExtractSubRegToPhysReg(DstReg, SrcReg, SubIdx,RealDstReg))
return false; // Not coalescable
SubIdx = 0;
}
}
}
unsigned LargeReg = SrcReg;
unsigned SmallReg = DstReg;
// Now determine the register class of the joined register.
if (isExtSubReg) {
if (SubIdx && DstRC && DstRC->isASubClass()) {
// This is a move to a sub-register class. However, the source is a
// sub-register of a larger register class. We don't know what should
// the register class be. FIXME.
Again = true;
return false;
}
if (!DstIsPhys && !SrcIsPhys)
NewRC = SrcRC;
} else if (!SrcIsPhys && !DstIsPhys) {
NewRC = getCommonSubClass(SrcRC, DstRC);
if (!NewRC) {
DEBUG(errs() << "\tDisjoint regclasses: "
<< SrcRC->getName() << ", "
<< DstRC->getName() << ".\n");
return false; // Not coalescable.
}
if (DstRC->getSize() > SrcRC->getSize())
std::swap(LargeReg, SmallReg);
}
// If we are joining two virtual registers and the resulting register
// class is more restrictive (fewer register, smaller size). Check if it's
// worth doing the merge.
if (!SrcIsPhys && !DstIsPhys &&
(isExtSubReg || DstRC->isASubClass()) &&
!isWinToJoinCrossClass(LargeReg, SmallReg,
allocatableRCRegs_[NewRC].count())) {
DEBUG(errs() << "\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;
}
}
// Will it create illegal extract_subreg / insert_subreg?
if (SrcIsPhys && HasIncompatibleSubRegDefUse(CopyMI, DstReg, SrcReg))
return false;
if (DstIsPhys && HasIncompatibleSubRegDefUse(CopyMI, SrcReg, DstReg))
return false;
LiveInterval &SrcInt = li_->getInterval(SrcReg);
LiveInterval &DstInt = li_->getInterval(DstReg);
assert(SrcInt.reg == SrcReg && DstInt.reg == DstReg &&
"Register mapping is horribly broken!");
DEBUG({
errs() << "\t\tInspecting "; SrcInt.print(errs(), tri_);
errs() << " and "; DstInt.print(errs(), tri_);
errs() << ": ";
});
// Save a copy of the virtual register live interval. We'll manually
// merge this into the "real" physical register live interval this is
// coalesced with.
LiveInterval *SavedLI = 0;
if (RealDstReg)
SavedLI = li_->dupInterval(&SrcInt);
else if (RealSrcReg)
SavedLI = li_->dupInterval(&DstInt);
// Check if it is necessary to propagate "isDead" property.
if (!isExtSubReg && !isInsSubReg && !isSubRegToReg) {
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)) {
// If the copy is in a loop, take care not to coalesce aggressively if the
// src is coming in from outside the loop (or the dst is out of the loop).
// If it's not in a loop, then determine whether to join them base purely
// by the length of the interval.
if (PhysJoinTweak) {
if (SrcIsPhys) {
if (!isWinToJoinVRWithSrcPhysReg(CopyMI, CopyMBB, DstInt, SrcInt)) {
mri_->setRegAllocationHint(DstInt.reg, 0, SrcReg);
++numAborts;
DEBUG(errs() << "\tMay tie down a physical register, abort!\n");
Again = true; // May be possible to coalesce later.
return false;
}
} else {
if (!isWinToJoinVRWithDstPhysReg(CopyMI, CopyMBB, DstInt, SrcInt)) {
mri_->setRegAllocationHint(SrcInt.reg, 0, DstReg);
++numAborts;
DEBUG(errs() << "\tMay tie down a physical register, abort!\n");
Again = true; // May be possible to coalesce later.
return false;
}
}
} else {
// 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.
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;
unsigned Length = li_->getApproximateInstructionCount(JoinVInt);
float Ratio = 1.0 / Threshold;
if (Length > Threshold &&
(((float)std::distance(mri_->use_begin(JoinVReg),
mri_->use_end()) / Length) < Ratio)) {
mri_->setRegAllocationHint(JoinVInt.reg, 0, JoinPReg);
++numAborts;
DEBUG(errs() << "\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.
DEBUG(errs() << "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 && !isSubRegToReg &&
ReMaterializeTrivialDef(SrcInt, DstReg, DstSubIdx, CopyMI))
return true;
// If we can eliminate the copy without merging the live ranges, do so now.
if (!isExtSubReg && !isInsSubReg && !isSubRegToReg &&
(AdjustCopiesBackFrom(SrcInt, DstInt, CopyMI) ||
RemoveCopyByCommutingDef(SrcInt, DstInt, CopyMI))) {
JoinedCopies.insert(CopyMI);
return true;
}
// Otherwise, we are unable to join the intervals.
DEBUG(errs() << "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 interval,
// 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);
for (LiveInterval::const_vni_iterator I = SavedLI->vni_begin(),
E = SavedLI->vni_end(); I != E; ++I) {
const VNInfo *ValNo = *I;
VNInfo *NewValNo = RealInt.getNextValue(ValNo->def, ValNo->getCopy(),
false, // updated at *
li_->getVNInfoAllocator());
NewValNo->setFlags(ValNo->getFlags()); // * updated here.
RealInt.addKills(NewValNo, ValNo->kills);
RealInt.MergeValueInAsValue(*SavedLI, ValNo, NewValNo);
}
RealInt.weight += SavedLI->weight;
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 || isSubRegToReg) &&
!SrcIsPhys && !DstIsPhys) {
if ((isExtSubReg && !Swapped) ||
((isInsSubReg || isSubRegToReg) && Swapped)) {
ResSrcInt->Copy(*ResDstInt, mri_, 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 (CrossRC)
++numCrossRCs;
// This may happen even if it's cross-rc coalescing. e.g.
// %reg1026<def> = SUBREG_TO_REG 0, %reg1037<kill>, 4
// reg1026 -> GR64, reg1037 -> GR32_ABCD. The resulting register will have to
// be allocate a register from GR64_ABCD.
if (NewRC)
mri_->setRegClass(DstReg, NewRC);
// 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);
UpdateRegDefsUses(SrcReg, DstReg, SubIdx);
// SrcReg is guarateed to be the register whose live interval that is
// being merged.
li_->removeInterval(SrcReg);
// Update regalloc hint.
tri_->UpdateRegAllocHint(SrcReg, DstReg, *mf_);
// Manually deleted the live interval copy.
if (SavedLI) {
SavedLI->clear();
delete SavedLI;
}
// If resulting interval has a preference that no longer fits because of subreg
// coalescing, just clear the preference.
unsigned Preference = getRegAllocPreference(ResDstInt->reg, *mf_, mri_, tri_);
if (Preference && (isExtSubReg || isInsSubReg || isSubRegToReg) &&
TargetRegisterInfo::isVirtualRegister(ResDstInt->reg)) {
const TargetRegisterClass *RC = mri_->getRegClass(ResDstInt->reg);
if (!RC->contains(Preference))
mri_->setRegAllocationHint(ResDstInt->reg, 0, 0);
}
DEBUG({
errs() << "\n\t\tJoined. Result = ";
ResDstInt->print(errs(), tri_);
errs() << "\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;
// FIXME: Do isPHIDef and isDefAccurate both need to be tested?
if ((LR->valno->isPHIDef() || !LR->valno->isDefAccurate()) &&
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, SrcSubIdx, DstSubIdx;
if (DefMI &&
tii_->isMoveInstr(*DefMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) &&
DstReg == li.reg && SrcReg == Reg) {
// Cache computed info.
LR->valno->def = LR->start;
LR->valno->setCopy(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
// coalesce them since the 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 = NULL;
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;
llvm_unreachable("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->setCopy(VNI->getCopy());
// Okay, the final step is to loop over the RHS live intervals, adding them to
// the LHS.
if (VNI->hasPHIKill())
LHSValNo->setHasPHIKill(true);
LHS.addKills(LHSValNo, VNI->kills);
LHS.MergeRangesInAsValue(RHS, LHSValNo);
LHS.ComputeJoinedWeight(RHS);
// Update regalloc hint if both are virtual registers.
if (TargetRegisterInfo::isVirtualRegister(LHS.reg) &&
TargetRegisterInfo::isVirtualRegister(RHS.reg)) {
std::pair<unsigned, unsigned> RHSPref = mri_->getRegAllocationHint(RHS.reg);
std::pair<unsigned, unsigned> LHSPref = mri_->getRegAllocationHint(LHS.reg);
if (RHSPref != LHSPref)
mri_->setRegAllocationHint(LHS.reg, RHSPref.first, RHSPref.second);
}
// Update the liveintervals of sub-registers.
if (TargetRegisterInfo::isPhysicalRegister(LHS.reg))
for (const unsigned *AS = tri_->getSubRegisters(LHS.reg); *AS; ++AS)
li_->getOrCreateInterval(*AS).MergeInClobberRanges(LHS,
li_->getVNInfoAllocator());
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)) {
// If it's coalescing a virtual register to a physical register, estimate
// its live interval length. This is the *cost* of scanning an entire live
// interval. If the cost is low, we'll do an exhaustive check instead.
// If this is something like this:
// BB1:
// v1024 = op
// ...
// BB2:
// ...
// RAX = v1024
//
// That is, the live interval of v1024 crosses a bb. Then we can't rely on
// less conservative check. It's possible a sub-register is defined before
// v1024 (or live in) and live out of BB1.
if (RHS.containsOneValue() &&
li_->intervalIsInOneMBB(RHS) &&
li_->getApproximateInstructionCount(RHS) <= 10) {
// Perform a more exhaustive check for some common cases.
if (li_->conflictsWithPhysRegRef(RHS, LHS.reg, true, JoinedCopies))
return false;
} else {
for (const unsigned* SR = tri_->getSubRegisters(LHS.reg); *SR; ++SR)
if (li_->hasInterval(*SR) && RHS.overlaps(li_->getInterval(*SR))) {
DEBUG({
errs() << "Interfere with sub-register ";
li_->getInterval(*SR).print(errs(), tri_);
});
return false;
}
}
} else if (TargetRegisterInfo::isPhysicalRegister(RHS.reg) &&
*tri_->getSubRegisters(RHS.reg)) {
if (LHS.containsOneValue() &&
li_->getApproximateInstructionCount(LHS) <= 10) {
// Perform a more exhaustive check for some common cases.
if (li_->conflictsWithPhysRegRef(LHS, RHS.reg, false, JoinedCopies))
return false;
} else {
for (const unsigned* SR = tri_->getSubRegisters(RHS.reg); *SR; ++SR)
if (li_->hasInterval(*SR) && LHS.overlaps(li_->getInterval(*SR))) {
DEBUG({
errs() << "Interfere with sub-register ";
li_->getInterval(*SR).print(errs(), 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(li_->getPrevSlot(RHSValNoInfo0->def))->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->isUnused() || VNI->getCopy() == 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(li_->getPrevSlot(VNI->def))->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->isUnused() || VNI->getCopy() == 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(li_->getPrevSlot(VNI->def))->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->isUnused())
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->isUnused())
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];
NewVNInfo[LHSValID]->removeKill(VNI->def);
if (VNI->hasPHIKill())
NewVNInfo[LHSValID]->setHasPHIKill(true);
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];
NewVNInfo[RHSValID]->removeKill(VNI->def);
if (VNI->hasPHIKill())
NewVNInfo[RHSValID]->setHasPHIKill(true);
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,
mri_);
Swapped = true;
} else {
LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo,
mri_);
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();
}
};
}
void SimpleRegisterCoalescing::CopyCoalesceInMBB(MachineBasicBlock *MBB,
std::vector<CopyRec> &TryAgain) {
DEBUG(errs() << ((Value*)MBB->getBasicBlock())->getName() << ":\n");
std::vector<CopyRec> VirtCopies;
std::vector<CopyRec> PhysCopies;
std::vector<CopyRec> ImpDefCopies;
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, SrcSubIdx, DstSubIdx;
if (Inst->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
DstReg = Inst->getOperand(0).getReg();
SrcReg = Inst->getOperand(1).getReg();
} else if (Inst->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
Inst->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) {
DstReg = Inst->getOperand(0).getReg();
SrcReg = Inst->getOperand(2).getReg();
} else if (!tii_->isMoveInstr(*Inst, SrcReg, DstReg, SrcSubIdx, DstSubIdx))
continue;
bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
if (li_->hasInterval(SrcReg) && li_->getInterval(SrcReg).empty())
ImpDefCopies.push_back(CopyRec(Inst, 0));
else if (SrcIsPhys || DstIsPhys)
PhysCopies.push_back(CopyRec(Inst, 0));
else
VirtCopies.push_back(CopyRec(Inst, 0));
}
// 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() {
DEBUG(errs() << "********** JOINING INTERVALS ***********\n");
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.
bool ProgressMade = true;
while (ProgressMade) {
ProgressMade = false;
for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) {
CopyRec &TheCopy = TryAgainList[i];
if (!TheCopy.MI)
continue;
bool Again = false;
bool Success = JoinCopy(TheCopy, Again);
if (Success || !Again) {
TheCopy.MI = 0; // Mark this one as done.
ProgressMade = true;
}
}
}
}
/// Return true if the two specified registers belong to different register
/// classes. The registers may be either phys or virt regs.
bool
SimpleRegisterCoalescing::differingRegisterClasses(unsigned RegA,
unsigned RegB) 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);
return RegClassA != RegClassB;
}
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(MachineInstrIndex Start,
MachineInstrIndex End,
unsigned Reg,
MachineInstrIndex &UseIdx) const{
UseIdx = MachineInstrIndex();
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, SrcSubIdx, DstSubIdx;
if (tii_->isMoveInstr(*UseMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) &&
SrcReg == DstReg)
// Ignore identity copies.
continue;
MachineInstrIndex Idx = li_->getInstructionIndex(UseMI);
if (Idx >= Start && Idx < End && Idx >= UseIdx) {
LastUse = &Use;
UseIdx = li_->getUseIndex(Idx);
}
}
return LastUse;
}
MachineInstrIndex s = Start;
MachineInstrIndex e = li_->getBaseIndex(li_->getPrevSlot(End));
while (e >= s) {
// Skip deleted instructions
MachineInstr *MI = li_->getInstructionFromIndex(e);
while (e != MachineInstrIndex() && li_->getPrevIndex(e) >= s && !MI) {
e = li_->getPrevIndex(e);
MI = li_->getInstructionFromIndex(e);
}
if (e < s || MI == NULL)
return NULL;
// Ignore identity copies.
unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
if (!(tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) &&
SrcReg == DstReg))
for (unsigned i = 0, NumOps = MI->getNumOperands(); i != NumOps; ++i) {
MachineOperand &Use = MI->getOperand(i);
if (Use.isReg() && Use.isUse() && Use.getReg() &&
tri_->regsOverlap(Use.getReg(), Reg)) {
UseIdx = li_->getUseIndex(e);
return &Use;
}
}
e = li_->getPrevIndex(e);
}
return NULL;
}
void SimpleRegisterCoalescing::printRegName(unsigned reg) const {
if (TargetRegisterInfo::isPhysicalRegister(reg))
errs() << tri_->getName(reg);
else
errs() << "%reg" << reg;
}
void SimpleRegisterCoalescing::releaseMemory() {
JoinedCopies.clear();
ReMatCopies.clear();
ReMatDefs.clear();
}
/// Returns true if the given live interval is zero length.
static bool isZeroLengthInterval(LiveInterval *li, LiveIntervals *li_) {
for (LiveInterval::Ranges::const_iterator
i = li->ranges.begin(), e = li->ranges.end(); i != e; ++i)
if (li_->getPrevIndex(i->end) > i->start)
return false;
return true;
}
void SimpleRegisterCoalescing::CalculateSpillWeights() {
SmallSet<unsigned, 4> Processed;
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
MachineBasicBlock* MBB = mbbi;
MachineInstrIndex MBBEnd = li_->getMBBEndIdx(MBB);
MachineLoop* loop = loopInfo->getLoopFor(MBB);
unsigned loopDepth = loop ? loop->getLoopDepth() : 0;
bool isExit = loop ? loop->isLoopExit(MBB) : false;
for (MachineBasicBlock::iterator mii = MBB->begin(), mie = MBB->end();
mii != mie; ++mii) {
MachineInstr *MI = mii;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &mopi = MI->getOperand(i);
if (!mopi.isReg() || mopi.getReg() == 0)
continue;
unsigned Reg = mopi.getReg();
if (!TargetRegisterInfo::isVirtualRegister(mopi.getReg()))
continue;
// Multiple uses of reg by the same instruction. It should not
// contribute to spill weight again.
if (!Processed.insert(Reg))
continue;
bool HasDef = mopi.isDef();
bool HasUse = !HasDef;
for (unsigned j = i+1; j != e; ++j) {
const MachineOperand &mopj = MI->getOperand(j);
if (!mopj.isReg() || mopj.getReg() != Reg)
continue;
HasDef |= mopj.isDef();
HasUse |= mopj.isUse();
if (HasDef && HasUse)
break;
}
LiveInterval &RegInt = li_->getInterval(Reg);
float Weight = li_->getSpillWeight(HasDef, HasUse, loopDepth);
if (HasDef && isExit) {
// Looks like this is a loop count variable update.
MachineInstrIndex DefIdx =
li_->getDefIndex(li_->getInstructionIndex(MI));
const LiveRange *DLR =
li_->getInterval(Reg).getLiveRangeContaining(DefIdx);
if (DLR->end > MBBEnd)
Weight *= 3.0F;
}
RegInt.weight += Weight;
}
Processed.clear();
}
}
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_)) {
LI.weight = HUGE_VALF;
continue;
}
bool isLoad = false;
SmallVector<LiveInterval*, 4> SpillIs;
if (li_->isReMaterializable(LI, SpillIs, 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.
std::pair<unsigned, unsigned> Hint = mri_->getRegAllocationHint(LI.reg);
if (Hint.first || Hint.second)
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;
}
}
}
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>();
DEBUG(errs() << "********** 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();
DEBUG({
errs() << "********** INTERVALS POST JOINING **********\n";
for (LiveIntervals::iterator I = li_->begin(), E = li_->end(); I != E; ++I){
I->second->print(errs(), tri_);
errs() << "\n";
}
});
}
// Perform a final pass over the instructions and compute spill weights
// and remove identity moves.
SmallVector<unsigned, 4> DeadDefs;
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
MachineBasicBlock* mbb = mbbi;
for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
mii != mie; ) {
MachineInstr *MI = mii;
unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
if (JoinedCopies.count(MI)) {
// Delete all coalesced copies.
if (!tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)) {
assert((MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG ||
MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) &&
"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;
}
// Now check if this is a remat'ed def instruction which is now dead.
if (ReMatDefs.count(MI)) {
bool isDead = true;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
if (TargetRegisterInfo::isVirtualRegister(Reg))
DeadDefs.push_back(Reg);
if (MO.isDead())
continue;
if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
!mri_->use_empty(Reg)) {
isDead = false;
break;
}
}
if (isDead) {
while (!DeadDefs.empty()) {
unsigned DeadDef = DeadDefs.back();
DeadDefs.pop_back();
RemoveDeadDef(li_->getInterval(DeadDef), MI);
}
li_->RemoveMachineInstrFromMaps(mii);
mii = mbbi->erase(mii);
continue;
} else
DeadDefs.clear();
}
// If the move will be an identity move delete it
bool isMove= tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx);
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 (MI->registerDefIsDead(DstReg)) {
if (!ShortenDeadCopySrcLiveRange(RegInt, MI))
ShortenDeadCopyLiveRange(RegInt, MI);
}
}
li_->RemoveMachineInstrFromMaps(MI);
mii = mbbi->erase(mii);
++numPeep;
} else {
++mii;
}
}
}
CalculateSpillWeights();
DEBUG(dump());
return true;
}
/// print - Implement the dump method.
void SimpleRegisterCoalescing::print(raw_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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