//===- RegisterCoalescer.cpp - Generic Register Coalescing Interface -------==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the generic RegisterCoalescer interface which
// is used as the common interface used by all clients and
// implementations of register coalescing.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regcoalescing"
#include "RegisterCoalescer.h"
#include "LiveDebugVariables.h"
#include "RegisterClassInfo.h"
#include "VirtRegMap.h"
#include "llvm/Pass.h"
#include "llvm/Value.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/Analysis/AliasAnalysis.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/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/OwningPtr.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(NumInflated , "Number of register classes inflated");
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>
EnablePhysicalJoin("join-physregs",
cl::desc("Join physical register copies"),
cl::init(false), cl::Hidden);
static cl::opt<bool>
VerifyCoalescing("verify-coalescing",
cl::desc("Verify machine instrs before and after register coalescing"),
cl::Hidden);
namespace {
class RegisterCoalescer : public MachineFunctionPass {
MachineFunction* MF;
MachineRegisterInfo* MRI;
const TargetMachine* TM;
const TargetRegisterInfo* TRI;
const TargetInstrInfo* TII;
LiveIntervals *LIS;
LiveDebugVariables *LDV;
const MachineLoopInfo* Loops;
AliasAnalysis *AA;
RegisterClassInfo RegClassInfo;
/// JoinedCopies - Keep track of copies eliminated due to coalescing.
///
SmallPtrSet<MachineInstr*, 32> JoinedCopies;
/// ReMatCopies - Keep track of copies eliminated due to remat.
///
SmallPtrSet<MachineInstr*, 32> ReMatCopies;
/// ReMatDefs - Keep track of definition instructions which have
/// been remat'ed.
SmallPtrSet<MachineInstr*, 8> ReMatDefs;
/// joinIntervals - join compatible live intervals
void joinIntervals();
/// CopyCoalesceInMBB - Coalesce copies in the specified MBB, putting
/// copies that cannot yet be coalesced into the "TryAgain" list.
void CopyCoalesceInMBB(MachineBasicBlock *MBB,
std::vector<MachineInstr*> &TryAgain);
/// 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 JoinCopy(MachineInstr *TheCopy, bool &Again);
/// JoinIntervals - Attempt to join these two intervals. On failure, this
/// returns false. The output "SrcInt" will not have been modified, so we
/// can use this information below to update aliases.
bool JoinIntervals(CoalescerPair &CP);
/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy. If
/// the source value number is defined by a copy from the destination reg
/// see if we can merge these two destination reg valno# into a single
/// value number, eliminating a copy.
bool AdjustCopiesBackFrom(const CoalescerPair &CP, MachineInstr *CopyMI);
/// HasOtherReachingDefs - Return true if there are definitions of IntB
/// other than BValNo val# that can reach uses of AValno val# of IntA.
bool HasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
VNInfo *AValNo, VNInfo *BValNo);
/// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy.
/// If the source value number 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.
bool RemoveCopyByCommutingDef(const CoalescerPair &CP,MachineInstr *CopyMI);
/// ReMaterializeTrivialDef - If the source of a copy is defined by a
/// trivial computation, replace the copy by rematerialize the definition.
/// If PreserveSrcInt is true, make sure SrcInt is valid after the call.
bool ReMaterializeTrivialDef(LiveInterval &SrcInt, bool PreserveSrcInt,
unsigned DstReg, MachineInstr *CopyMI);
/// shouldJoinPhys - Return true if a physreg copy should be joined.
bool shouldJoinPhys(CoalescerPair &CP);
/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
/// two virtual registers from different register classes.
bool isWinToJoinCrossClass(unsigned SrcReg,
unsigned DstReg,
const TargetRegisterClass *SrcRC,
const TargetRegisterClass *DstRC,
const TargetRegisterClass *NewRC);
/// 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 UpdateRegDefsUses(const CoalescerPair &CP);
/// 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 RemoveDeadDef(LiveInterval &li, MachineInstr *DefMI);
/// RemoveCopyFlag - If DstReg is no longer defined by CopyMI, clear the
/// VNInfo copy flag for DstReg and all aliases.
void RemoveCopyFlag(unsigned DstReg, const MachineInstr *CopyMI);
/// markAsJoined - Remember that CopyMI has already been joined.
void markAsJoined(MachineInstr *CopyMI);
/// eliminateUndefCopy - Handle copies of undef values.
bool eliminateUndefCopy(MachineInstr *CopyMI, const CoalescerPair &CP);
public:
static char ID; // Class identification, replacement for typeinfo
RegisterCoalescer() : MachineFunctionPass(ID) {
initializeRegisterCoalescerPass(*PassRegistry::getPassRegistry());
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
virtual void releaseMemory();
/// runOnMachineFunction - pass entry point
virtual bool runOnMachineFunction(MachineFunction&);
/// print - Implement the dump method.
virtual void print(raw_ostream &O, const Module* = 0) const;
};
} /// end anonymous namespace
char &llvm::RegisterCoalescerPassID = RegisterCoalescer::ID;
INITIALIZE_PASS_BEGIN(RegisterCoalescer, "simple-register-coalescing",
"Simple Register Coalescing", false, false)
INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables)
INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_DEPENDENCY(StrongPHIElimination)
INITIALIZE_PASS_DEPENDENCY(PHIElimination)
INITIALIZE_PASS_DEPENDENCY(TwoAddressInstructionPass)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(RegisterCoalescer, "simple-register-coalescing",
"Simple Register Coalescing", false, false)
char RegisterCoalescer::ID = 0;
static unsigned compose(const TargetRegisterInfo &tri, unsigned a, unsigned b) {
if (!a) return b;
if (!b) return a;
return tri.composeSubRegIndices(a, b);
}
static bool isMoveInstr(const TargetRegisterInfo &tri, const MachineInstr *MI,
unsigned &Src, unsigned &Dst,
unsigned &SrcSub, unsigned &DstSub) {
if (MI->isCopy()) {
Dst = MI->getOperand(0).getReg();
DstSub = MI->getOperand(0).getSubReg();
Src = MI->getOperand(1).getReg();
SrcSub = MI->getOperand(1).getSubReg();
} else if (MI->isSubregToReg()) {
Dst = MI->getOperand(0).getReg();
DstSub = compose(tri, MI->getOperand(0).getSubReg(),
MI->getOperand(3).getImm());
Src = MI->getOperand(2).getReg();
SrcSub = MI->getOperand(2).getSubReg();
} else
return false;
return true;
}
bool CoalescerPair::setRegisters(const MachineInstr *MI) {
SrcReg = DstReg = SubIdx = 0;
NewRC = 0;
Flipped = CrossClass = false;
unsigned Src, Dst, SrcSub, DstSub;
if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
return false;
Partial = SrcSub || DstSub;
// If one register is a physreg, it must be Dst.
if (TargetRegisterInfo::isPhysicalRegister(Src)) {
if (TargetRegisterInfo::isPhysicalRegister(Dst))
return false;
std::swap(Src, Dst);
std::swap(SrcSub, DstSub);
Flipped = true;
}
const MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo();
if (TargetRegisterInfo::isPhysicalRegister(Dst)) {
// Eliminate DstSub on a physreg.
if (DstSub) {
Dst = TRI.getSubReg(Dst, DstSub);
if (!Dst) return false;
DstSub = 0;
}
// Eliminate SrcSub by picking a corresponding Dst superregister.
if (SrcSub) {
Dst = TRI.getMatchingSuperReg(Dst, SrcSub, MRI.getRegClass(Src));
if (!Dst) return false;
SrcSub = 0;
} else if (!MRI.getRegClass(Src)->contains(Dst)) {
return false;
}
} else {
// Both registers are virtual.
// Both registers have subreg indices.
if (SrcSub && DstSub) {
// For now we only handle the case of identical indices in commensurate
// registers: Dreg:ssub_1 + Dreg:ssub_1 -> Dreg
// FIXME: Handle Qreg:ssub_3 + Dreg:ssub_1 as QReg:dsub_1 + Dreg.
if (SrcSub != DstSub)
return false;
const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
if (!TRI.getCommonSubClass(DstRC, SrcRC))
return false;
SrcSub = DstSub = 0;
}
// There can be no SrcSub.
if (SrcSub) {
std::swap(Src, Dst);
DstSub = SrcSub;
SrcSub = 0;
assert(!Flipped && "Unexpected flip");
Flipped = true;
}
// Find the new register class.
const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
if (DstSub)
NewRC = TRI.getMatchingSuperRegClass(DstRC, SrcRC, DstSub);
else
NewRC = TRI.getCommonSubClass(DstRC, SrcRC);
if (!NewRC)
return false;
CrossClass = NewRC != DstRC || NewRC != SrcRC;
}
// Check our invariants
assert(TargetRegisterInfo::isVirtualRegister(Src) && "Src must be virtual");
assert(!(TargetRegisterInfo::isPhysicalRegister(Dst) && DstSub) &&
"Cannot have a physical SubIdx");
SrcReg = Src;
DstReg = Dst;
SubIdx = DstSub;
return true;
}
bool CoalescerPair::flip() {
if (SubIdx || TargetRegisterInfo::isPhysicalRegister(DstReg))
return false;
std::swap(SrcReg, DstReg);
Flipped = !Flipped;
return true;
}
bool CoalescerPair::isCoalescable(const MachineInstr *MI) const {
if (!MI)
return false;
unsigned Src, Dst, SrcSub, DstSub;
if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
return false;
// Find the virtual register that is SrcReg.
if (Dst == SrcReg) {
std::swap(Src, Dst);
std::swap(SrcSub, DstSub);
} else if (Src != SrcReg) {
return false;
}
// Now check that Dst matches DstReg.
if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
if (!TargetRegisterInfo::isPhysicalRegister(Dst))
return false;
assert(!SubIdx && "Inconsistent CoalescerPair state.");
// DstSub could be set for a physreg from INSERT_SUBREG.
if (DstSub)
Dst = TRI.getSubReg(Dst, DstSub);
// Full copy of Src.
if (!SrcSub)
return DstReg == Dst;
// This is a partial register copy. Check that the parts match.
return TRI.getSubReg(DstReg, SrcSub) == Dst;
} else {
// DstReg is virtual.
if (DstReg != Dst)
return false;
// Registers match, do the subregisters line up?
return compose(TRI, SubIdx, SrcSub) == DstSub;
}
}
void RegisterCoalescer::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<AliasAnalysis>();
AU.addRequired<LiveIntervals>();
AU.addPreserved<LiveIntervals>();
AU.addRequired<LiveDebugVariables>();
AU.addPreserved<LiveDebugVariables>();
AU.addPreserved<SlotIndexes>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreservedID(MachineDominatorsID);
AU.addPreservedID(StrongPHIEliminationID);
AU.addPreservedID(PHIEliminationID);
AU.addPreservedID(TwoAddressInstructionPassID);
MachineFunctionPass::getAnalysisUsage(AU);
}
void RegisterCoalescer::markAsJoined(MachineInstr *CopyMI) {
/// Joined copies are not deleted immediately, but kept in JoinedCopies.
JoinedCopies.insert(CopyMI);
/// Mark all register operands of CopyMI as <undef> so they won't affect dead
/// code elimination.
for (MachineInstr::mop_iterator I = CopyMI->operands_begin(),
E = CopyMI->operands_end(); I != E; ++I)
if (I->isReg())
I->setIsUndef(true);
}
/// 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 RegisterCoalescer::AdjustCopiesBackFrom(const CoalescerPair &CP,
MachineInstr *CopyMI) {
// Bail if there is no dst interval - can happen when merging physical subreg
// operations.
if (!LIS->hasInterval(CP.getDstReg()))
return false;
LiveInterval &IntA =
LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
LiveInterval &IntB =
LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getDefIndex();
// BValNo is a value number in B that is defined by a copy from A. 'B3' in
// the example above.
LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);
if (BLR == IntB.end()) return false;
VNInfo *BValNo = BLR->valno;
// Get the location that B is defined at. Two options: either this value has
// an unknown definition point or it is defined at CopyIdx. If unknown, we
// can't process it.
if (!BValNo->isDefByCopy()) 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.
SlotIndex CopyUseIdx = CopyIdx.getUseIndex();
LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyUseIdx);
// The live range might not exist after fun with physreg coalescing.
if (ALR == IntA.end()) return false;
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.
if (!CP.isCoalescable(AValNo->getCopy()))
return false;
// Get the LiveRange in IntB that this value number starts with.
LiveInterval::iterator ValLR =
IntB.FindLiveRangeContaining(AValNo->def.getPrevSlot());
if (ValLR == IntB.end())
return false;
// Make sure that the end of the live range is inside the same block as
// CopyMI.
MachineInstr *ValLREndInst =
LIS->getInstructionFromIndex(ValLR->end.getPrevSlot());
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 aliases is overlapping the live interval of the virtual register.
// If so, do not coalesce.
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
for (const unsigned *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
if (LIS->hasInterval(*AS) && IntA.overlaps(LIS->getInterval(*AS))) {
DEBUG({
dbgs() << "\t\tInterfere with alias ";
LIS->getInterval(*AS).print(dbgs(), TRI);
});
return false;
}
}
DEBUG({
dbgs() << "Extending: ";
IntB.print(dbgs(), TRI);
});
SlotIndex 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 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) {
if (!LIS->hasInterval(*SR))
continue;
LiveInterval &SRLI = LIS->getInterval(*SR);
SRLI.addRange(LiveRange(FillerStart, FillerEnd,
SRLI.getNextValue(FillerStart, 0,
LIS->getVNInfoAllocator())));
}
}
// Okay, merge "B1" into the same value number as "B0".
if (BValNo != ValLR->valno) {
// If B1 is killed by a PHI, then the merged live range must also be killed
// by the same PHI, as B0 and B1 can not overlap.
bool HasPHIKill = BValNo->hasPHIKill();
IntB.MergeValueNumberInto(BValNo, ValLR->valno);
if (HasPHIKill)
ValLR->valno->setHasPHIKill(true);
}
DEBUG({
dbgs() << " result = ";
IntB.print(dbgs(), TRI);
dbgs() << "\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);
}
// 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 (ALR->end == CopyIdx)
LIS->shrinkToUses(&IntA);
++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 RegisterCoalescer::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 RegisterCoalescer::RemoveCopyByCommutingDef(const CoalescerPair &CP,
MachineInstr *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 (CP.isPhys() && CP.isFlipped())
return false;
// Bail if there is no dst interval.
if (!LIS->hasInterval(CP.getDstReg()))
return false;
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getDefIndex();
LiveInterval &IntA =
LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
LiveInterval &IntB =
LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
// BValNo is a value number in B that is defined by a copy from A. 'B3' in
// the example above.
VNInfo *BValNo = IntB.getVNInfoAt(CopyIdx);
if (!BValNo || !BValNo->isDefByCopy())
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.
VNInfo *AValNo = IntA.getVNInfoAt(CopyIdx.getUseIndex());
assert(AValNo && "COPY source not live");
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization.
if (AValNo->isPHIDef() || AValNo->isUnused() || AValNo->hasPHIKill())
return false;
MachineInstr *DefMI = LIS->getInstructionFromIndex(AValNo->def);
if (!DefMI)
return false;
const MCInstrDesc &MCID = DefMI->getDesc();
if (!MCID.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;
// Abort if the aliases of IntB.reg have values that are not simply the
// clobbers from the superreg.
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg))
for (const unsigned *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
if (LIS->hasInterval(*AS) &&
HasOtherReachingDefs(IntA, LIS->getInterval(*AS), AValNo, 0))
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_nodbg_iterator UI =
MRI->use_nodbg_begin(IntA.reg),
UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
MachineInstr *UseMI = &*UI;
SlotIndex UseIdx = LIS->getInstructionIndex(UseMI);
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR == IntA.end())
continue;
if (ULR->valno == AValNo && JoinedCopies.count(UseMI))
return false;
}
DEBUG(dbgs() << "\tRemoveCopyByCommutingDef: " << AValNo->def << '\t'
<< *DefMI);
// 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 (TargetRegisterInfo::isVirtualRegister(IntA.reg) &&
TargetRegisterInfo::isVirtualRegister(IntB.reg) &&
!MRI->constrainRegClass(IntB.reg, MRI->getRegClass(IntA.reg)))
return false;
if (NewMI != DefMI) {
LIS->ReplaceMachineInstrInMaps(DefMI, NewMI);
MBB->insert(DefMI, NewMI);
MBB->erase(DefMI);
}
unsigned OpIdx = NewMI->findRegisterUseOperandIdx(IntA.reg, false);
NewMI->getOperand(OpIdx).setIsKill();
// 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
// Update uses of IntA of the specific Val# with IntB.
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(IntA.reg),
UE = MRI->use_end(); UI != UE;) {
MachineOperand &UseMO = UI.getOperand();
MachineInstr *UseMI = &*UI;
++UI;
if (JoinedCopies.count(UseMI))
continue;
if (UseMI->isDebugValue()) {
// FIXME These don't have an instruction index. Not clear we have enough
// info to decide whether to do this replacement or not. For now do it.
UseMO.setReg(NewReg);
continue;
}
SlotIndex UseIdx = LIS->getInstructionIndex(UseMI).getUseIndex();
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR == IntA.end() || ULR->valno != AValNo)
continue;
if (TargetRegisterInfo::isPhysicalRegister(NewReg))
UseMO.substPhysReg(NewReg, *TRI);
else
UseMO.setReg(NewReg);
if (UseMI == CopyMI)
continue;
if (!UseMI->isCopy())
continue;
if (UseMI->getOperand(0).getReg() != IntB.reg ||
UseMI->getOperand(0).getSubReg())
continue;
// This copy will become a noop. If it's defining a new val#, merge it into
// BValNo.
SlotIndex DefIdx = UseIdx.getDefIndex();
VNInfo *DVNI = IntB.getVNInfoAt(DefIdx);
if (!DVNI)
continue;
DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
assert(DVNI->def == DefIdx);
BValNo = IntB.MergeValueNumberInto(BValNo, DVNI);
markAsJoined(UseMI);
}
// Extend BValNo by merging in IntA live ranges of AValNo. Val# definition
// is updated.
VNInfo *ValNo = BValNo;
ValNo->def = AValNo->def;
ValNo->setCopy(0);
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
AI != AE; ++AI) {
if (AI->valno != AValNo) continue;
IntB.addRange(LiveRange(AI->start, AI->end, ValNo));
}
DEBUG(dbgs() << "\t\textended: " << IntB << '\n');
IntA.removeValNo(AValNo);
DEBUG(dbgs() << "\t\ttrimmed: " << IntA << '\n');
++numCommutes;
return true;
}
/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
/// computation, replace the copy by rematerialize the definition.
bool RegisterCoalescer::ReMaterializeTrivialDef(LiveInterval &SrcInt,
bool preserveSrcInt,
unsigned DstReg,
MachineInstr *CopyMI) {
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getUseIndex();
LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
assert(SrcLR != SrcInt.end() && "Live range not found!");
VNInfo *ValNo = SrcLR->valno;
if (ValNo->isPHIDef() || ValNo->isUnused())
return false;
MachineInstr *DefMI = LIS->getInstructionFromIndex(ValNo->def);
if (!DefMI)
return false;
assert(DefMI && "Defining instruction disappeared");
const MCInstrDesc &MCID = DefMI->getDesc();
if (!MCID.isAsCheapAsAMove())
return false;
if (!TII->isTriviallyReMaterializable(DefMI, AA))
return false;
bool SawStore = false;
if (!DefMI->isSafeToMove(TII, AA, SawStore))
return false;
if (MCID.getNumDefs() != 1)
return false;
if (!DefMI->isImplicitDef()) {
// 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 = TII->getRegClass(MCID, 0, TRI);
if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
if (MRI->getRegClass(DstReg) != RC)
return false;
} else if (!RC->contains(DstReg))
return false;
}
RemoveCopyFlag(DstReg, CopyMI);
MachineBasicBlock *MBB = CopyMI->getParent();
MachineBasicBlock::iterator MII =
llvm::next(MachineBasicBlock::iterator(CopyMI));
TII->reMaterialize(*MBB, MII, DstReg, 0, DefMI, *TRI);
MachineInstr *NewMI = prior(MII);
// 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())
RemoveCopyFlag(MO.getReg(), CopyMI);
}
NewMI->copyImplicitOps(CopyMI);
LIS->ReplaceMachineInstrInMaps(CopyMI, NewMI);
CopyMI->eraseFromParent();
ReMatCopies.insert(CopyMI);
ReMatDefs.insert(DefMI);
DEBUG(dbgs() << "Remat: " << *NewMI);
++NumReMats;
// The source interval can become smaller because we removed a use.
if (preserveSrcInt)
LIS->shrinkToUses(&SrcInt);
return true;
}
/// eliminateUndefCopy - ProcessImpicitDefs may leave some copies of <undef>
/// values, it only removes local variables. When we have a copy like:
///
/// %vreg1 = COPY %vreg2<undef>
///
/// We delete the copy and remove the corresponding value number from %vreg1.
/// Any uses of that value number are marked as <undef>.
bool RegisterCoalescer::eliminateUndefCopy(MachineInstr *CopyMI,
const CoalescerPair &CP) {
SlotIndex Idx = LIS->getInstructionIndex(CopyMI);
LiveInterval *SrcInt = &LIS->getInterval(CP.getSrcReg());
if (SrcInt->liveAt(Idx))
return false;
LiveInterval *DstInt = &LIS->getInterval(CP.getDstReg());
if (DstInt->liveAt(Idx))
return false;
// No intervals are live-in to CopyMI - it is undef.
if (CP.isFlipped())
DstInt = SrcInt;
SrcInt = 0;
VNInfo *DeadVNI = DstInt->getVNInfoAt(Idx.getDefIndex());
assert(DeadVNI && "No value defined in DstInt");
DstInt->removeValNo(DeadVNI);
// Find new undef uses.
for (MachineRegisterInfo::reg_nodbg_iterator
I = MRI->reg_nodbg_begin(DstInt->reg), E = MRI->reg_nodbg_end();
I != E; ++I) {
MachineOperand &MO = I.getOperand();
if (MO.isDef() || MO.isUndef())
continue;
MachineInstr *MI = MO.getParent();
SlotIndex Idx = LIS->getInstructionIndex(MI);
if (DstInt->liveAt(Idx))
continue;
MO.setIsUndef(true);
DEBUG(dbgs() << "\tnew undef: " << Idx << '\t' << *MI);
}
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
RegisterCoalescer::UpdateRegDefsUses(const CoalescerPair &CP) {
bool DstIsPhys = CP.isPhys();
unsigned SrcReg = CP.getSrcReg();
unsigned DstReg = CP.getDstReg();
unsigned SubIdx = CP.getSubIdx();
// Update LiveDebugVariables.
LDV->renameRegister(SrcReg, DstReg, SubIdx);
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg);
MachineInstr *UseMI = I.skipInstruction();) {
// A PhysReg copy that won't be coalesced can perhaps be rematerialized
// instead.
if (DstIsPhys) {
if (UseMI->isFullCopy() &&
UseMI->getOperand(1).getReg() == SrcReg &&
UseMI->getOperand(0).getReg() != SrcReg &&
UseMI->getOperand(0).getReg() != DstReg &&
!JoinedCopies.count(UseMI) &&
ReMaterializeTrivialDef(LIS->getInterval(SrcReg), false,
UseMI->getOperand(0).getReg(), UseMI))
continue;
}
SmallVector<unsigned,8> Ops;
bool Reads, Writes;
tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
bool Kills = false, Deads = false;
// Replace SrcReg with DstReg in all UseMI operands.
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
MachineOperand &MO = UseMI->getOperand(Ops[i]);
Kills |= MO.isKill();
Deads |= MO.isDead();
// Make sure we don't create read-modify-write defs accidentally. We
// assume here that a SrcReg def cannot be joined into a live DstReg. If
// RegisterCoalescer starts tracking partially live registers, we will
// need to check the actual LiveInterval to determine if DstReg is live
// here.
if (SubIdx && !Reads)
MO.setIsUndef();
if (DstIsPhys)
MO.substPhysReg(DstReg, *TRI);
else
MO.substVirtReg(DstReg, SubIdx, *TRI);
}
// This instruction is a copy that will be removed.
if (JoinedCopies.count(UseMI))
continue;
if (SubIdx) {
// If UseMI was a simple SrcReg def, make sure we didn't turn it into a
// read-modify-write of DstReg.
if (Deads)
UseMI->addRegisterDead(DstReg, TRI);
else if (!Reads && Writes)
UseMI->addRegisterDefined(DstReg, TRI);
// Kill flags apply to the whole physical register.
if (DstIsPhys && Kills)
UseMI->addRegisterKilled(DstReg, TRI);
}
DEBUG({
dbgs() << "\t\tupdated: ";
if (!UseMI->isDebugValue())
dbgs() << LIS->getInstructionIndex(UseMI) << "\t";
dbgs() << *UseMI;
});
}
}
/// 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 *LIS,
const TargetRegisterInfo *TRI) {
if (li.empty()) {
if (TargetRegisterInfo::isPhysicalRegister(li.reg))
for (const unsigned* SR = TRI->getSubRegisters(li.reg); *SR; ++SR) {
if (!LIS->hasInterval(*SR))
continue;
LiveInterval &sli = LIS->getInterval(*SR);
if (sli.empty())
LIS->removeInterval(*SR);
}
LIS->removeInterval(li.reg);
return true;
}
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 RegisterCoalescer::RemoveDeadDef(LiveInterval &li,
MachineInstr *DefMI) {
SlotIndex DefIdx = LIS->getInstructionIndex(DefMI).getDefIndex();
LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx);
if (DefIdx != MLR->valno->def)
return false;
li.removeValNo(MLR->valno);
return removeIntervalIfEmpty(li, LIS, TRI);
}
void RegisterCoalescer::RemoveCopyFlag(unsigned DstReg,
const MachineInstr *CopyMI) {
SlotIndex DefIdx = LIS->getInstructionIndex(CopyMI).getDefIndex();
if (LIS->hasInterval(DstReg)) {
LiveInterval &LI = LIS->getInterval(DstReg);
if (const LiveRange *LR = LI.getLiveRangeContaining(DefIdx))
if (LR->valno->def == DefIdx)
LR->valno->setCopy(0);
}
if (!TargetRegisterInfo::isPhysicalRegister(DstReg))
return;
for (const unsigned* AS = TRI->getAliasSet(DstReg); *AS; ++AS) {
if (!LIS->hasInterval(*AS))
continue;
LiveInterval &LI = LIS->getInterval(*AS);
if (const LiveRange *LR = LI.getLiveRangeContaining(DefIdx))
if (LR->valno->def == DefIdx)
LR->valno->setCopy(0);
}
}
/// shouldJoinPhys - Return true if a copy involving a physreg should be joined.
/// 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!
bool RegisterCoalescer::shouldJoinPhys(CoalescerPair &CP) {
bool Allocatable = LIS->isAllocatable(CP.getDstReg());
LiveInterval &JoinVInt = LIS->getInterval(CP.getSrcReg());
/// Always join simple intervals that are defined by a single copy from a
/// reserved register. This doesn't increase register pressure, so it is
/// always beneficial.
if (!Allocatable && CP.isFlipped() && JoinVInt.containsOneValue())
return true;
if (!EnablePhysicalJoin) {
DEBUG(dbgs() << "\tPhysreg joins disabled.\n");
return false;
}
// Only coalesce to allocatable physreg, we don't want to risk modifying
// reserved registers.
if (!Allocatable) {
DEBUG(dbgs() << "\tRegister is an unallocatable physreg.\n");
return false; // Not coalescable.
}
// Don't join with physregs that have a ridiculous number of live
// ranges. The data structure performance is really bad when that
// happens.
if (LIS->hasInterval(CP.getDstReg()) &&
LIS->getInterval(CP.getDstReg()).ranges.size() > 1000) {
++numAborts;
DEBUG(dbgs()
<< "\tPhysical register live interval too complicated, abort!\n");
return false;
}
// FIXME: Why are we skipping this test for partial copies?
// CodeGen/X86/phys_subreg_coalesce-3.ll needs it.
if (!CP.isPartial()) {
const TargetRegisterClass *RC = MRI->getRegClass(CP.getSrcReg());
unsigned Threshold = RegClassInfo.getNumAllocatableRegs(RC) * 2;
unsigned Length = LIS->getApproximateInstructionCount(JoinVInt);
if (Length > Threshold) {
++numAborts;
DEBUG(dbgs() << "\tMay tie down a physical register, abort!\n");
return false;
}
}
return true;
}
/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
/// two virtual registers from different register classes.
bool
RegisterCoalescer::isWinToJoinCrossClass(unsigned SrcReg,
unsigned DstReg,
const TargetRegisterClass *SrcRC,
const TargetRegisterClass *DstRC,
const TargetRegisterClass *NewRC) {
unsigned NewRCCount = RegClassInfo.getNumAllocatableRegs(NewRC);
// This heuristics is good enough in practice, but it's obviously not *right*.
// 4 is a magic number that works well enough for x86, ARM, etc. It filter
// out all but the most restrictive register classes.
if (NewRCCount > 4 ||
// Early exit if the function is fairly small, coalesce aggressively if
// that's the case. For really special register classes with 3 or
// fewer registers, be a bit more careful.
(LIS->getFuncInstructionCount() / NewRCCount) < 8)
return true;
LiveInterval &SrcInt = LIS->getInterval(SrcReg);
LiveInterval &DstInt = LIS->getInterval(DstReg);
unsigned SrcSize = LIS->getApproximateInstructionCount(SrcInt);
unsigned DstSize = LIS->getApproximateInstructionCount(DstInt);
// Coalesce aggressively if the intervals are small compared to the number of
// registers in the new class. The number 4 is fairly arbitrary, chosen to be
// less aggressive than the 8 used for the whole function size.
const unsigned ThresSize = 4 * NewRCCount;
if (SrcSize <= ThresSize && DstSize <= ThresSize)
return true;
// Estimate *register use density*. If it doubles or more, abort.
unsigned SrcUses = std::distance(MRI->use_nodbg_begin(SrcReg),
MRI->use_nodbg_end());
unsigned DstUses = std::distance(MRI->use_nodbg_begin(DstReg),
MRI->use_nodbg_end());
unsigned NewUses = SrcUses + DstUses;
unsigned NewSize = SrcSize + DstSize;
if (SrcRC != NewRC && SrcSize > ThresSize) {
unsigned SrcRCCount = RegClassInfo.getNumAllocatableRegs(SrcRC);
if (NewUses*SrcSize*SrcRCCount > 2*SrcUses*NewSize*NewRCCount)
return false;
}
if (DstRC != NewRC && DstSize > ThresSize) {
unsigned DstRCCount = RegClassInfo.getNumAllocatableRegs(DstRC);
if (NewUses*DstSize*DstRCCount > 2*DstUses*NewSize*NewRCCount)
return false;
}
return true;
}
/// 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 RegisterCoalescer::JoinCopy(MachineInstr *CopyMI, bool &Again) {
Again = false;
if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
return false; // Already done.
DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
CoalescerPair CP(*TII, *TRI);
if (!CP.setRegisters(CopyMI)) {
DEBUG(dbgs() << "\tNot coalescable.\n");
return false;
}
// If they are already joined we continue.
if (CP.getSrcReg() == CP.getDstReg()) {
markAsJoined(CopyMI);
DEBUG(dbgs() << "\tCopy already coalesced.\n");
return false; // Not coalescable.
}
// Eliminate undefs.
if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) {
markAsJoined(CopyMI);
DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n");
return false; // Not coalescable.
}
DEBUG(dbgs() << "\tConsidering merging " << PrintReg(CP.getSrcReg(), TRI)
<< " with " << PrintReg(CP.getDstReg(), TRI, CP.getSubIdx())
<< "\n");
// Enforce policies.
if (CP.isPhys()) {
if (!shouldJoinPhys(CP)) {
// Before giving up coalescing, if definition of source is defined by
// trivial computation, try rematerializing it.
if (!CP.isFlipped() &&
ReMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
CP.getDstReg(), CopyMI))
return true;
return false;
}
} else {
// Avoid constraining virtual register regclass too much.
if (CP.isCrossClass()) {
DEBUG(dbgs() << "\tCross-class to " << CP.getNewRC()->getName() << ".\n");
if (DisableCrossClassJoin) {
DEBUG(dbgs() << "\tCross-class joins disabled.\n");
return false;
}
if (!isWinToJoinCrossClass(CP.getSrcReg(), CP.getDstReg(),
MRI->getRegClass(CP.getSrcReg()),
MRI->getRegClass(CP.getDstReg()),
CP.getNewRC())) {
DEBUG(dbgs() << "\tAvoid coalescing to constrained register class.\n");
Again = true; // May be possible to coalesce later.
return false;
}
}
// When possible, let DstReg be the larger interval.
if (!CP.getSubIdx() && LIS->getInterval(CP.getSrcReg()).ranges.size() >
LIS->getInterval(CP.getDstReg()).ranges.size())
CP.flip();
}
// 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.
if (!JoinIntervals(CP)) {
// Coalescing failed.
// If definition of source is defined by trivial computation, try
// rematerializing it.
if (!CP.isFlipped() &&
ReMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
CP.getDstReg(), CopyMI))
return true;
// If we can eliminate the copy without merging the live ranges, do so now.
if (!CP.isPartial()) {
if (AdjustCopiesBackFrom(CP, CopyMI) ||
RemoveCopyByCommutingDef(CP, CopyMI)) {
markAsJoined(CopyMI);
DEBUG(dbgs() << "\tTrivial!\n");
return true;
}
}
// Otherwise, we are unable to join the intervals.
DEBUG(dbgs() << "\tInterference!\n");
Again = true; // May be possible to coalesce later.
return false;
}
// 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 (CP.isCrossClass()) {
++numCrossRCs;
MRI->setRegClass(CP.getDstReg(), CP.getNewRC());
}
// Remember to delete the copy instruction.
markAsJoined(CopyMI);
UpdateRegDefsUses(CP);
// If we have extended the live range of a physical register, make sure we
// update live-in lists as well.
if (CP.isPhys()) {
SmallVector<MachineBasicBlock*, 16> BlockSeq;
// JoinIntervals invalidates the VNInfos in SrcInt, but we only need the
// ranges for this, and they are preserved.
LiveInterval &SrcInt = LIS->getInterval(CP.getSrcReg());
for (LiveInterval::const_iterator I = SrcInt.begin(), E = SrcInt.end();
I != E; ++I ) {
LIS->findLiveInMBBs(I->start, I->end, BlockSeq);
for (unsigned idx = 0, size = BlockSeq.size(); idx != size; ++idx) {
MachineBasicBlock &block = *BlockSeq[idx];
if (!block.isLiveIn(CP.getDstReg()))
block.addLiveIn(CP.getDstReg());
}
BlockSeq.clear();
}
}
// SrcReg is guarateed to be the register whose live interval that is
// being merged.
LIS->removeInterval(CP.getSrcReg());
// Update regalloc hint.
TRI->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *MF);
DEBUG({
LiveInterval &DstInt = LIS->getInterval(CP.getDstReg());
dbgs() << "\tJoined. Result = ";
DstInt.print(dbgs(), TRI);
dbgs() << "\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 value numbers");
// 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;
}
// Find out if we have something like
// A = X
// B = X
// if so, we can pretend this is actually
// A = X
// B = A
// which allows us to coalesce A and B.
// VNI is the definition of B. LR is the life range of A that includes
// the slot just before B. If we return true, we add "B = X" to DupCopies.
// This implies that A dominates B.
static bool RegistersDefinedFromSameValue(LiveIntervals &li,
const TargetRegisterInfo &tri,
CoalescerPair &CP,
VNInfo *VNI,
LiveRange *LR,
SmallVector<MachineInstr*, 8> &DupCopies) {
// FIXME: This is very conservative. For example, we don't handle
// physical registers.
MachineInstr *MI = VNI->getCopy();
if (!MI->isFullCopy() || CP.isPartial() || CP.isPhys())
return false;
unsigned Dst = MI->getOperand(0).getReg();
unsigned Src = MI->getOperand(1).getReg();
if (!TargetRegisterInfo::isVirtualRegister(Src) ||
!TargetRegisterInfo::isVirtualRegister(Dst))
return false;
unsigned A = CP.getDstReg();
unsigned B = CP.getSrcReg();
if (B == Dst)
std::swap(A, B);
assert(Dst == A);
VNInfo *Other = LR->valno;
if (!Other->isDefByCopy())
return false;
const MachineInstr *OtherMI = Other->getCopy();
if (!OtherMI->isFullCopy())
return false;
unsigned OtherDst = OtherMI->getOperand(0).getReg();
unsigned OtherSrc = OtherMI->getOperand(1).getReg();
if (!TargetRegisterInfo::isVirtualRegister(OtherSrc) ||
!TargetRegisterInfo::isVirtualRegister(OtherDst))
return false;
assert(OtherDst == B);
if (Src != OtherSrc)
return false;
// If the copies use two different value numbers of X, we cannot merge
// A and B.
LiveInterval &SrcInt = li.getInterval(Src);
// getVNInfoBefore returns NULL for undef copies. In this case, the
// optimization is still safe.
if (SrcInt.getVNInfoBefore(Other->def) != SrcInt.getVNInfoBefore(VNI->def))
return false;
DupCopies.push_back(MI);
return true;
}
/// JoinIntervals - Attempt to join these two intervals. On failure, this
/// returns false.
bool RegisterCoalescer::JoinIntervals(CoalescerPair &CP) {
LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
// If a live interval is a physical register, check for interference with any
// aliases. The interference check implemented here is a bit more conservative
// than the full interfeence check below. We allow overlapping live ranges
// only when one is a copy of the other.
if (CP.isPhys()) {
for (const unsigned *AS = TRI->getAliasSet(CP.getDstReg()); *AS; ++AS){
if (!LIS->hasInterval(*AS))
continue;
const LiveInterval &LHS = LIS->getInterval(*AS);
LiveInterval::const_iterator LI = LHS.begin();
for (LiveInterval::const_iterator RI = RHS.begin(), RE = RHS.end();
RI != RE; ++RI) {
LI = std::lower_bound(LI, LHS.end(), RI->start);
// Does LHS have an overlapping live range starting before RI?
if ((LI != LHS.begin() && LI[-1].end > RI->start) &&
(RI->start != RI->valno->def ||
!CP.isCoalescable(LIS->getInstructionFromIndex(RI->start)))) {
DEBUG({
dbgs() << "\t\tInterference from alias: ";
LHS.print(dbgs(), TRI);
dbgs() << "\n\t\tOverlap at " << RI->start << " and no copy.\n";
});
return false;
}
// Check that LHS ranges beginning in this range are copies.
for (; LI != LHS.end() && LI->start < RI->end; ++LI) {
if (LI->start != LI->valno->def ||
!CP.isCoalescable(LIS->getInstructionFromIndex(LI->start))) {
DEBUG({
dbgs() << "\t\tInterference from alias: ";
LHS.print(dbgs(), TRI);
dbgs() << "\n\t\tDef at " << LI->start << " is not a copy.\n";
});
return false;
}
}
}
}
}
// 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;
SmallVector<MachineInstr*, 8> DupCopies;
LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), TRI); dbgs() << "\n"; });
// 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->isDefByCopy()) // Src not defined by a copy?
continue;
// Never join with a register that has EarlyClobber redefs.
if (VNI->hasRedefByEC())
return false;
// Figure out the value # from the RHS.
LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot());
// The copy could be to an aliased physreg.
if (!lr) 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 #.
MachineInstr *MI = VNI->getCopy();
if (!CP.isCoalescable(MI) &&
!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
continue;
LHSValsDefinedFromRHS[VNI] = lr->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->isDefByCopy()) // Src not defined by a copy?
continue;
// Never join with a register that has EarlyClobber redefs.
if (VNI->hasRedefByEC())
return false;
// Figure out the value # from the LHS.
LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot());
// The copy could be to an aliased physreg.
if (!lr) 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 #.
MachineInstr *MI = VNI->getCopy();
if (!CP.isCoalescable(MI) &&
!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
continue;
RHSValsDefinedFromLHS[VNI] = lr->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 != IE && J != JE) {
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 (I != IE && J != JE) {
// 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 it's re-defined by an early clobber somewhere in the live range,
// then conservatively abort coalescing.
if (NewVNInfo[LHSValNoAssignments[I->valno->id]]->hasRedefByEC())
return false;
}
if (I->end < J->end)
++I;
else
++J;
}
// 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];
if (VNI->hasPHIKill())
NewVNInfo[LHSValID]->setHasPHIKill(true);
}
// 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];
if (VNI->hasPHIKill())
NewVNInfo[RHSValID]->setHasPHIKill(true);
}
if (LHSValNoAssignments.empty())
LHSValNoAssignments.push_back(-1);
if (RHSValNoAssignments.empty())
RHSValNoAssignments.push_back(-1);
SmallVector<unsigned, 8> SourceRegisters;
for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(),
E = DupCopies.end(); I != E; ++I) {
MachineInstr *MI = *I;
// We have pretended that the assignment to B in
// A = X
// B = X
// was actually a copy from A. Now that we decided to coalesce A and B,
// transform the code into
// A = X
// X = X
// and mark the X as coalesced to keep the illusion.
unsigned Src = MI->getOperand(1).getReg();
SourceRegisters.push_back(Src);
MI->getOperand(0).substVirtReg(Src, 0, *TRI);
markAsJoined(MI);
}
// If B = X was the last use of X in a liverange, we have to shrink it now
// that B = X is gone.
for (SmallVector<unsigned, 8>::iterator I = SourceRegisters.begin(),
E = SourceRegisters.end(); I != E; ++I) {
LIS->shrinkToUses(&LIS->getInterval(*I));
}
// If we get here, we know that we can coalesce the live ranges. Ask the
// intervals to coalesce themselves now.
LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo,
MRI);
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 {
// Deeper loops first
if (LHS.first != RHS.first)
return LHS.first > RHS.first;
// Prefer blocks that are more connected in the CFG. This takes care of
// the most difficult copies first while intervals are short.
unsigned cl = LHS.second->pred_size() + LHS.second->succ_size();
unsigned cr = RHS.second->pred_size() + RHS.second->succ_size();
if (cl != cr)
return cl > cr;
// As a last resort, sort by block number.
return LHS.second->getNumber() < RHS.second->getNumber();
}
};
}
void RegisterCoalescer::CopyCoalesceInMBB(MachineBasicBlock *MBB,
std::vector<MachineInstr*> &TryAgain) {
DEBUG(dbgs() << MBB->getName() << ":\n");
SmallVector<MachineInstr*, 8> VirtCopies;
SmallVector<MachineInstr*, 8> PhysCopies;
SmallVector<MachineInstr*, 8> 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;
if (Inst->isCopy()) {
DstReg = Inst->getOperand(0).getReg();
SrcReg = Inst->getOperand(1).getReg();
} else if (Inst->isSubregToReg()) {
DstReg = Inst->getOperand(0).getReg();
SrcReg = Inst->getOperand(2).getReg();
} else
continue;
bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
if (LIS->hasInterval(SrcReg) && LIS->getInterval(SrcReg).empty())
ImpDefCopies.push_back(Inst);
else if (SrcIsPhys || DstIsPhys)
PhysCopies.push_back(Inst);
else
VirtCopies.push_back(Inst);
}
// Try coalescing implicit copies and insert_subreg <undef> 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) {
MachineInstr *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) {
MachineInstr *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) {
MachineInstr *TheCopy = VirtCopies[i];
bool Again = false;
if (!JoinCopy(TheCopy, Again))
if (Again)
TryAgain.push_back(TheCopy);
}
}
void RegisterCoalescer::joinIntervals() {
DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n");
std::vector<MachineInstr*> TryAgainList;
if (Loops->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(Loops->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) {
MachineInstr *&TheCopy = TryAgainList[i];
if (!TheCopy)
continue;
bool Again = false;
bool Success = JoinCopy(TheCopy, Again);
if (Success || !Again) {
TheCopy= 0; // Mark this one as done.
ProgressMade = true;
}
}
}
}
void RegisterCoalescer::releaseMemory() {
JoinedCopies.clear();
ReMatCopies.clear();
ReMatDefs.clear();
}
bool RegisterCoalescer::runOnMachineFunction(MachineFunction &fn) {
MF = &fn;
MRI = &fn.getRegInfo();
TM = &fn.getTarget();
TRI = TM->getRegisterInfo();
TII = TM->getInstrInfo();
LIS = &getAnalysis<LiveIntervals>();
LDV = &getAnalysis<LiveDebugVariables>();
AA = &getAnalysis<AliasAnalysis>();
Loops = &getAnalysis<MachineLoopInfo>();
DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n"
<< "********** Function: "
<< ((Value*)MF->getFunction())->getName() << '\n');
if (VerifyCoalescing)
MF->verify(this, "Before register coalescing");
RegClassInfo.runOnMachineFunction(fn);
// Join (coalesce) intervals if requested.
if (EnableJoining) {
joinIntervals();
DEBUG({
dbgs() << "********** INTERVALS POST JOINING **********\n";
for (LiveIntervals::iterator I = LIS->begin(), E = LIS->end();
I != E; ++I){
I->second->print(dbgs(), TRI);
dbgs() << "\n";
}
});
}
// Perform a final pass over the instructions and compute spill weights
// and remove identity moves.
SmallVector<unsigned, 4> DeadDefs, InflateRegs;
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;
if (JoinedCopies.count(MI)) {
// Delete all coalesced copies.
bool DoDelete = true;
assert(MI->isCopyLike() && "Unrecognized copy instruction");
unsigned SrcReg = MI->getOperand(MI->isSubregToReg() ? 2 : 1).getReg();
unsigned DstReg = MI->getOperand(0).getReg();
// Collect candidates for register class inflation.
if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
RegClassInfo.isProperSubClass(MRI->getRegClass(SrcReg)))
InflateRegs.push_back(SrcReg);
if (TargetRegisterInfo::isVirtualRegister(DstReg) &&
RegClassInfo.isProperSubClass(MRI->getRegClass(DstReg)))
InflateRegs.push_back(DstReg);
if (TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
MI->getNumOperands() > 2)
// Do not delete extract_subreg, insert_subreg of physical
// registers unless the definition is dead. e.g.
// %DO<def> = INSERT_SUBREG %D0<undef>, %S0<kill>, 1
// or else the scavenger may complain. LowerSubregs will
// delete them later.
DoDelete = false;
if (MI->allDefsAreDead()) {
if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
LIS->hasInterval(SrcReg))
LIS->shrinkToUses(&LIS->getInterval(SrcReg));
DoDelete = true;
}
if (!DoDelete) {
// We need the instruction to adjust liveness, so make it a KILL.
if (MI->isSubregToReg()) {
MI->RemoveOperand(3);
MI->RemoveOperand(1);
}
MI->setDesc(TII->get(TargetOpcode::KILL));
mii = llvm::next(mii);
} else {
LIS->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);
// Remat may also enable register class inflation.
if (RegClassInfo.isProperSubClass(MRI->getRegClass(Reg)))
InflateRegs.push_back(Reg);
}
if (MO.isDead())
continue;
if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
!MRI->use_nodbg_empty(Reg)) {
isDead = false;
break;
}
}
if (isDead) {
while (!DeadDefs.empty()) {
unsigned DeadDef = DeadDefs.back();
DeadDefs.pop_back();
RemoveDeadDef(LIS->getInterval(DeadDef), MI);
}
LIS->RemoveMachineInstrFromMaps(mii);
mii = mbbi->erase(mii);
continue;
} else
DeadDefs.clear();
}
++mii;
// Check for now unnecessary kill flags.
if (LIS->isNotInMIMap(MI)) continue;
SlotIndex DefIdx = LIS->getInstructionIndex(MI).getDefIndex();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isKill()) continue;
unsigned reg = MO.getReg();
if (!reg || !LIS->hasInterval(reg)) continue;
if (!LIS->getInterval(reg).killedAt(DefIdx)) {
MO.setIsKill(false);
continue;
}
// When leaving a kill flag on a physreg, check if any subregs should
// remain alive.
if (!TargetRegisterInfo::isPhysicalRegister(reg))
continue;
for (const unsigned *SR = TRI->getSubRegisters(reg);
unsigned S = *SR; ++SR)
if (LIS->hasInterval(S) && LIS->getInterval(S).liveAt(DefIdx))
MI->addRegisterDefined(S, TRI);
}
}
}
// After deleting a lot of copies, register classes may be less constrained.
// Removing sub-register opreands may alow GR32_ABCD -> GR32 and DPR_VFP2 ->
// DPR inflation.
array_pod_sort(InflateRegs.begin(), InflateRegs.end());
InflateRegs.erase(std::unique(InflateRegs.begin(), InflateRegs.end()),
InflateRegs.end());
DEBUG(dbgs() << "Trying to inflate " << InflateRegs.size() << " regs.\n");
for (unsigned i = 0, e = InflateRegs.size(); i != e; ++i) {
unsigned Reg = InflateRegs[i];
if (MRI->reg_nodbg_empty(Reg))
continue;
if (MRI->recomputeRegClass(Reg, *TM)) {
DEBUG(dbgs() << PrintReg(Reg) << " inflated to "
<< MRI->getRegClass(Reg)->getName() << '\n');
++NumInflated;
}
}
DEBUG(dump());
DEBUG(LDV->dump());
if (VerifyCoalescing)
MF->verify(this, "After register coalescing");
return true;
}
/// print - Implement the dump method.
void RegisterCoalescer::print(raw_ostream &O, const Module* m) const {
LIS->print(O, m);
}