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llvm-6502/lib/CodeGen/RegisterCoalescer.cpp
Jakob Stoklund Olesen 9b82d50d20 Revert r139782, "RemoveCopyByCommutingDef doesn't need hasPHIKill()." 
It does, after all.

RemoveCopyByCommutingDef rewrites the uses of one particular value
number in A. It doesn't know how to rewrite phi uses, so there can't be
any.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139787 91177308-0d34-0410-b5e6-96231b3b80d8
2011-09-15 06:27:32 +00:00

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//===- 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, unsigned DstSubIdx,
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 (!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 = 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,
unsigned DstSubIdx,
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;
}
// If destination register has a sub-register index on it, make sure it
// matches the instruction register class.
if (DstSubIdx) {
const MCInstrDesc &MCID = DefMI->getDesc();
if (MCID.getNumDefs() != 1)
return false;
const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg);
const TargetRegisterClass *DstSubRC =
DstRC->getSubRegisterRegClass(DstSubIdx);
const TargetRegisterClass *DefRC = TII->getRegClass(MCID, 0, TRI);
if (DefRC == DstRC)
DstSubIdx = 0;
else if (DefRC != DstSubRC)
return false;
}
RemoveCopyFlag(DstReg, CopyMI);
MachineBasicBlock *MBB = CopyMI->getParent();
MachineBasicBlock::iterator MII =
llvm::next(MachineBasicBlock::iterator(CopyMI));
TII->reMaterialize(*MBB, MII, DstReg, DstSubIdx, 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(), 0, 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();
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(), 0, 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(), 0, 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);
}
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