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llvm-6502/lib/CodeGen/RegisterCoalescer.cpp
Rafael Espindola 9c3d5a70f4 Now that RegistersDefinedFromSameValue handles one instruction being an 
implicit_def, the other instruction can be anything, including instructions
that define multiple values. Be careful about that and don't assume what operand
0 is.
Fixes pr13249.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159509 91177308-0d34-0410-b5e6-96231b3b80d8
2012-07-01 17:08:01 +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 "regalloc"
#include "RegisterCoalescer.h"
#include "LiveDebugVariables.h"
#include "VirtRegMap.h"
#include "llvm/Pass.h"
#include "llvm/Value.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveRangeEdit.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.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(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>
VerifyCoalescing("verify-coalescing",
cl::desc("Verify machine instrs before and after register coalescing"),
cl::Hidden);
namespace {
class RegisterCoalescer : public MachineFunctionPass,
private LiveRangeEdit::Delegate {
MachineFunction* MF;
MachineRegisterInfo* MRI;
const TargetMachine* TM;
const TargetRegisterInfo* TRI;
const TargetInstrInfo* TII;
LiveIntervals *LIS;
LiveDebugVariables *LDV;
const MachineLoopInfo* Loops;
AliasAnalysis *AA;
RegisterClassInfo RegClassInfo;
/// WorkList - Copy instructions yet to be coalesced.
SmallVector<MachineInstr*, 8> WorkList;
/// ErasedInstrs - Set of instruction pointers that have been erased, and
/// that may be present in WorkList.
SmallPtrSet<MachineInstr*, 8> ErasedInstrs;
/// Dead instructions that are about to be deleted.
SmallVector<MachineInstr*, 8> DeadDefs;
/// Virtual registers to be considered for register class inflation.
SmallVector<unsigned, 8> InflateRegs;
/// Recursively eliminate dead defs in DeadDefs.
void eliminateDeadDefs();
/// LiveRangeEdit callback.
void LRE_WillEraseInstruction(MachineInstr *MI);
/// joinAllIntervals - join compatible live intervals
void joinAllIntervals();
/// copyCoalesceInMBB - Coalesce copies in the specified MBB, putting
/// copies that cannot yet be coalesced into WorkList.
void copyCoalesceInMBB(MachineBasicBlock *MBB);
/// copyCoalesceWorkList - Try to coalesce all copies in WorkList after
/// position From. Return true if any progress was made.
bool copyCoalesceWorkList(unsigned From = 0);
/// 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);
/// Attempt joining with a reserved physreg.
bool joinReservedPhysReg(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.
bool reMaterializeTrivialDef(LiveInterval &SrcInt, unsigned DstReg,
MachineInstr *CopyMI);
/// canJoinPhys - Return true if a physreg copy should be joined.
bool canJoinPhys(CoalescerPair &CP);
/// 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(unsigned SrcReg, unsigned DstReg, unsigned SubIdx);
/// 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::RegisterCoalescerID = 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_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 = 0;
SrcIdx = DstIdx = 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.
const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
// Both registers have subreg indices.
if (SrcSub && DstSub) {
// Copies between different sub-registers are never coalescable.
if (Src == Dst && SrcSub != DstSub)
return false;
NewRC = TRI.getCommonSuperRegClass(SrcRC, SrcSub, DstRC, DstSub,
SrcIdx, DstIdx);
if (!NewRC)
return false;
} else if (DstSub) {
// SrcReg will be merged with a sub-register of DstReg.
SrcIdx = DstSub;
NewRC = TRI.getMatchingSuperRegClass(DstRC, SrcRC, DstSub);
} else if (SrcSub) {
// DstReg will be merged with a sub-register of SrcReg.
DstIdx = SrcSub;
NewRC = TRI.getMatchingSuperRegClass(SrcRC, DstRC, SrcSub);
} else {
// This is a straight copy without sub-registers.
NewRC = TRI.getCommonSubClass(DstRC, SrcRC);
}
// The combined constraint may be impossible to satisfy.
if (!NewRC)
return false;
// Prefer SrcReg to be a sub-register of DstReg.
// FIXME: Coalescer should support subregs symmetrically.
if (DstIdx && !SrcIdx) {
std::swap(Src, Dst);
std::swap(SrcIdx, DstIdx);
Flipped = !Flipped;
}
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;
return true;
}
bool CoalescerPair::flip() {
if (TargetRegisterInfo::isPhysicalRegister(DstReg))
return false;
std::swap(SrcReg, DstReg);
std::swap(SrcIdx, DstIdx);
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(!DstIdx && !SrcIdx && "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, SrcIdx, SrcSub) == compose(TRI, DstIdx, 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);
MachineFunctionPass::getAnalysisUsage(AU);
}
void RegisterCoalescer::eliminateDeadDefs() {
SmallVector<LiveInterval*, 8> NewRegs;
LiveRangeEdit(0, NewRegs, *MF, *LIS, 0, this).eliminateDeadDefs(DeadDefs);
}
// Callback from eliminateDeadDefs().
void RegisterCoalescer::LRE_WillEraseInstruction(MachineInstr *MI) {
// MI may be in WorkList. Make sure we don't visit it.
ErasedInstrs.insert(MI);
}
/// 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) {
assert(!CP.isPartial() && "This doesn't work for partial copies.");
assert(!CP.isPhys() && "This doesn't work for physreg copies.");
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).getRegSlot();
// 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->def != CopyIdx) return false;
// AValNo is the value number in A that defines the copy, A3 in the example.
SlotIndex CopyUseIdx = CopyIdx.getRegSlot(true);
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 AValNo is defined as a copy from IntB, we can potentially process this.
// Get the instruction that defines this value number.
MachineInstr *ACopyMI = LIS->getInstructionFromIndex(AValNo->def);
if (!CP.isCoalescable(ACopyMI))
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;
DEBUG(dbgs() << "Extending: " << PrintReg(IntB.reg, 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;
// 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));
// 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 << '\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);
}
// Rewrite the copy. 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.
CopyMI->substituteRegister(IntA.reg, IntB.reg, 0, *TRI);
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) {
assert (!CP.isPhys());
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
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->def != CopyIdx)
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.getRegSlot(true));
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;
if (!DefMI->isCommutable())
return false;
// If DefMI is a two-address instruction then commuting it will change the
// destination register.
int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg);
assert(DefIdx != -1);
unsigned UseOpIdx;
if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx))
return false;
unsigned Op1, Op2, NewDstIdx;
if (!TII->findCommutedOpIndices(DefMI, Op1, Op2))
return false;
if (Op1 == UseOpIdx)
NewDstIdx = Op2;
else if (Op2 == UseOpIdx)
NewDstIdx = Op1;
else
return false;
MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
unsigned NewReg = NewDstMO.getReg();
if (NewReg != IntB.reg || !NewDstMO.isKill())
return false;
// Make sure there are no other definitions of IntB that would reach the
// uses which the new definition can reach.
if (hasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
return false;
// If some of the uses of IntA.reg is already coalesced away, return false.
// It's not possible to determine whether it's safe to perform the coalescing.
for (MachineRegisterInfo::use_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() || ULR->valno != AValNo)
continue;
// If this use is tied to a def, we can't rewrite the register.
if (UseMI->isRegTiedToDefOperand(UI.getOperandNo()))
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);
MachineBasicBlock::iterator Pos = DefMI;
MBB->insert(Pos, 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 (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).getRegSlot(true);
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.getRegSlot();
VNInfo *DVNI = IntB.getVNInfoAt(DefIdx);
if (!DVNI)
continue;
DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
assert(DVNI->def == DefIdx);
BValNo = IntB.MergeValueNumberInto(BValNo, DVNI);
ErasedInstrs.insert(UseMI);
LIS->RemoveMachineInstrFromMaps(UseMI);
UseMI->eraseFromParent();
}
// Extend BValNo by merging in IntA live ranges of AValNo. Val# definition
// is updated.
VNInfo *ValNo = BValNo;
ValNo->def = AValNo->def;
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,
unsigned DstReg,
MachineInstr *CopyMI) {
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot(true);
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");
if (!DefMI->isAsCheapAsAMove())
return false;
if (!TII->isTriviallyReMaterializable(DefMI, AA))
return false;
bool SawStore = false;
if (!DefMI->isSafeToMove(TII, AA, SawStore))
return false;
const MCInstrDesc &MCID = DefMI->getDesc();
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, *MF);
if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
if (MRI->getRegClass(DstReg) != RC)
return false;
} else if (!RC->contains(DstReg))
return false;
}
MachineBasicBlock *MBB = CopyMI->getParent();
MachineBasicBlock::iterator MII =
llvm::next(MachineBasicBlock::iterator(CopyMI));
TII->reMaterialize(*MBB, MII, DstReg, 0, DefMI, *TRI);
MachineInstr *NewMI = prior(MII);
// NewMI may have dead implicit defs (E.g. EFLAGS for MOV<bits>r0 on X86).
// We need to remember these so we can add intervals once we insert
// NewMI into SlotIndexes.
SmallVector<unsigned, 4> NewMIImplDefs;
for (unsigned i = NewMI->getDesc().getNumOperands(),
e = NewMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = NewMI->getOperand(i);
if (MO.isReg()) {
assert(MO.isDef() && MO.isImplicit() && MO.isDead() &&
TargetRegisterInfo::isPhysicalRegister(MO.getReg()));
NewMIImplDefs.push_back(MO.getReg());
}
}
// 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()) {
assert(MO.isImplicit() && "No explicit operands after implict operands.");
// Discard VReg implicit defs.
if (TargetRegisterInfo::isPhysicalRegister(MO.getReg())) {
NewMI->addOperand(MO);
}
}
}
LIS->ReplaceMachineInstrInMaps(CopyMI, NewMI);
SlotIndex NewMIIdx = LIS->getInstructionIndex(NewMI);
for (unsigned i = 0, e = NewMIImplDefs.size(); i != e; ++i) {
unsigned Reg = NewMIImplDefs[i];
for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units)
if (LiveInterval *LI = LIS->getCachedRegUnit(*Units))
LI->createDeadDef(NewMIIdx.getRegSlot(), LIS->getVNInfoAllocator());
}
CopyMI->eraseFromParent();
ErasedInstrs.insert(CopyMI);
DEBUG(dbgs() << "Remat: " << *NewMI);
++NumReMats;
// The source interval can become smaller because we removed a use.
LIS->shrinkToUses(&SrcInt, &DeadDefs);
if (!DeadDefs.empty())
eliminateDeadDefs();
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.getRegSlot());
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(unsigned SrcReg,
unsigned DstReg,
unsigned SubIdx) {
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
LiveInterval *DstInt = DstIsPhys ? 0 : &LIS->getInterval(DstReg);
// Update LiveDebugVariables.
LDV->renameRegister(SrcReg, DstReg, SubIdx);
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg);
MachineInstr *UseMI = I.skipInstruction();) {
SmallVector<unsigned,8> Ops;
bool Reads, Writes;
tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
// If SrcReg wasn't read, it may still be the case that DstReg is live-in
// because SrcReg is a sub-register.
if (DstInt && !Reads && SubIdx)
Reads = DstInt->liveAt(LIS->getInstructionIndex(UseMI));
// Replace SrcReg with DstReg in all UseMI operands.
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
MachineOperand &MO = UseMI->getOperand(Ops[i]);
// Adjust <undef> flags in case of sub-register joins. We don't want to
// turn a full def into a read-modify-write sub-register def and vice
// versa.
if (SubIdx && MO.isDef())
MO.setIsUndef(!Reads);
if (DstIsPhys)
MO.substPhysReg(DstReg, *TRI);
else
MO.substVirtReg(DstReg, SubIdx, *TRI);
}
DEBUG({
dbgs() << "\t\tupdated: ";
if (!UseMI->isDebugValue())
dbgs() << LIS->getInstructionIndex(UseMI) << "\t";
dbgs() << *UseMI;
});
}
}
/// canJoinPhys - Return true if a copy involving a physreg should be joined.
bool RegisterCoalescer::canJoinPhys(CoalescerPair &CP) {
/// 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 (!RegClassInfo.isReserved(CP.getDstReg())) {
DEBUG(dbgs() << "\tCan only merge into reserved registers.\n");
return false;
}
LiveInterval &JoinVInt = LIS->getInterval(CP.getSrcReg());
if (CP.isFlipped() && JoinVInt.containsOneValue())
return true;
DEBUG(dbgs() << "\tCannot join defs into reserved register.\n");
return false;
}
/// 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;
DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
CoalescerPair CP(*TRI);
if (!CP.setRegisters(CopyMI)) {
DEBUG(dbgs() << "\tNot coalescable.\n");
return false;
}
// Dead code elimination. This really should be handled by MachineDCE, but
// sometimes dead copies slip through, and we can't generate invalid live
// ranges.
if (!CP.isPhys() && CopyMI->allDefsAreDead()) {
DEBUG(dbgs() << "\tCopy is dead.\n");
DeadDefs.push_back(CopyMI);
eliminateDeadDefs();
return true;
}
// Eliminate undefs.
if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) {
DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n");
LIS->RemoveMachineInstrFromMaps(CopyMI);
CopyMI->eraseFromParent();
return false; // Not coalescable.
}
// Coalesced copies are normally removed immediately, but transformations
// like removeCopyByCommutingDef() can inadvertently create identity copies.
// When that happens, just join the values and remove the copy.
if (CP.getSrcReg() == CP.getDstReg()) {
LiveInterval &LI = LIS->getInterval(CP.getSrcReg());
DEBUG(dbgs() << "\tCopy already coalesced: " << LI << '\n');
LiveRangeQuery LRQ(LI, LIS->getInstructionIndex(CopyMI));
if (VNInfo *DefVNI = LRQ.valueDefined()) {
VNInfo *ReadVNI = LRQ.valueIn();
assert(ReadVNI && "No value before copy and no <undef> flag.");
assert(ReadVNI != DefVNI && "Cannot read and define the same value.");
LI.MergeValueNumberInto(DefVNI, ReadVNI);
DEBUG(dbgs() << "\tMerged values: " << LI << '\n');
}
LIS->RemoveMachineInstrFromMaps(CopyMI);
CopyMI->eraseFromParent();
return true;
}
// Enforce policies.
if (CP.isPhys()) {
DEBUG(dbgs() << "\tConsidering merging " << PrintReg(CP.getSrcReg(), TRI)
<< " with " << PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx())
<< '\n');
if (!canJoinPhys(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()),
CP.getDstReg(), CopyMI))
return true;
return false;
}
} else {
DEBUG({
dbgs() << "\tConsidering merging to " << CP.getNewRC()->getName()
<< " with ";
if (CP.getDstIdx() && CP.getSrcIdx())
dbgs() << PrintReg(CP.getDstReg()) << " in "
<< TRI->getSubRegIndexName(CP.getDstIdx()) << " and "
<< PrintReg(CP.getSrcReg()) << " in "
<< TRI->getSubRegIndexName(CP.getSrcIdx()) << '\n';
else
dbgs() << PrintReg(CP.getSrcReg(), TRI) << " in "
<< PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx()) << '\n';
});
// When possible, let DstReg be the larger interval.
if (!CP.isPartial() && 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()),
CP.getDstReg(), CopyMI))
return true;
// If we can eliminate the copy without merging the live ranges, do so now.
if (!CP.isPartial() && !CP.isPhys()) {
if (adjustCopiesBackFrom(CP, CopyMI) ||
removeCopyByCommutingDef(CP, CopyMI)) {
LIS->RemoveMachineInstrFromMaps(CopyMI);
CopyMI->eraseFromParent();
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());
}
// Removing sub-register copies can ease the register class constraints.
// Make sure we attempt to inflate the register class of DstReg.
if (!CP.isPhys() && RegClassInfo.isProperSubClass(CP.getNewRC()))
InflateRegs.push_back(CP.getDstReg());
// CopyMI has been erased by joinIntervals at this point. Remove it from
// ErasedInstrs since copyCoalesceWorkList() won't add a successful join back
// to the work list. This keeps ErasedInstrs from growing needlessly.
ErasedInstrs.erase(CopyMI);
// Rewrite all SrcReg operands to DstReg.
// Also update DstReg operands to include DstIdx if it is set.
if (CP.getDstIdx())
updateRegDefsUses(CP.getDstReg(), CP.getDstReg(), CP.getDstIdx());
updateRegDefsUses(CP.getSrcReg(), CP.getDstReg(), CP.getSrcIdx());
// SrcReg is guaranteed 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({
dbgs() << "\tJoined. Result = " << PrintReg(CP.getDstReg(), TRI);
if (!CP.isPhys())
dbgs() << LIS->getInterval(CP.getDstReg());
dbgs() << '\n';
});
++numJoins;
return true;
}
/// Attempt joining with a reserved physreg.
bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) {
assert(CP.isPhys() && "Must be a physreg copy");
assert(RegClassInfo.isReserved(CP.getDstReg()) && "Not a reserved register");
LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
DEBUG(dbgs() << "\t\tRHS = " << PrintReg(CP.getSrcReg()) << ' ' << RHS
<< '\n');
assert(CP.isFlipped() && RHS.containsOneValue() &&
"Invalid join with reserved register");
// Optimization for reserved registers like ESP. We can only merge with a
// reserved physreg if RHS has a single value that is a copy of CP.DstReg().
// The live range of the reserved register will look like a set of dead defs
// - we don't properly track the live range of reserved registers.
// Deny any overlapping intervals. This depends on all the reserved
// register live ranges to look like dead defs.
for (MCRegUnitIterator UI(CP.getDstReg(), TRI); UI.isValid(); ++UI)
if (RHS.overlaps(LIS->getRegUnit(*UI))) {
DEBUG(dbgs() << "\t\tInterference: " << PrintRegUnit(*UI, TRI) << '\n');
return false;
}
// Skip any value computations, we are not adding new values to the
// reserved register. Also skip merging the live ranges, the reserved
// register live range doesn't need to be accurate as long as all the
// defs are there.
// We don't track kills for reserved registers.
MRI->clearKillFlags(CP.getSrcReg());
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,
VNInfo *OtherVNI,
SmallVector<MachineInstr*, 8> &DupCopies) {
// FIXME: This is very conservative. For example, we don't handle
// physical registers.
MachineInstr *MI = li.getInstructionFromIndex(VNI->def);
if (!MI || CP.isPartial() || CP.isPhys())
return false;
unsigned A = CP.getDstReg();
if (!TargetRegisterInfo::isVirtualRegister(A))
return false;
unsigned B = CP.getSrcReg();
if (!TargetRegisterInfo::isVirtualRegister(B))
return false;
MachineInstr *OtherMI = li.getInstructionFromIndex(OtherVNI->def);
if (!OtherMI)
return false;
if (MI->isImplicitDef()) {
DupCopies.push_back(MI);
return true;
} else {
if (!MI->isFullCopy())
return false;
unsigned Src = MI->getOperand(1).getReg();
if (!TargetRegisterInfo::isVirtualRegister(Src))
return false;
if (!OtherMI->isFullCopy())
return false;
unsigned OtherSrc = OtherMI->getOperand(1).getReg();
if (!TargetRegisterInfo::isVirtualRegister(OtherSrc))
return false;
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(OtherVNI->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) {
// Handle physreg joins separately.
if (CP.isPhys())
return joinReservedPhysReg(CP);
LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
DEBUG(dbgs() << "\t\tRHS = " << PrintReg(CP.getSrcReg()) << ' ' << RHS
<< '\n');
// 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;
SmallVector<MachineInstr*, 8> DeadCopies;
LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
DEBUG(dbgs() << "\t\tLHS = " << PrintReg(CP.getDstReg(), TRI) << ' ' << LHS
<< '\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->isPHIDef())
continue;
MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
assert(MI && "Missing def");
if (!MI->isCopyLike() && !MI->isImplicitDef()) // Src not defined by a copy?
continue;
// Figure out the value # from the RHS.
VNInfo *OtherVNI = RHS.getVNInfoBefore(VNI->def);
// The copy could be to an aliased physreg.
if (!OtherVNI)
continue;
// DstReg is known to be a register in the LHS interval. If the src is
// from the RHS interval, we can use its value #.
if (CP.isCoalescable(MI))
DeadCopies.push_back(MI);
else if (!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, OtherVNI,
DupCopies))
continue;
LHSValsDefinedFromRHS[VNI] = OtherVNI;
}
// 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->isPHIDef())
continue;
MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
assert(MI && "Missing def");
if (!MI->isCopyLike() && !MI->isImplicitDef()) // Src not defined by a copy?
continue;
// Figure out the value # from the LHS.
VNInfo *OtherVNI = LHS.getVNInfoBefore(VNI->def);
// The copy could be to an aliased physreg.
if (!OtherVNI)
continue;
// DstReg is known to be a register in the RHS interval. If the src is
// from the LHS interval, we can use its value #.
if (CP.isCoalescable(MI))
DeadCopies.push_back(MI);
else if (!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, OtherVNI,
DupCopies))
continue;
RHSValsDefinedFromLHS[VNI] = OtherVNI;
}
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();
// Collect interval end points that will no longer be kills.
SmallVector<MachineInstr*, 8> LHSOldKills;
SmallVector<MachineInstr*, 8> RHSOldKills;
// 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.
// If so, check value # info to determine if they are really different.
if (I->end > J->start && J->end > I->start) {
// 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;
// Extended live ranges should no longer be killed.
if (!I->end.isBlock() && I->end < J->end)
if (MachineInstr *MI = LIS->getInstructionFromIndex(I->end))
LHSOldKills.push_back(MI);
if (!J->end.isBlock() && J->end < I->end)
if (MachineInstr *MI = LIS->getInstructionFromIndex(J->end))
RHSOldKills.push_back(MI);
}
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);
}
// Clear kill flags where live ranges are extended.
while (!LHSOldKills.empty())
LHSOldKills.pop_back_val()->clearRegisterKills(LHS.reg, TRI);
while (!RHSOldKills.empty())
RHSOldKills.pop_back_val()->clearRegisterKills(RHS.reg, TRI);
if (LHSValNoAssignments.empty())
LHSValNoAssignments.push_back(-1);
if (RHSValNoAssignments.empty())
RHSValNoAssignments.push_back(-1);
// Now erase all the redundant copies.
for (unsigned i = 0, e = DeadCopies.size(); i != e; ++i) {
MachineInstr *MI = DeadCopies[i];
if (!ErasedInstrs.insert(MI))
continue;
DEBUG(dbgs() << "\t\terased:\t" << LIS->getInstructionIndex(MI)
<< '\t' << *MI);
LIS->RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
}
SmallVector<unsigned, 8> SourceRegisters;
for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(),
E = DupCopies.end(); I != E; ++I) {
MachineInstr *MI = *I;
if (!ErasedInstrs.insert(MI))
continue;
// If MI is a copy, then 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
// In the case of the implicit_def, we just have to remove it.
if (!MI->isImplicitDef()) {
unsigned Src = MI->getOperand(1).getReg();
SourceRegisters.push_back(Src);
}
LIS->RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
}
// 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();
}
};
}
// Try joining WorkList copies starting from index From.
// Null out any successful joins.
bool RegisterCoalescer::copyCoalesceWorkList(unsigned From) {
assert(From <= WorkList.size() && "Out of range");
bool Progress = false;
for (unsigned i = From, e = WorkList.size(); i != e; ++i) {
if (!WorkList[i])
continue;
// Skip instruction pointers that have already been erased, for example by
// dead code elimination.
if (ErasedInstrs.erase(WorkList[i])) {
WorkList[i] = 0;
continue;
}
bool Again = false;
bool Success = joinCopy(WorkList[i], Again);
Progress |= Success;
if (Success || !Again)
WorkList[i] = 0;
}
return Progress;
}
void
RegisterCoalescer::copyCoalesceInMBB(MachineBasicBlock *MBB) {
DEBUG(dbgs() << MBB->getName() << ":\n");
// Collect all copy-like instructions in MBB. Don't start coalescing anything
// yet, it might invalidate the iterator.
const unsigned PrevSize = WorkList.size();
for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
MII != E; ++MII)
if (MII->isCopyLike())
WorkList.push_back(MII);
// Try coalescing the collected copies immediately, and remove the nulls.
// This prevents the WorkList from getting too large since most copies are
// joinable on the first attempt.
if (copyCoalesceWorkList(PrevSize))
WorkList.erase(std::remove(WorkList.begin() + PrevSize, WorkList.end(),
(MachineInstr*)0), WorkList.end());
}
void RegisterCoalescer::joinAllIntervals() {
DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n");
assert(WorkList.empty() && "Old data still around.");
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);
} 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);
}
// Joining intervals can allow other intervals to be joined. Iteratively join
// until we make no progress.
while (copyCoalesceWorkList())
/* empty */ ;
}
void RegisterCoalescer::releaseMemory() {
ErasedInstrs.clear();
WorkList.clear();
DeadDefs.clear();
InflateRegs.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)
joinAllIntervals();
// After deleting a lot of copies, register classes may be less constrained.
// Removing sub-register operands may allow 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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