[llvm-commits] [llvm] r65793 - /llvm/branches/Apple/Dib/lib/CodeGen/TwoAddressInstructionPass.cpp
Evan Cheng
evan.cheng at apple.com
Sun Mar 1 17:05:02 PST 2009
Author: evancheng
Date: Sun Mar 1 19:05:02 2009
New Revision: 65793
URL: http://llvm.org/viewvc/llvm-project?rev=65793&view=rev
Log:
Pull r65752 into Dib.
Modified:
llvm/branches/Apple/Dib/lib/CodeGen/TwoAddressInstructionPass.cpp
Modified: llvm/branches/Apple/Dib/lib/CodeGen/TwoAddressInstructionPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/Apple/Dib/lib/CodeGen/TwoAddressInstructionPass.cpp?rev=65793&r1=65792&r2=65793&view=diff
==============================================================================
--- llvm/branches/Apple/Dib/lib/CodeGen/TwoAddressInstructionPass.cpp (original)
+++ llvm/branches/Apple/Dib/lib/CodeGen/TwoAddressInstructionPass.cpp Sun Mar 1 19:05:02 2009
@@ -53,6 +53,7 @@
STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address");
STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk");
STATISTIC(NumReMats, "Number of instructions re-materialized");
+STATISTIC(NumDeletes, "Number of dead instructions deleted");
namespace {
class VISIBILITY_HIDDEN TwoAddressInstructionPass
@@ -62,28 +63,41 @@
MachineRegisterInfo *MRI;
LiveVariables *LV;
+ // DistanceMap - Keep track the distance of a MI from the start of the
+ // current basic block.
+ DenseMap<MachineInstr*, unsigned> DistanceMap;
+
+ // SrcRegMap - A map from virtual registers to physical registers which
+ // are likely targets to be coalesced to due to copies from physical
+ // registers to virtual registers. e.g. v1024 = move r0.
+ DenseMap<unsigned, unsigned> SrcRegMap;
+
+ // DstRegMap - A map from virtual registers to physical registers which
+ // are likely targets to be coalesced to due to copies to physical
+ // registers from virtual registers. e.g. r1 = move v1024.
+ DenseMap<unsigned, unsigned> DstRegMap;
+
bool Sink3AddrInstruction(MachineBasicBlock *MBB, MachineInstr *MI,
unsigned Reg,
MachineBasicBlock::iterator OldPos);
bool isProfitableToReMat(unsigned Reg, const TargetRegisterClass *RC,
MachineInstr *MI, MachineInstr *DefMI,
- MachineBasicBlock *MBB, unsigned Loc,
- DenseMap<MachineInstr*, unsigned> &DistanceMap);
+ MachineBasicBlock *MBB, unsigned Loc);
bool NoUseAfterLastDef(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist,
- DenseMap<MachineInstr*, unsigned> &DistanceMap,
unsigned &LastDef);
bool isProfitableToCommute(unsigned regB, unsigned regC,
MachineInstr *MI, MachineBasicBlock *MBB,
- unsigned Dist,
- DenseMap<MachineInstr*, unsigned> &DistanceMap);
+ unsigned Dist);
bool CommuteInstruction(MachineBasicBlock::iterator &mi,
MachineFunction::iterator &mbbi,
- unsigned RegC, unsigned Dist,
- DenseMap<MachineInstr*, unsigned> &DistanceMap);
+ unsigned RegB, unsigned RegC, unsigned Dist);
+
+ void ProcessCopy(MachineInstr *MI, MachineBasicBlock *MBB,
+ SmallPtrSet<MachineInstr*, 8> &Processed);
public:
static char ID; // Pass identification, replacement for typeid
TwoAddressInstructionPass() : MachineFunctionPass(&ID) {}
@@ -232,10 +246,9 @@
/// the register.
bool
TwoAddressInstructionPass::isProfitableToReMat(unsigned Reg,
- const TargetRegisterClass *RC,
- MachineInstr *MI, MachineInstr *DefMI,
- MachineBasicBlock *MBB, unsigned Loc,
- DenseMap<MachineInstr*, unsigned> &DistanceMap){
+ const TargetRegisterClass *RC,
+ MachineInstr *MI, MachineInstr *DefMI,
+ MachineBasicBlock *MBB, unsigned Loc) {
bool OtherUse = false;
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
UE = MRI->use_end(); UI != UE; ++UI) {
@@ -268,9 +281,8 @@
/// two-address instruction which is being processed. It also returns the last
/// def location by reference
bool TwoAddressInstructionPass::NoUseAfterLastDef(unsigned Reg,
- MachineBasicBlock *MBB, unsigned Dist,
- DenseMap<MachineInstr*, unsigned> &DistanceMap,
- unsigned &LastDef) {
+ MachineBasicBlock *MBB, unsigned Dist,
+ unsigned &LastDef) {
LastDef = 0;
unsigned LastUse = Dist;
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(Reg),
@@ -291,12 +303,110 @@
return !(LastUse > LastDef && LastUse < Dist);
}
+/// isCopyToReg - Return true if the specified MI is a copy instruction or
+/// a extract_subreg instruction. It also returns the source and destination
+/// registers and whether they are physical registers by reference.
+static bool isCopyToReg(MachineInstr &MI, const TargetInstrInfo *TII,
+ unsigned &SrcReg, unsigned &DstReg,
+ bool &IsSrcPhys, bool &IsDstPhys) {
+ SrcReg = 0;
+ DstReg = 0;
+ unsigned SrcSubIdx, DstSubIdx;
+ if (!TII->isMoveInstr(MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)) {
+ if (MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
+ DstReg = MI.getOperand(0).getReg();
+ SrcReg = MI.getOperand(1).getReg();
+ } else if (MI.getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
+ DstReg = MI.getOperand(0).getReg();
+ SrcReg = MI.getOperand(2).getReg();
+ }
+ }
+
+ if (DstReg) {
+ IsSrcPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
+ IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
+ return true;
+ }
+ return false;
+}
+
+/// isTwoAddrUse - Return true if the specified MI uses the specified register
+/// as a two-address use. If so, return the destination register by reference.
+static bool isTwoAddrUse(MachineInstr &MI, unsigned Reg, unsigned &DstReg) {
+ const TargetInstrDesc &TID = MI.getDesc();
+ for (unsigned i = 0, e = TID.getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI.getOperand(i);
+ if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg)
+ continue;
+ int ti = TID.getOperandConstraint(i, TOI::TIED_TO);
+ if (ti != -1) {
+ DstReg = MI.getOperand(ti).getReg();
+ return true;
+ }
+ }
+ return false;
+}
+
+/// findOnlyInterestingUse - Given a register, if has a single in-basic block
+/// use, return the use instruction if it's a copy or a two-address use.
+static
+MachineInstr *findOnlyInterestingUse(unsigned Reg, MachineBasicBlock *MBB,
+ MachineRegisterInfo *MRI,
+ const TargetInstrInfo *TII,
+ bool &isCopy,
+ unsigned &DstReg, bool &IsDstPhys) {
+ MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg);
+ if (UI == MRI->use_end())
+ return 0;
+ MachineInstr &UseMI = *UI;
+ if (++UI != MRI->use_end())
+ // More than one use.
+ return 0;
+ if (UseMI.getParent() != MBB)
+ return 0;
+ unsigned SrcReg;
+ bool IsSrcPhys;
+ if (isCopyToReg(UseMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys))
+ return &UseMI;
+ IsDstPhys = false;
+ if (isTwoAddrUse(UseMI, Reg, DstReg))
+ return &UseMI;
+ return 0;
+}
+
+/// getMappedReg - Return the physical register the specified virtual register
+/// might be mapped to.
+static unsigned
+getMappedReg(unsigned Reg, DenseMap<unsigned, unsigned> &RegMap) {
+ while (TargetRegisterInfo::isVirtualRegister(Reg)) {
+ DenseMap<unsigned, unsigned>::iterator SI = RegMap.find(Reg);
+ if (SI == RegMap.end())
+ return 0;
+ Reg = SI->second;
+ }
+ if (TargetRegisterInfo::isPhysicalRegister(Reg))
+ return Reg;
+ return 0;
+}
+
+/// regsAreCompatible - Return true if the two registers are equal or aliased.
+///
+static bool
+regsAreCompatible(unsigned RegA, unsigned RegB, const TargetRegisterInfo *TRI) {
+ if (RegA == RegB)
+ return true;
+ if (!RegA || !RegB)
+ return false;
+ return TRI->regsOverlap(RegA, RegB);
+}
+
+
/// isProfitableToReMat - Return true if it's potentially profitable to commute
/// the two-address instruction that's being processed.
bool
TwoAddressInstructionPass::isProfitableToCommute(unsigned regB, unsigned regC,
- MachineInstr *MI, MachineBasicBlock *MBB,
- unsigned Dist, DenseMap<MachineInstr*, unsigned> &DistanceMap) {
+ MachineInstr *MI, MachineBasicBlock *MBB,
+ unsigned Dist) {
// Determine if it's profitable to commute this two address instruction. In
// general, we want no uses between this instruction and the definition of
// the two-address register.
@@ -322,16 +432,31 @@
// %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
// let's see if it's worth commuting it.
+ // Look for situations like this:
+ // %reg1024<def> = MOV r1
+ // %reg1025<def> = MOV r0
+ // %reg1026<def> = ADD %reg1024, %reg1025
+ // r0 = MOV %reg1026
+ // Commute the ADD to hopefully eliminate an otherwise unavoidable copy.
+ unsigned FromRegB = getMappedReg(regB, SrcRegMap);
+ unsigned FromRegC = getMappedReg(regC, SrcRegMap);
+ unsigned ToRegB = getMappedReg(regB, DstRegMap);
+ unsigned ToRegC = getMappedReg(regC, DstRegMap);
+ if (!regsAreCompatible(FromRegB, ToRegB, TRI) &&
+ (regsAreCompatible(FromRegB, ToRegC, TRI) ||
+ regsAreCompatible(FromRegC, ToRegB, TRI)))
+ return true;
+
// If there is a use of regC between its last def (could be livein) and this
// instruction, then bail.
unsigned LastDefC = 0;
- if (!NoUseAfterLastDef(regC, MBB, Dist, DistanceMap, LastDefC))
+ if (!NoUseAfterLastDef(regC, MBB, Dist, LastDefC))
return false;
// If there is a use of regB between its last def (could be livein) and this
// instruction, then go ahead and make this transformation.
unsigned LastDefB = 0;
- if (!NoUseAfterLastDef(regB, MBB, Dist, DistanceMap, LastDefB))
+ if (!NoUseAfterLastDef(regB, MBB, Dist, LastDefB))
return true;
// Since there are no intervening uses for both registers, then commute
@@ -344,9 +469,8 @@
/// successful.
bool
TwoAddressInstructionPass::CommuteInstruction(MachineBasicBlock::iterator &mi,
- MachineFunction::iterator &mbbi,
- unsigned RegC, unsigned Dist,
- DenseMap<MachineInstr*, unsigned> &DistanceMap) {
+ MachineFunction::iterator &mbbi,
+ unsigned RegB, unsigned RegC, unsigned Dist) {
MachineInstr *MI = mi;
DOUT << "2addr: COMMUTING : " << *MI;
MachineInstr *NewMI = TII->commuteInstruction(MI);
@@ -368,6 +492,108 @@
mi = NewMI;
DistanceMap.insert(std::make_pair(NewMI, Dist));
}
+
+ // Update source register map.
+ unsigned FromRegC = getMappedReg(RegC, SrcRegMap);
+ if (FromRegC) {
+ unsigned RegA = MI->getOperand(0).getReg();
+ SrcRegMap[RegA] = FromRegC;
+ }
+
+ return true;
+}
+
+/// ProcessCopy - If the specified instruction is not yet processed, process it
+/// if it's a copy. For a copy instruction, we find the physical registers the
+/// source and destination registers might be mapped to. These are kept in
+/// point-to maps used to determine future optimizations. e.g.
+/// v1024 = mov r0
+/// v1025 = mov r1
+/// v1026 = add v1024, v1025
+/// r1 = mov r1026
+/// If 'add' is a two-address instruction, v1024, v1026 are both potentially
+/// coalesced to r0 (from the input side). v1025 is mapped to r1. v1026 is
+/// potentially joined with r1 on the output side. It's worthwhile to commute
+/// 'add' to eliminate a copy.
+void TwoAddressInstructionPass::ProcessCopy(MachineInstr *MI,
+ MachineBasicBlock *MBB,
+ SmallPtrSet<MachineInstr*, 8> &Processed) {
+ if (Processed.count(MI))
+ return;
+
+ bool IsSrcPhys, IsDstPhys;
+ unsigned SrcReg, DstReg;
+ if (!isCopyToReg(*MI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys))
+ return;
+
+ if (IsDstPhys && !IsSrcPhys)
+ DstRegMap.insert(std::make_pair(SrcReg, DstReg));
+ else if (!IsDstPhys && IsSrcPhys) {
+ bool isNew =
+ SrcRegMap.insert(std::make_pair(DstReg, SrcReg)).second;
+ isNew = isNew; // Silence compiler warning.
+ assert(isNew && "Can't map to two src physical registers!");
+
+ SmallVector<unsigned, 4> VirtRegPairs;
+ bool isCopy = false;
+ unsigned NewReg = 0;
+ while (MachineInstr *UseMI = findOnlyInterestingUse(DstReg, MBB, MRI,TII,
+ isCopy, NewReg, IsDstPhys)) {
+ if (isCopy) {
+ if (Processed.insert(UseMI))
+ break;
+ }
+
+ DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UseMI);
+ if (DI != DistanceMap.end())
+ // Earlier in the same MBB.Reached via a back edge.
+ break;
+
+ if (IsDstPhys) {
+ VirtRegPairs.push_back(NewReg);
+ break;
+ }
+ bool isNew = SrcRegMap.insert(std::make_pair(NewReg, DstReg)).second;
+ isNew = isNew; // Silence compiler warning.
+ assert(isNew && "Can't map to two src physical registers!");
+ VirtRegPairs.push_back(NewReg);
+ DstReg = NewReg;
+ }
+
+ if (!VirtRegPairs.empty()) {
+ unsigned ToReg = VirtRegPairs.back();
+ VirtRegPairs.pop_back();
+ while (!VirtRegPairs.empty()) {
+ unsigned FromReg = VirtRegPairs.back();
+ VirtRegPairs.pop_back();
+ bool isNew = DstRegMap.insert(std::make_pair(FromReg, ToReg)).second;
+ isNew = isNew; // Silence compiler warning.
+ assert(isNew && "Can't map to two dst physical registers!");
+ ToReg = FromReg;
+ }
+ }
+ }
+
+ Processed.insert(MI);
+}
+
+/// isSafeToDelete - If the specified instruction does not produce any side
+/// effects and all of its defs are dead, then it's safe to delete.
+static bool isSafeToDelete(MachineInstr *MI, const TargetInstrInfo *TII) {
+ const TargetInstrDesc &TID = MI->getDesc();
+ if (TID.mayStore() || TID.isCall())
+ return false;
+ if (TID.isTerminator() || TID.hasUnmodeledSideEffects())
+ return false;
+
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isDef())
+ continue;
+ if (!MO.isDead())
+ return false;
+ }
+
return true;
}
@@ -390,14 +616,14 @@
BitVector ReMatRegs;
ReMatRegs.resize(MRI->getLastVirtReg()+1);
- // DistanceMap - Keep track the distance of a MI from the start of the
- // current basic block.
- DenseMap<MachineInstr*, unsigned> DistanceMap;
-
+ SmallPtrSet<MachineInstr*, 8> Processed;
for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
mbbi != mbbe; ++mbbi) {
unsigned Dist = 0;
DistanceMap.clear();
+ SrcRegMap.clear();
+ DstRegMap.clear();
+ Processed.clear();
for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
mi != me; ) {
MachineBasicBlock::iterator nmi = next(mi);
@@ -405,6 +631,9 @@
bool FirstTied = true;
DistanceMap.insert(std::make_pair(mi, ++Dist));
+
+ ProcessCopy(&*mi, &*mbbi, Processed);
+
for (unsigned si = 1, e = TID.getNumOperands(); si < e; ++si) {
int ti = TID.getOperandConstraint(si, TOI::TIED_TO);
if (ti == -1)
@@ -450,6 +679,15 @@
// allow us to coalesce A and B together, eliminating the copy we are
// about to insert.
if (!mi->killsRegister(regB)) {
+ // If regA is dead and the instruction can be deleted, just delete
+ // it so it doesn't clobber regB.
+ if (mi->getOperand(ti).isDead() && isSafeToDelete(mi, TII)) {
+ mbbi->erase(mi); // Nuke the old inst.
+ mi = nmi;
+ ++NumDeletes;
+ break; // Done with this instruction.
+ }
+
// If this instruction is commutative, check to see if C dies. If
// so, swap the B and C operands. This makes the live ranges of A
// and C joinable.
@@ -459,7 +697,7 @@
"Not a proper commutative instruction!");
unsigned regC = mi->getOperand(3-si).getReg();
if (mi->killsRegister(regC)) {
- if (CommuteInstruction(mi, mbbi, regC, Dist, DistanceMap)) {
+ if (CommuteInstruction(mi, mbbi, regB, regC, Dist)) {
++NumCommuted;
regB = regC;
goto InstructionRearranged;
@@ -506,8 +744,8 @@
// If it's profitable to commute the instruction, do so.
if (TID.isCommutable() && mi->getNumOperands() >= 3) {
unsigned regC = mi->getOperand(3-si).getReg();
- if (isProfitableToCommute(regB, regC, mi, mbbi, Dist, DistanceMap))
- if (CommuteInstruction(mi, mbbi, regC, Dist, DistanceMap)) {
+ if (isProfitableToCommute(regB, regC, mi, mbbi, Dist))
+ if (CommuteInstruction(mi, mbbi, regB, regC, Dist)) {
++NumAggrCommuted;
++NumCommuted;
regB = regC;
@@ -522,7 +760,7 @@
if (DefMI &&
DefMI->getDesc().isAsCheapAsAMove() &&
DefMI->isSafeToReMat(TII, regB) &&
- isProfitableToReMat(regB, rc, mi, DefMI, mbbi, Dist,DistanceMap)){
+ isProfitableToReMat(regB, rc, mi, DefMI, mbbi, Dist)){
DEBUG(cerr << "2addr: REMATTING : " << *DefMI << "\n");
TII->reMaterialize(*mbbi, mi, regA, DefMI);
ReMatRegs.set(regB);
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