Author: evancheng
Date: Tue Aug 14 18:25:37 2007
New Revision: 41086
URL: http://llvm.org/viewvc/llvm-project?rev=41086&view=rev
Log:
- If a def is dead, do not spill it.
- If the defs of a spilled rematerializable MI are dead after the spill store
is deleted, delete
the def MI as well.
Modified:
llvm/trunk/lib/CodeGen/VirtRegMap.cpp
Modified: llvm/trunk/lib/CodeGen/VirtRegMap.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/VirtRegMap.cpp?rev=41086&r1=41085&r2=41086&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/VirtRegMap.cpp (original)
+++ llvm/trunk/lib/CodeGen/VirtRegMap.cpp Tue Aug 14 18:25:37 2007
@@ -36,6 +36,7 @@
STATISTIC(NumSpills, "Number of register spills");
STATISTIC(NumReMats, "Number of re-materialization");
+STATISTIC(NumDRM , "Number of re-materializable defs elided");
STATISTIC(NumStores, "Number of stores added");
STATISTIC(NumLoads , "Number of loads added");
STATISTIC(NumReused, "Number of values reused");
@@ -434,38 +435,14 @@
/// marked kill, then invalidate the information.
static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
- MachineInstr *NewDef = NULL) {
+ SmallVector<unsigned, 1> *KillRegs = NULL) {
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || !MO.isUse() || !MO.isKill())
continue;
unsigned Reg = MO.getReg();
- if (NewDef) {
- // Due to remat, it's possible this reg isn't being reused. That is,
- // the def of this reg (by prev MI) is now dead.
- bool FoundUse = false, Done = false;
- MachineBasicBlock::iterator I = MI, E = NewDef;
- ++I; ++E;
- for (; !Done && I != E; ++I) {
- MachineInstr *NMI = I;
- for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
- MachineOperand &MO = NMI->getOperand(j);
- if (!MO.isReg() || MO.getReg() != Reg)
- continue;
- if (MO.isUse())
- FoundUse = true;
- Done = true; // Stop after scanning all the operands of this MI.
- }
- }
- if (!FoundUse) {
- // Def is dead!
- MachineBasicBlock::iterator MII = MI;
- MachineInstr *DefMI = prior(MII);
- MachineOperand *DefOp = DefMI->findRegisterDefOperand(Reg);
- assert(DefOp && "Missing def?");
- DefOp->setIsDead();
- }
- }
+ if (KillRegs)
+ KillRegs->push_back(Reg);
if (KillOps[Reg] == &MO) {
RegKills.reset(Reg);
KillOps[Reg] = NULL;
@@ -473,6 +450,51 @@
}
}
+/// InvalidateRegDef - If the def operand of the specified def MI is now dead
+/// (since it's spill instruction is removed), mark it isDead. Also checks if
+/// the def MI has other definition operands that are not dead. Returns it by
+/// reference.
+static bool InvalidateRegDef(MachineBasicBlock::iterator I,
+ MachineInstr &NewDef, unsigned Reg,
+ bool &HasLiveDef) {
+ // Due to remat, it's possible this reg isn't being reused. That is,
+ // the def of this reg (by prev MI) is now dead.
+ MachineInstr *DefMI = I;
+ MachineOperand *DefOp = NULL;
+ for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = DefMI->getOperand(i);
+ if (MO.isReg() && MO.isDef()) {
+ if (MO.getReg() == Reg)
+ DefOp = &MO;
+ else if (!MO.isDead())
+ HasLiveDef = true;
+ }
+ }
+ if (!DefOp)
+ return false;
+
+ bool FoundUse = false, Done = false;
+ MachineBasicBlock::iterator E = NewDef;
+ ++I; ++E;
+ for (; !Done && I != E; ++I) {
+ MachineInstr *NMI = I;
+ for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
+ MachineOperand &MO = NMI->getOperand(j);
+ if (!MO.isReg() || MO.getReg() != Reg)
+ continue;
+ if (MO.isUse())
+ FoundUse = true;
+ Done = true; // Stop after scanning all the operands of this MI.
+ }
+ }
+ if (!FoundUse) {
+ // Def is dead!
+ DefOp->setIsDead();
+ return true;
+ }
+ return false;
+}
+
/// UpdateKills - Track and update kill info. If a MI reads a register that is
/// marked kill, then it must be due to register reuse. Transfer the kill info
/// over.
@@ -707,6 +729,9 @@
std::vector<MachineInstr*> MaybeDeadStores;
MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
+ // ReMatDefs - These are rematerializable def MIs which are not deleted.
+ SmallSet<MachineInstr*, 4> ReMatDefs;
+
// Keep track of kill information.
BitVector RegKills(MRI->getNumRegs());
std::vector<MachineOperand*> KillOps;
@@ -1077,6 +1102,10 @@
continue;
}
+ bool DoReMat = VRM.isReMaterialized(VirtReg);
+ if (DoReMat)
+ ReMatDefs.insert(&MI);
+
// The only vregs left are stack slot definitions.
int StackSlot = VRM.getStackSlot(VirtReg);
const TargetRegisterClass *RC =
MF.getSSARegMap()->getRegClass(VirtReg);
@@ -1099,43 +1128,68 @@
MF.setPhysRegUsed(PhysReg);
ReusedOperands.markClobbered(PhysReg);
- MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
- DOUT << "Store:\t" << *next(MII);
MI.getOperand(i).setReg(PhysReg);
+ if (!MO.isDead()) {
+ MRI->storeRegToStackSlot(MBB, next(MII), PhysReg, StackSlot, RC);
+ DOUT << "Store:\t" << *next(MII);
+
+ // If there is a dead store to this stack slot, nuke it now.
+ MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
+ if (LastStore) {
+ DOUT << "Removed dead store:\t" << *LastStore;
+ ++NumDSE;
+ SmallVector<unsigned, 1> KillRegs;
+ InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
+ MachineBasicBlock::iterator PrevMII = LastStore;
+ bool CheckDef = PrevMII != MBB.begin();
+ if (CheckDef)
+ --PrevMII;
+ MBB.erase(LastStore);
+ VRM.RemoveFromFoldedVirtMap(LastStore);
+ if (CheckDef) {
+ // Look at defs of killed registers on the store. Mark the defs
+ // as dead since the store has been deleted and they aren't
+ // being reused.
+ for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
+ bool HasOtherDef = false;
+ if (InvalidateRegDef(PrevMII, MI, KillRegs[j], HasOtherDef)) {
+ MachineInstr *DeadDef = PrevMII;
+ if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
+ // FIXME: This assumes a remat def does not have side
+ // effects.
+ MBB.erase(DeadDef);
+ VRM.RemoveFromFoldedVirtMap(DeadDef);
+ ++NumDRM;
+ }
+ }
+ }
+ }
+ }
+ LastStore = next(MII);
- // If there is a dead store to this stack slot, nuke it now.
- MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
- if (LastStore) {
- DOUT << "Removed dead store:\t" << *LastStore;
- ++NumDSE;
- InvalidateKills(*LastStore, RegKills, KillOps, &MI);
- MBB.erase(LastStore);
- VRM.RemoveFromFoldedVirtMap(LastStore);
- }
- LastStore = next(MII);
+ // If the stack slot value was previously available in some other
+ // register, change it now. Otherwise, make the register available,
+ // in PhysReg.
+ Spills.ModifyStackSlotOrReMat(StackSlot);
+ Spills.ClobberPhysReg(PhysReg);
+ Spills.addAvailable(StackSlot, LastStore, PhysReg);
+ ++NumStores;
- // If the stack slot value was previously available in some other
- // register, change it now. Otherwise, make the register available,
- // in PhysReg.
- Spills.ModifyStackSlotOrReMat(StackSlot);
- Spills.ClobberPhysReg(PhysReg);
- Spills.addAvailable(StackSlot, LastStore, PhysReg);
- ++NumStores;
-
- // Check to see if this is a noop copy. If so, eliminate the
- // instruction before considering the dest reg to be changed.
- {
- unsigned Src, Dst;
- if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
- ++NumDCE;
- DOUT << "Removing now-noop copy: " << MI;
- MBB.erase(&MI);
- Erased = true;
- VRM.RemoveFromFoldedVirtMap(&MI);
- UpdateKills(*LastStore, RegKills, KillOps);
- goto ProcessNextInst;
+ // Check to see if this is a noop copy. If so, eliminate the
+ // instruction before considering the dest reg to be changed.
+ {
+ unsigned Src, Dst;
+ if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
+ ++NumDCE;
+ DOUT << "Removing now-noop copy: " << MI;
+ MBB.erase(&MI);
+ Erased = true;
+ VRM.RemoveFromFoldedVirtMap(&MI);
+ UpdateKills(*LastStore, RegKills, KillOps);
+ goto ProcessNextInst;
+ }
}
- }
+ }
}
}
ProcessNextInst:
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