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Added some comments and reformatted others. No functionality change. 

Added two "FIXMEs" for code that looks dubious to me (but I could be
wrong).

llvm-svn: 47366
This commit is contained in:
Bill Wendling 2008-02-20 09:15:16 +00:00
parent 34c09e1a78
commit b912351ec9
1 changed files with 43 additions and 28 deletions
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71
llvm/lib/CodeGen/LiveVariables.cpp
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@ -161,7 +161,6 @@ void LiveVariables::MarkVirtRegAliveInBlock(VarInfo &VRInfo,
} }
} }
void LiveVariables::HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB, void LiveVariables::HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB,
MachineInstr *MI) { MachineInstr *MI) {
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo(); const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
@ -201,29 +200,42 @@ void LiveVariables::HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB,
MarkVirtRegAliveInBlock(VRInfo, MRI.getVRegDef(reg)->getParent(), *PI); MarkVirtRegAliveInBlock(VRInfo, MRI.getVRegDef(reg)->getParent(), *PI);
} }
/// HandlePhysRegUse - Turn previous partial def's into read/mod/writes. Add
/// implicit defs to a machine instruction if there was an earlier def of its
/// super-register.
void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) { void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
// Turn previous partial def's into read/mod/write. // Turn previous partial def's into read/mod/write.
for (unsigned i = 0, e = PhysRegPartDef[Reg].size(); i != e; ++i) { for (unsigned i = 0, e = PhysRegPartDef[Reg].size(); i != e; ++i) {
MachineInstr *Def = PhysRegPartDef[Reg][i]; MachineInstr *Def = PhysRegPartDef[Reg][i];
// First one is just a def. This means the use is reading some undef bits. // First one is just a def. This means the use is reading some undef bits.
if (i != 0) if (i != 0)
Def->addOperand(MachineOperand::CreateReg(Reg, false/*IsDef*/, Def->addOperand(MachineOperand::CreateReg(Reg,
true/*IsImp*/,true/*IsKill*/)); false /*IsDef*/,
Def->addOperand(MachineOperand::CreateReg(Reg,true/*IsDef*/,true/*IsImp*/)); true /*IsImp*/,
true /*IsKill*/));
Def->addOperand(MachineOperand::CreateReg(Reg,
true /*IsDef*/,
true /*IsImp*/));
} }
PhysRegPartDef[Reg].clear(); PhysRegPartDef[Reg].clear();
// There was an earlier def of a super-register. Add implicit def to that MI. // There was an earlier def of a super-register. Add implicit def to that MI.
// A: EAX = ... //
// B: = AX // A: EAX = ...
// B: ... = AX
//
// Add implicit def to A. // Add implicit def to A.
if (PhysRegInfo[Reg] && PhysRegInfo[Reg] != PhysRegPartUse[Reg] && if (PhysRegInfo[Reg] && PhysRegInfo[Reg] != PhysRegPartUse[Reg] &&
!PhysRegUsed[Reg]) { !PhysRegUsed[Reg]) {
MachineInstr *Def = PhysRegInfo[Reg]; MachineInstr *Def = PhysRegInfo[Reg];
if (!Def->findRegisterDefOperand(Reg)) if (!Def->findRegisterDefOperand(Reg))
Def->addOperand(MachineOperand::CreateReg(Reg, true/*IsDef*/, Def->addOperand(MachineOperand::CreateReg(Reg,
true/*IsImp*/)); true /*IsDef*/,
true /*IsImp*/));
} }
// There is a now a proper use, forget about the last partial use. // There is a now a proper use, forget about the last partial use.
@ -231,25 +243,30 @@ void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
PhysRegInfo[Reg] = MI; PhysRegInfo[Reg] = MI;
PhysRegUsed[Reg] = true; PhysRegUsed[Reg] = true;
// Now reset the use information for the sub-registers.
for (const unsigned *SubRegs = RegInfo->getSubRegisters(Reg); for (const unsigned *SubRegs = RegInfo->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) { unsigned SubReg = *SubRegs; ++SubRegs) {
// FIXME: Should we do: "PhysRegPartUse[SubReg] = NULL;" here?
PhysRegInfo[SubReg] = MI; PhysRegInfo[SubReg] = MI;
PhysRegUsed[SubReg] = true; PhysRegUsed[SubReg] = true;
} }
for (const unsigned *SuperRegs = RegInfo->getSuperRegisters(Reg); for (const unsigned *SuperRegs = RegInfo->getSuperRegisters(Reg);
unsigned SuperReg = *SuperRegs; ++SuperRegs) { unsigned SuperReg = *SuperRegs; ++SuperRegs) {
// Remember the partial use of this superreg if it was previously defined. // Remember the partial use of this super-register if it was previously
// defined.
bool HasPrevDef = PhysRegInfo[SuperReg] != NULL; bool HasPrevDef = PhysRegInfo[SuperReg] != NULL;
if (!HasPrevDef) {
if (!HasPrevDef)
// FIXME: This only goes back one level of super-registers. It might miss
// some.
for (const unsigned *SSRegs = RegInfo->getSuperRegisters(SuperReg); for (const unsigned *SSRegs = RegInfo->getSuperRegisters(SuperReg);
unsigned SSReg = *SSRegs; ++SSRegs) { unsigned SSReg = *SSRegs; ++SSRegs)
if (PhysRegInfo[SSReg] != NULL) { if (PhysRegInfo[SSReg] != NULL) {
HasPrevDef = true; HasPrevDef = true;
break; break;
} }
}
}
if (HasPrevDef) { if (HasPrevDef) {
PhysRegInfo[SuperReg] = MI; PhysRegInfo[SuperReg] = MI;
PhysRegPartUse[SuperReg] = MI; PhysRegPartUse[SuperReg] = MI;
@ -413,7 +430,7 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
std::fill(PhysRegUsed, PhysRegUsed + NumRegs, false); std::fill(PhysRegUsed, PhysRegUsed + NumRegs, false);
std::fill(PhysRegPartUse, PhysRegPartUse + NumRegs, (MachineInstr*)0); std::fill(PhysRegPartUse, PhysRegPartUse + NumRegs, (MachineInstr*)0);
/// Get some space for a respectable number of registers... /// Get some space for a respectable number of registers.
VirtRegInfo.resize(64); VirtRegInfo.resize(64);
analyzePHINodes(mf); analyzePHINodes(mf);
@ -422,9 +439,9 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
// function. This guarantees that we will see the definition of a virtual // function. This guarantees that we will see the definition of a virtual
// register before its uses due to dominance properties of SSA (except for PHI // register before its uses due to dominance properties of SSA (except for PHI
// nodes, which are treated as a special case). // nodes, which are treated as a special case).
//
MachineBasicBlock *Entry = MF->begin(); MachineBasicBlock *Entry = MF->begin();
SmallPtrSet<MachineBasicBlock*,16> Visited; SmallPtrSet<MachineBasicBlock*,16> Visited;
for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> > for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> >
DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited); DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
DFI != E; ++DFI) { DFI != E; ++DFI) {
@ -451,7 +468,7 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
if (MI->getOpcode() == TargetInstrInfo::PHI) if (MI->getOpcode() == TargetInstrInfo::PHI)
NumOperandsToProcess = 1; NumOperandsToProcess = 1;
// Process all uses... // Process all uses.
for (unsigned i = 0; i != NumOperandsToProcess; ++i) { for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
const MachineOperand &MO = MI->getOperand(i); const MachineOperand &MO = MI->getOperand(i);
@ -466,7 +483,7 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
} }
} }
// Process all defs... // Process all defs.
for (unsigned i = 0; i != NumOperandsToProcess; ++i) { for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
const MachineOperand &MO = MI->getOperand(i); const MachineOperand &MO = MI->getOperand(i);
@ -501,8 +518,8 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
MBB); MBB);
} }
// Finally, if the last instruction in the block is a return, make sure to mark // Finally, if the last instruction in the block is a return, make sure to
// it as using all of the live-out values in the function. // mark it as using all of the live-out values in the function.
if (!MBB->empty() && MBB->back().getDesc().isReturn()) { if (!MBB->empty() && MBB->back().getDesc().isReturn()) {
MachineInstr *Ret = &MBB->back(); MachineInstr *Ret = &MBB->back();
@ -520,7 +537,7 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
} }
// Loop over PhysRegInfo, killing any registers that are available at the // Loop over PhysRegInfo, killing any registers that are available at the
// end of the basic block. This also resets the PhysRegInfo map. // end of the basic block. This also resets the PhysRegInfo map.
for (unsigned i = 0; i != NumRegs; ++i) for (unsigned i = 0; i != NumRegs; ++i)
if (PhysRegInfo[i]) if (PhysRegInfo[i])
HandlePhysRegDef(i, 0); HandlePhysRegDef(i, 0);
@ -536,7 +553,6 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
// Convert and transfer the dead / killed information we have gathered into // Convert and transfer the dead / killed information we have gathered into
// VirtRegInfo onto MI's. // VirtRegInfo onto MI's.
//
for (unsigned i = 0, e1 = VirtRegInfo.size(); i != e1; ++i) for (unsigned i = 0, e1 = VirtRegInfo.size(); i != e1; ++i)
for (unsigned j = 0, e2 = VirtRegInfo[i].Kills.size(); j != e2; ++j) for (unsigned j = 0, e2 = VirtRegInfo[i].Kills.size(); j != e2; ++j)
if (VirtRegInfo[i].Kills[j] == if (VirtRegInfo[i].Kills[j] ==
@ -568,10 +584,10 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
return false; return false;
} }
/// instructionChanged - When the address of an instruction changes, this /// instructionChanged - When the address of an instruction changes, this method
/// method should be called so that live variables can update its internal /// should be called so that live variables can update its internal data
/// data structures. This removes the records for OldMI, transfering them to /// structures. This removes the records for OldMI, transfering them to the
/// the records for NewMI. /// records for NewMI.
void LiveVariables::instructionChanged(MachineInstr *OldMI, void LiveVariables::instructionChanged(MachineInstr *OldMI,
MachineInstr *NewMI) { MachineInstr *NewMI) {
// If the instruction defines any virtual registers, update the VarInfo, // If the instruction defines any virtual registers, update the VarInfo,
@ -632,9 +648,8 @@ void LiveVariables::removeVirtualRegistersDead(MachineInstr *MI) {
} }
/// analyzePHINodes - Gather information about the PHI nodes in here. In /// analyzePHINodes - Gather information about the PHI nodes in here. In
/// particular, we want to map the variable information of a virtual /// particular, we want to map the variable information of a virtual register
/// register which is used in a PHI node. We map that to the BB the vreg is /// which is used in a PHI node. We map that to the BB the vreg is coming from.
/// coming from.
/// ///
void LiveVariables::analyzePHINodes(const MachineFunction& Fn) { void LiveVariables::analyzePHINodes(const MachineFunction& Fn) {
for (MachineFunction::const_iterator I = Fn.begin(), E = Fn.end(); for (MachineFunction::const_iterator I = Fn.begin(), E = Fn.end();