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mi-sched: update PressureDiffs on-the-fly for liveness.

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This removes all expensive pressure tracking logic from the scheduling
critical path of node comparison.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189643 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2013-08-30 04:36:57 +00:00
parent 1362dcb589
commit 663bd99227
6 changed files with 97 additions and 31 deletions
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64
lib/CodeGen/MachineScheduler.cpp
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@ -156,8 +156,9 @@ static ScheduleDAGInstrs *createConvergingSched(MachineSchedContext *C);
/// Decrement this iterator until reaching the top or a non-debug instr.
static MachineBasicBlock::iterator
priorNonDebug(MachineBasicBlock::iterator I, MachineBasicBlock::iterator Beg) {
static MachineBasicBlock::const_iterator
priorNonDebug(MachineBasicBlock::const_iterator I,
MachineBasicBlock::const_iterator Beg) {
assert(I != Beg && "reached the top of the region, cannot decrement");
while (--I != Beg) {
if (!I->isDebugValue())
@ -166,6 +167,14 @@ priorNonDebug(MachineBasicBlock::iterator I, MachineBasicBlock::iterator Beg) {
return I;
}
/// Non-const version.
static MachineBasicBlock::iterator
priorNonDebug(MachineBasicBlock::iterator I,
MachineBasicBlock::const_iterator Beg) {
return const_cast<MachineInstr*>(
&*priorNonDebug(MachineBasicBlock::const_iterator(I), Beg));
}
/// If this iterator is a debug value, increment until reaching the End or a
/// non-debug instruction.
static MachineBasicBlock::iterator
@ -488,9 +497,16 @@ void ScheduleDAGMI::initRegPressure() {
dumpRegSetPressure(BotRPTracker.getLiveThru(), TRI));
};
// For each live out vreg reduce the pressure change associated with other
// uses of the same vreg below the live-out reaching def.
updatePressureDiffs(RPTracker.getPressure().LiveOutRegs);
// Account for liveness generated by the region boundary.
if (LiveRegionEnd != RegionEnd)
BotRPTracker.recede();
if (LiveRegionEnd != RegionEnd) {
SmallVector<unsigned, 8> LiveUses;
BotRPTracker.recede(&LiveUses);
updatePressureDiffs(LiveUses);
}
assert(BotRPTracker.getPos() == RegionEnd && "Can't find the region bottom");
@ -535,6 +551,42 @@ updateScheduledPressure(const std::vector<unsigned> &NewMaxPressure) {
});
}
/// Update the PressureDiff array for liveness after scheduling this
/// instruction.
void ScheduleDAGMI::updatePressureDiffs(ArrayRef<unsigned> LiveUses) {
for (unsigned LUIdx = 0, LUEnd = LiveUses.size(); LUIdx != LUEnd; ++LUIdx) {
/// FIXME: Currently assuming single-use physregs.
unsigned Reg = LiveUses[LUIdx];
if (!TRI->isVirtualRegister(Reg))
continue;
// This may be called before CurrentBottom has been initialized. However,
// BotRPTracker must have a valid position. We want the value live into the
// instruction or live out of the block, so ask for the previous
// instruction's live-out.
const LiveInterval &LI = LIS->getInterval(Reg);
VNInfo *VNI;
if (BotRPTracker.getPos() == BB->end())
VNI = LI.getVNInfoBefore(LIS->getMBBEndIdx(BB));
else {
LiveRangeQuery LRQ(LI, LIS->getInstructionIndex(BotRPTracker.getPos()));
VNI = LRQ.valueIn();
}
// RegisterPressureTracker guarantees that readsReg is true for LiveUses.
assert(VNI && "No live value at use.");
for (VReg2UseMap::iterator
UI = VRegUses.find(Reg); UI != VRegUses.end(); ++UI) {
SUnit *SU = UI->SU;
// If this use comes before the reaching def, it cannot be a last use, so
// descrease its pressure change.
if (!SU->isScheduled && SU != &ExitSU) {
LiveRangeQuery LRQ(LI, LIS->getInstructionIndex(SU->getInstr()));
if (LRQ.valueIn() == VNI)
getPressureDiff(SU).addPressureChange(Reg, true, &MRI);
}
}
}
}
/// schedule - Called back from MachineScheduler::runOnMachineFunction
/// after setting up the current scheduling region. [RegionBegin, RegionEnd)
/// only includes instructions that have DAG nodes, not scheduling boundaries.
@ -794,8 +846,10 @@ void ScheduleDAGMI::scheduleMI(SUnit *SU, bool IsTopNode) {
CurrentBottom = MI;
}
// Update bottom scheduled pressure.
BotRPTracker.recede();
SmallVector<unsigned, 8> LiveUses;
BotRPTracker.recede(&LiveUses);
assert(BotRPTracker.getPos() == CurrentBottom && "out of sync");
updatePressureDiffs(LiveUses);
updateScheduledPressure(BotRPTracker.getPressure().MaxSetPressure);
}
}