mi-sched: update PressureDiffs on-the-fly for liveness.
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
diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index e233d4a..a7a3bb8 100644
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -156,8 +156,9 @@
/// 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 @@
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 @@
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 @@
});
}
+/// 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 @@
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);
}
}