// Create the main cross-block interval.
const unsigned MainIntv = SE->openIntv();
- // First add all defs that are live out of a block.
+ // First handle all the blocks with uses.
ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
for (unsigned i = 0; i != UseBlocks.size(); ++i) {
const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
- bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
- bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
+ bool RegIn = BI.LiveIn &&
+ LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
+ bool RegOut = BI.LiveOut &&
+ LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
// Create separate intervals for isolated blocks with multiple uses.
- if (!RegIn && !RegOut && BI.FirstUse != BI.LastUse) {
+ //
+ // |---o---o---| Enter and leave on the stack.
+ // ____-----____ Create local interval for uses.
+ //
+ // | o---o---| Defined in block, leave on stack.
+ // -----____ Create local interval for uses.
+ //
+ // |---o---x | Enter on stack, killed in block.
+ // ____----- Create local interval for uses.
+ //
+ if (!RegIn && !RegOut) {
DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " isolated.\n");
- SE->splitSingleBlock(BI);
- SE->selectIntv(MainIntv);
+ if (!BI.isOneInstr()) {
+ SE->splitSingleBlock(BI);
+ SE->selectIntv(MainIntv);
+ }
continue;
}
- // Should the register be live out?
- if (!BI.LiveOut || !RegOut)
- continue;
-
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
Intf.moveToBlock(BI.MBB->getNumber());
- DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " -> EB#"
- << Bundles->getBundle(BI.MBB->getNumber(), 1)
+ DEBUG(dbgs() << "EB#" << Bundles->getBundle(BI.MBB->getNumber(), 0)
+ << (RegIn ? " => " : " -- ")
+ << "BB#" << BI.MBB->getNumber()
+ << (RegOut ? " => " : " -- ")
+ << " EB#" << Bundles->getBundle(BI.MBB->getNumber(), 1)
<< " [" << Start << ';'
<< SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
+ << ") uses [" << BI.FirstUse << ';' << BI.LastUse
<< ") intf [" << Intf.first() << ';' << Intf.last() << ')');
// The interference interval should either be invalid or overlap MBB.
assert((!Intf.hasInterference() || Intf.last() > Start)
&& "Bad interference");
- // Check interference leaving the block.
+ // We are now ready to decide where to split in the current block. There
+ // are many variables guiding the decision:
+ //
+ // - RegIn / RegOut: The global splitting algorithm's decisions for our
+ // ingoing and outgoing bundles.
+ //
+ // - BI.BlockIn / BI.BlockOut: Is the live range live-in and/or live-out
+ // from this block.
+ //
+ // - Intf.hasInterference(): Is there interference in this block.
+ //
+ // - Intf.first() / Inft.last(): The range of interference.
+ //
+ // The live range should be split such that MainIntv is live-in when RegIn
+ // is set, and live-out when RegOut is set. MainIntv should never overlap
+ // the interference, and the stack interval should never have more than one
+ // use per block.
+
+ // No splits can be inserted after LastSplitPoint, overlap instead.
+ SlotIndex LastSplitPoint = Stop;
+ if (BI.LiveOut)
+ LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
+
+ // At this point, we know that either RegIn or RegOut is set. We dealt with
+ // the all-stack case above.
+
+ // Blocks without interference are relatively easy.
if (!Intf.hasInterference()) {
- // Block is interference-free.
- DEBUG(dbgs() << ", no interference");
- if (!BI.LiveThrough) {
- DEBUG(dbgs() << ", not live-through.\n");
- SE->useIntv(SE->enterIntvBefore(BI.FirstUse), Stop);
- continue;
- }
- if (!RegIn) {
- // Block is live-through, but entry bundle is on the stack.
- // Reload just before the first use.
- DEBUG(dbgs() << ", not live-in, enter before first use.\n");
- SE->useIntv(SE->enterIntvBefore(BI.FirstUse), Stop);
- continue;
+ DEBUG(dbgs() << ", no interference.\n");
+ SE->selectIntv(MainIntv);
+ // The easiest case has MainIntv live through.
+ //
+ // |---o---o---| Live-in, live-out.
+ // ============= Use MainIntv everywhere.
+ //
+ SlotIndex From = Start, To = Stop;
+
+ // Block entry. Reload before the first use if MainIntv is not live-in.
+ //
+ // |---o-- Enter on stack.
+ // ____=== Reload before first use.
+ //
+ // | o-- Defined in block.
+ // === Use MainIntv from def.
+ //
+ if (!RegIn)
+ From = SE->enterIntvBefore(BI.FirstUse);
+
+ // Block exit. Handle cases where MainIntv is not live-out.
+ if (!BI.LiveOut)
+ //
+ // --x | Killed in block.
+ // === Use MainIntv up to kill.
+ //
+ To = SE->leaveIntvAfter(BI.LastUse);
+ else if (!RegOut) {
+ //
+ // --o---| Live-out on stack.
+ // ===____ Use MainIntv up to last use, switch to stack.
+ //
+ // -----o| Live-out on stack, last use after last split point.
+ // ====== Extend MainIntv to last use, overlapping.
+ // \____ Copy to stack interval before last split point.
+ //
+ if (BI.LastUse < LastSplitPoint)
+ To = SE->leaveIntvAfter(BI.LastUse);
+ else {
+ // The last use is after the last split point, it is probably an
+ // indirect branch.
+ To = SE->leaveIntvBefore(LastSplitPoint);
+ // Run a double interval from the split to the last use. This makes
+ // it possible to spill the complement without affecting the indirect
+ // branch.
+ SE->overlapIntv(To, BI.LastUse);
+ }
}
- DEBUG(dbgs() << ", live-through.\n");
- continue;
- }
-
- // Block has interference.
- DEBUG(dbgs() << ", interference to " << Intf.last());
- if (!BI.LiveThrough && Intf.last() <= BI.FirstUse) {
- // The interference doesn't reach the outgoing segment.
- DEBUG(dbgs() << " doesn't affect def from " << BI.FirstUse << '\n');
- SE->useIntv(BI.FirstUse, Stop);
+ // Paint in MainIntv liveness for this block.
+ SE->useIntv(From, To);
continue;
}
- SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
- if (Intf.last().getBoundaryIndex() < BI.LastUse) {
- // There are interference-free uses at the end of the block.
- // Find the first use that can get the live-out register.
- SmallVectorImpl<SlotIndex>::const_iterator UI =
- std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
- Intf.last().getBoundaryIndex());
- assert(UI != SA->UseSlots.end() && "Couldn't find last use");
- SlotIndex Use = *UI;
- assert(Use <= BI.LastUse && "Couldn't find last use");
- // Only attempt a split befroe the last split point.
- if (Use.getBaseIndex() <= LastSplitPoint) {
- DEBUG(dbgs() << ", free use at " << Use << ".\n");
- SlotIndex SegStart = SE->enterIntvBefore(Use);
- assert(SegStart >= Intf.last() && "Couldn't avoid interference");
- assert(SegStart < LastSplitPoint && "Impossible split point");
- SE->useIntv(SegStart, Stop);
- continue;
- }
- }
+ // We are now looking at a block with interference, and we know that either
+ // RegIn or RegOut is set.
+ assert(Intf.hasInterference() && (RegIn || RegOut) && "Bad invariant");
- // Interference is after the last use.
- DEBUG(dbgs() << " after last use.\n");
- SlotIndex SegStart = SE->enterIntvAtEnd(*BI.MBB);
- assert(SegStart >= Intf.last() && "Couldn't avoid interference");
- }
+ // If the live range is not live through the block, it is possible that the
+ // interference doesn't even overlap. Deal with those cases first. Since
+ // no copy instructions are required, we can tolerate interference starting
+ // or ending at the same instruction that kills or defines our live range.
- // Now all defs leading to live bundles are handled, do everything else.
- for (unsigned i = 0; i != UseBlocks.size(); ++i) {
- const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
- bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
- bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
+ // Live-in, killed before interference.
+ //
+ // ~~~ Interference after kill.
+ // |---o---x | Killed in block.
+ // ========= Use MainIntv everywhere.
+ //
+ if (RegIn && !BI.LiveOut && BI.LastUse <= Intf.first()) {
+ DEBUG(dbgs() << ", live-in, killed before interference.\n");
+ SE->selectIntv(MainIntv);
+ SlotIndex To = SE->leaveIntvAfter(BI.LastUse);
+ SE->useIntv(Start, To);
+ continue;
+ }
- // Is the register live-in?
- if (!BI.LiveIn || !RegIn)
+ // Live-out, defined after interference.
+ //
+ // ~~~ Interference before def.
+ // | o---o---| Defined in block.
+ // ========= Use MainIntv everywhere.
+ //
+ if (RegOut && !BI.LiveIn && BI.FirstUse >= Intf.last()) {
+ DEBUG(dbgs() << ", live-out, defined after interference.\n");
+ SE->selectIntv(MainIntv);
+ SlotIndex From = SE->enterIntvBefore(BI.FirstUse);
+ SE->useIntv(From, Stop);
continue;
+ }
- // We have an incoming register. Check for interference.
- SlotIndex Start, Stop;
- tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
- Intf.moveToBlock(BI.MBB->getNumber());
- DEBUG(dbgs() << "EB#" << Bundles->getBundle(BI.MBB->getNumber(), 0)
- << " -> BB#" << BI.MBB->getNumber() << " [" << Start << ';'
- << SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
- << ')');
+ // The interference is now known to overlap the live range, but it may
+ // still be easy to avoid if all the interference is on one side of the
+ // uses, and we enter or leave on the stack.
- // Check interference entering the block.
- if (!Intf.hasInterference()) {
- // Block is interference-free.
- DEBUG(dbgs() << ", no interference");
- if (!BI.LiveThrough) {
- DEBUG(dbgs() << ", killed in block.\n");
- SE->useIntv(Start, SE->leaveIntvAfter(BI.LastUse));
- continue;
- }
- if (!RegOut) {
- SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
- // Block is live-through, but exit bundle is on the stack.
- // Spill immediately after the last use.
- if (BI.LastUse < LastSplitPoint) {
- DEBUG(dbgs() << ", uses, stack-out.\n");
- SE->useIntv(Start, SE->leaveIntvAfter(BI.LastUse));
- continue;
- }
- // The last use is after the last split point, it is probably an
- // indirect jump.
- DEBUG(dbgs() << ", uses at " << BI.LastUse << " after split point "
- << LastSplitPoint << ", stack-out.\n");
- SlotIndex SegEnd = SE->leaveIntvBefore(LastSplitPoint);
- SE->useIntv(Start, SegEnd);
- // Run a double interval from the split to the last use.
- // This makes it possible to spill the complement without affecting the
- // indirect branch.
- SE->overlapIntv(SegEnd, BI.LastUse);
- continue;
+ // Live-out on stack, interference after last use.
+ //
+ // ~~~ Interference after last use.
+ // |---o---o---| Live-out on stack.
+ // =========____ Leave MainIntv after last use.
+ //
+ // ~ Interference after last use.
+ // |---o---o--o| Live-out on stack, late last use.
+ // =========____ Copy to stack after LSP, overlap MainIntv.
+ //
+ if (!RegOut && Intf.first() > BI.LastUse.getBoundaryIndex()) {
+ assert(RegIn && "Stack-in, stack-out should already be handled");
+ if (BI.LastUse < LastSplitPoint) {
+ DEBUG(dbgs() << ", live-in, stack-out, interference after last use.\n");
+ SE->selectIntv(MainIntv);
+ SlotIndex To = SE->leaveIntvAfter(BI.LastUse);
+ assert(To <= Intf.first() && "Expected to avoid interference");
+ SE->useIntv(Start, To);
+ } else {
+ DEBUG(dbgs() << ", live-in, stack-out, avoid last split point\n");
+ SE->selectIntv(MainIntv);
+ SlotIndex To = SE->leaveIntvBefore(LastSplitPoint);
+ assert(To <= Intf.first() && "Expected to avoid interference");
+ SE->overlapIntv(To, BI.LastUse);
+ SE->useIntv(Start, To);
}
- // Register is live-through.
- DEBUG(dbgs() << ", uses, live-through.\n");
- SE->useIntv(Start, Stop);
continue;
}
- // Block has interference.
- DEBUG(dbgs() << ", interference from " << Intf.first());
-
- if (!BI.LiveThrough && Intf.first() >= BI.LastUse) {
- // The interference doesn't reach the outgoing segment.
- DEBUG(dbgs() << " doesn't affect kill at " << BI.LastUse << '\n');
- SE->useIntv(Start, BI.LastUse);
+ // Live-in on stack, interference before first use.
+ //
+ // ~~~ Interference before first use.
+ // |---o---o---| Live-in on stack.
+ // ____========= Enter MainIntv before first use.
+ //
+ if (!RegIn && Intf.last() < BI.FirstUse.getBaseIndex()) {
+ assert(RegOut && "Stack-in, stack-out should already be handled");
+ DEBUG(dbgs() << ", stack-in, interference before first use.\n");
+ SE->selectIntv(MainIntv);
+ SlotIndex From = SE->enterIntvBefore(BI.FirstUse);
+ assert(From >= Intf.last() && "Expected to avoid interference");
+ SE->useIntv(From, Stop);
continue;
}
- if (Intf.first().getBaseIndex() > BI.FirstUse) {
- // There are interference-free uses at the beginning of the block.
- // Find the last use that can get the register.
- SmallVectorImpl<SlotIndex>::const_iterator UI =
- std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
- Intf.first().getBaseIndex());
- assert(UI != SA->UseSlots.begin() && "Couldn't find first use");
- SlotIndex Use = (--UI)->getBoundaryIndex();
- DEBUG(dbgs() << ", free use at " << *UI << ".\n");
- SlotIndex SegEnd = SE->leaveIntvAfter(Use);
- assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
- SE->useIntv(Start, SegEnd);
- continue;
+ // The interference is overlapping somewhere we wanted to use MainIntv. That
+ // means we need to create a local interval that can be allocated a
+ // different register.
+ DEBUG(dbgs() << ", creating local interval.\n");
+ unsigned LocalIntv = SE->openIntv();
+
+ // We may be creating copies directly between MainIntv and LocalIntv,
+ // bypassing the stack interval. When we do that, we should never use the
+ // leaveIntv* methods as they define values in the stack interval. By
+ // starting from the end of the block and working our way backwards, we can
+ // get by with only enterIntv* methods.
+ //
+ // When selecting split points, we generally try to maximize the stack
+ // interval as long at it contains no uses, maximize the main interval as
+ // long as it doesn't overlap interference, and minimize the local interval
+ // that we don't know how to allocate yet.
+
+ // Handle the block exit, set Pos to the first handled slot.
+ SlotIndex Pos = BI.LastUse;
+ if (RegOut) {
+ assert(Intf.last() < LastSplitPoint && "Cannot be live-out in register");
+ // Create a snippet of MainIntv that is live-out.
+ //
+ // ~~~ Interference overlapping uses.
+ // --o---| Live-out in MainIntv.
+ // ----=== Switch from LocalIntv to MainIntv after interference.
+ //
+ SE->selectIntv(MainIntv);
+ Pos = SE->enterIntvAfter(Intf.last());
+ assert(Pos >= Intf.last() && "Expected to avoid interference");
+ SE->useIntv(Pos, Stop);
+ SE->selectIntv(LocalIntv);
+ } else if (BI.LiveOut) {
+ if (BI.LastUse < LastSplitPoint) {
+ // Live-out on the stack.
+ //
+ // ~~~ Interference overlapping uses.
+ // --o---| Live-out on stack.
+ // ---____ Switch from LocalIntv to stack after last use.
+ //
+ Pos = SE->leaveIntvAfter(BI.LastUse);
+ } else {
+ // Live-out on the stack, last use after last split point.
+ //
+ // ~~~ Interference overlapping uses.
+ // --o--o| Live-out on stack, late use.
+ // ------ Copy to stack before LSP, overlap LocalIntv.
+ // \__
+ //
+ Pos = SE->leaveIntvBefore(LastSplitPoint);
+ // We need to overlap LocalIntv so it can reach LastUse.
+ SE->overlapIntv(Pos, BI.LastUse);
+ }
}
- // Interference is before the first use.
- DEBUG(dbgs() << " before first use.\n");
- SlotIndex SegEnd = SE->leaveIntvAtTop(*BI.MBB);
- assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
+ // When not live-out, leave Pos at LastUse. We have handled everything from
+ // Pos to Stop. Find the starting point for LocalIntv.
+ assert(SE->currentIntv() == LocalIntv && "Expecting local interval");
+
+ if (RegIn) {
+ assert(Start < Intf.first() && "Cannot be live-in with interference");
+ // Live-in in MainIntv, only use LocalIntv for interference.
+ //
+ // ~~~ Interference overlapping uses.
+ // |---o-- Live-in in MainIntv.
+ // ====--- Switch to LocalIntv before interference.
+ //
+ SlotIndex Switch = SE->enterIntvBefore(Intf.first());
+ assert(Switch <= Intf.first() && "Expected to avoid interference");
+ SE->useIntv(Switch, Pos);
+ SE->selectIntv(MainIntv);
+ SE->useIntv(Start, Switch);
+ } else {
+ // Live-in on stack, enter LocalIntv before first use.
+ //
+ // ~~~ Interference overlapping uses.
+ // |---o-- Live-in in MainIntv.
+ // ____--- Reload to LocalIntv before interference.
+ //
+ // Defined in block.
+ //
+ // ~~~ Interference overlapping uses.
+ // | o-- Defined in block.
+ // --- Begin LocalIntv at first use.
+ //
+ SlotIndex Switch = SE->enterIntvBefore(BI.FirstUse);
+ SE->useIntv(Switch, Pos);
+ }
}
// Handle live-through blocks.
+ SE->selectIntv(MainIntv);
for (unsigned i = 0, e = Cand.ActiveBlocks.size(); i != e; ++i) {
unsigned Number = Cand.ActiveBlocks[i];
bool RegIn = LiveBundles[Bundles->getBundle(Number, 0)];
projects / oota-llvm.git / commitdiff