diff options
| -rw-r--r-- | lib/CodeGen/RegAllocGreedy.cpp | 394 | ||||
| -rw-r--r-- | lib/CodeGen/SplitKit.cpp | 25 | ||||
| -rw-r--r-- | lib/CodeGen/SplitKit.h | 10 |
3 files changed, 291 insertions, 138 deletions
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp index d0e6a649a0..912d899534 100644 --- a/lib/CodeGen/RegAllocGreedy.cpp +++ b/lib/CodeGen/RegAllocGreedy.cpp @@ -763,32 +763,46 @@ void RAGreedy::splitAroundRegion(LiveInterval &VirtReg, // 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. @@ -797,150 +811,266 @@ void RAGreedy::splitAroundRegion(LiveInterval &VirtReg, 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)]; diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp index 55b1114b5b..a0952a0866 100644 --- a/lib/CodeGen/SplitKit.cpp +++ b/lib/CodeGen/SplitKit.cpp @@ -636,6 +636,7 @@ unsigned SplitEditor::openIntv() { void SplitEditor::selectIntv(unsigned Idx) { assert(Idx != 0 && "Cannot select the complement interval"); assert(Idx < Edit->size() && "Can only select previously opened interval"); + DEBUG(dbgs() << " selectIntv " << OpenIdx << " -> " << Idx << '\n'); OpenIdx = Idx; } @@ -656,6 +657,24 @@ SlotIndex SplitEditor::enterIntvBefore(SlotIndex Idx) { return VNI->def; } +SlotIndex SplitEditor::enterIntvAfter(SlotIndex Idx) { + assert(OpenIdx && "openIntv not called before enterIntvAfter"); + DEBUG(dbgs() << " enterIntvAfter " << Idx); + Idx = Idx.getBoundaryIndex(); + VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx); + if (!ParentVNI) { + DEBUG(dbgs() << ": not live\n"); + return Idx; + } + DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n'); + MachineInstr *MI = LIS.getInstructionFromIndex(Idx); + assert(MI && "enterIntvAfter called with invalid index"); + + VNInfo *VNI = defFromParent(OpenIdx, ParentVNI, Idx, *MI->getParent(), + llvm::next(MachineBasicBlock::iterator(MI))); + return VNI->def; +} + SlotIndex SplitEditor::enterIntvAtEnd(MachineBasicBlock &MBB) { assert(OpenIdx && "openIntv not called before enterIntvAtEnd"); SlotIndex End = LIS.getMBBEndIdx(&MBB); @@ -1007,12 +1026,6 @@ void SplitEditor::finish(SmallVectorImpl<unsigned> *LRMap) { markComplexMapped(i, ParentVNI); } -#ifndef NDEBUG - // Every new interval must have a def by now, otherwise the split is bogus. - for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I) - assert((*I)->hasAtLeastOneValue() && "Split interval has no value"); -#endif - // Transfer the simply mapped values, check if any are skipped. bool Skipped = transferValues(); if (Skipped) diff --git a/lib/CodeGen/SplitKit.h b/lib/CodeGen/SplitKit.h index 7174c0b55f..a9ccf40be2 100644 --- a/lib/CodeGen/SplitKit.h +++ b/lib/CodeGen/SplitKit.h @@ -81,6 +81,12 @@ public: bool LiveThrough; ///< Live in whole block (Templ 5. above). bool LiveIn; ///< Current reg is live in. bool LiveOut; ///< Current reg is live out. + + /// isOneInstr - Returns true when this BlockInfo describes a single + /// instruction. + bool isOneInstr() const { + return SlotIndex::isSameInstr(FirstUse, LastUse); + } }; private: @@ -360,6 +366,10 @@ public: /// Return the beginning of the new live range. SlotIndex enterIntvBefore(SlotIndex Idx); + /// enterIntvAfter - Enter the open interval after the instruction at Idx. + /// Return the beginning of the new live range. + SlotIndex enterIntvAfter(SlotIndex Idx); + /// enterIntvAtEnd - Enter the open interval at the end of MBB. /// Use the open interval from he inserted copy to the MBB end. /// Return the beginning of the new live range. |