// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
-//
+//
// This file contains a Partitioned Boolean Quadratic Programming (PBQP) based
// register allocator for LLVM. This allocator works by constructing a PBQP
// problem representing the register allocation problem under consideration,
// solving this using a PBQP solver, and mapping the solution back to a
// register assignment. If any variables are selected for spilling then spill
-// code is inserted and the process repeated.
+// code is inserted and the process repeated.
//
// The PBQP solver (pbqp.c) provided for this allocator uses a heuristic tuned
// for register allocation. For more information on PBQP for register
-// allocation see the following papers:
+// allocation, see the following papers:
//
// (1) Hames, L. and Scholz, B. 2006. Nearly optimal register allocation with
// PBQP. In Proceedings of the 7th Joint Modular Languages Conference
// architectures. In Proceedings of the Joint Conference on Languages,
// Compilers and Tools for Embedded Systems (LCTES'02), ACM Press, New York,
// NY, USA, 139-148.
-//
-// Author: Lang Hames
-// Email: lhames@gmail.com
//
//===----------------------------------------------------------------------===//
-// TODO:
-//
-// * Use of std::set in constructPBQPProblem destroys allocation order preference.
-// Switch to an order preserving container.
-//
-// * Coalescing support.
-
#define DEBUG_TYPE "regalloc"
-#include "PBQP.h"
+#include "LiveRangeEdit.h"
+#include "RenderMachineFunction.h"
+#include "Spiller.h"
#include "VirtRegMap.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/RegAllocRegistry.h"
+#include "RegisterCoalescer.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/LiveStackAnalysis.h"
+#include "llvm/CodeGen/RegAllocPBQP.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
-#include "llvm/Target/TargetMachine.h"
-#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/PBQP/HeuristicSolver.h"
+#include "llvm/CodeGen/PBQP/Graph.h"
+#include "llvm/CodeGen/PBQP/Heuristics/Briggs.h"
+#include "llvm/CodeGen/RegAllocRegistry.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include <limits>
#include <memory>
-#include <map>
#include <set>
#include <vector>
-#include <limits>
using namespace llvm;
static RegisterRegAlloc
-registerPBQPRepAlloc("pbqp", " PBQP register allocator",
- createPBQPRegisterAllocator);
+registerPBQPRepAlloc("pbqp", "PBQP register allocator",
+ createDefaultPBQPRegisterAllocator);
+static cl::opt<bool>
+pbqpCoalescing("pbqp-coalescing",
+ cl::desc("Attempt coalescing during PBQP register allocation."),
+ cl::init(false), cl::Hidden);
namespace {
- //!
- //! PBQP based allocators solve the register allocation problem by mapping
- //! register allocation problems to Partitioned Boolean Quadratic
- //! Programming problems.
- class VISIBILITY_HIDDEN PBQPRegAlloc : public MachineFunctionPass {
- public:
-
- static char ID;
-
- //! Construct a PBQP register allocator.
- PBQPRegAlloc() : MachineFunctionPass((intptr_t)&ID) {}
-
- //! Return the pass name.
- virtual const char* getPassName() const throw() {
- return "PBQP Register Allocator";
- }
+///
+/// PBQP based allocators solve the register allocation problem by mapping
+/// register allocation problems to Partitioned Boolean Quadratic
+/// Programming problems.
+class RegAllocPBQP : public MachineFunctionPass {
+public:
+
+ static char ID;
+
+ /// Construct a PBQP register allocator.
+ RegAllocPBQP(std::auto_ptr<PBQPBuilder> b, char *cPassID=0)
+ : MachineFunctionPass(ID), builder(b), customPassID(cPassID) {
+ initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
+ initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
+ initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
+ initializeLiveStacksPass(*PassRegistry::getPassRegistry());
+ initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
+ initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
+ initializeRenderMachineFunctionPass(*PassRegistry::getPassRegistry());
+ }
- //! PBQP analysis usage.
- virtual void getAnalysisUsage(AnalysisUsage &au) const {
- au.addRequired<LiveIntervals>();
- au.addRequired<MachineLoopInfo>();
- MachineFunctionPass::getAnalysisUsage(au);
- }
+ /// Return the pass name.
+ virtual const char* getPassName() const {
+ return "PBQP Register Allocator";
+ }
- //! Perform register allocation
- virtual bool runOnMachineFunction(MachineFunction &MF);
-
- private:
- typedef std::map<const LiveInterval*, unsigned> LI2NodeMap;
- typedef std::vector<const LiveInterval*> Node2LIMap;
- typedef std::vector<unsigned> AllowedSet;
- typedef std::vector<AllowedSet> AllowedSetMap;
- typedef std::set<unsigned> IgnoreSet;
-
- MachineFunction *mf;
- const TargetMachine *tm;
- const TargetRegisterInfo *tri;
- const TargetInstrInfo *tii;
- const MachineLoopInfo *loopInfo;
- MachineRegisterInfo *mri;
-
- LiveIntervals *li;
- VirtRegMap *vrm;
-
- LI2NodeMap li2Node;
- Node2LIMap node2LI;
- AllowedSetMap allowedSets;
- IgnoreSet ignoreSet;
-
- //! Builds a PBQP cost vector.
- template <typename Container>
- PBQPVector* buildCostVector(const Container &allowed,
- PBQPNum spillCost) const;
-
- //! \brief Builds a PBQP interference matrix.
- //!
- //! @return Either a pointer to a non-zero PBQP matrix representing the
- //! allocation option costs, or a null pointer for a zero matrix.
- //!
- //! Expects allowed sets for two interfering LiveIntervals. These allowed
- //! sets should contain only allocable registers from the LiveInterval's
- //! register class, with any interfering pre-colored registers removed.
- template <typename Container>
- PBQPMatrix* buildInterferenceMatrix(const Container &allowed1,
- const Container &allowed2) const;
-
- //!
- //! Expects allowed sets for two potentially coalescable LiveIntervals,
- //! and an estimated benefit due to coalescing. The allowed sets should
- //! contain only allocable registers from the LiveInterval's register
- //! classes, with any interfering pre-colored registers removed.
- template <typename Container>
- PBQPMatrix* buildCoalescingMatrix(const Container &allowed1,
- const Container &allowed2,
- PBQPNum cBenefit) const;
-
- //! \brief Helper function for constructInitialPBQPProblem().
- //!
- //! This function iterates over the Function we are about to allocate for
- //! and computes spill costs.
- void calcSpillCosts();
-
- //! \brief Scans the MachineFunction being allocated to find coalescing
- // opportunities.
- void findCoalescingOpportunities();
-
- //! \brief Constructs a PBQP problem representation of the register
- //! allocation problem for this function.
- //!
- //! @return a PBQP solver object for the register allocation problem.
- pbqp* constructPBQPProblem();
-
- //! \brief Given a solved PBQP problem maps this solution back to a register
- //! assignment.
- bool mapPBQPToRegAlloc(pbqp *problem);
-
- };
-
- char PBQPRegAlloc::ID = 0;
-}
+ /// PBQP analysis usage.
+ virtual void getAnalysisUsage(AnalysisUsage &au) const;
+ /// Perform register allocation
+ virtual bool runOnMachineFunction(MachineFunction &MF);
-template <typename Container>
-PBQPVector* PBQPRegAlloc::buildCostVector(const Container &allowed,
- PBQPNum spillCost) const {
+private:
- // Allocate vector. Additional element (0th) used for spill option
- PBQPVector *v = new PBQPVector(allowed.size() + 1);
+ typedef std::map<const LiveInterval*, unsigned> LI2NodeMap;
+ typedef std::vector<const LiveInterval*> Node2LIMap;
+ typedef std::vector<unsigned> AllowedSet;
+ typedef std::vector<AllowedSet> AllowedSetMap;
+ typedef std::pair<unsigned, unsigned> RegPair;
+ typedef std::map<RegPair, PBQP::PBQPNum> CoalesceMap;
+ typedef std::vector<PBQP::Graph::NodeItr> NodeVector;
+ typedef std::set<unsigned> RegSet;
- (*v)[0] = spillCost;
- return v;
-}
+ std::auto_ptr<PBQPBuilder> builder;
-template <typename Container>
-PBQPMatrix* PBQPRegAlloc::buildInterferenceMatrix(
- const Container &allowed1, const Container &allowed2) const {
-
- typedef typename Container::const_iterator ContainerIterator;
-
- // Construct a PBQP matrix representing the cost of allocation options. The
- // rows and columns correspond to the allocation options for the two live
- // intervals. Elements will be infinite where corresponding registers alias,
- // since we cannot allocate aliasing registers to interfering live intervals.
- // All other elements (non-aliasing combinations) will have zero cost. Note
- // that the spill option (element 0,0) has zero cost, since we can allocate
- // both intervals to memory safely (the cost for each individual allocation
- // to memory is accounted for by the cost vectors for each live interval).
- PBQPMatrix *m = new PBQPMatrix(allowed1.size() + 1, allowed2.size() + 1);
-
- // Assume this is a zero matrix until proven otherwise. Zero matrices occur
- // between interfering live ranges with non-overlapping register sets (e.g.
- // non-overlapping reg classes, or disjoint sets of allowed regs within the
- // same class). The term "overlapping" is used advisedly: sets which do not
- // intersect, but contain registers which alias, will have non-zero matrices.
- // We optimize zero matrices away to improve solver speed.
- bool isZeroMatrix = true;
-
-
- // Row index. Starts at 1, since the 0th row is for the spill option, which
- // is always zero.
- unsigned ri = 1;
-
- // Iterate over allowed sets, insert infinities where required.
- for (ContainerIterator a1Itr = allowed1.begin(), a1End = allowed1.end();
- a1Itr != a1End; ++a1Itr) {
-
- // Column index, starts at 1 as for row index.
- unsigned ci = 1;
- unsigned reg1 = *a1Itr;
-
- for (ContainerIterator a2Itr = allowed2.begin(), a2End = allowed2.end();
- a2Itr != a2End; ++a2Itr) {
-
- unsigned reg2 = *a2Itr;
-
- // If the row/column regs are identical or alias insert an infinity.
- if ((reg1 == reg2) || tri->areAliases(reg1, reg2)) {
- (*m)[ri][ci] = std::numeric_limits<PBQPNum>::infinity();
- isZeroMatrix = false;
- }
+ char *customPassID;
- ++ci;
- }
+ MachineFunction *mf;
+ const TargetMachine *tm;
+ const TargetRegisterInfo *tri;
+ const TargetInstrInfo *tii;
+ const MachineLoopInfo *loopInfo;
+ MachineRegisterInfo *mri;
+ RenderMachineFunction *rmf;
- ++ri;
- }
+ std::auto_ptr<Spiller> spiller;
+ LiveIntervals *lis;
+ LiveStacks *lss;
+ VirtRegMap *vrm;
- // If this turns out to be a zero matrix...
- if (isZeroMatrix) {
- // free it and return null.
- delete m;
- return 0;
- }
+ RegSet vregsToAlloc, emptyIntervalVRegs;
- // ...otherwise return the cost matrix.
- return m;
-}
+ /// \brief Finds the initial set of vreg intervals to allocate.
+ void findVRegIntervalsToAlloc();
-void PBQPRegAlloc::calcSpillCosts() {
+ /// \brief Given a solved PBQP problem maps this solution back to a register
+ /// assignment.
+ bool mapPBQPToRegAlloc(const PBQPRAProblem &problem,
+ const PBQP::Solution &solution);
- // Calculate the spill cost for each live interval by iterating over the
- // function counting loads and stores, with loop depth taken into account.
- for (MachineFunction::const_iterator bbItr = mf->begin(), bbEnd = mf->end();
- bbItr != bbEnd; ++bbItr) {
+ /// \brief Postprocessing before final spilling. Sets basic block "live in"
+ /// variables.
+ void finalizeAlloc() const;
- const MachineBasicBlock *mbb = &*bbItr;
- float loopDepth = loopInfo->getLoopDepth(mbb);
+};
- for (MachineBasicBlock::const_iterator
- iItr = mbb->begin(), iEnd = mbb->end(); iItr != iEnd; ++iItr) {
+char RegAllocPBQP::ID = 0;
- const MachineInstr *instr = &*iItr;
+} // End anonymous namespace.
- for (unsigned opNo = 0; opNo < instr->getNumOperands(); ++opNo) {
+unsigned PBQPRAProblem::getVRegForNode(PBQP::Graph::ConstNodeItr node) const {
+ Node2VReg::const_iterator vregItr = node2VReg.find(node);
+ assert(vregItr != node2VReg.end() && "No vreg for node.");
+ return vregItr->second;
+}
- const MachineOperand &mo = instr->getOperand(opNo);
+PBQP::Graph::NodeItr PBQPRAProblem::getNodeForVReg(unsigned vreg) const {
+ VReg2Node::const_iterator nodeItr = vreg2Node.find(vreg);
+ assert(nodeItr != vreg2Node.end() && "No node for vreg.");
+ return nodeItr->second;
- // We're not interested in non-registers...
- if (!mo.isReg())
- continue;
-
- unsigned moReg = mo.getReg();
+}
- // ...Or invalid registers...
- if (moReg == 0)
- continue;
+const PBQPRAProblem::AllowedSet&
+ PBQPRAProblem::getAllowedSet(unsigned vreg) const {
+ AllowedSetMap::const_iterator allowedSetItr = allowedSets.find(vreg);
+ assert(allowedSetItr != allowedSets.end() && "No pregs for vreg.");
+ const AllowedSet &allowedSet = allowedSetItr->second;
+ return allowedSet;
+}
- // ...Or physical registers...
- if (TargetRegisterInfo::isPhysicalRegister(moReg))
- continue;
+unsigned PBQPRAProblem::getPRegForOption(unsigned vreg, unsigned option) const {
+ assert(isPRegOption(vreg, option) && "Not a preg option.");
- assert ((mo.isUse() || mo.isDef()) &&
- "Not a use, not a def, what is it?");
+ const AllowedSet& allowedSet = getAllowedSet(vreg);
+ assert(option <= allowedSet.size() && "Option outside allowed set.");
+ return allowedSet[option - 1];
+}
- //... Just the virtual registers. We treat loads and stores as equal.
- li->getInterval(moReg).weight += powf(10.0f, loopDepth);
- }
+std::auto_ptr<PBQPRAProblem> PBQPBuilder::build(MachineFunction *mf,
+ const LiveIntervals *lis,
+ const MachineLoopInfo *loopInfo,
+ const RegSet &vregs) {
- }
+ typedef std::vector<const LiveInterval*> LIVector;
+
+ MachineRegisterInfo *mri = &mf->getRegInfo();
+ const TargetRegisterInfo *tri = mf->getTarget().getRegisterInfo();
+ std::auto_ptr<PBQPRAProblem> p(new PBQPRAProblem());
+ PBQP::Graph &g = p->getGraph();
+ RegSet pregs;
+
+ // Collect the set of preg intervals, record that they're used in the MF.
+ for (LiveIntervals::const_iterator itr = lis->begin(), end = lis->end();
+ itr != end; ++itr) {
+ if (TargetRegisterInfo::isPhysicalRegister(itr->first)) {
+ pregs.insert(itr->first);
+ mri->setPhysRegUsed(itr->first);
+ }
}
-}
+ BitVector reservedRegs = tri->getReservedRegs(*mf);
+
+ // Iterate over vregs.
+ for (RegSet::const_iterator vregItr = vregs.begin(), vregEnd = vregs.end();
+ vregItr != vregEnd; ++vregItr) {
+ unsigned vreg = *vregItr;
+ const TargetRegisterClass *trc = mri->getRegClass(vreg);
+ const LiveInterval *vregLI = &lis->getInterval(vreg);
+
+ // Compute an initial allowed set for the current vreg.
+ typedef std::vector<unsigned> VRAllowed;
+ VRAllowed vrAllowed;
+ ArrayRef<uint16_t> rawOrder = trc->getRawAllocationOrder(*mf);
+ for (unsigned i = 0; i != rawOrder.size(); ++i) {
+ unsigned preg = rawOrder[i];
+ if (!reservedRegs.test(preg)) {
+ vrAllowed.push_back(preg);
+ }
+ }
-pbqp* PBQPRegAlloc::constructPBQPProblem() {
+ // Remove any physical registers which overlap.
+ for (RegSet::const_iterator pregItr = pregs.begin(),
+ pregEnd = pregs.end();
+ pregItr != pregEnd; ++pregItr) {
+ unsigned preg = *pregItr;
+ const LiveInterval *pregLI = &lis->getInterval(preg);
- typedef std::vector<const LiveInterval*> LIVector;
- typedef std::set<unsigned> RegSet;
+ if (pregLI->empty()) {
+ continue;
+ }
- // These will store the physical & virtual intervals, respectively.
- LIVector physIntervals, virtIntervals;
+ if (!vregLI->overlaps(*pregLI)) {
+ continue;
+ }
- // Start by clearing the old node <-> live interval mappings & allowed sets
- li2Node.clear();
- node2LI.clear();
- allowedSets.clear();
+ // Remove the register from the allowed set.
+ VRAllowed::iterator eraseItr =
+ std::find(vrAllowed.begin(), vrAllowed.end(), preg);
- // Iterate over intervals classifying them as physical or virtual, and
- // constructing live interval <-> node number mappings.
- for (LiveIntervals::iterator itr = li->begin(), end = li->end();
- itr != end; ++itr) {
+ if (eraseItr != vrAllowed.end()) {
+ vrAllowed.erase(eraseItr);
+ }
+
+ // Also remove any aliases.
+ const uint16_t *aliasItr = tri->getAliasSet(preg);
+ if (aliasItr != 0) {
+ for (; *aliasItr != 0; ++aliasItr) {
+ VRAllowed::iterator eraseItr =
+ std::find(vrAllowed.begin(), vrAllowed.end(), *aliasItr);
- if (itr->second->getNumValNums() != 0) {
- DOUT << "Live range has " << itr->second->getNumValNums() << ": " << itr->second << "\n";
+ if (eraseItr != vrAllowed.end()) {
+ vrAllowed.erase(eraseItr);
+ }
+ }
+ }
}
- if (TargetRegisterInfo::isPhysicalRegister(itr->first)) {
- physIntervals.push_back(itr->second);
- mri->setPhysRegUsed(itr->second->reg);
+ // Construct the node.
+ PBQP::Graph::NodeItr node =
+ g.addNode(PBQP::Vector(vrAllowed.size() + 1, 0));
+
+ // Record the mapping and allowed set in the problem.
+ p->recordVReg(vreg, node, vrAllowed.begin(), vrAllowed.end());
+
+ PBQP::PBQPNum spillCost = (vregLI->weight != 0.0) ?
+ vregLI->weight : std::numeric_limits<PBQP::PBQPNum>::min();
+
+ addSpillCosts(g.getNodeCosts(node), spillCost);
+ }
+
+ for (RegSet::const_iterator vr1Itr = vregs.begin(), vrEnd = vregs.end();
+ vr1Itr != vrEnd; ++vr1Itr) {
+ unsigned vr1 = *vr1Itr;
+ const LiveInterval &l1 = lis->getInterval(vr1);
+ const PBQPRAProblem::AllowedSet &vr1Allowed = p->getAllowedSet(vr1);
+
+ for (RegSet::const_iterator vr2Itr = llvm::next(vr1Itr);
+ vr2Itr != vrEnd; ++vr2Itr) {
+ unsigned vr2 = *vr2Itr;
+ const LiveInterval &l2 = lis->getInterval(vr2);
+ const PBQPRAProblem::AllowedSet &vr2Allowed = p->getAllowedSet(vr2);
+
+ assert(!l2.empty() && "Empty interval in vreg set?");
+ if (l1.overlaps(l2)) {
+ PBQP::Graph::EdgeItr edge =
+ g.addEdge(p->getNodeForVReg(vr1), p->getNodeForVReg(vr2),
+ PBQP::Matrix(vr1Allowed.size()+1, vr2Allowed.size()+1, 0));
+
+ addInterferenceCosts(g.getEdgeCosts(edge), vr1Allowed, vr2Allowed, tri);
+ }
}
- else {
+ }
- // If we've allocated this virtual register interval a stack slot on a
- // previous round then it's not an allocation candidate
- if (ignoreSet.find(itr->first) != ignoreSet.end())
- continue;
+ return p;
+}
+
+void PBQPBuilder::addSpillCosts(PBQP::Vector &costVec,
+ PBQP::PBQPNum spillCost) {
+ costVec[0] = spillCost;
+}
+
+void PBQPBuilder::addInterferenceCosts(
+ PBQP::Matrix &costMat,
+ const PBQPRAProblem::AllowedSet &vr1Allowed,
+ const PBQPRAProblem::AllowedSet &vr2Allowed,
+ const TargetRegisterInfo *tri) {
+ assert(costMat.getRows() == vr1Allowed.size() + 1 && "Matrix height mismatch.");
+ assert(costMat.getCols() == vr2Allowed.size() + 1 && "Matrix width mismatch.");
- li2Node[itr->second] = node2LI.size();
- node2LI.push_back(itr->second);
- virtIntervals.push_back(itr->second);
+ for (unsigned i = 0; i != vr1Allowed.size(); ++i) {
+ unsigned preg1 = vr1Allowed[i];
+
+ for (unsigned j = 0; j != vr2Allowed.size(); ++j) {
+ unsigned preg2 = vr2Allowed[j];
+
+ if (tri->regsOverlap(preg1, preg2)) {
+ costMat[i + 1][j + 1] = std::numeric_limits<PBQP::PBQPNum>::infinity();
+ }
}
}
+}
- // Early out if there's no regs to allocate for.
- if (virtIntervals.empty())
- return 0;
+std::auto_ptr<PBQPRAProblem> PBQPBuilderWithCoalescing::build(
+ MachineFunction *mf,
+ const LiveIntervals *lis,
+ const MachineLoopInfo *loopInfo,
+ const RegSet &vregs) {
- // Construct a PBQP solver for this problem
- pbqp *solver = alloc_pbqp(virtIntervals.size());
+ std::auto_ptr<PBQPRAProblem> p = PBQPBuilder::build(mf, lis, loopInfo, vregs);
+ PBQP::Graph &g = p->getGraph();
- // Resize allowedSets container appropriately.
- allowedSets.resize(virtIntervals.size());
+ const TargetMachine &tm = mf->getTarget();
+ CoalescerPair cp(*tm.getInstrInfo(), *tm.getRegisterInfo());
- // Iterate over virtual register intervals to compute allowed sets...
- for (unsigned node = 0; node < node2LI.size(); ++node) {
+ // Scan the machine function and add a coalescing cost whenever CoalescerPair
+ // gives the Ok.
+ for (MachineFunction::const_iterator mbbItr = mf->begin(),
+ mbbEnd = mf->end();
+ mbbItr != mbbEnd; ++mbbItr) {
+ const MachineBasicBlock *mbb = &*mbbItr;
- // Grab pointers to the interval and its register class.
- const LiveInterval *li = node2LI[node];
- const TargetRegisterClass *liRC = mri->getRegClass(li->reg);
-
- // Start by assuming all allocable registers in the class are allowed...
- RegSet liAllowed(liRC->allocation_order_begin(*mf),
- liRC->allocation_order_end(*mf));
+ for (MachineBasicBlock::const_iterator miItr = mbb->begin(),
+ miEnd = mbb->end();
+ miItr != miEnd; ++miItr) {
+ const MachineInstr *mi = &*miItr;
- // If this range is non-empty then eliminate the physical registers which
- // overlap with this range, along with all their aliases.
- if (!li->empty()) {
- for (LIVector::iterator pItr = physIntervals.begin(),
- pEnd = physIntervals.end(); pItr != pEnd; ++pItr) {
+ if (!cp.setRegisters(mi)) {
+ continue; // Not coalescable.
+ }
- if (li->overlaps(**pItr)) {
+ if (cp.getSrcReg() == cp.getDstReg()) {
+ continue; // Already coalesced.
+ }
- unsigned pReg = (*pItr)->reg;
+ unsigned dst = cp.getDstReg(),
+ src = cp.getSrcReg();
- // Remove the overlapping reg...
- liAllowed.erase(pReg);
+ const float copyFactor = 0.5; // Cost of copy relative to load. Current
+ // value plucked randomly out of the air.
- const unsigned *aliasItr = tri->getAliasSet(pReg);
+ PBQP::PBQPNum cBenefit =
+ copyFactor * LiveIntervals::getSpillWeight(false, true,
+ loopInfo->getLoopDepth(mbb));
- if (aliasItr != 0) {
- // ...and its aliases.
- for (; *aliasItr != 0; ++aliasItr) {
- liAllowed.erase(*aliasItr);
- }
+ if (cp.isPhys()) {
+ if (!lis->isAllocatable(dst)) {
+ continue;
+ }
+ const PBQPRAProblem::AllowedSet &allowed = p->getAllowedSet(src);
+ unsigned pregOpt = 0;
+ while (pregOpt < allowed.size() && allowed[pregOpt] != dst) {
+ ++pregOpt;
+ }
+ if (pregOpt < allowed.size()) {
+ ++pregOpt; // +1 to account for spill option.
+ PBQP::Graph::NodeItr node = p->getNodeForVReg(src);
+ addPhysRegCoalesce(g.getNodeCosts(node), pregOpt, cBenefit);
+ }
+ } else {
+ const PBQPRAProblem::AllowedSet *allowed1 = &p->getAllowedSet(dst);
+ const PBQPRAProblem::AllowedSet *allowed2 = &p->getAllowedSet(src);
+ PBQP::Graph::NodeItr node1 = p->getNodeForVReg(dst);
+ PBQP::Graph::NodeItr node2 = p->getNodeForVReg(src);
+ PBQP::Graph::EdgeItr edge = g.findEdge(node1, node2);
+ if (edge == g.edgesEnd()) {
+ edge = g.addEdge(node1, node2, PBQP::Matrix(allowed1->size() + 1,
+ allowed2->size() + 1,
+ 0));
+ } else {
+ if (g.getEdgeNode1(edge) == node2) {
+ std::swap(node1, node2);
+ std::swap(allowed1, allowed2);
}
-
}
+ addVirtRegCoalesce(g.getEdgeCosts(edge), *allowed1, *allowed2,
+ cBenefit);
}
-
}
+ }
- // Copy the allowed set into a member vector for use when constructing cost
- // vectors & matrices, and mapping PBQP solutions back to assignments.
- allowedSets[node] = AllowedSet(liAllowed.begin(), liAllowed.end());
+ return p;
+}
+
+void PBQPBuilderWithCoalescing::addPhysRegCoalesce(PBQP::Vector &costVec,
+ unsigned pregOption,
+ PBQP::PBQPNum benefit) {
+ costVec[pregOption] += -benefit;
+}
- // Set the spill cost to the interval weight, or epsilon if the
- // interval weight is zero
- PBQPNum spillCost = (li->weight != 0.0) ?
- li->weight : std::numeric_limits<PBQPNum>::min();
+void PBQPBuilderWithCoalescing::addVirtRegCoalesce(
+ PBQP::Matrix &costMat,
+ const PBQPRAProblem::AllowedSet &vr1Allowed,
+ const PBQPRAProblem::AllowedSet &vr2Allowed,
+ PBQP::PBQPNum benefit) {
- // Build a cost vector for this interval.
- add_pbqp_nodecosts(solver, node,
- buildCostVector(allowedSets[node], spillCost));
+ assert(costMat.getRows() == vr1Allowed.size() + 1 && "Size mismatch.");
+ assert(costMat.getCols() == vr2Allowed.size() + 1 && "Size mismatch.");
+ for (unsigned i = 0; i != vr1Allowed.size(); ++i) {
+ unsigned preg1 = vr1Allowed[i];
+ for (unsigned j = 0; j != vr2Allowed.size(); ++j) {
+ unsigned preg2 = vr2Allowed[j];
+
+ if (preg1 == preg2) {
+ costMat[i + 1][j + 1] += -benefit;
+ }
+ }
}
+}
- // Now add the cost matrices...
- for (unsigned node1 = 0; node1 < node2LI.size(); ++node1) {
-
- const LiveInterval *li = node2LI[node1];
- if (li->empty())
- continue;
-
- // Test for live range overlaps and insert interference matrices.
- for (unsigned node2 = node1 + 1; node2 < node2LI.size(); ++node2) {
- const LiveInterval *li2 = node2LI[node2];
+void RegAllocPBQP::getAnalysisUsage(AnalysisUsage &au) const {
+ au.setPreservesCFG();
+ au.addRequired<AliasAnalysis>();
+ au.addPreserved<AliasAnalysis>();
+ au.addRequired<SlotIndexes>();
+ au.addPreserved<SlotIndexes>();
+ au.addRequired<LiveIntervals>();
+ //au.addRequiredID(SplitCriticalEdgesID);
+ if (customPassID)
+ au.addRequiredID(*customPassID);
+ au.addRequired<CalculateSpillWeights>();
+ au.addRequired<LiveStacks>();
+ au.addPreserved<LiveStacks>();
+ au.addRequired<MachineDominatorTree>();
+ au.addPreserved<MachineDominatorTree>();
+ au.addRequired<MachineLoopInfo>();
+ au.addPreserved<MachineLoopInfo>();
+ au.addRequired<VirtRegMap>();
+ au.addRequired<RenderMachineFunction>();
+ MachineFunctionPass::getAnalysisUsage(au);
+}
- if (li2->empty())
- continue;
+void RegAllocPBQP::findVRegIntervalsToAlloc() {
- if (li->overlaps(*li2)) {
- PBQPMatrix *m =
- buildInterferenceMatrix(allowedSets[node1], allowedSets[node2]);
+ // Iterate over all live ranges.
+ for (LiveIntervals::iterator itr = lis->begin(), end = lis->end();
+ itr != end; ++itr) {
- if (m != 0) {
- add_pbqp_edgecosts(solver, node1, node2, m);
- delete m;
- }
- }
+ // Ignore physical ones.
+ if (TargetRegisterInfo::isPhysicalRegister(itr->first))
+ continue;
+
+ LiveInterval *li = itr->second;
+
+ // If this live interval is non-empty we will use pbqp to allocate it.
+ // Empty intervals we allocate in a simple post-processing stage in
+ // finalizeAlloc.
+ if (!li->empty()) {
+ vregsToAlloc.insert(li->reg);
+ } else {
+ emptyIntervalVRegs.insert(li->reg);
}
}
-
- // We're done, PBQP problem constructed - return it.
- return solver;
}
-bool PBQPRegAlloc::mapPBQPToRegAlloc(pbqp *problem) {
-
+bool RegAllocPBQP::mapPBQPToRegAlloc(const PBQPRAProblem &problem,
+ const PBQP::Solution &solution) {
// Set to true if we have any spills
bool anotherRoundNeeded = false;
// Clear the existing allocation.
vrm->clearAllVirt();
-
- // Iterate over the nodes mapping the PBQP solution to a register assignment.
- for (unsigned node = 0; node < node2LI.size(); ++node) {
- unsigned symReg = node2LI[node]->reg,
- allocSelection = get_pbqp_solution(problem, node);
-
- // If the PBQP solution is non-zero it's a physical register...
- if (allocSelection != 0) {
- // Get the physical reg, subtracting 1 to account for the spill option.
- unsigned physReg = allowedSets[node][allocSelection - 1];
-
- // Add to the virt reg map and update the used phys regs.
- vrm->assignVirt2Phys(symReg, physReg);
- mri->setPhysRegUsed(physReg);
- }
- // ...Otherwise it's a spill.
- else {
-
- // Make sure we ignore this virtual reg on the next round
- // of allocation
- ignoreSet.insert(node2LI[node]->reg);
- float SSWeight;
+ const PBQP::Graph &g = problem.getGraph();
+ // Iterate over the nodes mapping the PBQP solution to a register
+ // assignment.
+ for (PBQP::Graph::ConstNodeItr node = g.nodesBegin(),
+ nodeEnd = g.nodesEnd();
+ node != nodeEnd; ++node) {
+ unsigned vreg = problem.getVRegForNode(node);
+ unsigned alloc = solution.getSelection(node);
+
+ if (problem.isPRegOption(vreg, alloc)) {
+ unsigned preg = problem.getPRegForOption(vreg, alloc);
+ DEBUG(dbgs() << "VREG " << vreg << " -> " << tri->getName(preg) << "\n");
+ assert(preg != 0 && "Invalid preg selected.");
+ vrm->assignVirt2Phys(vreg, preg);
+ } else if (problem.isSpillOption(vreg, alloc)) {
+ vregsToAlloc.erase(vreg);
+ SmallVector<LiveInterval*, 8> newSpills;
+ LiveRangeEdit LRE(lis->getInterval(vreg), newSpills);
+ spiller->spill(LRE);
+
+ DEBUG(dbgs() << "VREG " << vreg << " -> SPILLED (Cost: "
+ << LRE.getParent().weight << ", New vregs: ");
+
+ // Copy any newly inserted live intervals into the list of regs to
+ // allocate.
+ for (LiveRangeEdit::iterator itr = LRE.begin(), end = LRE.end();
+ itr != end; ++itr) {
+ assert(!(*itr)->empty() && "Empty spill range.");
+ DEBUG(dbgs() << (*itr)->reg << " ");
+ vregsToAlloc.insert((*itr)->reg);
+ }
- // Insert spill ranges for this live range
- SmallVector<LiveInterval*, 8> spillIs;
- std::vector<LiveInterval*> newSpills =
- li->addIntervalsForSpills(*node2LI[node], spillIs, loopInfo, *vrm,
- SSWeight);
+ DEBUG(dbgs() << ")\n");
// We need another round if spill intervals were added.
- anotherRoundNeeded |= !newSpills.empty();
+ anotherRoundNeeded |= !LRE.empty();
+ } else {
+ llvm_unreachable("Unknown allocation option.");
}
}
return !anotherRoundNeeded;
}
-bool PBQPRegAlloc::runOnMachineFunction(MachineFunction &MF) {
-
+
+void RegAllocPBQP::finalizeAlloc() const {
+ typedef LiveIntervals::iterator LIIterator;
+ typedef LiveInterval::Ranges::const_iterator LRIterator;
+
+ // First allocate registers for the empty intervals.
+ for (RegSet::const_iterator
+ itr = emptyIntervalVRegs.begin(), end = emptyIntervalVRegs.end();
+ itr != end; ++itr) {
+ LiveInterval *li = &lis->getInterval(*itr);
+
+ unsigned physReg = vrm->getRegAllocPref(li->reg);
+
+ if (physReg == 0) {
+ const TargetRegisterClass *liRC = mri->getRegClass(li->reg);
+ physReg = liRC->getRawAllocationOrder(*mf).front();
+ }
+
+ vrm->assignVirt2Phys(li->reg, physReg);
+ }
+
+ // Finally iterate over the basic blocks to compute and set the live-in sets.
+ SmallVector<MachineBasicBlock*, 8> liveInMBBs;
+ MachineBasicBlock *entryMBB = &*mf->begin();
+
+ for (LIIterator liItr = lis->begin(), liEnd = lis->end();
+ liItr != liEnd; ++liItr) {
+
+ const LiveInterval *li = liItr->second;
+ unsigned reg = 0;
+
+ // Get the physical register for this interval
+ if (TargetRegisterInfo::isPhysicalRegister(li->reg)) {
+ reg = li->reg;
+ } else if (vrm->isAssignedReg(li->reg)) {
+ reg = vrm->getPhys(li->reg);
+ } else {
+ // Ranges which are assigned a stack slot only are ignored.
+ continue;
+ }
+
+ if (reg == 0) {
+ // Filter out zero regs - they're for intervals that were spilled.
+ continue;
+ }
+
+ // Iterate over the ranges of the current interval...
+ for (LRIterator lrItr = li->begin(), lrEnd = li->end();
+ lrItr != lrEnd; ++lrItr) {
+
+ // Find the set of basic blocks which this range is live into...
+ if (lis->findLiveInMBBs(lrItr->start, lrItr->end, liveInMBBs)) {
+ // And add the physreg for this interval to their live-in sets.
+ for (unsigned i = 0; i != liveInMBBs.size(); ++i) {
+ if (liveInMBBs[i] != entryMBB) {
+ if (!liveInMBBs[i]->isLiveIn(reg)) {
+ liveInMBBs[i]->addLiveIn(reg);
+ }
+ }
+ }
+ liveInMBBs.clear();
+ }
+ }
+ }
+
+}
+
+bool RegAllocPBQP::runOnMachineFunction(MachineFunction &MF) {
+
mf = &MF;
tm = &mf->getTarget();
tri = tm->getRegisterInfo();
+ tii = tm->getInstrInfo();
mri = &mf->getRegInfo();
- li = &getAnalysis<LiveIntervals>();
+ lis = &getAnalysis<LiveIntervals>();
+ lss = &getAnalysis<LiveStacks>();
loopInfo = &getAnalysis<MachineLoopInfo>();
+ rmf = &getAnalysis<RenderMachineFunction>();
+
+ vrm = &getAnalysis<VirtRegMap>();
+ spiller.reset(createInlineSpiller(*this, MF, *vrm));
+
+ mri->freezeReservedRegs(MF);
- std::auto_ptr<VirtRegMap> vrmAutoPtr(new VirtRegMap(*mf));
- vrm = vrmAutoPtr.get();
+ DEBUG(dbgs() << "PBQP Register Allocating for " << mf->getFunction()->getName() << "\n");
// Allocator main loop:
- //
+ //
// * Map current regalloc problem to a PBQP problem
// * Solve the PBQP problem
// * Map the solution back to a register allocation
// * Spill if necessary
- //
+ //
// This process is continued till no more spills are generated.
- bool regallocComplete = false;
-
- // Calculate spill costs for intervals
- calcSpillCosts();
-
- while (!regallocComplete) {
- pbqp *problem = constructPBQPProblem();
-
- // Fast out if there's no problem to solve.
- if (problem == 0)
- return true;
-
- solve_pbqp(problem);
-
- regallocComplete = mapPBQPToRegAlloc(problem);
-
- free_pbqp(problem);
+ // Find the vreg intervals in need of allocation.
+ findVRegIntervalsToAlloc();
+
+ // If there are non-empty intervals allocate them using pbqp.
+ if (!vregsToAlloc.empty()) {
+
+ bool pbqpAllocComplete = false;
+ unsigned round = 0;
+
+ while (!pbqpAllocComplete) {
+ DEBUG(dbgs() << " PBQP Regalloc round " << round << ":\n");
+
+ std::auto_ptr<PBQPRAProblem> problem =
+ builder->build(mf, lis, loopInfo, vregsToAlloc);
+ PBQP::Solution solution =
+ PBQP::HeuristicSolver<PBQP::Heuristics::Briggs>::solve(
+ problem->getGraph());
+
+ pbqpAllocComplete = mapPBQPToRegAlloc(*problem, solution);
+
+ ++round;
+ }
}
- ignoreSet.clear();
+ // Finalise allocation, allocate empty ranges.
+ finalizeAlloc();
+
+ rmf->renderMachineFunction("After PBQP register allocation.", vrm);
+
+ vregsToAlloc.clear();
+ emptyIntervalVRegs.clear();
- std::auto_ptr<Spiller> spiller(createSpiller());
+ DEBUG(dbgs() << "Post alloc VirtRegMap:\n" << *vrm << "\n");
- spiller->runOnMachineFunction(*mf, *vrm);
-
- return true;
+ // Run rewriter
+ vrm->rewrite(lis->getSlotIndexes());
+
+ // All machine operands and other references to virtual registers have been
+ // replaced. Remove the virtual registers.
+ vrm->clearAllVirt();
+ mri->clearVirtRegs();
+
+ return true;
}
-FunctionPass* llvm::createPBQPRegisterAllocator() {
- return new PBQPRegAlloc();
+FunctionPass* llvm::createPBQPRegisterAllocator(
+ std::auto_ptr<PBQPBuilder> builder,
+ char *customPassID) {
+ return new RegAllocPBQP(builder, customPassID);
}
+FunctionPass* llvm::createDefaultPBQPRegisterAllocator() {
+ if (pbqpCoalescing) {
+ return createPBQPRegisterAllocator(
+ std::auto_ptr<PBQPBuilder>(new PBQPBuilderWithCoalescing()));
+ } // else
+ return createPBQPRegisterAllocator(
+ std::auto_ptr<PBQPBuilder>(new PBQPBuilder()));
+}
#undef DEBUG_TYPE
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