X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FExecutionDepsFix.cpp;h=b3a22c83a80867f20ffe3f9b9f72ad82c86ca3e5;hb=46c638cfc877176752dbf94e016d6ea0fc8afe76;hp=562a6106dc1181670aa5a313a1feed818326b3ab;hpb=c6af2432c802d241c8fffbe0371c023e6c58844e;p=oota-llvm.git diff --git a/lib/CodeGen/ExecutionDepsFix.cpp b/lib/CodeGen/ExecutionDepsFix.cpp index 562a6106dc1..b3a22c83a80 100644 --- a/lib/CodeGen/ExecutionDepsFix.cpp +++ b/lib/CodeGen/ExecutionDepsFix.cpp @@ -20,18 +20,22 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "execution-fix" #include "llvm/CodeGen/Passes.h" #include "llvm/ADT/PostOrderIterator.h" +#include "llvm/ADT/iterator_range.h" +#include "llvm/CodeGen/LivePhysRegs.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineRegisterInfo.h" #include "llvm/Support/Allocator.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Target/TargetInstrInfo.h" -#include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetSubtargetInfo.h" + using namespace llvm; +#define DEBUG_TYPE "execution-fix" + /// A DomainValue is a bit like LiveIntervals' ValNo, but it also keeps track /// of execution domains. /// @@ -71,6 +75,9 @@ struct DomainValue { // Is domain available? bool hasDomain(unsigned domain) const { + assert(domain < + static_cast(std::numeric_limits::digits) && + "undefined behavior"); return AvailableDomains & (1u << domain); } @@ -99,7 +106,7 @@ struct DomainValue { // Clear this DomainValue and point to next which has all its data. void clear() { AvailableDomains = 0; - Next = 0; + Next = nullptr; Instrs.clear(); } }; @@ -130,12 +137,18 @@ class ExeDepsFix : public MachineFunctionPass { MachineFunction *MF; const TargetInstrInfo *TII; const TargetRegisterInfo *TRI; - std::vector AliasMap; + std::vector> AliasMap; const unsigned NumRegs; LiveReg *LiveRegs; typedef DenseMap LiveOutMap; LiveOutMap LiveOuts; + /// List of undefined register reads in this block in forward order. + std::vector > UndefReads; + + /// Storage for register unit liveness. + LivePhysRegs LiveRegSet; + /// Current instruction number. /// The first instruction in each basic block is 0. int CurInstr; @@ -148,20 +161,20 @@ public: ExeDepsFix(const TargetRegisterClass *rc) : MachineFunctionPass(ID), RC(rc), NumRegs(RC->getNumRegs()) {} - virtual void getAnalysisUsage(AnalysisUsage &AU) const { + void getAnalysisUsage(AnalysisUsage &AU) const override { AU.setPreservesAll(); MachineFunctionPass::getAnalysisUsage(AU); } - virtual bool runOnMachineFunction(MachineFunction &MF); + bool runOnMachineFunction(MachineFunction &MF) override; - virtual const char *getPassName() const { + const char *getPassName() const override { return "Execution dependency fix"; } private: - // Register mapping. - int regIndex(unsigned Reg); + iterator_range::const_iterator> + regIndizes(unsigned Reg) const; // DomainValue allocation. DomainValue *alloc(int domain = -1); @@ -185,16 +198,20 @@ private: void processDefs(MachineInstr*, bool Kill); void visitSoftInstr(MachineInstr*, unsigned mask); void visitHardInstr(MachineInstr*, unsigned domain); + bool shouldBreakDependence(MachineInstr*, unsigned OpIdx, unsigned Pref); + void processUndefReads(MachineBasicBlock*); }; } char ExeDepsFix::ID = 0; -/// Translate TRI register number to an index into our smaller tables of -/// interesting registers. Return -1 for boring registers. -int ExeDepsFix::regIndex(unsigned Reg) { +/// Translate TRI register number to a list of indizes into our stmaller tables +/// of interesting registers. +iterator_range::const_iterator> +ExeDepsFix::regIndizes(unsigned Reg) const { assert(Reg < AliasMap.size() && "Invalid register"); - return AliasMap[Reg]; + const auto &Entry = AliasMap[Reg]; + return make_range(Entry.begin(), Entry.end()); } DomainValue *ExeDepsFix::alloc(int domain) { @@ -266,7 +283,7 @@ void ExeDepsFix::kill(int rx) { return; release(LiveRegs[rx].Value); - LiveRegs[rx].Value = 0; + LiveRegs[rx].Value = nullptr; } /// Force register rx into domain. @@ -327,9 +344,11 @@ bool ExeDepsFix::merge(DomainValue *A, DomainValue *B) { // All uses of B are referred to A. B->Next = retain(A); - for (unsigned rx = 0; rx != NumRegs; ++rx) + for (unsigned rx = 0; rx != NumRegs; ++rx) { + assert(LiveRegs && "no space allocated for live registers"); if (LiveRegs[rx].Value == B) setLiveReg(rx, A); + } return true; } @@ -341,13 +360,17 @@ void ExeDepsFix::enterBasicBlock(MachineBasicBlock *MBB) { // Reset instruction counter in each basic block. CurInstr = 0; + // Set up UndefReads to track undefined register reads. + UndefReads.clear(); + LiveRegSet.clear(); + // Set up LiveRegs to represent registers entering MBB. if (!LiveRegs) LiveRegs = new LiveReg[NumRegs]; // Default values are 'nothing happened a long time ago'. for (unsigned rx = 0; rx != NumRegs; ++rx) { - LiveRegs[rx].Value = 0; + LiveRegs[rx].Value = nullptr; LiveRegs[rx].Def = -(1 << 20); } @@ -355,13 +378,12 @@ void ExeDepsFix::enterBasicBlock(MachineBasicBlock *MBB) { if (MBB->pred_empty()) { for (MachineBasicBlock::livein_iterator i = MBB->livein_begin(), e = MBB->livein_end(); i != e; ++i) { - int rx = regIndex(*i); - if (rx < 0) - continue; - // Treat function live-ins as if they were defined just before the first - // instruction. Usually, function arguments are set up immediately - // before the call. - LiveRegs[rx].Def = -1; + for (int rx : regIndizes(*i)) { + // Treat function live-ins as if they were defined just before the first + // instruction. Usually, function arguments are set up immediately + // before the call. + LiveRegs[rx].Def = -1; + } } DEBUG(dbgs() << "BB#" << MBB->getNumber() << ": entry\n"); return; @@ -391,7 +413,7 @@ void ExeDepsFix::enterBasicBlock(MachineBasicBlock *MBB) { // We have a live DomainValue from more than one predecessor. if (LiveRegs[rx].Value->isCollapsed()) { - // We are already collapsed, but predecessor is not. Force him. + // We are already collapsed, but predecessor is not. Force it. unsigned Domain = LiveRegs[rx].Value->getFirstDomain(); if (!pdv->isCollapsed() && pdv->hasDomain(Domain)) collapse(pdv, Domain); @@ -427,7 +449,7 @@ void ExeDepsFix::leaveBasicBlock(MachineBasicBlock *MBB) { release(LiveRegs[i].Value); delete[] LiveRegs; } - LiveRegs = 0; + LiveRegs = nullptr; } void ExeDepsFix::visitInstr(MachineInstr *MI) { @@ -448,10 +470,46 @@ void ExeDepsFix::visitInstr(MachineInstr *MI) { processDefs(MI, !DomP.first); } +/// \brief Return true to if it makes sense to break dependence on a partial def +/// or undef use. +bool ExeDepsFix::shouldBreakDependence(MachineInstr *MI, unsigned OpIdx, + unsigned Pref) { + unsigned reg = MI->getOperand(OpIdx).getReg(); + for (int rx : regIndizes(reg)) { + unsigned Clearance = CurInstr - LiveRegs[rx].Def; + DEBUG(dbgs() << "Clearance: " << Clearance << ", want " << Pref); + + if (Pref > Clearance) { + DEBUG(dbgs() << ": Break dependency.\n"); + continue; + } + // The current clearance seems OK, but we may be ignoring a def from a + // back-edge. + if (!SeenUnknownBackEdge || Pref <= unsigned(CurInstr)) { + DEBUG(dbgs() << ": OK .\n"); + return false; + } + // A def from an unprocessed back-edge may make us break this dependency. + DEBUG(dbgs() << ": Wait for back-edge to resolve.\n"); + return false; + } + return true; +} + // Update def-ages for registers defined by MI. // If Kill is set, also kill off DomainValues clobbered by the defs. +// +// Also break dependencies on partial defs and undef uses. void ExeDepsFix::processDefs(MachineInstr *MI, bool Kill) { assert(!MI->isDebugValue() && "Won't process debug values"); + + // Break dependence on undef uses. Do this before updating LiveRegs below. + unsigned OpNum; + unsigned Pref = TII->getUndefRegClearance(MI, OpNum, TRI); + if (Pref) { + if (shouldBreakDependence(MI, OpNum, Pref)) + UndefReads.push_back(std::make_pair(MI, OpNum)); + } const MCInstrDesc &MCID = MI->getDesc(); for (unsigned i = 0, e = MI->isVariadic() ? MI->getNumOperands() : MCID.getNumDefs(); @@ -463,45 +521,62 @@ void ExeDepsFix::processDefs(MachineInstr *MI, bool Kill) { break; if (MO.isUse()) continue; - int rx = regIndex(MO.getReg()); - if (rx < 0) - continue; + for (int rx : regIndizes(MO.getReg())) { + // This instruction explicitly defines rx. + DEBUG(dbgs() << TRI->getName(RC->getRegister(rx)) << ":\t" << CurInstr + << '\t' << *MI); + + // Check clearance before partial register updates. + // Call breakDependence before setting LiveRegs[rx].Def. + unsigned Pref = TII->getPartialRegUpdateClearance(MI, i, TRI); + if (Pref && shouldBreakDependence(MI, i, Pref)) + TII->breakPartialRegDependency(MI, i, TRI); + + // How many instructions since rx was last written? + LiveRegs[rx].Def = CurInstr; + + // Kill off domains redefined by generic instructions. + if (Kill) + kill(rx); + } + } + ++CurInstr; +} - // This instruction explicitly defines rx. - DEBUG(dbgs() << TRI->getName(RC->getRegister(rx)) << ":\t" << CurInstr - << '\t' << *MI); +/// \break Break false dependencies on undefined register reads. +/// +/// Walk the block backward computing precise liveness. This is expensive, so we +/// only do it on demand. Note that the occurrence of undefined register reads +/// that should be broken is very rare, but when they occur we may have many in +/// a single block. +void ExeDepsFix::processUndefReads(MachineBasicBlock *MBB) { + if (UndefReads.empty()) + return; - // How many instructions since rx was last written? - unsigned Clearance = CurInstr - LiveRegs[rx].Def; - LiveRegs[rx].Def = CurInstr; + // Collect this block's live out register units. + LiveRegSet.init(TRI); + LiveRegSet.addLiveOuts(MBB); - // Kill off domains redefined by generic instructions. - if (Kill) - kill(rx); + MachineInstr *UndefMI = UndefReads.back().first; + unsigned OpIdx = UndefReads.back().second; - // Verify clearance before partial register updates. - unsigned Pref = TII->getPartialRegUpdateClearance(MI, i, TRI); - if (!Pref) - continue; - DEBUG(dbgs() << "Clearance: " << Clearance << ", want " << Pref); - if (Pref > Clearance) { - DEBUG(dbgs() << ": Break dependency.\n"); - TII->breakPartialRegDependency(MI, i, TRI); - continue; - } + for (MachineBasicBlock::reverse_iterator I = MBB->rbegin(), E = MBB->rend(); + I != E; ++I) { + // Update liveness, including the current instruction's defs. + LiveRegSet.stepBackward(*I); - // The current clearance seems OK, but we may be ignoring a def from a - // back-edge. - if (!SeenUnknownBackEdge || Pref <= unsigned(CurInstr)) { - DEBUG(dbgs() << ": OK.\n"); - continue; - } + if (UndefMI == &*I) { + if (!LiveRegSet.contains(UndefMI->getOperand(OpIdx).getReg())) + TII->breakPartialRegDependency(UndefMI, OpIdx, TRI); - // A def from an unprocessed back-edge may make us break this dependency. - DEBUG(dbgs() << ": Wait for back-edge to resolve.\n"); - } + UndefReads.pop_back(); + if (UndefReads.empty()) + return; - ++CurInstr; + UndefMI = UndefReads.back().first; + OpIdx = UndefReads.back().second; + } + } } // A hard instruction only works in one domain. All input registers will be @@ -512,19 +587,19 @@ void ExeDepsFix::visitHardInstr(MachineInstr *mi, unsigned domain) { e = mi->getDesc().getNumOperands(); i != e; ++i) { MachineOperand &mo = mi->getOperand(i); if (!mo.isReg()) continue; - int rx = regIndex(mo.getReg()); - if (rx < 0) continue; - force(rx, domain); + for (int rx : regIndizes(mo.getReg())) { + force(rx, domain); + } } // Kill all defs and force them. for (unsigned i = 0, e = mi->getDesc().getNumDefs(); i != e; ++i) { MachineOperand &mo = mi->getOperand(i); if (!mo.isReg()) continue; - int rx = regIndex(mo.getReg()); - if (rx < 0) continue; - kill(rx); - force(rx, domain); + for (int rx : regIndizes(mo.getReg())) { + kill(rx); + force(rx, domain); + } } } @@ -541,15 +616,16 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) { e = mi->getDesc().getNumOperands(); i != e; ++i) { MachineOperand &mo = mi->getOperand(i); if (!mo.isReg()) continue; - int rx = regIndex(mo.getReg()); - if (rx < 0) continue; - if (DomainValue *dv = LiveRegs[rx].Value) { + for (int rx : regIndizes(mo.getReg())) { + DomainValue *dv = LiveRegs[rx].Value; + if (dv == nullptr) + continue; // Bitmask of domains that dv and available have in common. unsigned common = dv->getCommonDomains(available); // Is it possible to use this collapsed register for free? if (dv->isCollapsed()) { // Restrict available domains to the ones in common with the operand. - // If there are no common domains, we must pay the cross-domain + // If there are no common domains, we must pay the cross-domain // penalty for this operand. if (common) available = common; } else if (common) @@ -573,8 +649,9 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) { // Kill off any remaining uses that don't match available, and build a list of // incoming DomainValues that we want to merge. SmallVector Regs; - for (SmallVector::iterator i=used.begin(), e=used.end(); i!=e; ++i) { + for (SmallVectorImpl::iterator i=used.begin(), e=used.end(); i!=e; ++i) { int rx = *i; + assert(LiveRegs && "no space allocated for live registers"); const LiveReg &LR = LiveRegs[rx]; // This useless DomainValue could have been missed above. if (!LR.Value->getCommonDomains(available)) { @@ -583,7 +660,7 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) { } // Sorted insertion. bool Inserted = false; - for (SmallVector::iterator i = Regs.begin(), e = Regs.end(); + for (SmallVectorImpl::iterator i = Regs.begin(), e = Regs.end(); i != e && !Inserted; ++i) { if (LR.Def < i->Def) { Inserted = true; @@ -596,7 +673,7 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) { // doms are now sorted in order of appearance. Try to merge them all, giving // priority to the latest ones. - DomainValue *dv = 0; + DomainValue *dv = nullptr; while (!Regs.empty()) { if (!dv) { dv = Regs.pop_back_val().Value; @@ -614,9 +691,11 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) { continue; // If latest didn't merge, it is useless now. Kill all registers using it. - for (SmallVector::iterator i=used.begin(), e=used.end(); i != e; ++i) - if (LiveRegs[*i].Value == Latest) - kill(*i); + for (int i : used) { + assert(LiveRegs && "no space allocated for live registers"); + if (LiveRegs[i].Value == Latest) + kill(i); + } } // dv is the DomainValue we are going to use for this instruction. @@ -633,24 +712,24 @@ void ExeDepsFix::visitSoftInstr(MachineInstr *mi, unsigned mask) { ii != ee; ++ii) { MachineOperand &mo = *ii; if (!mo.isReg()) continue; - int rx = regIndex(mo.getReg()); - if (rx < 0) continue; - if (!LiveRegs[rx].Value || (mo.isDef() && LiveRegs[rx].Value != dv)) { - kill(rx); - setLiveReg(rx, dv); + for (int rx : regIndizes(mo.getReg())) { + if (!LiveRegs[rx].Value || (mo.isDef() && LiveRegs[rx].Value != dv)) { + kill(rx); + setLiveReg(rx, dv); + } } } } bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) { MF = &mf; - TII = MF->getTarget().getInstrInfo(); - TRI = MF->getTarget().getRegisterInfo(); - LiveRegs = 0; + TII = MF->getSubtarget().getInstrInfo(); + TRI = MF->getSubtarget().getRegisterInfo(); + LiveRegs = nullptr; assert(NumRegs == RC->getNumRegs() && "Bad regclass"); DEBUG(dbgs() << "********** FIX EXECUTION DEPENDENCIES: " - << RC->getName() << " **********\n"); + << TRI->getRegClassName(RC) << " **********\n"); // If no relevant registers are used in the function, we can skip it // completely. @@ -665,13 +744,13 @@ bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) { // Initialize the AliasMap on the first use. if (AliasMap.empty()) { - // Given a PhysReg, AliasMap[PhysReg] is either the relevant index into RC, - // or -1. - AliasMap.resize(TRI->getNumRegs(), -1); + // Given a PhysReg, AliasMap[PhysReg] returns a list of indices into RC and + // therefore the LiveRegs array. + AliasMap.resize(TRI->getNumRegs()); for (unsigned i = 0, e = RC->getNumRegs(); i != e; ++i) for (MCRegAliasIterator AI(RC->getRegister(i), TRI, true); AI.isValid(); ++AI) - AliasMap[*AI] = i; + AliasMap[*AI].push_back(i); } MachineBasicBlock *Entry = MF->begin(); @@ -686,6 +765,7 @@ bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) { for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E; ++I) visitInstr(I); + processUndefReads(MBB); leaveBasicBlock(MBB); } @@ -698,6 +778,7 @@ bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) { ++I) if (!I->isDebugValue()) processDefs(I, false); + processUndefReads(MBB); leaveBasicBlock(MBB); } @@ -713,6 +794,7 @@ bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) { delete[] FI->second; } LiveOuts.clear(); + UndefReads.clear(); Avail.clear(); Allocator.DestroyAll();