From 2d4e6d3f123f824709be4884e9e2e2f1a4579858 Mon Sep 17 00:00:00 2001 From: David Greene Date: Tue, 28 Jul 2009 16:49:24 +0000 Subject: [PATCH] Add reload and remat backscheduling. This is disabled by default. Use -schedule-spills=true to enable. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77327 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/VirtRegRewriter.cpp | 176 +++++++++++++++++++++++++++----- 1 file changed, 150 insertions(+), 26 deletions(-) diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp index 06a3a3a2dfd..460b508a804 100644 --- a/lib/CodeGen/VirtRegRewriter.cpp +++ b/lib/CodeGen/VirtRegRewriter.cpp @@ -12,6 +12,7 @@ #include "llvm/Support/Compiler.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetLowering.h" #include "llvm/ADT/DepthFirstIterator.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" @@ -47,10 +48,14 @@ RewriterOpt("rewriter", clEnumValEnd), cl::init(local)); +cl::opt +ScheduleSpills("schedule-spills", + cl::desc("Schedule spill code"), + cl::init(false)); + VirtRegRewriter::~VirtRegRewriter() {} - /// This class is intended for use with the new spilling framework only. It /// rewrites vreg def/uses to use the assigned preg, but does not insert any /// spill code. @@ -61,6 +66,10 @@ struct VISIBILITY_HIDDEN TrivialRewriter : public VirtRegRewriter { DOUT << "********** REWRITE MACHINE CODE **********\n"; DEBUG(errs() << "********** Function: " << MF.getFunction()->getName() << '\n'); + DOUT << "**** Machine Instrs" + << "(NOTE! Does not include spills and reloads!) ****\n"; + DEBUG(MF.dump()); + MachineRegisterInfo *mri = &MF.getRegInfo(); bool changed = false; @@ -82,6 +91,10 @@ struct VISIBILITY_HIDDEN TrivialRewriter : public VirtRegRewriter { } } } + + + DOUT << "**** Post Machine Instrs ****\n"; + DEBUG(MF.dump()); return changed; } @@ -214,6 +227,76 @@ public: // ************************************************************************ // +// Given a location where a reload of a spilled register or a remat of +// a constant is to be inserted, attempt to find a safe location to +// insert the load at an earlier point in the basic-block, to hide +// latency of the load and to avoid address-generation interlock +// issues. +static MachineBasicBlock::iterator +ComputeReloadLoc(MachineBasicBlock::iterator const InsertLoc, + MachineBasicBlock::iterator const Begin, + unsigned PhysReg, + const TargetRegisterInfo *TRI, + bool DoReMat, + int SSorRMId, + const TargetInstrInfo *TII, + const MachineFunction &MF) +{ + if (!ScheduleSpills) + return InsertLoc; + + // Spill backscheduling is of primary interest to addresses, so + // don't do anything if the register isn't in the register class + // used for pointers. + + const TargetLowering *TL = MF.getTarget().getTargetLowering(); + + if (!TL->isTypeLegal(TL->getPointerTy())) + // Believe it or not, this is true on PIC16. + return InsertLoc; + + const TargetRegisterClass *ptrRegClass = + TL->getRegClassFor(TL->getPointerTy()); + if (!ptrRegClass->contains(PhysReg)) + return InsertLoc; + + // Scan upwards through the preceding instructions. If an instruction doesn't + // reference the stack slot or the register we're loading, we can + // backschedule the reload up past it. + MachineBasicBlock::iterator NewInsertLoc = InsertLoc; + while (NewInsertLoc != Begin) { + MachineBasicBlock::iterator Prev = prior(NewInsertLoc); + for (unsigned i = 0; i < Prev->getNumOperands(); ++i) { + MachineOperand &Op = Prev->getOperand(i); + if (!DoReMat && Op.isFI() && Op.getIndex() == SSorRMId) + goto stop; + } + if (Prev->findRegisterUseOperandIdx(PhysReg) != -1 || + Prev->findRegisterDefOperand(PhysReg)) + goto stop; + for (const unsigned *Alias = TRI->getAliasSet(PhysReg); *Alias; ++Alias) + if (Prev->findRegisterUseOperandIdx(*Alias) != -1 || + Prev->findRegisterDefOperand(*Alias)) + goto stop; + NewInsertLoc = Prev; + } +stop:; + + // If we made it to the beginning of the block, turn around and move back + // down just past any existing reloads. They're likely to be reloads/remats + // for instructions earlier than what our current reload/remat is for, so + // they should be scheduled earlier. + if (NewInsertLoc == Begin) { + int FrameIdx; + while (InsertLoc != NewInsertLoc && + (TII->isLoadFromStackSlot(NewInsertLoc, FrameIdx) || + TII->isTriviallyReMaterializable(NewInsertLoc))) + ++NewInsertLoc; + } + + return NewInsertLoc; +} + // ReusedOp - For each reused operand, we keep track of a bit of information, // in case we need to rollback upon processing a new operand. See comments // below. @@ -717,14 +800,23 @@ unsigned ReuseInfo::GetRegForReload(const TargetRegisterClass *RC, unsigned NewPhysReg = GetRegForReload(RC, NewOp.AssignedPhysReg, MF, MI, Spills, MaybeDeadStores, Rejected, RegKills, KillOps, VRM); - - MachineBasicBlock::iterator MII = MI; - if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) { - ReMaterialize(*MBB, MII, NewPhysReg, NewOp.VirtReg, TII, TRI,VRM); - } else { - TII->loadRegFromStackSlot(*MBB, MII, NewPhysReg, + + bool DoReMat = NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT; + int SSorRMId = DoReMat + ? VRM.getReMatId(NewOp.VirtReg) : NewOp.StackSlotOrReMat; + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MI, MBB->begin(), PhysReg, TRI, + DoReMat, SSorRMId, TII, MF); + + if (DoReMat) { + ReMaterialize(*MBB, InsertLoc, NewPhysReg, NewOp.VirtReg, TII, + TRI, VRM); + } else { + TII->loadRegFromStackSlot(*MBB, InsertLoc, NewPhysReg, NewOp.StackSlotOrReMat, AliasRC); - MachineInstr *LoadMI = prior(MII); + MachineInstr *LoadMI = prior(InsertLoc); VRM.addSpillSlotUse(NewOp.StackSlotOrReMat, LoadMI); // Any stores to this stack slot are not dead anymore. MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL; @@ -739,9 +831,8 @@ unsigned ReuseInfo::GetRegForReload(const TargetRegisterClass *RC, MI->getOperand(NewOp.Operand).setSubReg(0); Spills.addAvailable(NewOp.StackSlotOrReMat, NewPhysReg); - --MII; - UpdateKills(*MII, TRI, RegKills, KillOps); - DOUT << '\t' << *MII; + UpdateKills(*prior(InsertLoc), TRI, RegKills, KillOps); + DOUT << '\t' << *prior(InsertLoc); DOUT << "Reuse undone!\n"; --NumReused; @@ -1003,6 +1094,10 @@ private: if (!FoldsStackSlotModRef(*NextMII, SS, PhysReg, TII, TRI, VRM)) return false; + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MII, MBB.begin(), PhysReg, TRI, false, SS, TII, MF); + // Load from SS to the spare physical register. TII->loadRegFromStackSlot(MBB, MII, PhysReg, SS, RC); // This invalidates Phys. @@ -1469,8 +1564,15 @@ private: TII->storeRegToStackSlot(MBB, MII, PhysReg, true, SS, RC); MachineInstr *StoreMI = prior(MII); VRM.addSpillSlotUse(SS, StoreMI); - TII->loadRegFromStackSlot(MBB, next(MII), PhysReg, SS, RC); - MachineInstr *LoadMI = next(MII); + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(next(MII), MBB.begin(), PhysReg, TRI, false, + SS, TII, MF); + + TII->loadRegFromStackSlot(MBB, InsertLoc, PhysReg, SS, RC); + + MachineInstr *LoadMI = prior(InsertLoc); VRM.addSpillSlotUse(SS, LoadMI); ++NumPSpills; } @@ -1527,7 +1629,13 @@ private: // If the reloaded / remat value is available in another register, // copy it to the desired register. - TII->copyRegToReg(MBB, &MI, Phys, InReg, RC, RC); + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MII, MBB.begin(), Phys, TRI, DoReMat, + SSorRMId, TII, MF); + + TII->copyRegToReg(MBB, InsertLoc, Phys, InReg, RC, RC); // This invalidates Phys. Spills.ClobberPhysReg(Phys); @@ -1535,7 +1643,7 @@ private: Spills.addAvailable(SSorRMId, Phys); // Mark is killed. - MachineInstr *CopyMI = prior(MII); + MachineInstr *CopyMI = prior(InsertLoc); MachineOperand *KillOpnd = CopyMI->findRegisterUseOperand(InReg); KillOpnd->setIsKill(); UpdateKills(*CopyMI, TRI, RegKills, KillOps); @@ -1545,12 +1653,17 @@ private: continue; } + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MII, MBB.begin(), Phys, TRI, DoReMat, + SSorRMId, TII, MF); + if (VRM.isReMaterialized(VirtReg)) { - ReMaterialize(MBB, MII, Phys, VirtReg, TII, TRI, VRM); + ReMaterialize(MBB, InsertLoc, Phys, VirtReg, TII, TRI, VRM); } else { const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg); - TII->loadRegFromStackSlot(MBB, &MI, Phys, SSorRMId, RC); - MachineInstr *LoadMI = prior(MII); + TII->loadRegFromStackSlot(MBB, InsertLoc, Phys, SSorRMId, RC); + MachineInstr *LoadMI = prior(InsertLoc); VRM.addSpillSlotUse(SSorRMId, LoadMI); ++NumLoads; } @@ -1560,7 +1673,7 @@ private: // Remember it's available. Spills.addAvailable(SSorRMId, Phys); - UpdateKills(*prior(MII), TRI, RegKills, KillOps); + UpdateKills(*prior(InsertLoc), TRI, RegKills, KillOps); DOUT << '\t' << *prior(MII); } } @@ -1798,9 +1911,15 @@ private: const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg); RegInfo->setPhysRegUsed(DesignatedReg); ReusedOperands.markClobbered(DesignatedReg); - TII->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC); - MachineInstr *CopyMI = prior(MII); + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(&MI, MBB.begin(), PhysReg, TRI, DoReMat, + SSorRMId, TII, MF); + + TII->copyRegToReg(MBB, InsertLoc, DesignatedReg, PhysReg, RC, RC); + + MachineInstr *CopyMI = prior(InsertLoc); UpdateKills(*CopyMI, TRI, RegKills, KillOps); // This invalidates DesignatedReg. @@ -1833,12 +1952,17 @@ private: if (AvoidReload) ++NumAvoided; else { + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MII, MBB.begin(), PhysReg, TRI, DoReMat, + SSorRMId, TII, MF); + if (DoReMat) { - ReMaterialize(MBB, MII, PhysReg, VirtReg, TII, TRI, VRM); + ReMaterialize(MBB, InsertLoc, PhysReg, VirtReg, TII, TRI, VRM); } else { const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg); - TII->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC); - MachineInstr *LoadMI = prior(MII); + TII->loadRegFromStackSlot(MBB, InsertLoc, PhysReg, SSorRMId, RC); + MachineInstr *LoadMI = prior(InsertLoc); VRM.addSpillSlotUse(SSorRMId, LoadMI); ++NumLoads; } @@ -1857,8 +1981,8 @@ private: KilledMIRegs.insert(VirtReg); } - UpdateKills(*prior(MII), TRI, RegKills, KillOps); - DOUT << '\t' << *prior(MII); + UpdateKills(*prior(InsertLoc), TRI, RegKills, KillOps); + DOUT << '\t' << *prior(InsertLoc); } unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg; MI.getOperand(i).setReg(RReg);