X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FRegAllocSimple.cpp;h=6b95af82fda415860e83810b0539fa9c76f43e6d;hb=a3c58f1c060bb97371ad06bf10c4836845e0f5a3;hp=0c363dcd1686505806a15bc2cf5f656cd06b0f7d;hpb=8ed9eb5ca3bbbb90dad28e5e21f0359c4710e478;p=oota-llvm.git diff --git a/lib/CodeGen/RegAllocSimple.cpp b/lib/CodeGen/RegAllocSimple.cpp index 0c363dcd168..6b95af82fda 100644 --- a/lib/CodeGen/RegAllocSimple.cpp +++ b/lib/CodeGen/RegAllocSimple.cpp @@ -1,58 +1,38 @@ -//===-- RegAllocSimple.cpp - A simple generic register allocator --- ------===// +//===-- RegAllocSimple.cpp - A simple generic register allocator ----------===// // -// This file implements a simple register allocator. *Very* simple. +// This file implements a simple register allocator. *Very* simple: It immediate +// spills every value right after it is computed, and it reloads all used +// operands from the spill area to temporary registers before each instruction. +// It does not keep values in registers across instructions. // //===----------------------------------------------------------------------===// -#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/Passes.h" +#include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstr.h" -#include "llvm/Target/MachineInstrInfo.h" +#include "llvm/CodeGen/SSARegMap.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetMachine.h" #include "Support/Statistic.h" #include -#include - -#if 0 -/// PhysRegClassMap - Construct a mapping of physical register numbers to their -/// register classes. -/// -/// NOTE: This class will eventually be pulled out to somewhere shared. -/// -class PhysRegClassMap { - std::map PhysReg2RegClassMap; -public: - PhysRegClassMap(const MRegisterInfo *RI) { - for (MRegisterInfo::const_iterator I = RI->regclass_begin(), - E = RI->regclass_end(); I != E; ++I) - for (unsigned i=0; i < (*I)->getNumRegs(); ++i) - PhysReg2RegClassMap[(*I)->getRegister(i)] = *I; - } - - const TargetRegisterClass *operator[](unsigned Reg) { - assert(PhysReg2RegClassMap[Reg] && "Register is not a known physreg!"); - return PhysReg2RegClassMap[Reg]; - } - - const TargetRegisterClass *get(unsigned Reg) { return operator[](Reg); } -}; -#endif - namespace { Statistic<> NumSpilled ("ra-simple", "Number of registers spilled"); Statistic<> NumReloaded("ra-simple", "Number of registers reloaded"); - class RegAllocSimple : public FunctionPass { - TargetMachine &TM; + class RegAllocSimple : public MachineFunctionPass { MachineFunction *MF; + const TargetMachine *TM; const MRegisterInfo *RegInfo; - unsigned NumBytesAllocated; - // Maps SSA Regs => offsets on the stack where these values are stored - std::map VirtReg2OffsetMap; + // StackSlotForVirtReg - Maps SSA Regs => frame index on the stack where + // these values are spilled + std::map StackSlotForVirtReg; - // RegsUsed - Keep track of what registers are currently in use. - std::set RegsUsed; + // RegsUsed - Keep track of what registers are currently in use. This is a + // bitset. + std::vector RegsUsed; // RegClassIdx - Maps RegClass => which index we can take a register // from. Since this is a simple register allocator, when we need a register @@ -60,39 +40,24 @@ namespace { std::map RegClassIdx; public: - - RegAllocSimple(TargetMachine &tm) - : TM(tm), RegInfo(tm.getRegisterInfo()) { - RegsUsed.insert(RegInfo->getFramePointer()); - RegsUsed.insert(RegInfo->getStackPointer()); - - cleanupAfterFunction(); - } - - bool runOnFunction(Function &Fn) { - return runOnMachineFunction(MachineFunction::get(&Fn)); - } - virtual const char *getPassName() const { return "Simple Register Allocator"; } - private: /// runOnMachineFunction - Register allocate the whole function bool runOnMachineFunction(MachineFunction &Fn); + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + AU.addRequiredID(PHIEliminationID); // Eliminate PHI nodes + MachineFunctionPass::getAnalysisUsage(AU); + } + private: /// AllocateBasicBlock - Register allocate the specified basic block. void AllocateBasicBlock(MachineBasicBlock &MBB); - /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions - /// in predecessor basic blocks. - void EliminatePHINodes(MachineBasicBlock &MBB); - - /// getStackSpaceFor - This returns the offset of the specified virtual /// register on the stack, allocating space if neccesary. - unsigned getStackSpaceFor(unsigned VirtReg, - const TargetRegisterClass *regClass); + int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC); /// Given a virtual register, return a compatible physical register that is /// currently unused. @@ -101,185 +66,74 @@ namespace { /// unsigned getFreeReg(unsigned virtualReg); - /// Returns all `borrowed' registers back to the free pool - void clearAllRegs() { - RegClassIdx.clear(); - } - - /// Invalidates any references, real or implicit, to physical registers - /// - void invalidatePhysRegs(const MachineInstr *MI) { - unsigned Opcode = MI->getOpcode(); - const MachineInstrDescriptor &Desc = TM.getInstrInfo().get(Opcode); - const unsigned *regs = Desc.ImplicitUses; - while (*regs) - RegsUsed.insert(*regs++); - - regs = Desc.ImplicitDefs; - while (*regs) - RegsUsed.insert(*regs++); - } - - void cleanupAfterFunction() { - VirtReg2OffsetMap.clear(); - NumBytesAllocated = 4; // FIXME: This is X86 specific - } - /// Moves value from memory into that register - MachineBasicBlock::iterator - moveUseToReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I, - unsigned VirtReg, unsigned &PhysReg); + unsigned reloadVirtReg(MachineBasicBlock &MBB, + MachineBasicBlock::iterator &I, unsigned VirtReg); /// Saves reg value on the stack (maps virtual register to stack value) - MachineBasicBlock::iterator - saveVirtRegToStack(MachineBasicBlock &MBB, MachineBasicBlock::iterator I, - unsigned VirtReg, unsigned PhysReg); + void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I, + unsigned VirtReg, unsigned PhysReg); }; } /// getStackSpaceFor - This allocates space for the specified virtual /// register to be held on the stack. -unsigned RegAllocSimple::getStackSpaceFor(unsigned VirtReg, - const TargetRegisterClass *regClass) { +int RegAllocSimple::getStackSpaceFor(unsigned VirtReg, + const TargetRegisterClass *RC) { // Find the location VirtReg would belong... - std::map::iterator I = - VirtReg2OffsetMap.lower_bound(VirtReg); + std::map::iterator I = + StackSlotForVirtReg.lower_bound(VirtReg); - if (I != VirtReg2OffsetMap.end() && I->first == VirtReg) + if (I != StackSlotForVirtReg.end() && I->first == VirtReg) return I->second; // Already has space allocated? - unsigned RegSize = regClass->getDataSize(); - - // Align NumBytesAllocated. We should be using TargetData alignment stuff - // to determine this, but we don't know the LLVM type associated with the - // virtual register. Instead, just align to a multiple of the size for now. - NumBytesAllocated += RegSize-1; - NumBytesAllocated = NumBytesAllocated/RegSize*RegSize; + // Allocate a new stack object for this spill location... + int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC); // Assign the slot... - VirtReg2OffsetMap.insert(I, std::make_pair(VirtReg, NumBytesAllocated)); - - // Reserve the space! - NumBytesAllocated += RegSize; - return NumBytesAllocated-RegSize; + StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx)); + + return FrameIdx; } unsigned RegAllocSimple::getFreeReg(unsigned virtualReg) { - const TargetRegisterClass* regClass = MF->getRegClass(virtualReg); - - unsigned regIdx = RegClassIdx[regClass]++; - assert(regIdx < regClass->getNumRegs() && "Not enough registers!"); - unsigned physReg = regClass->getRegister(regIdx); - - if (RegsUsed.find(physReg) == RegsUsed.end()) - return physReg; - else - return getFreeReg(virtualReg); + const TargetRegisterClass* RC = MF->getSSARegMap()->getRegClass(virtualReg); + TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF); + TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF); + + while (1) { + unsigned regIdx = RegClassIdx[RC]++; + assert(RI+regIdx != RE && "Not enough registers!"); + unsigned PhysReg = *(RI+regIdx); + + if (!RegsUsed[PhysReg]) + return PhysReg; + } } -MachineBasicBlock::iterator -RegAllocSimple::moveUseToReg (MachineBasicBlock &MBB, - MachineBasicBlock::iterator I, - unsigned VirtReg, unsigned &PhysReg) -{ - const TargetRegisterClass* regClass = MF->getRegClass(VirtReg); - unsigned stackOffset = getStackSpaceFor(VirtReg, regClass); - PhysReg = getFreeReg(VirtReg); +unsigned RegAllocSimple::reloadVirtReg(MachineBasicBlock &MBB, + MachineBasicBlock::iterator &I, + unsigned VirtReg) { + const TargetRegisterClass* RC = MF->getSSARegMap()->getRegClass(VirtReg); + int FrameIdx = getStackSpaceFor(VirtReg, RC); + unsigned PhysReg = getFreeReg(VirtReg); // Add move instruction(s) ++NumReloaded; - return RegInfo->loadRegOffset2Reg(MBB, I, PhysReg, - RegInfo->getFramePointer(), - -stackOffset, regClass->getDataSize()); + RegInfo->loadRegFromStackSlot(MBB, I, PhysReg, FrameIdx, RC); + return PhysReg; } -MachineBasicBlock::iterator -RegAllocSimple::saveVirtRegToStack (MachineBasicBlock &MBB, - MachineBasicBlock::iterator I, - unsigned VirtReg, unsigned PhysReg) -{ - const TargetRegisterClass* regClass = MF->getRegClass(VirtReg); - unsigned stackOffset = getStackSpaceFor(VirtReg, regClass); +void RegAllocSimple::spillVirtReg(MachineBasicBlock &MBB, + MachineBasicBlock::iterator &I, + unsigned VirtReg, unsigned PhysReg) { + const TargetRegisterClass* RC = MF->getSSARegMap()->getRegClass(VirtReg); + int FrameIdx = getStackSpaceFor(VirtReg, RC); // Add move instruction(s) ++NumSpilled; - return RegInfo->storeReg2RegOffset(MBB, I, PhysReg, - RegInfo->getFramePointer(), - -stackOffset, regClass->getDataSize()); -} - - -/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in -/// predecessor basic blocks. -/// -void RegAllocSimple::EliminatePHINodes(MachineBasicBlock &MBB) { - const MachineInstrInfo &MII = TM.getInstrInfo(); - - while (MBB.front()->getOpcode() == MachineInstrInfo::PHI) { - MachineInstr *MI = MBB.front(); - // Unlink the PHI node from the basic block... but don't delete the PHI yet - MBB.erase(MBB.begin()); - - DEBUG(std::cerr << "num ops: " << MI->getNumOperands() << "\n"); - assert(MI->getOperand(0).isVirtualRegister() && - "PHI node doesn't write virt reg?"); - - unsigned virtualReg = MI->getOperand(0).getAllocatedRegNum(); - - for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) { - MachineOperand &opVal = MI->getOperand(i-1); - - // Get the MachineBasicBlock equivalent of the BasicBlock that is the - // source path the phi - MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock(); - - // Check to make sure we haven't already emitted the copy for this block. - // This can happen because PHI nodes may have multiple entries for the - // same basic block. It doesn't matter which entry we use though, because - // all incoming values are guaranteed to be the same for a particular bb. - // - // Note that this is N^2 in the number of phi node entries, but since the - // # of entries is tiny, this is not a problem. - // - bool HaveNotEmitted = true; - for (int op = MI->getNumOperands() - 1; op != i; op -= 2) - if (&opBlock == MI->getOperand(op).getMachineBasicBlock()) { - HaveNotEmitted = false; - break; - } - - if (HaveNotEmitted) { - MachineBasicBlock::iterator opI = opBlock.end(); - MachineInstr *opMI = *--opI; - - // must backtrack over ALL the branches in the previous block - while (MII.isBranch(opMI->getOpcode()) && opI != opBlock.begin()) - opMI = *--opI; - - // move back to the first branch instruction so new instructions - // are inserted right in front of it and not in front of a non-branch - if (!MII.isBranch(opMI->getOpcode())) - ++opI; - - unsigned dataSize = MF->getRegClass(virtualReg)->getDataSize(); - - // Retrieve the constant value from this op, move it to target - // register of the phi - if (opVal.isImmediate()) { - opI = RegInfo->moveImm2Reg(opBlock, opI, virtualReg, - (unsigned) opVal.getImmedValue(), - dataSize); - } else { - opI = RegInfo->moveReg2Reg(opBlock, opI, virtualReg, - opVal.getAllocatedRegNum(), dataSize); - } - } - } - - // really delete the PHI instruction now! - delete MI; - } + RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIdx, RC); } @@ -290,10 +144,20 @@ void RegAllocSimple::AllocateBasicBlock(MachineBasicBlock &MBB) { std::map Virt2PhysRegMap; MachineInstr *MI = *I; + + RegsUsed.resize(MRegisterInfo::FirstVirtualRegister); // a preliminary pass that will invalidate any registers that // are used by the instruction (including implicit uses) - invalidatePhysRegs(MI); + unsigned Opcode = MI->getOpcode(); + const TargetInstrDescriptor &Desc = TM->getInstrInfo().get(Opcode); + if (const unsigned *Regs = Desc.ImplicitUses) + while (*Regs) + RegsUsed[*Regs++] = true; + + if (const unsigned *Regs = Desc.ImplicitDefs) + while (*Regs) + RegsUsed[*Regs++] = true; // Loop over uses, move from memory into registers for (int i = MI->getNumOperands() - 1; i >= 0; --i) { @@ -303,14 +167,14 @@ void RegAllocSimple::AllocateBasicBlock(MachineBasicBlock &MBB) { unsigned virtualReg = (unsigned) op.getAllocatedRegNum(); DEBUG(std::cerr << "op: " << op << "\n"); DEBUG(std::cerr << "\t inst[" << i << "]: "; - MI->print(std::cerr, TM)); + MI->print(std::cerr, *TM)); // make sure the same virtual register maps to the same physical // register in any given instruction unsigned physReg = Virt2PhysRegMap[virtualReg]; if (physReg == 0) { if (op.opIsDef()) { - if (TM.getInstrInfo().isTwoAddrInstr(MI->getOpcode()) && i == 0) { + if (TM->getInstrInfo().isTwoAddrInstr(MI->getOpcode()) && i == 0) { // must be same register number as the first operand // This maps a = b + c into b += c, and saves b into a's spot assert(MI->getOperand(1).isRegister() && @@ -322,55 +186,42 @@ void RegAllocSimple::AllocateBasicBlock(MachineBasicBlock &MBB) { } else { physReg = getFreeReg(virtualReg); } - I = --saveVirtRegToStack(MBB, ++I, virtualReg, physReg); + ++I; + spillVirtReg(MBB, I, virtualReg, physReg); + --I; } else { - I = moveUseToReg(MBB, I, virtualReg, physReg); + physReg = reloadVirtReg(MBB, I, virtualReg); + Virt2PhysRegMap[virtualReg] = physReg; } - Virt2PhysRegMap[virtualReg] = physReg; } MI->SetMachineOperandReg(i, physReg); DEBUG(std::cerr << "virt: " << virtualReg << ", phys: " << op.getAllocatedRegNum() << "\n"); } } - clearAllRegs(); + RegClassIdx.clear(); + RegsUsed.clear(); } } + /// runOnMachineFunction - Register allocate the whole function /// bool RegAllocSimple::runOnMachineFunction(MachineFunction &Fn) { DEBUG(std::cerr << "Machine Function " << "\n"); MF = &Fn; - - // First pass: eliminate PHI instructions by inserting copies into predecessor - // blocks. - for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end(); - MBB != MBBe; ++MBB) - EliminatePHINodes(*MBB); + TM = &MF->getTarget(); + RegInfo = TM->getRegisterInfo(); // Loop over all of the basic blocks, eliminating virtual register references for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end(); MBB != MBBe; ++MBB) AllocateBasicBlock(*MBB); - // Add prologue to the function... - RegInfo->emitPrologue(Fn, NumBytesAllocated); - - const MachineInstrInfo &MII = TM.getInstrInfo(); - - // Add epilogue to restore the callee-save registers in each exiting block - for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end(); - MBB != MBBe; ++MBB) { - // If last instruction is a return instruction, add an epilogue - if (MII.isReturn(MBB->back()->getOpcode())) - RegInfo->emitEpilogue(*MBB, NumBytesAllocated); - } - - cleanupAfterFunction(); + StackSlotForVirtReg.clear(); return true; } -Pass *createSimpleX86RegisterAllocator(TargetMachine &TM) { - return new RegAllocSimple(TM); +Pass *createSimpleRegisterAllocator() { + return new RegAllocSimple(); }