From: Chris Lattner Date: Sat, 28 Dec 2002 20:42:14 +0000 (+0000) Subject: * Convert to be a MachineFunctionPass instance X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=600dee4aaee093b6b45011c5461f43fd7855a5d6;p=oota-llvm.git * Convert to be a MachineFunctionPass instance * Use new FunctionFrameInfo object to manage stack slots instead of doing it directly * Adjust to new MRegisterInfo API * Don't take a TM as a ctor argument * Don't keep track of which callee saved registers are modified * Don't emit prolog/epilog code or spill/restore code for callee saved regs * Use new allocation_order_begin/end iterators to simplify dramatically the logic for picking registers to allocate * Machine PHI nodes can no longer contain constant arguments * Use a bitvector to keep track of registers used instead of a set * Fix problem where explicitly referenced registers would be added to regsused set and never removed git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5196 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/CodeGen/RegAllocSimple.cpp b/lib/CodeGen/RegAllocSimple.cpp index 707f1cee870..5666887336e 100644 --- a/lib/CodeGen/RegAllocSimple.cpp +++ b/lib/CodeGen/RegAllocSimple.cpp @@ -1,33 +1,37 @@ //===-- 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/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstr.h" #include "llvm/CodeGen/SSARegMap.h" +#include "llvm/CodeGen/FunctionFrameInfo.h" #include "llvm/Target/MachineInstrInfo.h" #include "llvm/Target/TargetMachine.h" #include "Support/Statistic.h" #include -#include 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 @@ -35,27 +39,14 @@ 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); + private: /// AllocateBasicBlock - Register allocate the specified basic block. void AllocateBasicBlock(MachineBasicBlock &MBB); @@ -63,18 +54,9 @@ namespace { /// in predecessor basic blocks. void EliminatePHINodes(MachineBasicBlock &MBB); - /// EmitPrologue/EmitEpilogue - Use the register info object to add a - /// prologue/epilogue to the function and save/restore any callee saved - /// registers we are responsible for. - /// - void EmitPrologue(); - void EmitEpilogue(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. @@ -83,30 +65,6 @@ 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); - if (const unsigned *regs = Desc.ImplicitUses) - while (*regs) - RegsUsed.insert(*regs++); - - if (const unsigned *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 unsigned reloadVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I, unsigned VirtReg); @@ -120,69 +78,62 @@ namespace { /// 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->getSize(), RC->getAlignment()); // 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* RC = MF->getSSARegMap()->getRegClass(virtualReg); - - unsigned regIdx = RegClassIdx[RC]++; - assert(regIdx < RC->getNumRegs() && "Not enough registers!"); - unsigned physReg = RC->getRegister(regIdx); - - if (RegsUsed.find(physReg) == RegsUsed.end()) - return physReg; - else - return getFreeReg(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; + } } unsigned RegAllocSimple::reloadVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I, unsigned VirtReg) { const TargetRegisterClass* RC = MF->getSSARegMap()->getRegClass(VirtReg); - unsigned stackOffset = getStackSpaceFor(VirtReg, RC); + int FrameIdx = getStackSpaceFor(VirtReg, RC); unsigned PhysReg = getFreeReg(VirtReg); // Add move instruction(s) ++NumReloaded; - RegInfo->loadRegOffset2Reg(MBB, I, PhysReg, RegInfo->getFramePointer(), - -stackOffset, RC); + RegInfo->loadRegFromStackSlot(MBB, I, PhysReg, FrameIdx, RC); return PhysReg; } void RegAllocSimple::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I, - unsigned VirtReg, unsigned PhysReg) -{ + unsigned VirtReg, unsigned PhysReg) { const TargetRegisterClass* RC = MF->getSSARegMap()->getRegClass(VirtReg); - unsigned stackOffset = getStackSpaceFor(VirtReg, RC); + int FrameIdx = getStackSpaceFor(VirtReg, RC); // Add move instruction(s) ++NumSpilled; - RegInfo->storeReg2RegOffset(MBB, I, PhysReg, RegInfo->getFramePointer(), - -stackOffset, RC); + RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIdx, RC); } @@ -190,7 +141,7 @@ void RegAllocSimple::spillVirtReg(MachineBasicBlock &MBB, /// predecessor basic blocks. /// void RegAllocSimple::EliminatePHINodes(MachineBasicBlock &MBB) { - const MachineInstrInfo &MII = TM.getInstrInfo(); + const MachineInstrInfo &MII = TM->getInstrInfo(); while (MBB.front()->getOpcode() == MachineInstrInfo::PHI) { MachineInstr *MI = MBB.front(); @@ -242,15 +193,9 @@ void RegAllocSimple::EliminatePHINodes(MachineBasicBlock &MBB) { const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(virtualReg); - // Retrieve the constant value from this op, move it to target - // register of the phi - if (opVal.isImmediate()) { - RegInfo->moveImm2Reg(opBlock, opI, virtualReg, - (unsigned) opVal.getImmedValue(), RC); - } else { - RegInfo->moveReg2Reg(opBlock, opI, virtualReg, - opVal.getAllocatedRegNum(), RC); - } + assert(opVal.isVirtualRegister() && + "Machine PHI Operands must all be virtual registers!"); + RegInfo->copyRegToReg(opBlock, opI, virtualReg, opVal.getReg(), RC); } } @@ -267,10 +212,20 @@ 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 MachineInstrDescriptor &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) { @@ -280,14 +235,14 @@ 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() && @@ -312,56 +267,9 @@ void RegAllocSimple::AllocateBasicBlock(MachineBasicBlock &MBB) { ", phys: " << op.getAllocatedRegNum() << "\n"); } } - clearAllRegs(); - } -} - - -/// EmitPrologue - Use the register info object to add a prologue to the -/// function and save any callee saved registers we are responsible for. -/// -void RegAllocSimple::EmitPrologue() { - // Get a list of the callee saved registers, so that we can save them on entry - // to the function. - // - MachineBasicBlock &MBB = MF->front(); // Prolog goes in entry BB - MachineBasicBlock::iterator I = MBB.begin(); - - const unsigned *CSRegs = RegInfo->getCalleeSaveRegs(); - for (unsigned i = 0; CSRegs[i]; ++i) { - const TargetRegisterClass *RegClass = RegInfo->getRegClass(CSRegs[i]); - unsigned Offset = getStackSpaceFor(CSRegs[i], RegClass); - - // Insert the spill to the stack frame... - RegInfo->storeReg2RegOffset(MBB, I,CSRegs[i],RegInfo->getFramePointer(), - -Offset, RegClass); - ++NumSpilled; + RegClassIdx.clear(); + RegsUsed.clear(); } - - // Add prologue to the function... - RegInfo->emitPrologue(*MF, NumBytesAllocated); -} - - -/// EmitEpilogue - Use the register info object to add a epilogue to the -/// function and restore any callee saved registers we are responsible for. -/// -void RegAllocSimple::EmitEpilogue(MachineBasicBlock &MBB) { - // Insert instructions before the return. - MachineBasicBlock::iterator I = MBB.end()-1; - - const unsigned *CSRegs = RegInfo->getCalleeSaveRegs(); - for (unsigned i = 0; CSRegs[i]; ++i) { - const TargetRegisterClass *RegClass = RegInfo->getRegClass(CSRegs[i]); - unsigned Offset = getStackSpaceFor(CSRegs[i], RegClass); - - RegInfo->loadRegOffset2Reg(MBB, I, CSRegs[i],RegInfo->getFramePointer(), - -Offset, RegClass); - --I; // Insert in reverse order - ++NumReloaded; - } - - RegInfo->emitEpilogue(MBB, NumBytesAllocated); } @@ -370,6 +278,8 @@ void RegAllocSimple::EmitEpilogue(MachineBasicBlock &MBB) { bool RegAllocSimple::runOnMachineFunction(MachineFunction &Fn) { DEBUG(std::cerr << "Machine Function " << "\n"); MF = &Fn; + TM = &MF->getTarget(); + RegInfo = TM->getRegisterInfo(); // First pass: eliminate PHI instructions by inserting copies into predecessor // blocks. @@ -382,27 +292,10 @@ bool RegAllocSimple::runOnMachineFunction(MachineFunction &Fn) { MBB != MBBe; ++MBB) AllocateBasicBlock(*MBB); - // Round stack allocation up to a nice alignment to keep the stack aligned - // FIXME: This is X86 specific! Move to frame manager - NumBytesAllocated = (NumBytesAllocated + 3) & ~3; - - // Emit a prologue for the function... - EmitPrologue(); - - 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())) - EmitEpilogue(*MBB); - } - - cleanupAfterFunction(); + StackSlotForVirtReg.clear(); return true; } -Pass *createSimpleRegisterAllocator(TargetMachine &TM) { - return new RegAllocSimple(TM); +Pass *createSimpleRegisterAllocator() { + return new RegAllocSimple(); }