From 0ed4cf4bf3b65e54d3ccb9a3bf1505efbd1b864c Mon Sep 17 00:00:00 2001 From: Chen Zheng Date: Sun, 17 Jan 2021 23:53:33 -0500 Subject: [PATCH] [PowerPC] support register pressure reduction in machine combiner. Reassociating some patterns to generate more fma instructions to reduce register pressure. Reviewed By: jsji Differential Revision: https://reviews.llvm.org/D92071 --- llvm/include/llvm/CodeGen/MachineCombinerPattern.h | 5 + llvm/lib/CodeGen/MachineCombiner.cpp | 3 + llvm/lib/Target/PowerPC/PPCInstrInfo.cpp | 517 +++++++++++++++++++-- llvm/lib/Target/PowerPC/PPCInstrInfo.h | 22 +- .../CodeGen/PowerPC/register-pressure-reduction.ll | 135 ++++++ 5 files changed, 637 insertions(+), 45 deletions(-) create mode 100644 llvm/test/CodeGen/PowerPC/register-pressure-reduction.ll diff --git a/llvm/include/llvm/CodeGen/MachineCombinerPattern.h b/llvm/include/llvm/CodeGen/MachineCombinerPattern.h index e9f52fb..ac0cc70 100644 --- a/llvm/include/llvm/CodeGen/MachineCombinerPattern.h +++ b/llvm/include/llvm/CodeGen/MachineCombinerPattern.h @@ -29,6 +29,11 @@ enum class MachineCombinerPattern { REASSOC_XY_AMM_BMM, REASSOC_XMM_AMM_BMM, + // These are patterns matched by the PowerPC to reassociate FMA and FSUB to + // reduce register pressure. + REASSOC_XY_BCA, + REASSOC_XY_BAC, + // These are multiply-add patterns matched by the AArch64 machine combiner. MULADDW_OP1, MULADDW_OP2, diff --git a/llvm/lib/CodeGen/MachineCombiner.cpp b/llvm/lib/CodeGen/MachineCombiner.cpp index 878912a..e2b6cfe 100644 --- a/llvm/lib/CodeGen/MachineCombiner.cpp +++ b/llvm/lib/CodeGen/MachineCombiner.cpp @@ -279,6 +279,9 @@ static CombinerObjective getCombinerObjective(MachineCombinerPattern P) { case MachineCombinerPattern::REASSOC_XY_AMM_BMM: case MachineCombinerPattern::REASSOC_XMM_AMM_BMM: return CombinerObjective::MustReduceDepth; + case MachineCombinerPattern::REASSOC_XY_BCA: + case MachineCombinerPattern::REASSOC_XY_BAC: + return CombinerObjective::MustReduceRegisterPressure; default: return CombinerObjective::Default; } diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp index 75a498b..9e3c6c5 100644 --- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp +++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp @@ -21,12 +21,15 @@ #include "llvm/ADT/Statistic.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/CodeGen/LiveIntervals.h" +#include "llvm/CodeGen/MachineConstantPool.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineMemOperand.h" #include "llvm/CodeGen/MachineRegisterInfo.h" #include "llvm/CodeGen/PseudoSourceValue.h" +#include "llvm/CodeGen/RegisterClassInfo.h" +#include "llvm/CodeGen/RegisterPressure.h" #include "llvm/CodeGen/ScheduleDAG.h" #include "llvm/CodeGen/SlotIndexes.h" #include "llvm/CodeGen/StackMaps.h" @@ -73,6 +76,14 @@ static cl::opt UseOldLatencyCalc("ppc-old-latency-calc", cl::Hidden, cl::desc("Use the old (incorrect) instruction latency calculation")); +static cl::opt + FMARPFactor("ppc-fma-rp-factor", cl::Hidden, cl::init(1.5), + cl::desc("register pressure factor for the transformations.")); + +static cl::opt EnableFMARegPressureReduction( + "ppc-fma-rp-reduction", cl::Hidden, cl::init(true), + cl::desc("enable register pressure reduce in machine combiner pass.")); + // Pin the vtable to this file. void PPCInstrInfo::anchor() {} @@ -278,21 +289,23 @@ bool PPCInstrInfo::isAssociativeAndCommutative(const MachineInstr &Inst) const { #define InfoArrayIdxFMULInst 2 #define InfoArrayIdxAddOpIdx 3 #define InfoArrayIdxMULOpIdx 4 +#define InfoArrayIdxFSubInst 5 // Array keeps info for FMA instructions: // Index 0(InfoArrayIdxFMAInst): FMA instruction; -// Index 1(InfoArrayIdxFAddInst): ADD instruction assoaicted with FMA; -// Index 2(InfoArrayIdxFMULInst): MUL instruction assoaicted with FMA; +// Index 1(InfoArrayIdxFAddInst): ADD instruction associated with FMA; +// Index 2(InfoArrayIdxFMULInst): MUL instruction associated with FMA; // Index 3(InfoArrayIdxAddOpIdx): ADD operand index in FMA operands; // Index 4(InfoArrayIdxMULOpIdx): first MUL operand index in FMA operands; -// second MUL operand index is plus 1. -static const uint16_t FMAOpIdxInfo[][5] = { +// second MUL operand index is plus 1; +// Index 5(InfoArrayIdxFSubInst): SUB instruction associated with FMA. +static const uint16_t FMAOpIdxInfo[][6] = { // FIXME: Add more FMA instructions like XSNMADDADP and so on. - {PPC::XSMADDADP, PPC::XSADDDP, PPC::XSMULDP, 1, 2}, - {PPC::XSMADDASP, PPC::XSADDSP, PPC::XSMULSP, 1, 2}, - {PPC::XVMADDADP, PPC::XVADDDP, PPC::XVMULDP, 1, 2}, - {PPC::XVMADDASP, PPC::XVADDSP, PPC::XVMULSP, 1, 2}, - {PPC::FMADD, PPC::FADD, PPC::FMUL, 3, 1}, - {PPC::FMADDS, PPC::FADDS, PPC::FMULS, 3, 1}}; + {PPC::XSMADDADP, PPC::XSADDDP, PPC::XSMULDP, 1, 2, PPC::XSSUBDP}, + {PPC::XSMADDASP, PPC::XSADDSP, PPC::XSMULSP, 1, 2, PPC::XSSUBSP}, + {PPC::XVMADDADP, PPC::XVADDDP, PPC::XVMULDP, 1, 2, PPC::XVSUBDP}, + {PPC::XVMADDASP, PPC::XVADDSP, PPC::XVMULSP, 1, 2, PPC::XVSUBSP}, + {PPC::FMADD, PPC::FADD, PPC::FMUL, 3, 1, PPC::FSUB}, + {PPC::FMADDS, PPC::FADDS, PPC::FMULS, 3, 1, PPC::FSUBS}}; // Check if an opcode is a FMA instruction. If it is, return the index in array // FMAOpIdxInfo. Otherwise, return -1. @@ -303,6 +316,8 @@ int16_t PPCInstrInfo::getFMAOpIdxInfo(unsigned Opcode) const { return -1; } +// On PowerPC target, we have two kinds of patterns related to FMA: +// 1: Improve ILP. // Try to reassociate FMA chains like below: // // Pattern 1: @@ -326,11 +341,35 @@ int16_t PPCInstrInfo::getFMAOpIdxInfo(unsigned Opcode) const { // // breaking the dependency between A and B, allowing FMA to be executed in // parallel (or back-to-back in a pipeline) instead of depending on each other. +// +// 2: Reduce register pressure. +// Try to reassociate FMA with FSUB and a constant like below: +// C is a floatint point const. +// +// Pattern 1: +// A = FSUB X, Y (Leaf) +// D = FMA B, C, A (Root) +// --> +// A = FMA B, Y, -C +// D = FMA A, X, C +// +// Pattern 2: +// A = FSUB X, Y (Leaf) +// D = FMA B, A, C (Root) +// --> +// A = FMA B, Y, -C +// D = FMA A, X, C +// +// Before the transformation, A must be assigned with different hardware +// register with D. After the transformation, A and D must be assigned with +// same hardware register due to TIE attricute of FMA instructions. +// bool PPCInstrInfo::getFMAPatterns( - MachineInstr &Root, - SmallVectorImpl &Patterns) const { + MachineInstr &Root, SmallVectorImpl &Patterns, + bool DoRegPressureReduce) const { MachineBasicBlock *MBB = Root.getParent(); - const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo(); + const MachineRegisterInfo *MRI = &MBB->getParent()->getRegInfo(); + const TargetRegisterInfo *TRI = &getRegisterInfo(); auto IsAllOpsVirtualReg = [](const MachineInstr &Instr) { for (const auto &MO : Instr.explicit_operands()) @@ -339,9 +378,10 @@ bool PPCInstrInfo::getFMAPatterns( return true; }; - auto IsReassociableAdd = [&](const MachineInstr &Instr) { + auto IsReassociableAddOrSub = [&](const MachineInstr &Instr, + unsigned OpType) { if (Instr.getOpcode() != - FMAOpIdxInfo[getFMAOpIdxInfo(Root.getOpcode())][InfoArrayIdxFAddInst]) + FMAOpIdxInfo[getFMAOpIdxInfo(Root.getOpcode())][OpType]) return false; // Instruction can be reassociated. @@ -354,11 +394,17 @@ bool PPCInstrInfo::getFMAPatterns( if (!IsAllOpsVirtualReg(Instr)) return false; + // For register pressure reassociation, the FSub must have only one use as + // we want to delete the sub to save its def. + if (OpType == InfoArrayIdxFSubInst && + !MRI->hasOneNonDBGUse(Instr.getOperand(0).getReg())) + return false; + return true; }; auto IsReassociableFMA = [&](const MachineInstr &Instr, int16_t &AddOpIdx, - bool IsLeaf) { + int16_t &MulOpIdx, bool IsLeaf) { int16_t Idx = getFMAOpIdxInfo(Instr.getOpcode()); if (Idx < 0) return false; @@ -373,53 +419,343 @@ bool PPCInstrInfo::getFMAPatterns( if (!IsAllOpsVirtualReg(Instr)) return false; + MulOpIdx = FMAOpIdxInfo[Idx][InfoArrayIdxMULOpIdx]; if (IsLeaf) return true; AddOpIdx = FMAOpIdxInfo[Idx][InfoArrayIdxAddOpIdx]; const MachineOperand &OpAdd = Instr.getOperand(AddOpIdx); - MachineInstr *MIAdd = MRI.getUniqueVRegDef(OpAdd.getReg()); + MachineInstr *MIAdd = MRI->getUniqueVRegDef(OpAdd.getReg()); // If 'add' operand's def is not in current block, don't do ILP related opt. if (!MIAdd || MIAdd->getParent() != MBB) return false; // If this is not Leaf FMA Instr, its 'add' operand should only have one use // as this fma will be changed later. - return IsLeaf ? true : MRI.hasOneNonDBGUse(OpAdd.getReg()); + return IsLeaf ? true : MRI->hasOneNonDBGUse(OpAdd.getReg()); }; int16_t AddOpIdx = -1; + int16_t MulOpIdx = -1; + + bool IsUsedOnceL = false; + bool IsUsedOnceR = false; + MachineInstr *MULInstrL = nullptr; + MachineInstr *MULInstrR = nullptr; + + auto IsRPReductionCandidate = [&]() { + // Currently, we only support float and double. + // FIXME: add support for other types. + unsigned Opcode = Root.getOpcode(); + if (Opcode != PPC::XSMADDASP && Opcode != PPC::XSMADDADP) + return false; + + // Root must be a valid FMA like instruction. + // Treat it as leaf as we don't care its add operand. + if (IsReassociableFMA(Root, AddOpIdx, MulOpIdx, true)) { + assert((MulOpIdx >= 0) && "mul operand index not right!"); + Register MULRegL = TRI->lookThruSingleUseCopyChain( + Root.getOperand(MulOpIdx).getReg(), MRI); + Register MULRegR = TRI->lookThruSingleUseCopyChain( + Root.getOperand(MulOpIdx + 1).getReg(), MRI); + if (!MULRegL && !MULRegR) + return false; + + if (MULRegL && !MULRegR) { + MULRegR = + TRI->lookThruCopyLike(Root.getOperand(MulOpIdx + 1).getReg(), MRI); + IsUsedOnceL = true; + } else if (!MULRegL && MULRegR) { + MULRegL = + TRI->lookThruCopyLike(Root.getOperand(MulOpIdx).getReg(), MRI); + IsUsedOnceR = true; + } else { + IsUsedOnceL = true; + IsUsedOnceR = true; + } + + if (!Register::isVirtualRegister(MULRegL) || + !Register::isVirtualRegister(MULRegR)) + return false; + + MULInstrL = MRI->getVRegDef(MULRegL); + MULInstrR = MRI->getVRegDef(MULRegR); + return true; + } + return false; + }; + + // Register pressure fma reassociation patterns. + if (DoRegPressureReduce && IsRPReductionCandidate()) { + assert((MULInstrL && MULInstrR) && "wrong register preduction candidate!"); + // Register pressure pattern 1 + if (isLoadFromConstantPool(MULInstrL) && IsUsedOnceR && + IsReassociableAddOrSub(*MULInstrR, InfoArrayIdxFSubInst)) { + LLVM_DEBUG(dbgs() << "add pattern REASSOC_XY_BCA\n"); + Patterns.push_back(MachineCombinerPattern::REASSOC_XY_BCA); + return true; + } + + // Register pressure pattern 2 + if ((isLoadFromConstantPool(MULInstrR) && IsUsedOnceL && + IsReassociableAddOrSub(*MULInstrL, InfoArrayIdxFSubInst))) { + LLVM_DEBUG(dbgs() << "add pattern REASSOC_XY_BAC\n"); + Patterns.push_back(MachineCombinerPattern::REASSOC_XY_BAC); + return true; + } + } + + // ILP fma reassociation patterns. // Root must be a valid FMA like instruction. - if (!IsReassociableFMA(Root, AddOpIdx, false)) + AddOpIdx = -1; + if (!IsReassociableFMA(Root, AddOpIdx, MulOpIdx, false)) return false; assert((AddOpIdx >= 0) && "add operand index not right!"); Register RegB = Root.getOperand(AddOpIdx).getReg(); - MachineInstr *Prev = MRI.getUniqueVRegDef(RegB); + MachineInstr *Prev = MRI->getUniqueVRegDef(RegB); // Prev must be a valid FMA like instruction. AddOpIdx = -1; - if (!IsReassociableFMA(*Prev, AddOpIdx, false)) + if (!IsReassociableFMA(*Prev, AddOpIdx, MulOpIdx, false)) return false; assert((AddOpIdx >= 0) && "add operand index not right!"); Register RegA = Prev->getOperand(AddOpIdx).getReg(); - MachineInstr *Leaf = MRI.getUniqueVRegDef(RegA); + MachineInstr *Leaf = MRI->getUniqueVRegDef(RegA); AddOpIdx = -1; - if (IsReassociableFMA(*Leaf, AddOpIdx, true)) { + if (IsReassociableFMA(*Leaf, AddOpIdx, MulOpIdx, true)) { Patterns.push_back(MachineCombinerPattern::REASSOC_XMM_AMM_BMM); + LLVM_DEBUG(dbgs() << "add pattern REASSOC_XMM_AMM_BMM\n"); return true; } - if (IsReassociableAdd(*Leaf)) { + if (IsReassociableAddOrSub(*Leaf, InfoArrayIdxFAddInst)) { Patterns.push_back(MachineCombinerPattern::REASSOC_XY_AMM_BMM); + LLVM_DEBUG(dbgs() << "add pattern REASSOC_XY_AMM_BMM\n"); return true; } return false; } +void PPCInstrInfo::finalizeInsInstrs( + MachineInstr &Root, MachineCombinerPattern &P, + SmallVectorImpl &InsInstrs) const { + assert(!InsInstrs.empty() && "Instructions set to be inserted is empty!"); + + MachineFunction *MF = Root.getMF(); + MachineRegisterInfo *MRI = &MF->getRegInfo(); + const TargetRegisterInfo *TRI = &getRegisterInfo(); + MachineConstantPool *MCP = MF->getConstantPool(); + + int16_t Idx = getFMAOpIdxInfo(Root.getOpcode()); + if (Idx < 0) + return; + + uint16_t FirstMulOpIdx = FMAOpIdxInfo[Idx][InfoArrayIdxMULOpIdx]; + + // For now we only need to fix up placeholder for register pressure reduce + // patterns. + Register ConstReg = 0; + switch (P) { + case MachineCombinerPattern::REASSOC_XY_BCA: + ConstReg = + TRI->lookThruCopyLike(Root.getOperand(FirstMulOpIdx).getReg(), MRI); + break; + case MachineCombinerPattern::REASSOC_XY_BAC: + ConstReg = + TRI->lookThruCopyLike(Root.getOperand(FirstMulOpIdx + 1).getReg(), MRI); + break; + default: + // Not register pressure reduce patterns. + return; + } + + MachineInstr *ConstDefInstr = MRI->getVRegDef(ConstReg); + // Get const value from const pool. + const Constant *C = getConstantFromConstantPool(ConstDefInstr); + assert(isa(C) && "not a valid constant!"); + + // Get negative fp const. + APFloat F1((dyn_cast(C))->getValueAPF()); + F1.changeSign(); + Constant *NegC = ConstantFP::get(dyn_cast(C)->getContext(), F1); + Align Alignment = MF->getDataLayout().getPrefTypeAlign(C->getType()); + + // Put negative fp const into constant pool. + unsigned ConstPoolIdx = MCP->getConstantPoolIndex(NegC, Alignment); + + MachineOperand *Placeholder = nullptr; + // Record the placeholder PPC::ZERO8 we add in reassociateFMA. + for (auto *Inst : InsInstrs) { + for (MachineOperand &Operand : Inst->explicit_operands()) { + assert(Operand.isReg() && "Invalid instruction in InsInstrs!"); + if (Operand.getReg() == PPC::ZERO8) { + Placeholder = &Operand; + break; + } + } + } + + assert(Placeholder && "Placeholder does not exist!"); + + // Generate instructions to load the const fp from constant pool. + // We only support PPC64 and medium code model. + Register LoadNewConst = + generateLoadForNewConst(ConstPoolIdx, &Root, C->getType(), InsInstrs); + + // Fill the placeholder with the new load from constant pool. + Placeholder->setReg(LoadNewConst); +} + +bool PPCInstrInfo::shouldReduceRegisterPressure( + MachineBasicBlock *MBB, RegisterClassInfo *RegClassInfo) const { + + if (!EnableFMARegPressureReduction) + return false; + + // Currently, we only enable register pressure reducing in machine combiner + // for: 1: PPC64; 2: Code Model is Medium; 3: Power9 which also has vector + // support. + // + // So we need following instructions to access a TOC entry: + // + // %6:g8rc_and_g8rc_nox0 = ADDIStocHA8 $x2, %const.0 + // %7:vssrc = DFLOADf32 target-flags(ppc-toc-lo) %const.0, + // killed %6:g8rc_and_g8rc_nox0, implicit $x2 :: (load 4 from constant-pool) + // + // FIXME: add more supported targets, like Small and Large code model, PPC32, + // AIX. + if (!(Subtarget.isPPC64() && Subtarget.hasP9Vector() && + Subtarget.getTargetMachine().getCodeModel() == CodeModel::Medium)) + return false; + + const TargetRegisterInfo *TRI = &getRegisterInfo(); + MachineFunction *MF = MBB->getParent(); + MachineRegisterInfo *MRI = &MF->getRegInfo(); + + auto GetMBBPressure = [&](MachineBasicBlock *MBB) -> std::vector { + RegionPressure Pressure; + RegPressureTracker RPTracker(Pressure); + + // Initialize the register pressure tracker. + RPTracker.init(MBB->getParent(), RegClassInfo, nullptr, MBB, MBB->end(), + /*TrackLaneMasks*/ false, /*TrackUntiedDefs=*/true); + + for (MachineBasicBlock::iterator MII = MBB->instr_end(), + MIE = MBB->instr_begin(); + MII != MIE; --MII) { + MachineInstr &MI = *std::prev(MII); + if (MI.isDebugValue() || MI.isDebugLabel()) + continue; + RegisterOperands RegOpers; + RegOpers.collect(MI, *TRI, *MRI, false, false); + RPTracker.recedeSkipDebugValues(); + assert(&*RPTracker.getPos() == &MI && "RPTracker sync error!"); + RPTracker.recede(RegOpers); + } + + // Close the RPTracker to finalize live ins. + RPTracker.closeRegion(); + + return RPTracker.getPressure().MaxSetPressure; + }; + + // For now we only care about float and double type fma. + unsigned VSSRCLimit = TRI->getRegPressureSetLimit( + *MBB->getParent(), PPC::RegisterPressureSets::VSSRC); + + // Only reduce register pressure when pressure is high. + return GetMBBPressure(MBB)[PPC::RegisterPressureSets::VSSRC] > + (float)VSSRCLimit * FMARPFactor; +} + +bool PPCInstrInfo::isLoadFromConstantPool(MachineInstr *I) const { + // I has only one memory operand which is load from constant pool. + if (!I->hasOneMemOperand()) + return false; + + MachineMemOperand *Op = I->memoperands()[0]; + return Op->isLoad() && Op->getPseudoValue() && + Op->getPseudoValue()->kind() == PseudoSourceValue::ConstantPool; +} + +Register PPCInstrInfo::generateLoadForNewConst( + unsigned Idx, MachineInstr *MI, Type *Ty, + SmallVectorImpl &InsInstrs) const { + // Now we only support PPC64, Medium code model and P9 with vector. + // We have immutable pattern to access const pool. See function + // shouldReduceRegisterPressure. + assert((Subtarget.isPPC64() && Subtarget.hasP9Vector() && + Subtarget.getTargetMachine().getCodeModel() == CodeModel::Medium) && + "Target not supported!\n"); + + MachineFunction *MF = MI->getMF(); + MachineRegisterInfo *MRI = &MF->getRegInfo(); + + // Generate ADDIStocHA8 + Register VReg1 = MRI->createVirtualRegister(&PPC::G8RC_and_G8RC_NOX0RegClass); + MachineInstrBuilder TOCOffset = + BuildMI(*MF, MI->getDebugLoc(), get(PPC::ADDIStocHA8), VReg1) + .addReg(PPC::X2) + .addConstantPoolIndex(Idx); + + assert((Ty->isFloatTy() || Ty->isDoubleTy()) && + "Only float and double are supported!"); + + unsigned LoadOpcode; + // Should be float type or double type. + if (Ty->isFloatTy()) + LoadOpcode = PPC::DFLOADf32; + else + LoadOpcode = PPC::DFLOADf64; + + const TargetRegisterClass *RC = MRI->getRegClass(MI->getOperand(0).getReg()); + Register VReg2 = MRI->createVirtualRegister(RC); + MachineMemOperand *MMO = MF->getMachineMemOperand( + MachinePointerInfo::getConstantPool(*MF), MachineMemOperand::MOLoad, + Ty->getScalarSizeInBits() / 8, MF->getDataLayout().getPrefTypeAlign(Ty)); + + // Generate Load from constant pool. + MachineInstrBuilder Load = + BuildMI(*MF, MI->getDebugLoc(), get(LoadOpcode), VReg2) + .addConstantPoolIndex(Idx) + .addReg(VReg1, getKillRegState(true)) + .addMemOperand(MMO); + + Load->getOperand(1).setTargetFlags(PPCII::MO_TOC_LO); + + // Insert the toc load instructions into InsInstrs. + InsInstrs.insert(InsInstrs.begin(), Load); + InsInstrs.insert(InsInstrs.begin(), TOCOffset); + return VReg2; +} + +// This function returns the const value in constant pool if the \p I is a load +// from constant pool. +const Constant * +PPCInstrInfo::getConstantFromConstantPool(MachineInstr *I) const { + MachineFunction *MF = I->getMF(); + MachineRegisterInfo *MRI = &MF->getRegInfo(); + MachineConstantPool *MCP = MF->getConstantPool(); + assert(I->mayLoad() && "Should be a load instruction.\n"); + for (auto MO : I->uses()) { + if (!MO.isReg()) + continue; + Register Reg = MO.getReg(); + if (Reg == 0 || !Register::isVirtualRegister(Reg)) + continue; + // Find the toc address. + MachineInstr *DefMI = MRI->getVRegDef(Reg); + for (auto MO2 : DefMI->uses()) + if (MO2.isCPI()) + return (MCP->getConstants())[MO2.getIndex()].Val.ConstVal; + } + return nullptr; +} + bool PPCInstrInfo::getMachineCombinerPatterns( MachineInstr &Root, SmallVectorImpl &Patterns, bool DoRegPressureReduce) const { @@ -428,7 +764,7 @@ bool PPCInstrInfo::getMachineCombinerPatterns( if (Subtarget.getTargetMachine().getOptLevel() != CodeGenOpt::Aggressive) return false; - if (getFMAPatterns(Root, Patterns)) + if (getFMAPatterns(Root, Patterns, DoRegPressureReduce)) return true; return TargetInstrInfo::getMachineCombinerPatterns(Root, Patterns, @@ -443,6 +779,8 @@ void PPCInstrInfo::genAlternativeCodeSequence( switch (Pattern) { case MachineCombinerPattern::REASSOC_XY_AMM_BMM: case MachineCombinerPattern::REASSOC_XMM_AMM_BMM: + case MachineCombinerPattern::REASSOC_XY_BCA: + case MachineCombinerPattern::REASSOC_XY_BAC: reassociateFMA(Root, Pattern, InsInstrs, DelInstrs, InstrIdxForVirtReg); break; default: @@ -453,8 +791,6 @@ void PPCInstrInfo::genAlternativeCodeSequence( } } -// Currently, only handle two patterns REASSOC_XY_AMM_BMM and -// REASSOC_XMM_AMM_BMM. See comments for getFMAPatterns. void PPCInstrInfo::reassociateFMA( MachineInstr &Root, MachineCombinerPattern Pattern, SmallVectorImpl &InsInstrs, @@ -462,6 +798,7 @@ void PPCInstrInfo::reassociateFMA( DenseMap &InstrIdxForVirtReg) const { MachineFunction *MF = Root.getMF(); MachineRegisterInfo &MRI = MF->getRegInfo(); + const TargetRegisterInfo *TRI = &getRegisterInfo(); MachineOperand &OpC = Root.getOperand(0); Register RegC = OpC.getReg(); const TargetRegisterClass *RC = MRI.getRegClass(RegC); @@ -471,13 +808,42 @@ void PPCInstrInfo::reassociateFMA( int16_t Idx = getFMAOpIdxInfo(FmaOp); assert(Idx >= 0 && "Root must be a FMA instruction"); + bool IsILPReassociate = + (Pattern == MachineCombinerPattern::REASSOC_XY_AMM_BMM) || + (Pattern == MachineCombinerPattern::REASSOC_XMM_AMM_BMM); + uint16_t AddOpIdx = FMAOpIdxInfo[Idx][InfoArrayIdxAddOpIdx]; uint16_t FirstMulOpIdx = FMAOpIdxInfo[Idx][InfoArrayIdxMULOpIdx]; - MachineInstr *Prev = MRI.getUniqueVRegDef(Root.getOperand(AddOpIdx).getReg()); - MachineInstr *Leaf = - MRI.getUniqueVRegDef(Prev->getOperand(AddOpIdx).getReg()); - uint16_t IntersectedFlags = - Root.getFlags() & Prev->getFlags() & Leaf->getFlags(); + + MachineInstr *Prev = nullptr; + MachineInstr *Leaf = nullptr; + switch (Pattern) { + default: + llvm_unreachable("not recognized pattern!"); + case MachineCombinerPattern::REASSOC_XY_AMM_BMM: + case MachineCombinerPattern::REASSOC_XMM_AMM_BMM: + Prev = MRI.getUniqueVRegDef(Root.getOperand(AddOpIdx).getReg()); + Leaf = MRI.getUniqueVRegDef(Prev->getOperand(AddOpIdx).getReg()); + break; + case MachineCombinerPattern::REASSOC_XY_BAC: { + Register MULReg = + TRI->lookThruCopyLike(Root.getOperand(FirstMulOpIdx).getReg(), &MRI); + Leaf = MRI.getVRegDef(MULReg); + break; + } + case MachineCombinerPattern::REASSOC_XY_BCA: { + Register MULReg = TRI->lookThruCopyLike( + Root.getOperand(FirstMulOpIdx + 1).getReg(), &MRI); + Leaf = MRI.getVRegDef(MULReg); + break; + } + } + + uint16_t IntersectedFlags = 0; + if (IsILPReassociate) + IntersectedFlags = Root.getFlags() & Prev->getFlags() & Leaf->getFlags(); + else + IntersectedFlags = Root.getFlags() & Leaf->getFlags(); auto GetOperandInfo = [&](const MachineOperand &Operand, Register &Reg, bool &KillFlag) { @@ -487,36 +853,51 @@ void PPCInstrInfo::reassociateFMA( }; auto GetFMAInstrInfo = [&](const MachineInstr &Instr, Register &MulOp1, - Register &MulOp2, bool &MulOp1KillFlag, - bool &MulOp2KillFlag) { + Register &MulOp2, Register &AddOp, + bool &MulOp1KillFlag, bool &MulOp2KillFlag, + bool &AddOpKillFlag) { GetOperandInfo(Instr.getOperand(FirstMulOpIdx), MulOp1, MulOp1KillFlag); GetOperandInfo(Instr.getOperand(FirstMulOpIdx + 1), MulOp2, MulOp2KillFlag); + GetOperandInfo(Instr.getOperand(AddOpIdx), AddOp, AddOpKillFlag); }; - Register RegM11, RegM12, RegX, RegY, RegM21, RegM22, RegM31, RegM32; + Register RegM11, RegM12, RegX, RegY, RegM21, RegM22, RegM31, RegM32, RegA11, + RegA21, RegB; bool KillX = false, KillY = false, KillM11 = false, KillM12 = false, - KillM21 = false, KillM22 = false, KillM31 = false, KillM32 = false; + KillM21 = false, KillM22 = false, KillM31 = false, KillM32 = false, + KillA11 = false, KillA21 = false, KillB = false; - GetFMAInstrInfo(Root, RegM31, RegM32, KillM31, KillM32); - GetFMAInstrInfo(*Prev, RegM21, RegM22, KillM21, KillM22); + GetFMAInstrInfo(Root, RegM31, RegM32, RegB, KillM31, KillM32, KillB); + + if (IsILPReassociate) + GetFMAInstrInfo(*Prev, RegM21, RegM22, RegA21, KillM21, KillM22, KillA21); if (Pattern == MachineCombinerPattern::REASSOC_XMM_AMM_BMM) { - GetFMAInstrInfo(*Leaf, RegM11, RegM12, KillM11, KillM12); + GetFMAInstrInfo(*Leaf, RegM11, RegM12, RegA11, KillM11, KillM12, KillA11); GetOperandInfo(Leaf->getOperand(AddOpIdx), RegX, KillX); } else if (Pattern == MachineCombinerPattern::REASSOC_XY_AMM_BMM) { GetOperandInfo(Leaf->getOperand(1), RegX, KillX); GetOperandInfo(Leaf->getOperand(2), RegY, KillY); + } else { + // Get FSUB instruction info. + GetOperandInfo(Leaf->getOperand(1), RegX, KillX); + GetOperandInfo(Leaf->getOperand(2), RegY, KillY); } // Create new virtual registers for the new results instead of // recycling legacy ones because the MachineCombiner's computation of the // critical path requires a new register definition rather than an existing // one. + // For register pressure reassociation, we only need create one virtual + // register for the new fma. Register NewVRA = MRI.createVirtualRegister(RC); InstrIdxForVirtReg.insert(std::make_pair(NewVRA, 0)); - Register NewVRB = MRI.createVirtualRegister(RC); - InstrIdxForVirtReg.insert(std::make_pair(NewVRB, 1)); + Register NewVRB = 0; + if (IsILPReassociate) { + NewVRB = MRI.createVirtualRegister(RC); + InstrIdxForVirtReg.insert(std::make_pair(NewVRB, 1)); + } Register NewVRD = 0; if (Pattern == MachineCombinerPattern::REASSOC_XMM_AMM_BMM) { @@ -535,7 +916,11 @@ void PPCInstrInfo::reassociateFMA( MI->getOperand(FirstMulOpIdx + 1).setIsKill(KillRegMul2); }; - if (Pattern == MachineCombinerPattern::REASSOC_XY_AMM_BMM) { + MachineInstrBuilder NewARegPressure, NewCRegPressure; + switch (Pattern) { + default: + llvm_unreachable("not recognized pattern!"); + case MachineCombinerPattern::REASSOC_XY_AMM_BMM: { // Create new instructions for insertion. MachineInstrBuilder MINewB = BuildMI(*MF, Prev->getDebugLoc(), get(FmaOp), NewVRB) @@ -568,7 +953,9 @@ void PPCInstrInfo::reassociateFMA( InsInstrs.push_back(MINewA); InsInstrs.push_back(MINewB); InsInstrs.push_back(MINewC); - } else if (Pattern == MachineCombinerPattern::REASSOC_XMM_AMM_BMM) { + break; + } + case MachineCombinerPattern::REASSOC_XMM_AMM_BMM: { assert(NewVRD && "new FMA register not created!"); // Create new instructions for insertion. MachineInstrBuilder MINewA = @@ -610,6 +997,47 @@ void PPCInstrInfo::reassociateFMA( InsInstrs.push_back(MINewB); InsInstrs.push_back(MINewD); InsInstrs.push_back(MINewC); + break; + } + case MachineCombinerPattern::REASSOC_XY_BAC: + case MachineCombinerPattern::REASSOC_XY_BCA: { + Register VarReg; + bool KillVarReg = false; + if (Pattern == MachineCombinerPattern::REASSOC_XY_BCA) { + VarReg = RegM31; + KillVarReg = KillM31; + } else { + VarReg = RegM32; + KillVarReg = KillM32; + } + // We don't want to get negative const from memory pool too early, as the + // created entry will not be deleted even if it has no users. Since all + // operand of Leaf and Root are virtual register, we use zero register + // here as a placeholder. When the InsInstrs is selected in + // MachineCombiner, we call finalizeInsInstrs to replace the zero register + // with a virtual register which is a load from constant pool. + NewARegPressure = BuildMI(*MF, Root.getDebugLoc(), get(FmaOp), NewVRA) + .addReg(RegB, getKillRegState(RegB)) + .addReg(RegY, getKillRegState(KillY)) + .addReg(PPC::ZERO8); + NewCRegPressure = BuildMI(*MF, Root.getDebugLoc(), get(FmaOp), RegC) + .addReg(NewVRA, getKillRegState(true)) + .addReg(RegX, getKillRegState(KillX)) + .addReg(VarReg, getKillRegState(KillVarReg)); + // For now, we only support xsmaddadp/xsmaddasp, their add operand are + // both at index 1, no need to adjust. + // FIXME: when add more fma instructions support, like fma/fmas, adjust + // the operand index here. + break; + } + } + + if (!IsILPReassociate) { + setSpecialOperandAttr(*NewARegPressure, IntersectedFlags); + setSpecialOperandAttr(*NewCRegPressure, IntersectedFlags); + + InsInstrs.push_back(NewARegPressure); + InsInstrs.push_back(NewCRegPressure); } assert(!InsInstrs.empty() && @@ -617,7 +1045,8 @@ void PPCInstrInfo::reassociateFMA( // Record old instructions for deletion. DelInstrs.push_back(Leaf); - DelInstrs.push_back(Prev); + if (IsILPReassociate) + DelInstrs.push_back(Prev); DelInstrs.push_back(&Root); } diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.h b/llvm/lib/Target/PowerPC/PPCInstrInfo.h index 962456e..c6ef174 100644 --- a/llvm/lib/Target/PowerPC/PPCInstrInfo.h +++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.h @@ -252,6 +252,11 @@ class PPCInstrInfo : public PPCGenInstrInfo { SmallVectorImpl &InsInstrs, SmallVectorImpl &DelInstrs, DenseMap &InstrIdxForVirtReg) const; + bool isLoadFromConstantPool(MachineInstr *I) const; + Register + generateLoadForNewConst(unsigned Idx, MachineInstr *MI, Type *Ty, + SmallVectorImpl &InsInstrs) const; + const Constant *getConstantFromConstantPool(MachineInstr *I) const; virtual void anchor(); protected: @@ -343,7 +348,8 @@ public: /// chain ending in \p Root. All potential patterns are output in the \p /// P array. bool getFMAPatterns(MachineInstr &Root, - SmallVectorImpl &P) const; + SmallVectorImpl &P, + bool DoRegPressureReduce) const; /// Return true when there is potentially a faster code sequence /// for an instruction chain ending in . All potential patterns are @@ -352,6 +358,20 @@ public: SmallVectorImpl &P, bool DoRegPressureReduce) const override; + /// On PowerPC, we leverage machine combiner pass to reduce register pressure + /// when the register pressure is high for one BB. + /// Return true if register pressure for \p MBB is high and ABI is supported + /// to reduce register pressure. Otherwise return false. + bool + shouldReduceRegisterPressure(MachineBasicBlock *MBB, + RegisterClassInfo *RegClassInfo) const override; + + /// Fixup the placeholders we put in genAlternativeCodeSequence() for + /// MachineCombiner. + void + finalizeInsInstrs(MachineInstr &Root, MachineCombinerPattern &P, + SmallVectorImpl &InsInstrs) const override; + bool isAssociativeAndCommutative(const MachineInstr &Inst) const override; /// On PowerPC, we try to reassociate FMA chain which will increase diff --git a/llvm/test/CodeGen/PowerPC/register-pressure-reduction.ll b/llvm/test/CodeGen/PowerPC/register-pressure-reduction.ll new file mode 100644 index 0000000..281734e --- /dev/null +++ b/llvm/test/CodeGen/PowerPC/register-pressure-reduction.ll @@ -0,0 +1,135 @@ +; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py +; RUN: llc -verify-machineinstrs -ppc-asm-full-reg-names -O3 < %s \ +; RUN: -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr9 | FileCheck %s +; RUN: llc -verify-machineinstrs -ppc-asm-full-reg-names -O3 < %s \ +; RUN: -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 | FileCheck %s --check-prefix=CHECK-P8 +; RUN: llc -verify-machineinstrs -ppc-asm-full-reg-names -ppc-fma-rp-factor=0.0 -O3 < %s \ +; RUN: -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr9 | FileCheck %s --check-prefix=CHECK-FMA + +@global_val = external global float, align 4 + +define float @foo_float(float %0, float %1, float %2, float %3) { +; CHECK-LABEL: foo_float: +; CHECK: # %bb.0: +; CHECK-NEXT: addis r3, r2, .LCPI0_0@toc@ha +; CHECK-NEXT: xsmulsp f1, f2, f1 +; CHECK-NEXT: xssubsp f0, f3, f4 +; CHECK-NEXT: lfs f2, .LCPI0_0@toc@l(r3) +; CHECK-NEXT: xsmaddasp f1, f0, f2 +; CHECK-NEXT: blr +; +; CHECK-P8-LABEL: foo_float: +; CHECK-P8: # %bb.0: +; CHECK-P8-NEXT: xsmulsp f1, f2, f1 +; CHECK-P8-NEXT: addis r3, r2, .LCPI0_0@toc@ha +; CHECK-P8-NEXT: xssubsp f0, f3, f4 +; CHECK-P8-NEXT: lfs f2, .LCPI0_0@toc@l(r3) +; CHECK-P8-NEXT: xsmaddasp f1, f0, f2 +; CHECK-P8-NEXT: blr +; +; CHECK-FMA-LABEL: foo_float: +; CHECK-FMA: # %bb.0: +; CHECK-FMA-NEXT: addis r3, r2, .LCPI0_0@toc@ha +; CHECK-FMA-NEXT: xsmulsp f1, f2, f1 +; CHECK-FMA-NEXT: lfs f0, .LCPI0_0@toc@l(r3) +; CHECK-FMA-NEXT: addis r3, r2, .LCPI0_1@toc@ha +; CHECK-FMA-NEXT: lfs f2, .LCPI0_1@toc@l(r3) +; CHECK-FMA-NEXT: xsmaddasp f1, f4, f2 +; CHECK-FMA-NEXT: xsmaddasp f1, f3, f0 +; CHECK-FMA-NEXT: blr + %5 = fmul reassoc nsz float %1, %0 + %6 = fsub reassoc nsz float %2, %3 + %7 = fmul reassoc nsz float %6, 0x3DB2533FE0000000 + %8 = fadd reassoc nsz float %7, %5 + ret float %8 +} + +define double @foo_double(double %0, double %1, double %2, double %3) { +; CHECK-LABEL: foo_double: +; CHECK: # %bb.0: +; CHECK-NEXT: xsmuldp f1, f2, f1 +; CHECK-NEXT: xssubdp f0, f3, f4 +; CHECK-NEXT: addis r3, r2, .LCPI1_0@toc@ha +; CHECK-NEXT: lfd f2, .LCPI1_0@toc@l(r3) +; CHECK-NEXT: xsmaddadp f1, f0, f2 +; CHECK-NEXT: blr +; +; CHECK-P8-LABEL: foo_double: +; CHECK-P8: # %bb.0: +; CHECK-P8-NEXT: xsmuldp f1, f2, f1 +; CHECK-P8-NEXT: addis r3, r2, .LCPI1_0@toc@ha +; CHECK-P8-NEXT: xssubdp f0, f3, f4 +; CHECK-P8-NEXT: lfd f2, .LCPI1_0@toc@l(r3) +; CHECK-P8-NEXT: xsmaddadp f1, f0, f2 +; CHECK-P8-NEXT: blr +; +; CHECK-FMA-LABEL: foo_double: +; CHECK-FMA: # %bb.0: +; CHECK-FMA-NEXT: addis r3, r2, .LCPI1_0@toc@ha +; CHECK-FMA-NEXT: xsmuldp f1, f2, f1 +; CHECK-FMA-NEXT: lfd f0, .LCPI1_0@toc@l(r3) +; CHECK-FMA-NEXT: addis r3, r2, .LCPI1_1@toc@ha +; CHECK-FMA-NEXT: lfd f2, .LCPI1_1@toc@l(r3) +; CHECK-FMA-NEXT: xsmaddadp f1, f4, f2 +; CHECK-FMA-NEXT: xsmaddadp f1, f3, f0 +; CHECK-FMA-NEXT: blr + %5 = fmul reassoc nsz double %1, %0 + %6 = fsub reassoc nsz double %2, %3 + %7 = fmul reassoc nsz double %6, 0x3DB2533FE68CADDE + %8 = fadd reassoc nsz double %7, %5 + ret double %8 +} + +define float @foo_float_reuse_const(float %0, float %1, float %2, float %3) { +; CHECK-LABEL: foo_float_reuse_const: +; CHECK: # %bb.0: +; CHECK-NEXT: addis r3, r2, .LCPI2_0@toc@ha +; CHECK-NEXT: xsmulsp f1, f2, f1 +; CHECK-NEXT: xssubsp f0, f3, f4 +; CHECK-NEXT: lfs f3, .LCPI2_0@toc@l(r3) +; CHECK-NEXT: addis r3, r2, .LCPI2_1@toc@ha +; CHECK-NEXT: xsmaddasp f1, f0, f3 +; CHECK-NEXT: lfs f0, .LCPI2_1@toc@l(r3) +; CHECK-NEXT: addis r3, r2, .LC0@toc@ha +; CHECK-NEXT: ld r3, .LC0@toc@l(r3) +; CHECK-NEXT: xsmulsp f0, f2, f0 +; CHECK-NEXT: stfs f0, 0(r3) +; CHECK-NEXT: blr +; +; CHECK-P8-LABEL: foo_float_reuse_const: +; CHECK-P8: # %bb.0: +; CHECK-P8-NEXT: xsmulsp f1, f2, f1 +; CHECK-P8-NEXT: addis r3, r2, .LCPI2_0@toc@ha +; CHECK-P8-NEXT: addis r4, r2, .LCPI2_1@toc@ha +; CHECK-P8-NEXT: xssubsp f0, f3, f4 +; CHECK-P8-NEXT: lfs f3, .LCPI2_0@toc@l(r3) +; CHECK-P8-NEXT: lfs f4, .LCPI2_1@toc@l(r4) +; CHECK-P8-NEXT: addis r3, r2, .LC0@toc@ha +; CHECK-P8-NEXT: ld r3, .LC0@toc@l(r3) +; CHECK-P8-NEXT: xsmaddasp f1, f0, f3 +; CHECK-P8-NEXT: xsmulsp f0, f2, f4 +; CHECK-P8-NEXT: stfsx f0, 0, r3 +; CHECK-P8-NEXT: blr +; +; CHECK-FMA-LABEL: foo_float_reuse_const: +; CHECK-FMA: # %bb.0: +; CHECK-FMA-NEXT: addis r3, r2, .LCPI2_0@toc@ha +; CHECK-FMA-NEXT: xsmulsp f1, f2, f1 +; CHECK-FMA-NEXT: lfs f0, .LCPI2_0@toc@l(r3) +; CHECK-FMA-NEXT: addis r3, r2, .LCPI2_1@toc@ha +; CHECK-FMA-NEXT: lfs f5, .LCPI2_1@toc@l(r3) +; CHECK-FMA-NEXT: addis r3, r2, .LC0@toc@ha +; CHECK-FMA-NEXT: ld r3, .LC0@toc@l(r3) +; CHECK-FMA-NEXT: xsmaddasp f1, f4, f5 +; CHECK-FMA-NEXT: xsmaddasp f1, f3, f0 +; CHECK-FMA-NEXT: xsmulsp f0, f2, f5 +; CHECK-FMA-NEXT: stfs f0, 0(r3) +; CHECK-FMA-NEXT: blr + %5 = fmul reassoc nsz float %1, %0 + %6 = fsub reassoc nsz float %2, %3 + %7 = fmul reassoc nsz float %6, 0x3DB2533FE0000000 + %8 = fadd reassoc nsz float %7, %5 + %9 = fmul reassoc nsz float %1, 0xBDB2533FE0000000 + store float %9, float* @global_val, align 4 + ret float %8 +} -- 2.7.4