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Diffstat (limited to 'lib/Target/PowerPC/PPCVSXFMAMutate.cpp')
| -rw-r--r-- | lib/Target/PowerPC/PPCVSXFMAMutate.cpp | 335 |
1 files changed, 335 insertions, 0 deletions
diff --git a/lib/Target/PowerPC/PPCVSXFMAMutate.cpp b/lib/Target/PowerPC/PPCVSXFMAMutate.cpp new file mode 100644 index 0000000..f352fa6 --- /dev/null +++ b/lib/Target/PowerPC/PPCVSXFMAMutate.cpp @@ -0,0 +1,335 @@ +//===--------------- PPCVSXFMAMutate.cpp - VSX FMA Mutation ---------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This pass mutates the form of VSX FMA instructions to avoid unnecessary +// copies. +// +//===----------------------------------------------------------------------===// + +#include "PPCInstrInfo.h" +#include "MCTargetDesc/PPCPredicates.h" +#include "PPC.h" +#include "PPCInstrBuilder.h" +#include "PPCMachineFunctionInfo.h" +#include "PPCTargetMachine.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/CodeGen/LiveIntervalAnalysis.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/ScheduleDAG.h" +#include "llvm/CodeGen/SlotIndexes.h" +#include "llvm/MC/MCAsmInfo.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/TargetRegistry.h" +#include "llvm/Support/raw_ostream.h" + +using namespace llvm; + +static cl::opt<bool> DisableVSXFMAMutate("disable-ppc-vsx-fma-mutation", +cl::desc("Disable VSX FMA instruction mutation"), cl::Hidden); + +#define DEBUG_TYPE "ppc-vsx-fma-mutate" + +namespace llvm { namespace PPC { + int getAltVSXFMAOpcode(uint16_t Opcode); +} } + +namespace { + // PPCVSXFMAMutate pass - For copies between VSX registers and non-VSX registers + // (Altivec and scalar floating-point registers), we need to transform the + // copies into subregister copies with other restrictions. + struct PPCVSXFMAMutate : public MachineFunctionPass { + static char ID; + PPCVSXFMAMutate() : MachineFunctionPass(ID) { + initializePPCVSXFMAMutatePass(*PassRegistry::getPassRegistry()); + } + + LiveIntervals *LIS; + const PPCInstrInfo *TII; + +protected: + bool processBlock(MachineBasicBlock &MBB) { + bool Changed = false; + + MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo(); + const TargetRegisterInfo *TRI = &TII->getRegisterInfo(); + for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end(); + I != IE; ++I) { + MachineInstr *MI = I; + + // The default (A-type) VSX FMA form kills the addend (it is taken from + // the target register, which is then updated to reflect the result of + // the FMA). If the instruction, however, kills one of the registers + // used for the product, then we can use the M-form instruction (which + // will take that value from the to-be-defined register). + + int AltOpc = PPC::getAltVSXFMAOpcode(MI->getOpcode()); + if (AltOpc == -1) + continue; + + // This pass is run after register coalescing, and so we're looking for + // a situation like this: + // ... + // %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9 + // %vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16, + // %RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16 + // ... + // %vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19, + // %RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19 + // ... + // Where we can eliminate the copy by changing from the A-type to the + // M-type instruction. Specifically, for this example, this means: + // %vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16, + // %RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16 + // is replaced by: + // %vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9, + // %RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9 + // and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9 + + SlotIndex FMAIdx = LIS->getInstructionIndex(MI); + + VNInfo *AddendValNo = + LIS->getInterval(MI->getOperand(1).getReg()).Query(FMAIdx).valueIn(); + MachineInstr *AddendMI = LIS->getInstructionFromIndex(AddendValNo->def); + + // The addend and this instruction must be in the same block. + + if (!AddendMI || AddendMI->getParent() != MI->getParent()) + continue; + + // The addend must be a full copy within the same register class. + + if (!AddendMI->isFullCopy()) + continue; + + unsigned AddendSrcReg = AddendMI->getOperand(1).getReg(); + if (TargetRegisterInfo::isVirtualRegister(AddendSrcReg)) { + if (MRI.getRegClass(AddendMI->getOperand(0).getReg()) != + MRI.getRegClass(AddendSrcReg)) + continue; + } else { + // If AddendSrcReg is a physical register, make sure the destination + // register class contains it. + if (!MRI.getRegClass(AddendMI->getOperand(0).getReg()) + ->contains(AddendSrcReg)) + continue; + } + + // In theory, there could be other uses of the addend copy before this + // fma. We could deal with this, but that would require additional + // logic below and I suspect it will not occur in any relevant + // situations. Additionally, check whether the copy source is killed + // prior to the fma. In order to replace the addend here with the + // source of the copy, it must still be live here. We can't use + // interval testing for a physical register, so as long as we're + // walking the MIs we may as well test liveness here. + bool OtherUsers = false, KillsAddendSrc = false; + for (auto J = std::prev(I), JE = MachineBasicBlock::iterator(AddendMI); + J != JE; --J) { + if (J->readsVirtualRegister(AddendMI->getOperand(0).getReg())) { + OtherUsers = true; + break; + } + if (J->modifiesRegister(AddendSrcReg, TRI) || + J->killsRegister(AddendSrcReg, TRI)) { + KillsAddendSrc = true; + break; + } + } + + if (OtherUsers || KillsAddendSrc) + continue; + + // Find one of the product operands that is killed by this instruction. + + unsigned KilledProdOp = 0, OtherProdOp = 0; + if (LIS->getInterval(MI->getOperand(2).getReg()) + .Query(FMAIdx).isKill()) { + KilledProdOp = 2; + OtherProdOp = 3; + } else if (LIS->getInterval(MI->getOperand(3).getReg()) + .Query(FMAIdx).isKill()) { + KilledProdOp = 3; + OtherProdOp = 2; + } + + // If there are no killed product operands, then this transformation is + // likely not profitable. + if (!KilledProdOp) + continue; + + // For virtual registers, verify that the addend source register + // is live here (as should have been assured above). + assert((!TargetRegisterInfo::isVirtualRegister(AddendSrcReg) || + LIS->getInterval(AddendSrcReg).liveAt(FMAIdx)) && + "Addend source register is not live!"); + + // Transform: (O2 * O3) + O1 -> (O2 * O1) + O3. + + unsigned AddReg = AddendMI->getOperand(1).getReg(); + unsigned KilledProdReg = MI->getOperand(KilledProdOp).getReg(); + unsigned OtherProdReg = MI->getOperand(OtherProdOp).getReg(); + + unsigned AddSubReg = AddendMI->getOperand(1).getSubReg(); + unsigned KilledProdSubReg = MI->getOperand(KilledProdOp).getSubReg(); + unsigned OtherProdSubReg = MI->getOperand(OtherProdOp).getSubReg(); + + bool AddRegKill = AddendMI->getOperand(1).isKill(); + bool KilledProdRegKill = MI->getOperand(KilledProdOp).isKill(); + bool OtherProdRegKill = MI->getOperand(OtherProdOp).isKill(); + + bool AddRegUndef = AddendMI->getOperand(1).isUndef(); + bool KilledProdRegUndef = MI->getOperand(KilledProdOp).isUndef(); + bool OtherProdRegUndef = MI->getOperand(OtherProdOp).isUndef(); + + unsigned OldFMAReg = MI->getOperand(0).getReg(); + + // The transformation doesn't work well with things like: + // %vreg5 = A-form-op %vreg5, %vreg11, %vreg5; + // so leave such things alone. + if (OldFMAReg == KilledProdReg) + continue; + + assert(OldFMAReg == AddendMI->getOperand(0).getReg() && + "Addend copy not tied to old FMA output!"); + + DEBUG(dbgs() << "VSX FMA Mutation:\n " << *MI;); + + MI->getOperand(0).setReg(KilledProdReg); + MI->getOperand(1).setReg(KilledProdReg); + MI->getOperand(3).setReg(AddReg); + MI->getOperand(2).setReg(OtherProdReg); + + MI->getOperand(0).setSubReg(KilledProdSubReg); + MI->getOperand(1).setSubReg(KilledProdSubReg); + MI->getOperand(3).setSubReg(AddSubReg); + MI->getOperand(2).setSubReg(OtherProdSubReg); + + MI->getOperand(1).setIsKill(KilledProdRegKill); + MI->getOperand(3).setIsKill(AddRegKill); + MI->getOperand(2).setIsKill(OtherProdRegKill); + + MI->getOperand(1).setIsUndef(KilledProdRegUndef); + MI->getOperand(3).setIsUndef(AddRegUndef); + MI->getOperand(2).setIsUndef(OtherProdRegUndef); + + MI->setDesc(TII->get(AltOpc)); + + DEBUG(dbgs() << " -> " << *MI); + + // The killed product operand was killed here, so we can reuse it now + // for the result of the fma. + + LiveInterval &FMAInt = LIS->getInterval(OldFMAReg); + VNInfo *FMAValNo = FMAInt.getVNInfoAt(FMAIdx.getRegSlot()); + for (auto UI = MRI.reg_nodbg_begin(OldFMAReg), UE = MRI.reg_nodbg_end(); + UI != UE;) { + MachineOperand &UseMO = *UI; + MachineInstr *UseMI = UseMO.getParent(); + ++UI; + + // Don't replace the result register of the copy we're about to erase. + if (UseMI == AddendMI) + continue; + + UseMO.setReg(KilledProdReg); + UseMO.setSubReg(KilledProdSubReg); + } + + // Extend the live intervals of the killed product operand to hold the + // fma result. + + LiveInterval &NewFMAInt = LIS->getInterval(KilledProdReg); + for (LiveInterval::iterator AI = FMAInt.begin(), AE = FMAInt.end(); + AI != AE; ++AI) { + // Don't add the segment that corresponds to the original copy. + if (AI->valno == AddendValNo) + continue; + + VNInfo *NewFMAValNo = + NewFMAInt.getNextValue(AI->start, + LIS->getVNInfoAllocator()); + + NewFMAInt.addSegment(LiveInterval::Segment(AI->start, AI->end, + NewFMAValNo)); + } + DEBUG(dbgs() << " extended: " << NewFMAInt << '\n'); + + FMAInt.removeValNo(FMAValNo); + DEBUG(dbgs() << " trimmed: " << FMAInt << '\n'); + + // Remove the (now unused) copy. + + DEBUG(dbgs() << " removing: " << *AddendMI << '\n'); + LIS->RemoveMachineInstrFromMaps(AddendMI); + AddendMI->eraseFromParent(); + + Changed = true; + } + + return Changed; + } + +public: + bool runOnMachineFunction(MachineFunction &MF) override { + // If we don't have VSX then go ahead and return without doing + // anything. + const PPCSubtarget &STI = MF.getSubtarget<PPCSubtarget>(); + if (!STI.hasVSX()) + return false; + + LIS = &getAnalysis<LiveIntervals>(); + + TII = STI.getInstrInfo(); + + bool Changed = false; + + if (DisableVSXFMAMutate) + return Changed; + + for (MachineFunction::iterator I = MF.begin(); I != MF.end();) { + MachineBasicBlock &B = *I++; + if (processBlock(B)) + Changed = true; + } + + return Changed; + } + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.addRequired<LiveIntervals>(); + AU.addPreserved<LiveIntervals>(); + AU.addRequired<SlotIndexes>(); + AU.addPreserved<SlotIndexes>(); + MachineFunctionPass::getAnalysisUsage(AU); + } + }; +} + +INITIALIZE_PASS_BEGIN(PPCVSXFMAMutate, DEBUG_TYPE, + "PowerPC VSX FMA Mutation", false, false) +INITIALIZE_PASS_DEPENDENCY(LiveIntervals) +INITIALIZE_PASS_DEPENDENCY(SlotIndexes) +INITIALIZE_PASS_END(PPCVSXFMAMutate, DEBUG_TYPE, + "PowerPC VSX FMA Mutation", false, false) + +char &llvm::PPCVSXFMAMutateID = PPCVSXFMAMutate::ID; + +char PPCVSXFMAMutate::ID = 0; +FunctionPass* +llvm::createPPCVSXFMAMutatePass() { return new PPCVSXFMAMutate(); } + + |