Jingyue Wu | 9c71150 | 2015-06-24 20:20:16 +0000 | [diff] [blame] | 1 | //===-- NVPTXPeephole.cpp - NVPTX Peephole Optimiztions -------------------===// |
| 2 | // |
| 3 | // The LLVM Compiler Infrastructure |
| 4 | // |
| 5 | // This file is distributed under the University of Illinois Open Source |
| 6 | // License. See LICENSE.TXT for details. |
| 7 | // |
| 8 | //===----------------------------------------------------------------------===// |
| 9 | // |
| 10 | // In NVPTX, NVPTXFrameLowering will emit following instruction at the beginning |
| 11 | // of a MachineFunction. |
| 12 | // |
| 13 | // mov %SPL, %depot |
| 14 | // cvta.local %SP, %SPL |
| 15 | // |
| 16 | // Because Frame Index is a generic address and alloca can only return generic |
| 17 | // pointer, without this pass the instructions producing alloca'ed address will |
| 18 | // be based on %SP. NVPTXLowerAlloca tends to help replace store and load on |
| 19 | // this address with their .local versions, but this may introduce a lot of |
| 20 | // cvta.to.local instructions. Performance can be improved if we avoid casting |
| 21 | // address back and forth and directly calculate local address based on %SPL. |
| 22 | // This peephole pass optimizes these cases, for example |
| 23 | // |
| 24 | // It will transform the following pattern |
Jingyue Wu | 77b5b38 | 2015-07-01 20:08:06 +0000 | [diff] [blame^] | 25 | // %vreg0<def> = LEA_ADDRi64 %VRFrame, 4 |
Jingyue Wu | 9c71150 | 2015-06-24 20:20:16 +0000 | [diff] [blame] | 26 | // %vreg1<def> = cvta_to_local_yes_64 %vreg0 |
| 27 | // |
| 28 | // into |
| 29 | // %vreg1<def> = LEA_ADDRi64 %VRFrameLocal, 4 |
| 30 | // |
| 31 | // %VRFrameLocal is the virtual register name of %SPL |
| 32 | // |
| 33 | //===----------------------------------------------------------------------===// |
| 34 | |
| 35 | #include "NVPTX.h" |
| 36 | #include "llvm/CodeGen/MachineFunctionPass.h" |
| 37 | #include "llvm/CodeGen/MachineInstrBuilder.h" |
| 38 | #include "llvm/CodeGen/MachineRegisterInfo.h" |
Jingyue Wu | 9c71150 | 2015-06-24 20:20:16 +0000 | [diff] [blame] | 39 | #include "llvm/Target/TargetRegisterInfo.h" |
| 40 | #include "llvm/Target/TargetInstrInfo.h" |
| 41 | |
| 42 | using namespace llvm; |
| 43 | |
| 44 | #define DEBUG_TYPE "nvptx-peephole" |
| 45 | |
| 46 | namespace llvm { |
| 47 | void initializeNVPTXPeepholePass(PassRegistry &); |
| 48 | } |
| 49 | |
| 50 | namespace { |
| 51 | struct NVPTXPeephole : public MachineFunctionPass { |
| 52 | public: |
| 53 | static char ID; |
| 54 | NVPTXPeephole() : MachineFunctionPass(ID) { |
| 55 | initializeNVPTXPeepholePass(*PassRegistry::getPassRegistry()); |
| 56 | } |
| 57 | |
| 58 | bool runOnMachineFunction(MachineFunction &MF) override; |
| 59 | |
| 60 | const char *getPassName() const override { |
| 61 | return "NVPTX optimize redundant cvta.to.local instruction"; |
| 62 | } |
| 63 | |
| 64 | void getAnalysisUsage(AnalysisUsage &AU) const override { |
| 65 | MachineFunctionPass::getAnalysisUsage(AU); |
| 66 | } |
| 67 | }; |
| 68 | } |
| 69 | |
| 70 | char NVPTXPeephole::ID = 0; |
| 71 | |
| 72 | INITIALIZE_PASS(NVPTXPeephole, "nvptx-peephole", "NVPTX Peephole", false, false) |
| 73 | |
| 74 | static bool isCVTAToLocalCombinationCandidate(MachineInstr &Root) { |
| 75 | auto &MBB = *Root.getParent(); |
| 76 | auto &MF = *MBB.getParent(); |
| 77 | // Check current instruction is cvta.to.local |
| 78 | if (Root.getOpcode() != NVPTX::cvta_to_local_yes_64 && |
| 79 | Root.getOpcode() != NVPTX::cvta_to_local_yes) |
| 80 | return false; |
| 81 | |
| 82 | auto &Op = Root.getOperand(1); |
| 83 | const auto &MRI = MF.getRegInfo(); |
| 84 | MachineInstr *GenericAddrDef = nullptr; |
| 85 | if (Op.isReg() && TargetRegisterInfo::isVirtualRegister(Op.getReg())) { |
| 86 | GenericAddrDef = MRI.getUniqueVRegDef(Op.getReg()); |
| 87 | } |
| 88 | |
| 89 | // Check the register operand is uniquely defined by LEA_ADDRi instruction |
| 90 | if (!GenericAddrDef || GenericAddrDef->getParent() != &MBB || |
| 91 | (GenericAddrDef->getOpcode() != NVPTX::LEA_ADDRi64 && |
| 92 | GenericAddrDef->getOpcode() != NVPTX::LEA_ADDRi)) { |
| 93 | return false; |
| 94 | } |
| 95 | |
| 96 | // Check the LEA_ADDRi operand is Frame index |
| 97 | auto &BaseAddrOp = GenericAddrDef->getOperand(1); |
Jingyue Wu | 77b5b38 | 2015-07-01 20:08:06 +0000 | [diff] [blame^] | 98 | if (BaseAddrOp.isReg() && BaseAddrOp.getReg() == NVPTX::VRFrame) { |
Jingyue Wu | 9c71150 | 2015-06-24 20:20:16 +0000 | [diff] [blame] | 99 | return true; |
| 100 | } |
| 101 | |
| 102 | return false; |
| 103 | } |
| 104 | |
| 105 | static void CombineCVTAToLocal(MachineInstr &Root) { |
| 106 | auto &MBB = *Root.getParent(); |
| 107 | auto &MF = *MBB.getParent(); |
| 108 | const auto &MRI = MF.getRegInfo(); |
| 109 | const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); |
| 110 | auto &Prev = *MRI.getUniqueVRegDef(Root.getOperand(1).getReg()); |
| 111 | |
Jingyue Wu | 9c71150 | 2015-06-24 20:20:16 +0000 | [diff] [blame] | 112 | MachineInstrBuilder MIB = |
| 113 | BuildMI(MF, Root.getDebugLoc(), TII->get(Prev.getOpcode()), |
| 114 | Root.getOperand(0).getReg()) |
| 115 | .addReg(NVPTX::VRFrameLocal) |
Jingyue Wu | 77b5b38 | 2015-07-01 20:08:06 +0000 | [diff] [blame^] | 116 | .addOperand(Prev.getOperand(2)); |
Jingyue Wu | 9c71150 | 2015-06-24 20:20:16 +0000 | [diff] [blame] | 117 | |
| 118 | MBB.insert((MachineBasicBlock::iterator)&Root, MIB); |
| 119 | |
| 120 | // Check if MRI has only one non dbg use, which is Root |
| 121 | if (MRI.hasOneNonDBGUse(Prev.getOperand(0).getReg())) { |
| 122 | Prev.eraseFromParentAndMarkDBGValuesForRemoval(); |
| 123 | } |
| 124 | Root.eraseFromParentAndMarkDBGValuesForRemoval(); |
| 125 | } |
| 126 | |
| 127 | bool NVPTXPeephole::runOnMachineFunction(MachineFunction &MF) { |
| 128 | bool Changed = false; |
| 129 | // Loop over all of the basic blocks. |
| 130 | for (auto &MBB : MF) { |
| 131 | // Traverse the basic block. |
| 132 | auto BlockIter = MBB.begin(); |
| 133 | |
| 134 | while (BlockIter != MBB.end()) { |
| 135 | auto &MI = *BlockIter++; |
| 136 | if (isCVTAToLocalCombinationCandidate(MI)) { |
| 137 | CombineCVTAToLocal(MI); |
| 138 | Changed = true; |
| 139 | } |
| 140 | } // Instruction |
| 141 | } // Basic Block |
Jingyue Wu | 77b5b38 | 2015-07-01 20:08:06 +0000 | [diff] [blame^] | 142 | |
| 143 | // Remove unnecessary %VRFrame = cvta.local %VRFrameLocal |
| 144 | const auto &MRI = MF.getRegInfo(); |
| 145 | if (MRI.use_empty(NVPTX::VRFrame)) { |
| 146 | if (auto MI = MRI.getUniqueVRegDef(NVPTX::VRFrame)) { |
| 147 | MI->eraseFromParentAndMarkDBGValuesForRemoval(); |
| 148 | } |
| 149 | } |
| 150 | |
Jingyue Wu | 9c71150 | 2015-06-24 20:20:16 +0000 | [diff] [blame] | 151 | return Changed; |
| 152 | } |
| 153 | |
| 154 | MachineFunctionPass *llvm::createNVPTXPeephole() { return new NVPTXPeephole(); } |