| //===-- SIShrinkInstructions.cpp - Shrink Instructions --------------------===// | |
| // | |
| // The LLVM Compiler Infrastructure | |
| // | |
| // This file is distributed under the University of Illinois Open Source | |
| // License. See LICENSE.TXT for details. | |
| // | |
| /// The pass tries to use the 32-bit encoding for instructions when possible. | |
| //===----------------------------------------------------------------------===// | |
| // | |
| #include "AMDGPU.h" | |
| #include "AMDGPUSubtarget.h" | |
| #include "SIInstrInfo.h" | |
| #include "MCTargetDesc/AMDGPUMCTargetDesc.h" | |
| #include "llvm/ADT/Statistic.h" | |
| #include "llvm/CodeGen/MachineFunctionPass.h" | |
| #include "llvm/CodeGen/MachineInstrBuilder.h" | |
| #include "llvm/CodeGen/MachineRegisterInfo.h" | |
| #include "llvm/IR/Constants.h" | |
| #include "llvm/IR/Function.h" | |
| #include "llvm/IR/LLVMContext.h" | |
| #include "llvm/Support/Debug.h" | |
| #include "llvm/Support/raw_ostream.h" | |
| #include "llvm/Target/TargetMachine.h" | |
| #define DEBUG_TYPE "si-shrink-instructions" | |
| STATISTIC(NumInstructionsShrunk, | |
| "Number of 64-bit instruction reduced to 32-bit."); | |
| STATISTIC(NumLiteralConstantsFolded, | |
| "Number of literal constants folded into 32-bit instructions."); | |
| using namespace llvm; | |
| namespace { | |
| class SIShrinkInstructions : public MachineFunctionPass { | |
| public: | |
| static char ID; | |
| public: | |
| SIShrinkInstructions() : MachineFunctionPass(ID) { | |
| } | |
| bool runOnMachineFunction(MachineFunction &MF) override; | |
| StringRef getPassName() const override { return "SI Shrink Instructions"; } | |
| void getAnalysisUsage(AnalysisUsage &AU) const override { | |
| AU.setPreservesCFG(); | |
| MachineFunctionPass::getAnalysisUsage(AU); | |
| } | |
| }; | |
| } // End anonymous namespace. | |
| INITIALIZE_PASS(SIShrinkInstructions, DEBUG_TYPE, | |
| "SI Shrink Instructions", false, false) | |
| char SIShrinkInstructions::ID = 0; | |
| FunctionPass *llvm::createSIShrinkInstructionsPass() { | |
| return new SIShrinkInstructions(); | |
| } | |
| static bool canShrink(MachineInstr &MI, const SIInstrInfo *TII, | |
| const SIRegisterInfo &TRI, | |
| const MachineRegisterInfo &MRI) { | |
| const MachineOperand *Src2 = TII->getNamedOperand(MI, AMDGPU::OpName::src2); | |
| // Can't shrink instruction with three operands. | |
| // FIXME: v_cndmask_b32 has 3 operands and is shrinkable, but we need to add | |
| // a special case for it. It can only be shrunk if the third operand | |
| // is vcc. We should handle this the same way we handle vopc, by addding | |
| // a register allocation hint pre-regalloc and then do the shrinking | |
| // post-regalloc. | |
| if (Src2) { | |
| switch (MI.getOpcode()) { | |
| default: return false; | |
| case AMDGPU::V_ADDC_U32_e64: | |
| case AMDGPU::V_SUBB_U32_e64: | |
| case AMDGPU::V_SUBBREV_U32_e64: { | |
| const MachineOperand *Src1 | |
| = TII->getNamedOperand(MI, AMDGPU::OpName::src1); | |
| if (!Src1->isReg() || !TRI.isVGPR(MRI, Src1->getReg())) | |
| return false; | |
| // Additional verification is needed for sdst/src2. | |
| return true; | |
| } | |
| case AMDGPU::V_MAC_F32_e64: | |
| case AMDGPU::V_MAC_F16_e64: | |
| case AMDGPU::V_FMAC_F32_e64: | |
| if (!Src2->isReg() || !TRI.isVGPR(MRI, Src2->getReg()) || | |
| TII->hasModifiersSet(MI, AMDGPU::OpName::src2_modifiers)) | |
| return false; | |
| break; | |
| case AMDGPU::V_CNDMASK_B32_e64: | |
| break; | |
| } | |
| } | |
| const MachineOperand *Src1 = TII->getNamedOperand(MI, AMDGPU::OpName::src1); | |
| if (Src1 && (!Src1->isReg() || !TRI.isVGPR(MRI, Src1->getReg()) || | |
| TII->hasModifiersSet(MI, AMDGPU::OpName::src1_modifiers))) | |
| return false; | |
| // We don't need to check src0, all input types are legal, so just make sure | |
| // src0 isn't using any modifiers. | |
| if (TII->hasModifiersSet(MI, AMDGPU::OpName::src0_modifiers)) | |
| return false; | |
| // Check output modifiers | |
| return !TII->hasModifiersSet(MI, AMDGPU::OpName::omod) && | |
| !TII->hasModifiersSet(MI, AMDGPU::OpName::clamp); | |
| } | |
| /// This function checks \p MI for operands defined by a move immediate | |
| /// instruction and then folds the literal constant into the instruction if it | |
| /// can. This function assumes that \p MI is a VOP1, VOP2, or VOPC instructions. | |
| static bool foldImmediates(MachineInstr &MI, const SIInstrInfo *TII, | |
| MachineRegisterInfo &MRI, bool TryToCommute = true) { | |
| assert(TII->isVOP1(MI) || TII->isVOP2(MI) || TII->isVOPC(MI)); | |
| int Src0Idx = AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::src0); | |
| // Try to fold Src0 | |
| MachineOperand &Src0 = MI.getOperand(Src0Idx); | |
| if (Src0.isReg()) { | |
| unsigned Reg = Src0.getReg(); | |
| if (TargetRegisterInfo::isVirtualRegister(Reg) && MRI.hasOneUse(Reg)) { | |
| MachineInstr *Def = MRI.getUniqueVRegDef(Reg); | |
| if (Def && Def->isMoveImmediate()) { | |
| MachineOperand &MovSrc = Def->getOperand(1); | |
| bool ConstantFolded = false; | |
| if (MovSrc.isImm() && (isInt<32>(MovSrc.getImm()) || | |
| isUInt<32>(MovSrc.getImm()))) { | |
| // It's possible to have only one component of a super-reg defined by | |
| // a single mov, so we need to clear any subregister flag. | |
| Src0.setSubReg(0); | |
| Src0.ChangeToImmediate(MovSrc.getImm()); | |
| ConstantFolded = true; | |
| } else if (MovSrc.isFI()) { | |
| Src0.setSubReg(0); | |
| Src0.ChangeToFrameIndex(MovSrc.getIndex()); | |
| ConstantFolded = true; | |
| } | |
| if (ConstantFolded) { | |
| assert(MRI.use_empty(Reg)); | |
| Def->eraseFromParent(); | |
| ++NumLiteralConstantsFolded; | |
| return true; | |
| } | |
| } | |
| } | |
| } | |
| // We have failed to fold src0, so commute the instruction and try again. | |
| if (TryToCommute && MI.isCommutable()) { | |
| if (TII->commuteInstruction(MI)) { | |
| if (foldImmediates(MI, TII, MRI, false)) | |
| return true; | |
| // Commute back. | |
| TII->commuteInstruction(MI); | |
| } | |
| } | |
| return false; | |
| } | |
| // Copy MachineOperand with all flags except setting it as implicit. | |
| static void copyFlagsToImplicitVCC(MachineInstr &MI, | |
| const MachineOperand &Orig) { | |
| for (MachineOperand &Use : MI.implicit_operands()) { | |
| if (Use.isUse() && Use.getReg() == AMDGPU::VCC) { | |
| Use.setIsUndef(Orig.isUndef()); | |
| Use.setIsKill(Orig.isKill()); | |
| return; | |
| } | |
| } | |
| } | |
| static bool isKImmOperand(const SIInstrInfo *TII, const MachineOperand &Src) { | |
| return isInt<16>(Src.getImm()) && | |
| !TII->isInlineConstant(*Src.getParent(), | |
| Src.getParent()->getOperandNo(&Src)); | |
| } | |
| static bool isKUImmOperand(const SIInstrInfo *TII, const MachineOperand &Src) { | |
| return isUInt<16>(Src.getImm()) && | |
| !TII->isInlineConstant(*Src.getParent(), | |
| Src.getParent()->getOperandNo(&Src)); | |
| } | |
| static bool isKImmOrKUImmOperand(const SIInstrInfo *TII, | |
| const MachineOperand &Src, | |
| bool &IsUnsigned) { | |
| if (isInt<16>(Src.getImm())) { | |
| IsUnsigned = false; | |
| return !TII->isInlineConstant(Src); | |
| } | |
| if (isUInt<16>(Src.getImm())) { | |
| IsUnsigned = true; | |
| return !TII->isInlineConstant(Src); | |
| } | |
| return false; | |
| } | |
| /// \returns true if the constant in \p Src should be replaced with a bitreverse | |
| /// of an inline immediate. | |
| static bool isReverseInlineImm(const SIInstrInfo *TII, | |
| const MachineOperand &Src, | |
| int32_t &ReverseImm) { | |
| if (!isInt<32>(Src.getImm()) || TII->isInlineConstant(Src)) | |
| return false; | |
| ReverseImm = reverseBits<int32_t>(static_cast<int32_t>(Src.getImm())); | |
| return ReverseImm >= -16 && ReverseImm <= 64; | |
| } | |
| /// Copy implicit register operands from specified instruction to this | |
| /// instruction that are not part of the instruction definition. | |
| static void copyExtraImplicitOps(MachineInstr &NewMI, MachineFunction &MF, | |
| const MachineInstr &MI) { | |
| for (unsigned i = MI.getDesc().getNumOperands() + | |
| MI.getDesc().getNumImplicitUses() + | |
| MI.getDesc().getNumImplicitDefs(), e = MI.getNumOperands(); | |
| i != e; ++i) { | |
| const MachineOperand &MO = MI.getOperand(i); | |
| if ((MO.isReg() && MO.isImplicit()) || MO.isRegMask()) | |
| NewMI.addOperand(MF, MO); | |
| } | |
| } | |
| static void shrinkScalarCompare(const SIInstrInfo *TII, MachineInstr &MI) { | |
| // cmpk instructions do scc = dst <cc op> imm16, so commute the instruction to | |
| // get constants on the RHS. | |
| if (!MI.getOperand(0).isReg()) | |
| TII->commuteInstruction(MI, false, 0, 1); | |
| const MachineOperand &Src1 = MI.getOperand(1); | |
| if (!Src1.isImm()) | |
| return; | |
| int SOPKOpc = AMDGPU::getSOPKOp(MI.getOpcode()); | |
| if (SOPKOpc == -1) | |
| return; | |
| // eq/ne is special because the imm16 can be treated as signed or unsigned, | |
| // and initially selectd to the unsigned versions. | |
| if (SOPKOpc == AMDGPU::S_CMPK_EQ_U32 || SOPKOpc == AMDGPU::S_CMPK_LG_U32) { | |
| bool HasUImm; | |
| if (isKImmOrKUImmOperand(TII, Src1, HasUImm)) { | |
| if (!HasUImm) { | |
| SOPKOpc = (SOPKOpc == AMDGPU::S_CMPK_EQ_U32) ? | |
| AMDGPU::S_CMPK_EQ_I32 : AMDGPU::S_CMPK_LG_I32; | |
| } | |
| MI.setDesc(TII->get(SOPKOpc)); | |
| } | |
| return; | |
| } | |
| const MCInstrDesc &NewDesc = TII->get(SOPKOpc); | |
| if ((TII->sopkIsZext(SOPKOpc) && isKUImmOperand(TII, Src1)) || | |
| (!TII->sopkIsZext(SOPKOpc) && isKImmOperand(TII, Src1))) { | |
| MI.setDesc(NewDesc); | |
| } | |
| } | |
| bool SIShrinkInstructions::runOnMachineFunction(MachineFunction &MF) { | |
| if (skipFunction(MF.getFunction())) | |
| return false; | |
| MachineRegisterInfo &MRI = MF.getRegInfo(); | |
| const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>(); | |
| const SIInstrInfo *TII = ST.getInstrInfo(); | |
| const SIRegisterInfo &TRI = TII->getRegisterInfo(); | |
| std::vector<unsigned> I1Defs; | |
| for (MachineFunction::iterator BI = MF.begin(), BE = MF.end(); | |
| BI != BE; ++BI) { | |
| MachineBasicBlock &MBB = *BI; | |
| MachineBasicBlock::iterator I, Next; | |
| for (I = MBB.begin(); I != MBB.end(); I = Next) { | |
| Next = std::next(I); | |
| MachineInstr &MI = *I; | |
| if (MI.getOpcode() == AMDGPU::V_MOV_B32_e32) { | |
| // If this has a literal constant source that is the same as the | |
| // reversed bits of an inline immediate, replace with a bitreverse of | |
| // that constant. This saves 4 bytes in the common case of materializing | |
| // sign bits. | |
| // Test if we are after regalloc. We only want to do this after any | |
| // optimizations happen because this will confuse them. | |
| // XXX - not exactly a check for post-regalloc run. | |
| MachineOperand &Src = MI.getOperand(1); | |
| if (Src.isImm() && | |
| TargetRegisterInfo::isPhysicalRegister(MI.getOperand(0).getReg())) { | |
| int32_t ReverseImm; | |
| if (isReverseInlineImm(TII, Src, ReverseImm)) { | |
| MI.setDesc(TII->get(AMDGPU::V_BFREV_B32_e32)); | |
| Src.setImm(ReverseImm); | |
| continue; | |
| } | |
| } | |
| } | |
| // Combine adjacent s_nops to use the immediate operand encoding how long | |
| // to wait. | |
| // | |
| // s_nop N | |
| // s_nop M | |
| // => | |
| // s_nop (N + M) | |
| if (MI.getOpcode() == AMDGPU::S_NOP && | |
| Next != MBB.end() && | |
| (*Next).getOpcode() == AMDGPU::S_NOP) { | |
| MachineInstr &NextMI = *Next; | |
| // The instruction encodes the amount to wait with an offset of 1, | |
| // i.e. 0 is wait 1 cycle. Convert both to cycles and then convert back | |
| // after adding. | |
| uint8_t Nop0 = MI.getOperand(0).getImm() + 1; | |
| uint8_t Nop1 = NextMI.getOperand(0).getImm() + 1; | |
| // Make sure we don't overflow the bounds. | |
| if (Nop0 + Nop1 <= 8) { | |
| NextMI.getOperand(0).setImm(Nop0 + Nop1 - 1); | |
| MI.eraseFromParent(); | |
| } | |
| continue; | |
| } | |
| // FIXME: We also need to consider movs of constant operands since | |
| // immediate operands are not folded if they have more than one use, and | |
| // the operand folding pass is unaware if the immediate will be free since | |
| // it won't know if the src == dest constraint will end up being | |
| // satisfied. | |
| if (MI.getOpcode() == AMDGPU::S_ADD_I32 || | |
| MI.getOpcode() == AMDGPU::S_MUL_I32) { | |
| const MachineOperand *Dest = &MI.getOperand(0); | |
| MachineOperand *Src0 = &MI.getOperand(1); | |
| MachineOperand *Src1 = &MI.getOperand(2); | |
| if (!Src0->isReg() && Src1->isReg()) { | |
| if (TII->commuteInstruction(MI, false, 1, 2)) | |
| std::swap(Src0, Src1); | |
| } | |
| // FIXME: This could work better if hints worked with subregisters. If | |
| // we have a vector add of a constant, we usually don't get the correct | |
| // allocation due to the subregister usage. | |
| if (TargetRegisterInfo::isVirtualRegister(Dest->getReg()) && | |
| Src0->isReg()) { | |
| MRI.setRegAllocationHint(Dest->getReg(), 0, Src0->getReg()); | |
| MRI.setRegAllocationHint(Src0->getReg(), 0, Dest->getReg()); | |
| continue; | |
| } | |
| if (Src0->isReg() && Src0->getReg() == Dest->getReg()) { | |
| if (Src1->isImm() && isKImmOperand(TII, *Src1)) { | |
| unsigned Opc = (MI.getOpcode() == AMDGPU::S_ADD_I32) ? | |
| AMDGPU::S_ADDK_I32 : AMDGPU::S_MULK_I32; | |
| MI.setDesc(TII->get(Opc)); | |
| MI.tieOperands(0, 1); | |
| } | |
| } | |
| } | |
| // Try to use s_cmpk_* | |
| if (MI.isCompare() && TII->isSOPC(MI)) { | |
| shrinkScalarCompare(TII, MI); | |
| continue; | |
| } | |
| // Try to use S_MOVK_I32, which will save 4 bytes for small immediates. | |
| if (MI.getOpcode() == AMDGPU::S_MOV_B32) { | |
| const MachineOperand &Dst = MI.getOperand(0); | |
| MachineOperand &Src = MI.getOperand(1); | |
| if (Src.isImm() && | |
| TargetRegisterInfo::isPhysicalRegister(Dst.getReg())) { | |
| int32_t ReverseImm; | |
| if (isKImmOperand(TII, Src)) | |
| MI.setDesc(TII->get(AMDGPU::S_MOVK_I32)); | |
| else if (isReverseInlineImm(TII, Src, ReverseImm)) { | |
| MI.setDesc(TII->get(AMDGPU::S_BREV_B32)); | |
| Src.setImm(ReverseImm); | |
| } | |
| } | |
| continue; | |
| } | |
| if (!TII->hasVALU32BitEncoding(MI.getOpcode())) | |
| continue; | |
| if (!canShrink(MI, TII, TRI, MRI)) { | |
| // Try commuting the instruction and see if that enables us to shrink | |
| // it. | |
| if (!MI.isCommutable() || !TII->commuteInstruction(MI) || | |
| !canShrink(MI, TII, TRI, MRI)) | |
| continue; | |
| } | |
| // getVOPe32 could be -1 here if we started with an instruction that had | |
| // a 32-bit encoding and then commuted it to an instruction that did not. | |
| if (!TII->hasVALU32BitEncoding(MI.getOpcode())) | |
| continue; | |
| int Op32 = AMDGPU::getVOPe32(MI.getOpcode()); | |
| if (TII->isVOPC(Op32)) { | |
| unsigned DstReg = MI.getOperand(0).getReg(); | |
| if (TargetRegisterInfo::isVirtualRegister(DstReg)) { | |
| // VOPC instructions can only write to the VCC register. We can't | |
| // force them to use VCC here, because this is only one register and | |
| // cannot deal with sequences which would require multiple copies of | |
| // VCC, e.g. S_AND_B64 (vcc = V_CMP_...), (vcc = V_CMP_...) | |
| // | |
| // So, instead of forcing the instruction to write to VCC, we provide | |
| // a hint to the register allocator to use VCC and then we will run | |
| // this pass again after RA and shrink it if it outputs to VCC. | |
| MRI.setRegAllocationHint(MI.getOperand(0).getReg(), 0, AMDGPU::VCC); | |
| continue; | |
| } | |
| if (DstReg != AMDGPU::VCC) | |
| continue; | |
| } | |
| if (Op32 == AMDGPU::V_CNDMASK_B32_e32) { | |
| // We shrink V_CNDMASK_B32_e64 using regalloc hints like we do for VOPC | |
| // instructions. | |
| const MachineOperand *Src2 = | |
| TII->getNamedOperand(MI, AMDGPU::OpName::src2); | |
| if (!Src2->isReg()) | |
| continue; | |
| unsigned SReg = Src2->getReg(); | |
| if (TargetRegisterInfo::isVirtualRegister(SReg)) { | |
| MRI.setRegAllocationHint(SReg, 0, AMDGPU::VCC); | |
| continue; | |
| } | |
| if (SReg != AMDGPU::VCC) | |
| continue; | |
| } | |
| // Check for the bool flag output for instructions like V_ADD_I32_e64. | |
| const MachineOperand *SDst = TII->getNamedOperand(MI, | |
| AMDGPU::OpName::sdst); | |
| // Check the carry-in operand for v_addc_u32_e64. | |
| const MachineOperand *Src2 = TII->getNamedOperand(MI, | |
| AMDGPU::OpName::src2); | |
| if (SDst) { | |
| if (SDst->getReg() != AMDGPU::VCC) { | |
| if (TargetRegisterInfo::isVirtualRegister(SDst->getReg())) | |
| MRI.setRegAllocationHint(SDst->getReg(), 0, AMDGPU::VCC); | |
| continue; | |
| } | |
| // All of the instructions with carry outs also have an SGPR input in | |
| // src2. | |
| if (Src2 && Src2->getReg() != AMDGPU::VCC) { | |
| if (TargetRegisterInfo::isVirtualRegister(Src2->getReg())) | |
| MRI.setRegAllocationHint(Src2->getReg(), 0, AMDGPU::VCC); | |
| continue; | |
| } | |
| } | |
| // We can shrink this instruction | |
| LLVM_DEBUG(dbgs() << "Shrinking " << MI); | |
| MachineInstrBuilder Inst32 = | |
| BuildMI(MBB, I, MI.getDebugLoc(), TII->get(Op32)); | |
| // Add the dst operand if the 32-bit encoding also has an explicit $vdst. | |
| // For VOPC instructions, this is replaced by an implicit def of vcc. | |
| int Op32DstIdx = AMDGPU::getNamedOperandIdx(Op32, AMDGPU::OpName::vdst); | |
| if (Op32DstIdx != -1) { | |
| // dst | |
| Inst32.add(MI.getOperand(0)); | |
| } else { | |
| assert(MI.getOperand(0).getReg() == AMDGPU::VCC && | |
| "Unexpected case"); | |
| } | |
| Inst32.add(*TII->getNamedOperand(MI, AMDGPU::OpName::src0)); | |
| const MachineOperand *Src1 = | |
| TII->getNamedOperand(MI, AMDGPU::OpName::src1); | |
| if (Src1) | |
| Inst32.add(*Src1); | |
| if (Src2) { | |
| int Op32Src2Idx = AMDGPU::getNamedOperandIdx(Op32, AMDGPU::OpName::src2); | |
| if (Op32Src2Idx != -1) { | |
| Inst32.add(*Src2); | |
| } else { | |
| // In the case of V_CNDMASK_B32_e32, the explicit operand src2 is | |
| // replaced with an implicit read of vcc. This was already added | |
| // during the initial BuildMI, so find it to preserve the flags. | |
| copyFlagsToImplicitVCC(*Inst32, *Src2); | |
| } | |
| } | |
| ++NumInstructionsShrunk; | |
| // Copy extra operands not present in the instruction definition. | |
| copyExtraImplicitOps(*Inst32, MF, MI); | |
| MI.eraseFromParent(); | |
| foldImmediates(*Inst32, TII, MRI); | |
| LLVM_DEBUG(dbgs() << "e32 MI = " << *Inst32 << '\n'); | |
| } | |
| } | |
| return false; | |
| } |