[llvm] Co-issue packed instructions by unpacking (PR #151704)
Jeffrey Byrnes via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 7 15:35:40 PDT 2025
================
@@ -225,6 +247,290 @@ bool GCNPreRAOptimizationsImpl::processReg(Register Reg) {
return true;
}
+bool GCNPreRAOptimizationsImpl::isUnpackingSupportedInstr(MachineInstr &MI) const {
+ unsigned Opcode = MI.getOpcode();
+ switch (Opcode) {
+ case AMDGPU::V_PK_ADD_F32:
+ case AMDGPU::V_PK_MUL_F32:
+ return true;
+
+ default:
+ return false;
+
+ }
+}
+
+uint16_t GCNPreRAOptimizationsImpl::mapToUnpackedOpcode(MachineInstr &I) {
+ unsigned Opcode = I.getOpcode();
+ // use 64 bit encoding to allow use of VOP3 instructions.
+ // VOP3 instructions allow VOP3P source modifiers to be translated to VOP3
+ // e32 instructions are VOP2 and don't allow source modifiers
+ switch (Opcode) {
+ case AMDGPU::V_PK_ADD_F32:
+ return AMDGPU::V_ADD_F32_e64;
+ case AMDGPU::V_PK_MUL_F32:
+ return AMDGPU::V_MUL_F32_e64;
+ default:
+ return std::numeric_limits<uint16_t>::max();
+
+ }
+}
+
+SmallVector<MachineInstr *, 2>
+GCNPreRAOptimizationsImpl::copyToVregAndInsertMI(MachineInstr &I,
+ unsigned SGPRSrcPos) {
+ SmallVector<MachineInstr *, 2> MIList;
+
+ MachineBasicBlock &MBB = *I.getParent();
+ MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
+ MachineFunction &MF = *MBB.getParent();
+ const DebugLoc &DL = I.getDebugLoc();
+
+ Register TmpReg = MRI.createVirtualRegister(&AMDGPU::VReg_64_Align2RegClass);
+ MachineInstr *CopySGPR1 =
+ BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY))
+ .addDef(TmpReg, RegState::Undef)
+ .addReg(I.getOperand(SGPRSrcPos).getReg(), 0, AMDGPU::sub0);
+ unsigned SubIdx = TRI->composeSubRegIndices(
+ AMDGPU::sub0, CopySGPR1->getOperand(0).getSubReg());
+ CopySGPR1->getOperand(0).setReg(CopySGPR1->getOperand(0).getReg());
+ CopySGPR1->getOperand(0).setSubReg(SubIdx);
+ LIS->InsertMachineInstrInMaps(*CopySGPR1);
+ MIList.push_back(CopySGPR1);
+
+ MachineInstr *CopySGPR2 =
+ BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY))
+ .addDef(TmpReg)
+ .addReg(I.getOperand(SGPRSrcPos).getReg(), 0, AMDGPU::sub1);
+ SubIdx = TRI->composeSubRegIndices(AMDGPU::sub1,
+ CopySGPR2->getOperand(0).getSubReg());
+ CopySGPR2->getOperand(0).setReg(CopySGPR2->getOperand(0).getReg());
+ CopySGPR2->getOperand(0).setSubReg(SubIdx);
+ LIS->InsertMachineInstrInMaps(*CopySGPR2);
+ MIList.push_back(CopySGPR2);
+ return MIList;
+}
+
+bool GCNPreRAOptimizationsImpl::createListOfPackedInstr(
+ MachineInstr &BeginMI, DenseSet<MachineInstr *> &instrsToUnpack) {
+ auto *BB = BeginMI.getParent();
+ auto *MF = BB->getParent();
+ int NumInst = 0;
+
+ auto E = BB->end();
+ auto SchedModel = TII->getSchedModel();
+ const MCSchedClassDesc *SchedClassDesc = SchedModel.resolveSchedClass(&BeginMI);
+ const int NumMFMACycles = SchedModel.getWriteProcResBegin(SchedClassDesc)->ReleaseAtCycle;
+ int TotalCyclesBetweenCandidates = 0;
+ for (auto I = std::next(BeginMI.getIterator()); I != E; ++I) {
+ MachineInstr &Instr = *I;
+ const MCSchedClassDesc *instrSchedClassDesc = SchedModel.resolveSchedClass(&Instr);
+ TotalCyclesBetweenCandidates += SchedModel.getWriteProcResBegin(instrSchedClassDesc)->ReleaseAtCycle;
+ if (Instr.isMetaInstruction())
+ continue;
+
+ if (Instr.isTerminator())
+ return false;
+
+ if (TotalCyclesBetweenCandidates > NumMFMACycles)
+ return false;
+
+ if ((isUnpackingSupportedInstr(Instr)) && TII->isNeverCoissue(Instr)) {
+ TotalCyclesBetweenCandidates += 1;
+ instrsToUnpack.insert(&Instr);
+ }
+ }
+ return true;
+}
+
+SmallVector<MachineInstr *, 2> GCNPreRAOptimizationsImpl::insertUnpackedMI(
+ MachineInstr &I, MachineOperand &DstMO, MachineOperand &LoSrcMO1, MachineOperand &LoSrcMO2,
+ MachineOperand &HiSrcMO1, MachineOperand &HiSrcMO2, bool isVreg_64) {
+
+ SmallVector<MachineInstr *, 2> MIList;
+ MachineBasicBlock &MBB = *I.getParent();
+ MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
+ MachineFunction &MF = *MBB.getParent();
+ const DebugLoc &DL = I.getDebugLoc();
+ Register DstReg = DstMO.getReg();
+
+ unsigned SrcSubIdx1 =
+ TRI->composeSubRegIndices(LoSrcMO1.getSubReg(), AMDGPU::sub0);
+ unsigned SrcSubIdx2 =
+ TRI->composeSubRegIndices(LoSrcMO2.getSubReg(), AMDGPU::sub0);
+ unsigned DestSubIdx =
+ TRI->composeSubRegIndices(DstMO.getSubReg(), AMDGPU::sub0);
+
+ const MCInstrDesc instrDesc = I.getDesc();
+
+ int clampIdx = AMDGPU::getNamedOperandIdx(I.getOpcode(), AMDGPU::OpName::clamp);
+ int64_t clampVal = I.getOperand(clampIdx).getImm();
+
+ int src0_modifiers_Idx = AMDGPU::getNamedOperandIdx(I.getOpcode(), AMDGPU::OpName::src0_modifiers);
+ int src1_modifiers_Idx = AMDGPU::getNamedOperandIdx(I.getOpcode(), AMDGPU::OpName::src1_modifiers);
+ unsigned src0_Mods = I.getOperand(src0_modifiers_Idx).getImm();
+ unsigned src1_Mods = I.getOperand(src1_modifiers_Idx).getImm();
+
+ //don't worry about abs values. Packed instructions (VOP3P) do not support them
+ unsigned Lo_src0_mods = 0;
+ unsigned Lo_src1_mods = 0;
+ uint16_t unpackedOpcode = mapToUnpackedOpcode(I);
+ MachineInstrBuilder Op0L_Op1L = BuildMI(MBB, I, DL, TII->get(unpackedOpcode));
+ Op0L_Op1L.addDef(DstReg, 0, DestSubIdx); //vdst
+ if (src0_Mods & SISrcMods::OP_SEL_0) {
+ if (src0_Mods & SISrcMods::NEG) {
+ Lo_src0_mods |= SISrcMods::NEG;
+ }
+ Op0L_Op1L.addImm(Lo_src0_mods); //src0_modifiers
+ unsigned Src0SubIdx = TRI->composeSubRegIndices(LoSrcMO1.getSubReg(), AMDGPU::sub1);
+ Op0L_Op1L.addReg(LoSrcMO1.getReg(), 0, Src0SubIdx); //src0
+ }
+ else {
+ Op0L_Op1L.addImm(Lo_src0_mods); //src0_modifiers
+ unsigned Src0SubIdx = TRI->composeSubRegIndices(LoSrcMO1.getSubReg(), AMDGPU::sub0);
+ Op0L_Op1L.addReg(LoSrcMO1.getReg(), 0, Src0SubIdx); //src0 //if op_sel == 0, select register 0 of reg:sub0_sub1
+ }
+
+ if (src1_Mods & SISrcMods::OP_SEL_0) {
+ if (src1_Mods & SISrcMods::NEG) {
+ Lo_src1_mods |= SISrcMods::NEG;
+ }
+ Op0L_Op1L.addImm(Lo_src1_mods); //src0_modifiers
+ unsigned Src1SubIdx = TRI->composeSubRegIndices(LoSrcMO2.getSubReg(), AMDGPU::sub1);
+ Op0L_Op1L.addReg(LoSrcMO2.getReg(), 0, Src1SubIdx); //src0
+ }
+ else {
+ Op0L_Op1L.addImm(Lo_src1_mods); //src0_modifiers
+ unsigned Src1SubIdx = TRI->composeSubRegIndices(LoSrcMO2.getSubReg(), AMDGPU::sub0);
+ Op0L_Op1L.addReg(LoSrcMO2.getReg(), 0, Src1SubIdx); //src0 //if op_sel_hi == 0, select register 0 of reg:sub0_sub1
+ }
+ Op0L_Op1L.addImm(clampVal); //clamp
+ //packed instructions do not support output modifiers. safe to assign them 0 for this use case
+ Op0L_Op1L.addImm(0); //omod
+
+ if (isVreg_64) {
+ Op0L_Op1L->getOperand(0).setIsUndef();
+ }
+ else if (I.getOperand(0).isUndef()){
+ Op0L_Op1L->getOperand(0).setIsUndef();
+ }
+
+ LIS->InsertMachineInstrInMaps(*Op0L_Op1L);
+
+ SrcSubIdx1 =
+ TRI->composeSubRegIndices(LoSrcMO1.getSubReg(), AMDGPU::sub1);
+ SrcSubIdx2 =
+ TRI->composeSubRegIndices(LoSrcMO2.getSubReg(), AMDGPU::sub1);
+ DestSubIdx =
+ TRI->composeSubRegIndices(DstMO.getSubReg(), AMDGPU::sub1);
+
+ //don't worry about abs values. Packed instructions (VOP3P) do not support them
+ unsigned Hi_src0_mods = 0;
+ unsigned Hi_src1_mods = 0;
+
+ MachineInstrBuilder Op0H_Op1H = BuildMI(MBB, I, DL, TII->get(unpackedOpcode));
+ Op0H_Op1H.addDef(DstReg, 0, DestSubIdx); //vdst
+ if (src0_Mods & SISrcMods::OP_SEL_1) {
+ if (src0_Mods & SISrcMods::NEG_HI) {
+ Hi_src0_mods |= SISrcMods::NEG;
+ }
+ Op0H_Op1H.addImm(Hi_src0_mods); //src0_modifiers
+ unsigned Src0SubIdx = TRI->composeSubRegIndices(HiSrcMO1.getSubReg(), AMDGPU::sub1);
+ Op0H_Op1H.addReg(HiSrcMO1.getReg(), 0, Src0SubIdx); //src0
+ }
+ else {
+ Op0H_Op1H.addImm(Hi_src0_mods); //src0_modifiers
+ unsigned Src0SubIdx = TRI->composeSubRegIndices(HiSrcMO1.getSubReg(), AMDGPU::sub0);
+ Op0H_Op1H.addReg(HiSrcMO1.getReg(), 0, Src0SubIdx); //src0 //if op_sel_hi == 0, select register 0 of reg:sub0_sub1
+ }
+
+ if (src1_Mods & SISrcMods::OP_SEL_1) {
+ if (src1_Mods & SISrcMods::NEG_HI) {
+ Hi_src1_mods |= SISrcMods::NEG;
+ }
+ Op0H_Op1H.addImm(Hi_src1_mods); //src0_modifiers
+ unsigned Src1SubIdx = TRI->composeSubRegIndices(HiSrcMO2.getSubReg(), AMDGPU::sub1);
+ Op0H_Op1H.addReg(HiSrcMO2.getReg(), 0, Src1SubIdx); //src0
+ }
+ else {
+ Op0H_Op1H.addImm(Hi_src1_mods); //src0_modifiers
+ unsigned Src1SubIdx = TRI->composeSubRegIndices(HiSrcMO2.getSubReg(), AMDGPU::sub0);
+ Op0H_Op1H.addReg(HiSrcMO2.getReg(), 0, Src1SubIdx); //src0 //if op_sel_hi == 0, select register 0 of reg:sub0_sub1
+ }
+ Op0H_Op1H.addImm(clampVal); //clamp
+ //packed instructions do not support output modifiers. safe to assign them 0 for this use case
+ Op0H_Op1H.addImm(0); //omod
+ LIS->InsertMachineInstrInMaps(*Op0H_Op1H);
+
+ if (I.getFlag(MachineInstr::MIFlag::NoFPExcept)) {
+ Op0L_Op1L->setFlag(MachineInstr::MIFlag::NoFPExcept);
+ Op0H_Op1H->setFlag(MachineInstr::MIFlag::NoFPExcept);
+ }
+ LIS->RemoveMachineInstrFromMaps(I);
+ I.eraseFromParent();
+ LIS->removeInterval(DstReg);
+ LIS->createAndComputeVirtRegInterval(DstReg);
+ MIList.push_back(Op0L_Op1L);
+ MIList.push_back(Op0H_Op1H);
+ return MIList;
+}
+
+void GCNPreRAOptimizationsImpl::insertMI(MachineInstr &I) {
+ MachineBasicBlock &MBB = *I.getParent();
+ MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
+ MachineFunction &MF = *MBB.getParent();
+
+ Register DstReg = I.getOperand(0).getReg();
+ Register SrcReg1 = I.getOperand(2).getReg();
+ Register SrcReg2 = I.getOperand(4).getReg();
+
+ MachineOperand &DstMO = I.getOperand(0);
+ MachineOperand &SrcMO1 = I.getOperand(2);
+ MachineOperand &SrcMO2 = I.getOperand(4);
+
+ MachineBasicBlock::iterator MII = I;
+ const DebugLoc &DL = I.getDebugLoc();
+ const TargetRegisterClass *DstRC = MRI.getRegClass(I.getOperand(0).getReg());
+ const TargetRegisterClass *Src0RC = MRI.getRegClass(I.getOperand(2).getReg());
+ const TargetRegisterClass *Src1RC = MRI.getRegClass(I.getOperand(4).getReg());
+ const TargetRegisterClass *Src0SubRC =
+ TRI->getSubRegisterClass(Src0RC, AMDGPU::sub0);
+ const TargetRegisterClass *SrcRC = TRI->getSubClassWithSubReg(Src0RC, 1);
+
+ if (Src1RC->getID() == AMDGPU::SGPR_64RegClassID) {
+ // try with sgpr32
+ SmallVector<MachineInstr *, 2> copyInstrs = copyToVregAndInsertMI(I, 4);
----------------
jrbyrnes wrote:
For the current list of instructions which we're supporting unpacking for (i.e. VOP3 V_ADD and V_MUL), we shouldn't need to insert SGPR->VGPR copies.
If we want to do this, we should be checking the register class requirements of the new user, and we also need to check whether it is still profitable in terms of latency savings if we need to introduce copy latency.
https://github.com/llvm/llvm-project/pull/151704
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