//===----------------------- SIFrameLowering.cpp --------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //==-----------------------------------------------------------------------===// #include "SIFrameLowering.h" #include "AMDGPUSubtarget.h" #include "SIInstrInfo.h" #include "SIMachineFunctionInfo.h" #include "SIRegisterInfo.h" #include "MCTargetDesc/AMDGPUMCTargetDesc.h" #include "llvm/CodeGen/LivePhysRegs.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/RegisterScavenging.h" using namespace llvm; #define DEBUG_TYPE "frame-info" // Find a scratch register that we can use at the start of the prologue to // re-align the stack pointer. We avoid using callee-save registers since they // may appear to be free when this is called from canUseAsPrologue (during // shrink wrapping), but then no longer be free when this is called from // emitPrologue. // // FIXME: This is a bit conservative, since in the above case we could use one // of the callee-save registers as a scratch temp to re-align the stack pointer, // but we would then have to make sure that we were in fact saving at least one // callee-save register in the prologue, which is additional complexity that // doesn't seem worth the benefit. static MCRegister findScratchNonCalleeSaveRegister(MachineRegisterInfo &MRI, LivePhysRegs &LiveRegs, const TargetRegisterClass &RC, bool Unused = false) { // Mark callee saved registers as used so we will not choose them. const MCPhysReg *CSRegs = MRI.getCalleeSavedRegs(); for (unsigned i = 0; CSRegs[i]; ++i) LiveRegs.addReg(CSRegs[i]); if (Unused) { // We are looking for a register that can be used throughout the entire // function, so any use is unacceptable. for (MCRegister Reg : RC) { if (!MRI.isPhysRegUsed(Reg) && LiveRegs.available(MRI, Reg)) return Reg; } } else { for (MCRegister Reg : RC) { if (LiveRegs.available(MRI, Reg)) return Reg; } } // If we require an unused register, this is used in contexts where failure is // an option and has an alternative plan. In other contexts, this must // succeed0. if (!Unused) report_fatal_error("failed to find free scratch register"); return MCRegister(); } static void getVGPRSpillLaneOrTempRegister(MachineFunction &MF, LivePhysRegs &LiveRegs, Register &TempSGPR, Optional &FrameIndex, bool IsFP) { SIMachineFunctionInfo *MFI = MF.getInfo(); MachineFrameInfo &FrameInfo = MF.getFrameInfo(); #ifndef NDEBUG const GCNSubtarget &ST = MF.getSubtarget(); const SIRegisterInfo *TRI = ST.getRegisterInfo(); #endif // We need to save and restore the current FP/BP. // 1: If there is already a VGPR with free lanes, use it. We // may already have to pay the penalty for spilling a CSR VGPR. if (MFI->haveFreeLanesForSGPRSpill(MF, 1)) { int NewFI = FrameInfo.CreateStackObject(4, Align(4), true, nullptr, TargetStackID::SGPRSpill); if (!MFI->allocateSGPRSpillToVGPR(MF, NewFI)) llvm_unreachable("allocate SGPR spill should have worked"); FrameIndex = NewFI; LLVM_DEBUG(auto Spill = MFI->getSGPRToVGPRSpills(NewFI).front(); dbgs() << "Spilling " << (IsFP ? "FP" : "BP") << " to " << printReg(Spill.VGPR, TRI) << ':' << Spill.Lane << '\n'); return; } // 2: Next, try to save the FP/BP in an unused SGPR. TempSGPR = findScratchNonCalleeSaveRegister( MF.getRegInfo(), LiveRegs, AMDGPU::SReg_32_XM0_XEXECRegClass, true); if (!TempSGPR) { int NewFI = FrameInfo.CreateStackObject(4, Align(4), true, nullptr, TargetStackID::SGPRSpill); if (MFI->allocateSGPRSpillToVGPR(MF, NewFI)) { // 3: There's no free lane to spill, and no free register to save FP/BP, // so we're forced to spill another VGPR to use for the spill. FrameIndex = NewFI; LLVM_DEBUG( auto Spill = MFI->getSGPRToVGPRSpills(NewFI).front(); dbgs() << (IsFP ? "FP" : "BP") << " requires fallback spill to " << printReg(Spill.VGPR, TRI) << ':' << Spill.Lane << '\n';); } else { // Remove dead index MF.getFrameInfo().RemoveStackObject(NewFI); // 4: If all else fails, spill the FP/BP to memory. FrameIndex = FrameInfo.CreateSpillStackObject(4, Align(4)); LLVM_DEBUG(dbgs() << "Reserved FI " << FrameIndex << " for spilling " << (IsFP ? "FP" : "BP") << '\n'); } } else { LLVM_DEBUG(dbgs() << "Saving " << (IsFP ? "FP" : "BP") << " with copy to " << printReg(TempSGPR, TRI) << '\n'); } } // We need to specially emit stack operations here because a different frame // register is used than in the rest of the function, as getFrameRegister would // use. static void buildPrologSpill(const GCNSubtarget &ST, LivePhysRegs &LiveRegs, MachineBasicBlock &MBB, MachineBasicBlock::iterator I, const SIInstrInfo *TII, Register SpillReg, Register ScratchRsrcReg, Register SPReg, int FI) { MachineFunction *MF = MBB.getParent(); MachineFrameInfo &MFI = MF->getFrameInfo(); int64_t Offset = MFI.getObjectOffset(FI); MachineMemOperand *MMO = MF->getMachineMemOperand( MachinePointerInfo::getFixedStack(*MF, FI), MachineMemOperand::MOStore, 4, MFI.getObjectAlign(FI)); if (ST.enableFlatScratch()) { if (TII->isLegalFLATOffset(Offset, AMDGPUAS::PRIVATE_ADDRESS, true)) { BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::SCRATCH_STORE_DWORD_SADDR)) .addReg(SpillReg, RegState::Kill) .addReg(SPReg) .addImm(Offset) .addImm(0) // glc .addImm(0) // slc .addImm(0) // dlc .addMemOperand(MMO); return; } } else if (SIInstrInfo::isLegalMUBUFImmOffset(Offset)) { BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::BUFFER_STORE_DWORD_OFFSET)) .addReg(SpillReg, RegState::Kill) .addReg(ScratchRsrcReg) .addReg(SPReg) .addImm(Offset) .addImm(0) // glc .addImm(0) // slc .addImm(0) // tfe .addImm(0) // dlc .addImm(0) // swz .addMemOperand(MMO); return; } // Don't clobber the TmpVGPR if we also need a scratch reg for the stack // offset in the spill. LiveRegs.addReg(SpillReg); if (ST.enableFlatScratch()) { MCPhysReg OffsetReg = findScratchNonCalleeSaveRegister( MF->getRegInfo(), LiveRegs, AMDGPU::SReg_32_XM0RegClass); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::S_ADD_U32), OffsetReg) .addReg(SPReg) .addImm(Offset); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::SCRATCH_STORE_DWORD_SADDR)) .addReg(SpillReg, RegState::Kill) .addReg(OffsetReg, RegState::Kill) .addImm(0) .addImm(0) // glc .addImm(0) // slc .addImm(0) // dlc .addMemOperand(MMO); } else { MCPhysReg OffsetReg = findScratchNonCalleeSaveRegister( MF->getRegInfo(), LiveRegs, AMDGPU::VGPR_32RegClass); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::V_MOV_B32_e32), OffsetReg) .addImm(Offset); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::BUFFER_STORE_DWORD_OFFEN)) .addReg(SpillReg, RegState::Kill) .addReg(OffsetReg, RegState::Kill) .addReg(ScratchRsrcReg) .addReg(SPReg) .addImm(0) .addImm(0) // glc .addImm(0) // slc .addImm(0) // tfe .addImm(0) // dlc .addImm(0) // swz .addMemOperand(MMO); } LiveRegs.removeReg(SpillReg); } static void buildEpilogReload(const GCNSubtarget &ST, LivePhysRegs &LiveRegs, MachineBasicBlock &MBB, MachineBasicBlock::iterator I, const SIInstrInfo *TII, Register SpillReg, Register ScratchRsrcReg, Register SPReg, int FI) { MachineFunction *MF = MBB.getParent(); MachineFrameInfo &MFI = MF->getFrameInfo(); int64_t Offset = MFI.getObjectOffset(FI); MachineMemOperand *MMO = MF->getMachineMemOperand( MachinePointerInfo::getFixedStack(*MF, FI), MachineMemOperand::MOLoad, 4, MFI.getObjectAlign(FI)); if (ST.enableFlatScratch()) { if (TII->isLegalFLATOffset(Offset, AMDGPUAS::PRIVATE_ADDRESS, true)) { BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::SCRATCH_LOAD_DWORD_SADDR), SpillReg) .addReg(SPReg) .addImm(Offset) .addImm(0) // glc .addImm(0) // slc .addImm(0) // dlc .addMemOperand(MMO); return; } MCPhysReg OffsetReg = findScratchNonCalleeSaveRegister( MF->getRegInfo(), LiveRegs, AMDGPU::SReg_32_XM0RegClass); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::S_ADD_U32), OffsetReg) .addReg(SPReg) .addImm(Offset); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::SCRATCH_LOAD_DWORD_SADDR), SpillReg) .addReg(OffsetReg, RegState::Kill) .addImm(0) .addImm(0) // glc .addImm(0) // slc .addImm(0) // dlc .addMemOperand(MMO); return; } if (SIInstrInfo::isLegalMUBUFImmOffset(Offset)) { BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::BUFFER_LOAD_DWORD_OFFSET), SpillReg) .addReg(ScratchRsrcReg) .addReg(SPReg) .addImm(Offset) .addImm(0) // glc .addImm(0) // slc .addImm(0) // tfe .addImm(0) // dlc .addImm(0) // swz .addMemOperand(MMO); return; } MCPhysReg OffsetReg = findScratchNonCalleeSaveRegister( MF->getRegInfo(), LiveRegs, AMDGPU::VGPR_32RegClass); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::V_MOV_B32_e32), OffsetReg) .addImm(Offset); BuildMI(MBB, I, DebugLoc(), TII->get(AMDGPU::BUFFER_LOAD_DWORD_OFFEN), SpillReg) .addReg(OffsetReg, RegState::Kill) .addReg(ScratchRsrcReg) .addReg(SPReg) .addImm(0) .addImm(0) // glc .addImm(0) // slc .addImm(0) // tfe .addImm(0) // dlc .addImm(0) // swz .addMemOperand(MMO); } static void buildGitPtr(MachineBasicBlock &MBB, MachineBasicBlock::iterator I, const DebugLoc &DL, const SIInstrInfo *TII, Register TargetReg) { MachineFunction *MF = MBB.getParent(); const SIMachineFunctionInfo *MFI = MF->getInfo(); const SIRegisterInfo *TRI = &TII->getRegisterInfo(); const MCInstrDesc &SMovB32 = TII->get(AMDGPU::S_MOV_B32); Register TargetLo = TRI->getSubReg(TargetReg, AMDGPU::sub0); Register TargetHi = TRI->getSubReg(TargetReg, AMDGPU::sub1); if (MFI->getGITPtrHigh() != 0xffffffff) { BuildMI(MBB, I, DL, SMovB32, TargetHi) .addImm(MFI->getGITPtrHigh()) .addReg(TargetReg, RegState::ImplicitDefine); } else { const MCInstrDesc &GetPC64 = TII->get(AMDGPU::S_GETPC_B64); BuildMI(MBB, I, DL, GetPC64, TargetReg); } Register GitPtrLo = MFI->getGITPtrLoReg(*MF); MF->getRegInfo().addLiveIn(GitPtrLo); MBB.addLiveIn(GitPtrLo); BuildMI(MBB, I, DL, SMovB32, TargetLo) .addReg(GitPtrLo); } // Emit flat scratch setup code, assuming `MFI->hasFlatScratchInit()` void SIFrameLowering::emitEntryFunctionFlatScratchInit( MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I, const DebugLoc &DL, Register ScratchWaveOffsetReg) const { const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); const SIRegisterInfo *TRI = &TII->getRegisterInfo(); const SIMachineFunctionInfo *MFI = MF.getInfo(); // We don't need this if we only have spills since there is no user facing // scratch. // TODO: If we know we don't have flat instructions earlier, we can omit // this from the input registers. // // TODO: We only need to know if we access scratch space through a flat // pointer. Because we only detect if flat instructions are used at all, // this will be used more often than necessary on VI. Register FlatScrInitLo; Register FlatScrInitHi; if (ST.isAmdPalOS()) { // Extract the scratch offset from the descriptor in the GIT LivePhysRegs LiveRegs; LiveRegs.init(*TRI); LiveRegs.addLiveIns(MBB); // Find unused reg to load flat scratch init into MachineRegisterInfo &MRI = MF.getRegInfo(); Register FlatScrInit = AMDGPU::NoRegister; ArrayRef AllSGPR64s = TRI->getAllSGPR64(MF); unsigned NumPreloaded = (MFI->getNumPreloadedSGPRs() + 1) / 2; AllSGPR64s = AllSGPR64s.slice( std::min(static_cast(AllSGPR64s.size()), NumPreloaded)); Register GITPtrLoReg = MFI->getGITPtrLoReg(MF); for (MCPhysReg Reg : AllSGPR64s) { if (LiveRegs.available(MRI, Reg) && MRI.isAllocatable(Reg) && !TRI->isSubRegisterEq(Reg, GITPtrLoReg)) { FlatScrInit = Reg; break; } } assert(FlatScrInit && "Failed to find free register for scratch init"); FlatScrInitLo = TRI->getSubReg(FlatScrInit, AMDGPU::sub0); FlatScrInitHi = TRI->getSubReg(FlatScrInit, AMDGPU::sub1); buildGitPtr(MBB, I, DL, TII, FlatScrInit); // We now have the GIT ptr - now get the scratch descriptor from the entry // at offset 0 (or offset 16 for a compute shader). MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS); const MCInstrDesc &LoadDwordX2 = TII->get(AMDGPU::S_LOAD_DWORDX2_IMM); auto *MMO = MF.getMachineMemOperand( PtrInfo, MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant | MachineMemOperand::MODereferenceable, 8, Align(4)); unsigned Offset = MF.getFunction().getCallingConv() == CallingConv::AMDGPU_CS ? 16 : 0; const GCNSubtarget &Subtarget = MF.getSubtarget(); unsigned EncodedOffset = AMDGPU::convertSMRDOffsetUnits(Subtarget, Offset); BuildMI(MBB, I, DL, LoadDwordX2, FlatScrInit) .addReg(FlatScrInit) .addImm(EncodedOffset) // offset .addImm(0) // glc .addImm(0) // dlc .addMemOperand(MMO); // Mask the offset in [47:0] of the descriptor const MCInstrDesc &SAndB32 = TII->get(AMDGPU::S_AND_B32); BuildMI(MBB, I, DL, SAndB32, FlatScrInitHi) .addReg(FlatScrInitHi) .addImm(0xffff); } else { Register FlatScratchInitReg = MFI->getPreloadedReg(AMDGPUFunctionArgInfo::FLAT_SCRATCH_INIT); assert(FlatScratchInitReg); MachineRegisterInfo &MRI = MF.getRegInfo(); MRI.addLiveIn(FlatScratchInitReg); MBB.addLiveIn(FlatScratchInitReg); FlatScrInitLo = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub0); FlatScrInitHi = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub1); } // Do a 64-bit pointer add. if (ST.flatScratchIsPointer()) { if (ST.getGeneration() >= AMDGPUSubtarget::GFX10) { BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), FlatScrInitLo) .addReg(FlatScrInitLo) .addReg(ScratchWaveOffsetReg); BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32), FlatScrInitHi) .addReg(FlatScrInitHi) .addImm(0); BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32)). addReg(FlatScrInitLo). addImm(int16_t(AMDGPU::Hwreg::ID_FLAT_SCR_LO | (31 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_))); BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32)). addReg(FlatScrInitHi). addImm(int16_t(AMDGPU::Hwreg::ID_FLAT_SCR_HI | (31 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_))); return; } // For GFX9. BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), AMDGPU::FLAT_SCR_LO) .addReg(FlatScrInitLo) .addReg(ScratchWaveOffsetReg); BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32), AMDGPU::FLAT_SCR_HI) .addReg(FlatScrInitHi) .addImm(0); return; } assert(ST.getGeneration() < AMDGPUSubtarget::GFX9); // Copy the size in bytes. BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), AMDGPU::FLAT_SCR_LO) .addReg(FlatScrInitHi, RegState::Kill); // Add wave offset in bytes to private base offset. // See comment in AMDKernelCodeT.h for enable_sgpr_flat_scratch_init. BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), FlatScrInitLo) .addReg(FlatScrInitLo) .addReg(ScratchWaveOffsetReg); // Convert offset to 256-byte units. BuildMI(MBB, I, DL, TII->get(AMDGPU::S_LSHR_B32), AMDGPU::FLAT_SCR_HI) .addReg(FlatScrInitLo, RegState::Kill) .addImm(8); } // Note SGPRSpill stack IDs should only be used for SGPR spilling to VGPRs, not // memory. They should have been removed by now. static bool allStackObjectsAreDead(const MachineFrameInfo &MFI) { for (int I = MFI.getObjectIndexBegin(), E = MFI.getObjectIndexEnd(); I != E; ++I) { if (!MFI.isDeadObjectIndex(I)) return false; } return true; } // Shift down registers reserved for the scratch RSRC. Register SIFrameLowering::getEntryFunctionReservedScratchRsrcReg( MachineFunction &MF) const { const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); const SIRegisterInfo *TRI = &TII->getRegisterInfo(); MachineRegisterInfo &MRI = MF.getRegInfo(); SIMachineFunctionInfo *MFI = MF.getInfo(); assert(MFI->isEntryFunction()); Register ScratchRsrcReg = MFI->getScratchRSrcReg(); if (!ScratchRsrcReg || (!MRI.isPhysRegUsed(ScratchRsrcReg) && allStackObjectsAreDead(MF.getFrameInfo()))) return Register(); if (ST.hasSGPRInitBug() || ScratchRsrcReg != TRI->reservedPrivateSegmentBufferReg(MF)) return ScratchRsrcReg; // We reserved the last registers for this. Shift it down to the end of those // which were actually used. // // FIXME: It might be safer to use a pseudoregister before replacement. // FIXME: We should be able to eliminate unused input registers. We only // cannot do this for the resources required for scratch access. For now we // skip over user SGPRs and may leave unused holes. unsigned NumPreloaded = (MFI->getNumPreloadedSGPRs() + 3) / 4; ArrayRef AllSGPR128s = TRI->getAllSGPR128(MF); AllSGPR128s = AllSGPR128s.slice(std::min(static_cast(AllSGPR128s.size()), NumPreloaded)); // Skip the last N reserved elements because they should have already been // reserved for VCC etc. Register GITPtrLoReg = MFI->getGITPtrLoReg(MF); for (MCPhysReg Reg : AllSGPR128s) { // Pick the first unallocated one. Make sure we don't clobber the other // reserved input we needed. Also for PAL, make sure we don't clobber // the GIT pointer passed in SGPR0 or SGPR8. if (!MRI.isPhysRegUsed(Reg) && MRI.isAllocatable(Reg) && !TRI->isSubRegisterEq(Reg, GITPtrLoReg)) { MRI.replaceRegWith(ScratchRsrcReg, Reg); MFI->setScratchRSrcReg(Reg); return Reg; } } return ScratchRsrcReg; } static unsigned getScratchScaleFactor(const GCNSubtarget &ST) { return ST.enableFlatScratch() ? 1 : ST.getWavefrontSize(); } void SIFrameLowering::emitEntryFunctionPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const { assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported"); // FIXME: If we only have SGPR spills, we won't actually be using scratch // memory since these spill to VGPRs. We should be cleaning up these unused // SGPR spill frame indices somewhere. // FIXME: We still have implicit uses on SGPR spill instructions in case they // need to spill to vector memory. It's likely that will not happen, but at // this point it appears we need the setup. This part of the prolog should be // emitted after frame indices are eliminated. // FIXME: Remove all of the isPhysRegUsed checks SIMachineFunctionInfo *MFI = MF.getInfo(); const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); const SIRegisterInfo *TRI = &TII->getRegisterInfo(); MachineRegisterInfo &MRI = MF.getRegInfo(); const Function &F = MF.getFunction(); assert(MFI->isEntryFunction()); Register PreloadedScratchWaveOffsetReg = MFI->getPreloadedReg( AMDGPUFunctionArgInfo::PRIVATE_SEGMENT_WAVE_BYTE_OFFSET); // FIXME: Hack to not crash in situations which emitted an error. if (!PreloadedScratchWaveOffsetReg) return; // We need to do the replacement of the private segment buffer register even // if there are no stack objects. There could be stores to undef or a // constant without an associated object. // // This will return `Register()` in cases where there are no actual // uses of the SRSRC. Register ScratchRsrcReg; if (!ST.enableFlatScratch()) ScratchRsrcReg = getEntryFunctionReservedScratchRsrcReg(MF); // Make the selected register live throughout the function. if (ScratchRsrcReg) { for (MachineBasicBlock &OtherBB : MF) { if (&OtherBB != &MBB) { OtherBB.addLiveIn(ScratchRsrcReg); } } } // Now that we have fixed the reserved SRSRC we need to locate the // (potentially) preloaded SRSRC. Register PreloadedScratchRsrcReg; if (ST.isAmdHsaOrMesa(F)) { PreloadedScratchRsrcReg = MFI->getPreloadedReg(AMDGPUFunctionArgInfo::PRIVATE_SEGMENT_BUFFER); if (ScratchRsrcReg && PreloadedScratchRsrcReg) { // We added live-ins during argument lowering, but since they were not // used they were deleted. We're adding the uses now, so add them back. MRI.addLiveIn(PreloadedScratchRsrcReg); MBB.addLiveIn(PreloadedScratchRsrcReg); } } // Debug location must be unknown since the first debug location is used to // determine the end of the prologue. DebugLoc DL; MachineBasicBlock::iterator I = MBB.begin(); // We found the SRSRC first because it needs four registers and has an // alignment requirement. If the SRSRC that we found is clobbering with // the scratch wave offset, which may be in a fixed SGPR or a free SGPR // chosen by SITargetLowering::allocateSystemSGPRs, COPY the scratch // wave offset to a free SGPR. Register ScratchWaveOffsetReg; if (TRI->isSubRegisterEq(ScratchRsrcReg, PreloadedScratchWaveOffsetReg)) { ArrayRef AllSGPRs = TRI->getAllSGPR32(MF); unsigned NumPreloaded = MFI->getNumPreloadedSGPRs(); AllSGPRs = AllSGPRs.slice( std::min(static_cast(AllSGPRs.size()), NumPreloaded)); Register GITPtrLoReg = MFI->getGITPtrLoReg(MF); for (MCPhysReg Reg : AllSGPRs) { if (!MRI.isPhysRegUsed(Reg) && MRI.isAllocatable(Reg) && !TRI->isSubRegisterEq(ScratchRsrcReg, Reg) && GITPtrLoReg != Reg) { ScratchWaveOffsetReg = Reg; BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), ScratchWaveOffsetReg) .addReg(PreloadedScratchWaveOffsetReg, RegState::Kill); break; } } } else { ScratchWaveOffsetReg = PreloadedScratchWaveOffsetReg; } assert(ScratchWaveOffsetReg); if (requiresStackPointerReference(MF)) { Register SPReg = MFI->getStackPtrOffsetReg(); assert(SPReg != AMDGPU::SP_REG); BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), SPReg) .addImm(MF.getFrameInfo().getStackSize() * getScratchScaleFactor(ST)); } if (hasFP(MF)) { Register FPReg = MFI->getFrameOffsetReg(); assert(FPReg != AMDGPU::FP_REG); BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), FPReg).addImm(0); } if (MFI->hasFlatScratchInit() || ScratchRsrcReg) { MRI.addLiveIn(PreloadedScratchWaveOffsetReg); MBB.addLiveIn(PreloadedScratchWaveOffsetReg); } if (MFI->hasFlatScratchInit()) { emitEntryFunctionFlatScratchInit(MF, MBB, I, DL, ScratchWaveOffsetReg); } if (ScratchRsrcReg) { emitEntryFunctionScratchRsrcRegSetup(MF, MBB, I, DL, PreloadedScratchRsrcReg, ScratchRsrcReg, ScratchWaveOffsetReg); } } // Emit scratch RSRC setup code, assuming `ScratchRsrcReg != AMDGPU::NoReg` void SIFrameLowering::emitEntryFunctionScratchRsrcRegSetup( MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I, const DebugLoc &DL, Register PreloadedScratchRsrcReg, Register ScratchRsrcReg, Register ScratchWaveOffsetReg) const { const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); const SIRegisterInfo *TRI = &TII->getRegisterInfo(); const SIMachineFunctionInfo *MFI = MF.getInfo(); const Function &Fn = MF.getFunction(); if (ST.isAmdPalOS()) { // The pointer to the GIT is formed from the offset passed in and either // the amdgpu-git-ptr-high function attribute or the top part of the PC Register Rsrc01 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0_sub1); buildGitPtr(MBB, I, DL, TII, Rsrc01); // We now have the GIT ptr - now get the scratch descriptor from the entry // at offset 0 (or offset 16 for a compute shader). MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS); const MCInstrDesc &LoadDwordX4 = TII->get(AMDGPU::S_LOAD_DWORDX4_IMM); auto MMO = MF.getMachineMemOperand(PtrInfo, MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant | MachineMemOperand::MODereferenceable, 16, Align(4)); unsigned Offset = Fn.getCallingConv() == CallingConv::AMDGPU_CS ? 16 : 0; const GCNSubtarget &Subtarget = MF.getSubtarget(); unsigned EncodedOffset = AMDGPU::convertSMRDOffsetUnits(Subtarget, Offset); BuildMI(MBB, I, DL, LoadDwordX4, ScratchRsrcReg) .addReg(Rsrc01) .addImm(EncodedOffset) // offset .addImm(0) // glc .addImm(0) // dlc .addReg(ScratchRsrcReg, RegState::ImplicitDefine) .addMemOperand(MMO); } else if (ST.isMesaGfxShader(Fn) || !PreloadedScratchRsrcReg) { assert(!ST.isAmdHsaOrMesa(Fn)); const MCInstrDesc &SMovB32 = TII->get(AMDGPU::S_MOV_B32); Register Rsrc2 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub2); Register Rsrc3 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub3); // Use relocations to get the pointer, and setup the other bits manually. uint64_t Rsrc23 = TII->getScratchRsrcWords23(); if (MFI->hasImplicitBufferPtr()) { Register Rsrc01 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0_sub1); if (AMDGPU::isCompute(MF.getFunction().getCallingConv())) { const MCInstrDesc &Mov64 = TII->get(AMDGPU::S_MOV_B64); BuildMI(MBB, I, DL, Mov64, Rsrc01) .addReg(MFI->getImplicitBufferPtrUserSGPR()) .addReg(ScratchRsrcReg, RegState::ImplicitDefine); } else { const MCInstrDesc &LoadDwordX2 = TII->get(AMDGPU::S_LOAD_DWORDX2_IMM); MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS); auto MMO = MF.getMachineMemOperand( PtrInfo, MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant | MachineMemOperand::MODereferenceable, 8, Align(4)); BuildMI(MBB, I, DL, LoadDwordX2, Rsrc01) .addReg(MFI->getImplicitBufferPtrUserSGPR()) .addImm(0) // offset .addImm(0) // glc .addImm(0) // dlc .addMemOperand(MMO) .addReg(ScratchRsrcReg, RegState::ImplicitDefine); MF.getRegInfo().addLiveIn(MFI->getImplicitBufferPtrUserSGPR()); MBB.addLiveIn(MFI->getImplicitBufferPtrUserSGPR()); } } else { Register Rsrc0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0); Register Rsrc1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1); BuildMI(MBB, I, DL, SMovB32, Rsrc0) .addExternalSymbol("SCRATCH_RSRC_DWORD0") .addReg(ScratchRsrcReg, RegState::ImplicitDefine); BuildMI(MBB, I, DL, SMovB32, Rsrc1) .addExternalSymbol("SCRATCH_RSRC_DWORD1") .addReg(ScratchRsrcReg, RegState::ImplicitDefine); } BuildMI(MBB, I, DL, SMovB32, Rsrc2) .addImm(Rsrc23 & 0xffffffff) .addReg(ScratchRsrcReg, RegState::ImplicitDefine); BuildMI(MBB, I, DL, SMovB32, Rsrc3) .addImm(Rsrc23 >> 32) .addReg(ScratchRsrcReg, RegState::ImplicitDefine); } else if (ST.isAmdHsaOrMesa(Fn)) { assert(PreloadedScratchRsrcReg); if (ScratchRsrcReg != PreloadedScratchRsrcReg) { BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), ScratchRsrcReg) .addReg(PreloadedScratchRsrcReg, RegState::Kill); } } // Add the scratch wave offset into the scratch RSRC. // // We only want to update the first 48 bits, which is the base address // pointer, without touching the adjacent 16 bits of flags. We know this add // cannot carry-out from bit 47, otherwise the scratch allocation would be // impossible to fit in the 48-bit global address space. // // TODO: Evaluate if it is better to just construct an SRD using the flat // scratch init and some constants rather than update the one we are passed. Register ScratchRsrcSub0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0); Register ScratchRsrcSub1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1); // We cannot Kill ScratchWaveOffsetReg here because we allow it to be used in // the kernel body via inreg arguments. BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), ScratchRsrcSub0) .addReg(ScratchRsrcSub0) .addReg(ScratchWaveOffsetReg) .addReg(ScratchRsrcReg, RegState::ImplicitDefine); BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32), ScratchRsrcSub1) .addReg(ScratchRsrcSub1) .addImm(0) .addReg(ScratchRsrcReg, RegState::ImplicitDefine); } bool SIFrameLowering::isSupportedStackID(TargetStackID::Value ID) const { switch (ID) { case TargetStackID::Default: case TargetStackID::NoAlloc: case TargetStackID::SGPRSpill: return true; case TargetStackID::SVEVector: return false; } llvm_unreachable("Invalid TargetStackID::Value"); } // Activate all lanes, returns saved exec. static Register buildScratchExecCopy(LivePhysRegs &LiveRegs, MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI, bool IsProlog) { Register ScratchExecCopy; MachineRegisterInfo &MRI = MF.getRegInfo(); const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); const SIRegisterInfo &TRI = TII->getRegisterInfo(); SIMachineFunctionInfo *FuncInfo = MF.getInfo(); DebugLoc DL; if (LiveRegs.empty()) { if (IsProlog) { LiveRegs.init(TRI); LiveRegs.addLiveIns(MBB); if (FuncInfo->SGPRForFPSaveRestoreCopy) LiveRegs.removeReg(FuncInfo->SGPRForFPSaveRestoreCopy); if (FuncInfo->SGPRForBPSaveRestoreCopy) LiveRegs.removeReg(FuncInfo->SGPRForBPSaveRestoreCopy); } else { // In epilog. LiveRegs.init(*ST.getRegisterInfo()); LiveRegs.addLiveOuts(MBB); LiveRegs.stepBackward(*MBBI); } } ScratchExecCopy = findScratchNonCalleeSaveRegister( MRI, LiveRegs, *TRI.getWaveMaskRegClass()); if (!IsProlog) LiveRegs.removeReg(ScratchExecCopy); const unsigned OrSaveExec = ST.isWave32() ? AMDGPU::S_OR_SAVEEXEC_B32 : AMDGPU::S_OR_SAVEEXEC_B64; BuildMI(MBB, MBBI, DL, TII->get(OrSaveExec), ScratchExecCopy).addImm(-1); return ScratchExecCopy; } void SIFrameLowering::emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const { SIMachineFunctionInfo *FuncInfo = MF.getInfo(); if (FuncInfo->isEntryFunction()) { emitEntryFunctionPrologue(MF, MBB); return; } const MachineFrameInfo &MFI = MF.getFrameInfo(); MachineRegisterInfo &MRI = MF.getRegInfo(); const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); const SIRegisterInfo &TRI = TII->getRegisterInfo(); Register StackPtrReg = FuncInfo->getStackPtrOffsetReg(); Register FramePtrReg = FuncInfo->getFrameOffsetReg(); Register BasePtrReg = TRI.hasBasePointer(MF) ? TRI.getBaseRegister() : Register(); LivePhysRegs LiveRegs; MachineBasicBlock::iterator MBBI = MBB.begin(); DebugLoc DL; bool HasFP = false; bool HasBP = false; uint32_t NumBytes = MFI.getStackSize(); uint32_t RoundedSize = NumBytes; // To avoid clobbering VGPRs in lanes that weren't active on function entry, // turn on all lanes before doing the spill to memory. Register ScratchExecCopy; bool HasFPSaveIndex = FuncInfo->FramePointerSaveIndex.hasValue(); bool SpillFPToMemory = false; // A StackID of SGPRSpill implies that this is a spill from SGPR to VGPR. // Otherwise we are spilling the FP to memory. if (HasFPSaveIndex) { SpillFPToMemory = MFI.getStackID(*FuncInfo->FramePointerSaveIndex) != TargetStackID::SGPRSpill; } bool HasBPSaveIndex = FuncInfo->BasePointerSaveIndex.hasValue(); bool SpillBPToMemory = false; // A StackID of SGPRSpill implies that this is a spill from SGPR to VGPR. // Otherwise we are spilling the BP to memory. if (HasBPSaveIndex) { SpillBPToMemory = MFI.getStackID(*FuncInfo->BasePointerSaveIndex) != TargetStackID::SGPRSpill; } // Emit the copy if we need an FP, and are using a free SGPR to save it. if (FuncInfo->SGPRForFPSaveRestoreCopy) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FuncInfo->SGPRForFPSaveRestoreCopy) .addReg(FramePtrReg) .setMIFlag(MachineInstr::FrameSetup); } // Emit the copy if we need a BP, and are using a free SGPR to save it. if (FuncInfo->SGPRForBPSaveRestoreCopy) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FuncInfo->SGPRForBPSaveRestoreCopy) .addReg(BasePtrReg) .setMIFlag(MachineInstr::FrameSetup); } // If a copy has been emitted for FP and/or BP, Make the SGPRs // used in the copy instructions live throughout the function. SmallVector TempSGPRs; if (FuncInfo->SGPRForFPSaveRestoreCopy) TempSGPRs.push_back(FuncInfo->SGPRForFPSaveRestoreCopy); if (FuncInfo->SGPRForBPSaveRestoreCopy) TempSGPRs.push_back(FuncInfo->SGPRForBPSaveRestoreCopy); if (!TempSGPRs.empty()) { for (MachineBasicBlock &MBB : MF) { for (MCPhysReg Reg : TempSGPRs) MBB.addLiveIn(Reg); MBB.sortUniqueLiveIns(); } } for (const SIMachineFunctionInfo::SGPRSpillVGPRCSR &Reg : FuncInfo->getSGPRSpillVGPRs()) { if (!Reg.FI.hasValue()) continue; if (!ScratchExecCopy) ScratchExecCopy = buildScratchExecCopy(LiveRegs, MF, MBB, MBBI, true); buildPrologSpill(ST, LiveRegs, MBB, MBBI, TII, Reg.VGPR, FuncInfo->getScratchRSrcReg(), StackPtrReg, Reg.FI.getValue()); } if (HasFPSaveIndex && SpillFPToMemory) { assert(!MFI.isDeadObjectIndex(FuncInfo->FramePointerSaveIndex.getValue())); if (!ScratchExecCopy) ScratchExecCopy = buildScratchExecCopy(LiveRegs, MF, MBB, MBBI, true); MCPhysReg TmpVGPR = findScratchNonCalleeSaveRegister( MRI, LiveRegs, AMDGPU::VGPR_32RegClass); BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_MOV_B32_e32), TmpVGPR) .addReg(FramePtrReg); buildPrologSpill(ST, LiveRegs, MBB, MBBI, TII, TmpVGPR, FuncInfo->getScratchRSrcReg(), StackPtrReg, FuncInfo->FramePointerSaveIndex.getValue()); } if (HasBPSaveIndex && SpillBPToMemory) { assert(!MFI.isDeadObjectIndex(*FuncInfo->BasePointerSaveIndex)); if (!ScratchExecCopy) ScratchExecCopy = buildScratchExecCopy(LiveRegs, MF, MBB, MBBI, true); MCPhysReg TmpVGPR = findScratchNonCalleeSaveRegister( MRI, LiveRegs, AMDGPU::VGPR_32RegClass); BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_MOV_B32_e32), TmpVGPR) .addReg(BasePtrReg); buildPrologSpill(ST, LiveRegs, MBB, MBBI, TII, TmpVGPR, FuncInfo->getScratchRSrcReg(), StackPtrReg, *FuncInfo->BasePointerSaveIndex); } if (ScratchExecCopy) { // FIXME: Split block and make terminator. unsigned ExecMov = ST.isWave32() ? AMDGPU::S_MOV_B32 : AMDGPU::S_MOV_B64; MCRegister Exec = ST.isWave32() ? AMDGPU::EXEC_LO : AMDGPU::EXEC; BuildMI(MBB, MBBI, DL, TII->get(ExecMov), Exec) .addReg(ScratchExecCopy, RegState::Kill); LiveRegs.addReg(ScratchExecCopy); } // In this case, spill the FP to a reserved VGPR. if (HasFPSaveIndex && !SpillFPToMemory) { const int FI = FuncInfo->FramePointerSaveIndex.getValue(); assert(!MFI.isDeadObjectIndex(FI)); assert(MFI.getStackID(FI) == TargetStackID::SGPRSpill); ArrayRef Spill = FuncInfo->getSGPRToVGPRSpills(FI); assert(Spill.size() == 1); // Save FP before setting it up. // FIXME: This should respect spillSGPRToVGPR; BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_WRITELANE_B32), Spill[0].VGPR) .addReg(FramePtrReg) .addImm(Spill[0].Lane) .addReg(Spill[0].VGPR, RegState::Undef); } // In this case, spill the BP to a reserved VGPR. if (HasBPSaveIndex && !SpillBPToMemory) { const int BasePtrFI = *FuncInfo->BasePointerSaveIndex; assert(!MFI.isDeadObjectIndex(BasePtrFI)); assert(MFI.getStackID(BasePtrFI) == TargetStackID::SGPRSpill); ArrayRef Spill = FuncInfo->getSGPRToVGPRSpills(BasePtrFI); assert(Spill.size() == 1); // Save BP before setting it up. // FIXME: This should respect spillSGPRToVGPR; BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_WRITELANE_B32), Spill[0].VGPR) .addReg(BasePtrReg) .addImm(Spill[0].Lane) .addReg(Spill[0].VGPR, RegState::Undef); } if (TRI.needsStackRealignment(MF)) { HasFP = true; const unsigned Alignment = MFI.getMaxAlign().value(); RoundedSize += Alignment; if (LiveRegs.empty()) { LiveRegs.init(TRI); LiveRegs.addLiveIns(MBB); LiveRegs.addReg(FuncInfo->SGPRForFPSaveRestoreCopy); LiveRegs.addReg(FuncInfo->SGPRForBPSaveRestoreCopy); } Register ScratchSPReg = findScratchNonCalleeSaveRegister( MRI, LiveRegs, AMDGPU::SReg_32_XM0RegClass); assert(ScratchSPReg && ScratchSPReg != FuncInfo->SGPRForFPSaveRestoreCopy && ScratchSPReg != FuncInfo->SGPRForBPSaveRestoreCopy); // s_add_u32 tmp_reg, s32, NumBytes // s_and_b32 s32, tmp_reg, 0b111...0000 BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_ADD_U32), ScratchSPReg) .addReg(StackPtrReg) .addImm((Alignment - 1) * getScratchScaleFactor(ST)) .setMIFlag(MachineInstr::FrameSetup); BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_AND_B32), FramePtrReg) .addReg(ScratchSPReg, RegState::Kill) .addImm(-Alignment * getScratchScaleFactor(ST)) .setMIFlag(MachineInstr::FrameSetup); FuncInfo->setIsStackRealigned(true); } else if ((HasFP = hasFP(MF))) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrReg) .addReg(StackPtrReg) .setMIFlag(MachineInstr::FrameSetup); } // If we need a base pointer, set it up here. It's whatever the value of // the stack pointer is at this point. Any variable size objects will be // allocated after this, so we can still use the base pointer to reference // the incoming arguments. if ((HasBP = TRI.hasBasePointer(MF))) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), BasePtrReg) .addReg(StackPtrReg) .setMIFlag(MachineInstr::FrameSetup); } if (HasFP && RoundedSize != 0) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_ADD_U32), StackPtrReg) .addReg(StackPtrReg) .addImm(RoundedSize * getScratchScaleFactor(ST)) .setMIFlag(MachineInstr::FrameSetup); } assert((!HasFP || (FuncInfo->SGPRForFPSaveRestoreCopy || FuncInfo->FramePointerSaveIndex)) && "Needed to save FP but didn't save it anywhere"); assert((HasFP || (!FuncInfo->SGPRForFPSaveRestoreCopy && !FuncInfo->FramePointerSaveIndex)) && "Saved FP but didn't need it"); assert((!HasBP || (FuncInfo->SGPRForBPSaveRestoreCopy || FuncInfo->BasePointerSaveIndex)) && "Needed to save BP but didn't save it anywhere"); assert((HasBP || (!FuncInfo->SGPRForBPSaveRestoreCopy && !FuncInfo->BasePointerSaveIndex)) && "Saved BP but didn't need it"); } void SIFrameLowering::emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const { const SIMachineFunctionInfo *FuncInfo = MF.getInfo(); if (FuncInfo->isEntryFunction()) return; const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); MachineRegisterInfo &MRI = MF.getRegInfo(); const SIRegisterInfo &TRI = TII->getRegisterInfo(); MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator(); LivePhysRegs LiveRegs; DebugLoc DL; const MachineFrameInfo &MFI = MF.getFrameInfo(); uint32_t NumBytes = MFI.getStackSize(); uint32_t RoundedSize = FuncInfo->isStackRealigned() ? NumBytes + MFI.getMaxAlign().value() : NumBytes; const Register StackPtrReg = FuncInfo->getStackPtrOffsetReg(); const Register FramePtrReg = FuncInfo->getFrameOffsetReg(); const Register BasePtrReg = TRI.hasBasePointer(MF) ? TRI.getBaseRegister() : Register(); bool HasFPSaveIndex = FuncInfo->FramePointerSaveIndex.hasValue(); bool SpillFPToMemory = false; if (HasFPSaveIndex) { SpillFPToMemory = MFI.getStackID(*FuncInfo->FramePointerSaveIndex) != TargetStackID::SGPRSpill; } bool HasBPSaveIndex = FuncInfo->BasePointerSaveIndex.hasValue(); bool SpillBPToMemory = false; if (HasBPSaveIndex) { SpillBPToMemory = MFI.getStackID(*FuncInfo->BasePointerSaveIndex) != TargetStackID::SGPRSpill; } if (RoundedSize != 0 && hasFP(MF)) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_SUB_U32), StackPtrReg) .addReg(StackPtrReg) .addImm(RoundedSize * getScratchScaleFactor(ST)) .setMIFlag(MachineInstr::FrameDestroy); } if (FuncInfo->SGPRForFPSaveRestoreCopy) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrReg) .addReg(FuncInfo->SGPRForFPSaveRestoreCopy) .setMIFlag(MachineInstr::FrameSetup); } if (FuncInfo->SGPRForBPSaveRestoreCopy) { BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), BasePtrReg) .addReg(FuncInfo->SGPRForBPSaveRestoreCopy) .setMIFlag(MachineInstr::FrameSetup); } Register ScratchExecCopy; if (HasFPSaveIndex) { const int FI = FuncInfo->FramePointerSaveIndex.getValue(); assert(!MFI.isDeadObjectIndex(FI)); if (SpillFPToMemory) { if (!ScratchExecCopy) ScratchExecCopy = buildScratchExecCopy(LiveRegs, MF, MBB, MBBI, false); MCPhysReg TempVGPR = findScratchNonCalleeSaveRegister( MRI, LiveRegs, AMDGPU::VGPR_32RegClass); buildEpilogReload(ST, LiveRegs, MBB, MBBI, TII, TempVGPR, FuncInfo->getScratchRSrcReg(), StackPtrReg, FI); BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_READFIRSTLANE_B32), FramePtrReg) .addReg(TempVGPR, RegState::Kill); } else { // Reload from VGPR spill. assert(MFI.getStackID(FI) == TargetStackID::SGPRSpill); ArrayRef Spill = FuncInfo->getSGPRToVGPRSpills(FI); assert(Spill.size() == 1); BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_READLANE_B32), FramePtrReg) .addReg(Spill[0].VGPR) .addImm(Spill[0].Lane); } } if (HasBPSaveIndex) { const int BasePtrFI = *FuncInfo->BasePointerSaveIndex; assert(!MFI.isDeadObjectIndex(BasePtrFI)); if (SpillBPToMemory) { if (!ScratchExecCopy) ScratchExecCopy = buildScratchExecCopy(LiveRegs, MF, MBB, MBBI, false); MCPhysReg TempVGPR = findScratchNonCalleeSaveRegister( MRI, LiveRegs, AMDGPU::VGPR_32RegClass); buildEpilogReload(ST, LiveRegs, MBB, MBBI, TII, TempVGPR, FuncInfo->getScratchRSrcReg(), StackPtrReg, BasePtrFI); BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_READFIRSTLANE_B32), BasePtrReg) .addReg(TempVGPR, RegState::Kill); } else { // Reload from VGPR spill. assert(MFI.getStackID(BasePtrFI) == TargetStackID::SGPRSpill); ArrayRef Spill = FuncInfo->getSGPRToVGPRSpills(BasePtrFI); assert(Spill.size() == 1); BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::V_READLANE_B32), BasePtrReg) .addReg(Spill[0].VGPR) .addImm(Spill[0].Lane); } } for (const SIMachineFunctionInfo::SGPRSpillVGPRCSR &Reg : FuncInfo->getSGPRSpillVGPRs()) { if (!Reg.FI.hasValue()) continue; if (!ScratchExecCopy) ScratchExecCopy = buildScratchExecCopy(LiveRegs, MF, MBB, MBBI, false); buildEpilogReload(ST, LiveRegs, MBB, MBBI, TII, Reg.VGPR, FuncInfo->getScratchRSrcReg(), StackPtrReg, Reg.FI.getValue()); } if (ScratchExecCopy) { // FIXME: Split block and make terminator. unsigned ExecMov = ST.isWave32() ? AMDGPU::S_MOV_B32 : AMDGPU::S_MOV_B64; MCRegister Exec = ST.isWave32() ? AMDGPU::EXEC_LO : AMDGPU::EXEC; BuildMI(MBB, MBBI, DL, TII->get(ExecMov), Exec) .addReg(ScratchExecCopy, RegState::Kill); } } #ifndef NDEBUG static bool allSGPRSpillsAreDead(const MachineFunction &MF) { const MachineFrameInfo &MFI = MF.getFrameInfo(); const SIMachineFunctionInfo *FuncInfo = MF.getInfo(); for (int I = MFI.getObjectIndexBegin(), E = MFI.getObjectIndexEnd(); I != E; ++I) { if (!MFI.isDeadObjectIndex(I) && MFI.getStackID(I) == TargetStackID::SGPRSpill && (I != FuncInfo->FramePointerSaveIndex && I != FuncInfo->BasePointerSaveIndex)) { return false; } } return true; } #endif StackOffset SIFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI, Register &FrameReg) const { const SIRegisterInfo *RI = MF.getSubtarget().getRegisterInfo(); FrameReg = RI->getFrameRegister(MF); return StackOffset::getFixed(MF.getFrameInfo().getObjectOffset(FI)); } void SIFrameLowering::processFunctionBeforeFrameFinalized( MachineFunction &MF, RegScavenger *RS) const { MachineFrameInfo &MFI = MF.getFrameInfo(); const GCNSubtarget &ST = MF.getSubtarget(); const SIRegisterInfo *TRI = ST.getRegisterInfo(); SIMachineFunctionInfo *FuncInfo = MF.getInfo(); FuncInfo->removeDeadFrameIndices(MFI); assert(allSGPRSpillsAreDead(MF) && "SGPR spill should have been removed in SILowerSGPRSpills"); // FIXME: The other checks should be redundant with allStackObjectsAreDead, // but currently hasNonSpillStackObjects is set only from source // allocas. Stack temps produced from legalization are not counted currently. if (!allStackObjectsAreDead(MFI)) { assert(RS && "RegScavenger required if spilling"); if (FuncInfo->isEntryFunction()) { int ScavengeFI = MFI.CreateFixedObject( TRI->getSpillSize(AMDGPU::SGPR_32RegClass), 0, false); RS->addScavengingFrameIndex(ScavengeFI); } else { int ScavengeFI = MFI.CreateStackObject( TRI->getSpillSize(AMDGPU::SGPR_32RegClass), TRI->getSpillAlign(AMDGPU::SGPR_32RegClass), false); RS->addScavengingFrameIndex(ScavengeFI); } } } // Only report VGPRs to generic code. void SIFrameLowering::determineCalleeSaves(MachineFunction &MF, BitVector &SavedVGPRs, RegScavenger *RS) const { TargetFrameLowering::determineCalleeSaves(MF, SavedVGPRs, RS); SIMachineFunctionInfo *MFI = MF.getInfo(); if (MFI->isEntryFunction()) return; MachineFrameInfo &FrameInfo = MF.getFrameInfo(); const GCNSubtarget &ST = MF.getSubtarget(); const SIRegisterInfo *TRI = ST.getRegisterInfo(); // Ignore the SGPRs the default implementation found. SavedVGPRs.clearBitsNotInMask(TRI->getAllVGPRRegMask()); // hasFP only knows about stack objects that already exist. We're now // determining the stack slots that will be created, so we have to predict // them. Stack objects force FP usage with calls. // // Note a new VGPR CSR may be introduced if one is used for the spill, but we // don't want to report it here. // // FIXME: Is this really hasReservedCallFrame? const bool WillHaveFP = FrameInfo.hasCalls() && (SavedVGPRs.any() || !allStackObjectsAreDead(FrameInfo)); // VGPRs used for SGPR spilling need to be specially inserted in the prolog, // so don't allow the default insertion to handle them. for (auto SSpill : MFI->getSGPRSpillVGPRs()) SavedVGPRs.reset(SSpill.VGPR); LivePhysRegs LiveRegs; LiveRegs.init(*TRI); if (WillHaveFP || hasFP(MF)) { getVGPRSpillLaneOrTempRegister(MF, LiveRegs, MFI->SGPRForFPSaveRestoreCopy, MFI->FramePointerSaveIndex, true); } if (TRI->hasBasePointer(MF)) { if (MFI->SGPRForFPSaveRestoreCopy) LiveRegs.addReg(MFI->SGPRForFPSaveRestoreCopy); getVGPRSpillLaneOrTempRegister(MF, LiveRegs, MFI->SGPRForBPSaveRestoreCopy, MFI->BasePointerSaveIndex, false); } } void SIFrameLowering::determineCalleeSavesSGPR(MachineFunction &MF, BitVector &SavedRegs, RegScavenger *RS) const { TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS); const SIMachineFunctionInfo *MFI = MF.getInfo(); if (MFI->isEntryFunction()) return; const GCNSubtarget &ST = MF.getSubtarget(); const SIRegisterInfo *TRI = ST.getRegisterInfo(); // The SP is specifically managed and we don't want extra spills of it. SavedRegs.reset(MFI->getStackPtrOffsetReg()); SavedRegs.clearBitsInMask(TRI->getAllVGPRRegMask()); } bool SIFrameLowering::assignCalleeSavedSpillSlots( MachineFunction &MF, const TargetRegisterInfo *TRI, std::vector &CSI) const { if (CSI.empty()) return true; // Early exit if no callee saved registers are modified! const SIMachineFunctionInfo *FuncInfo = MF.getInfo(); if (!FuncInfo->SGPRForFPSaveRestoreCopy && !FuncInfo->SGPRForBPSaveRestoreCopy) return false; const GCNSubtarget &ST = MF.getSubtarget(); const SIRegisterInfo *RI = ST.getRegisterInfo(); Register FramePtrReg = FuncInfo->getFrameOffsetReg(); Register BasePtrReg = RI->getBaseRegister(); unsigned NumModifiedRegs = 0; if (FuncInfo->SGPRForFPSaveRestoreCopy) NumModifiedRegs++; if (FuncInfo->SGPRForBPSaveRestoreCopy) NumModifiedRegs++; for (auto &CS : CSI) { if (CS.getReg() == FramePtrReg && FuncInfo->SGPRForFPSaveRestoreCopy) { CS.setDstReg(FuncInfo->SGPRForFPSaveRestoreCopy); if (--NumModifiedRegs) break; } else if (CS.getReg() == BasePtrReg && FuncInfo->SGPRForBPSaveRestoreCopy) { CS.setDstReg(FuncInfo->SGPRForBPSaveRestoreCopy); if (--NumModifiedRegs) break; } } return false; } MachineBasicBlock::iterator SIFrameLowering::eliminateCallFramePseudoInstr( MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I) const { int64_t Amount = I->getOperand(0).getImm(); if (Amount == 0) return MBB.erase(I); const GCNSubtarget &ST = MF.getSubtarget(); const SIInstrInfo *TII = ST.getInstrInfo(); const DebugLoc &DL = I->getDebugLoc(); unsigned Opc = I->getOpcode(); bool IsDestroy = Opc == TII->getCallFrameDestroyOpcode(); uint64_t CalleePopAmount = IsDestroy ? I->getOperand(1).getImm() : 0; if (!hasReservedCallFrame(MF)) { Amount = alignTo(Amount, getStackAlign()); assert(isUInt<32>(Amount) && "exceeded stack address space size"); const SIMachineFunctionInfo *MFI = MF.getInfo(); Register SPReg = MFI->getStackPtrOffsetReg(); unsigned Op = IsDestroy ? AMDGPU::S_SUB_U32 : AMDGPU::S_ADD_U32; BuildMI(MBB, I, DL, TII->get(Op), SPReg) .addReg(SPReg) .addImm(Amount * getScratchScaleFactor(ST)); } else if (CalleePopAmount != 0) { llvm_unreachable("is this used?"); } return MBB.erase(I); } /// Returns true if the frame will require a reference to the stack pointer. /// /// This is the set of conditions common to setting up the stack pointer in a /// kernel, and for using a frame pointer in a callable function. /// /// FIXME: Should also check hasOpaqueSPAdjustment and if any inline asm /// references SP. static bool frameTriviallyRequiresSP(const MachineFrameInfo &MFI) { return MFI.hasVarSizedObjects() || MFI.hasStackMap() || MFI.hasPatchPoint(); } // The FP for kernels is always known 0, so we never really need to setup an // explicit register for it. However, DisableFramePointerElim will force us to // use a register for it. bool SIFrameLowering::hasFP(const MachineFunction &MF) const { const MachineFrameInfo &MFI = MF.getFrameInfo(); // For entry functions we can use an immediate offset in most cases, so the // presence of calls doesn't imply we need a distinct frame pointer. if (MFI.hasCalls() && !MF.getInfo()->isEntryFunction()) { // All offsets are unsigned, so need to be addressed in the same direction // as stack growth. // FIXME: This function is pretty broken, since it can be called before the // frame layout is determined or CSR spills are inserted. return MFI.getStackSize() != 0; } return frameTriviallyRequiresSP(MFI) || MFI.isFrameAddressTaken() || MF.getSubtarget().getRegisterInfo()->needsStackRealignment(MF) || MF.getTarget().Options.DisableFramePointerElim(MF); } // This is essentially a reduced version of hasFP for entry functions. Since the // stack pointer is known 0 on entry to kernels, we never really need an FP // register. We may need to initialize the stack pointer depending on the frame // properties, which logically overlaps many of the cases where an ordinary // function would require an FP. bool SIFrameLowering::requiresStackPointerReference( const MachineFunction &MF) const { // Callable functions always require a stack pointer reference. assert(MF.getInfo()->isEntryFunction() && "only expected to call this for entry points"); const MachineFrameInfo &MFI = MF.getFrameInfo(); // Entry points ordinarily don't need to initialize SP. We have to set it up // for callees if there are any. Also note tail calls are impossible/don't // make any sense for kernels. if (MFI.hasCalls()) return true; // We still need to initialize the SP if we're doing anything weird that // references the SP, like variable sized stack objects. return frameTriviallyRequiresSP(MFI); }