forked from OSchip/llvm-project
285 lines
10 KiB
C++
285 lines
10 KiB
C++
//===----------------------- SIFrameLowering.cpp --------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//==-----------------------------------------------------------------------===//
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#include "SIFrameLowering.h"
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#include "SIInstrInfo.h"
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#include "SIMachineFunctionInfo.h"
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#include "SIRegisterInfo.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/RegisterScavenging.h"
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using namespace llvm;
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static bool hasOnlySGPRSpills(const SIMachineFunctionInfo *FuncInfo,
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const MachineFrameInfo *FrameInfo) {
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return FuncInfo->hasSpilledSGPRs() &&
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(!FuncInfo->hasSpilledVGPRs() && !FuncInfo->hasNonSpillStackObjects());
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}
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static ArrayRef<MCPhysReg> getAllSGPR128() {
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return makeArrayRef(AMDGPU::SReg_128RegClass.begin(),
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AMDGPU::SReg_128RegClass.getNumRegs());
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}
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static ArrayRef<MCPhysReg> getAllSGPRs() {
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return makeArrayRef(AMDGPU::SGPR_32RegClass.begin(),
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AMDGPU::SGPR_32RegClass.getNumRegs());
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}
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void SIFrameLowering::emitPrologue(MachineFunction &MF,
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MachineBasicBlock &MBB) const {
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if (!MF.getFrameInfo()->hasStackObjects())
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return;
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assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
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SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
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// If we only have SGPR spills, we won't actually be using scratch memory
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// since these spill to VGPRs.
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//
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// FIXME: We should be cleaning up these unused SGPR spill frame indices
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// somewhere.
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if (hasOnlySGPRSpills(MFI, MF.getFrameInfo()))
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return;
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const SIInstrInfo *TII =
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static_cast<const SIInstrInfo *>(MF.getSubtarget().getInstrInfo());
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const SIRegisterInfo *TRI = &TII->getRegisterInfo();
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const AMDGPUSubtarget &ST = MF.getSubtarget<AMDGPUSubtarget>();
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MachineRegisterInfo &MRI = MF.getRegInfo();
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MachineBasicBlock::iterator I = MBB.begin();
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// We need to insert initialization of the scratch resource descriptor.
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unsigned ScratchRsrcReg = MFI->getScratchRSrcReg();
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assert(ScratchRsrcReg != AMDGPU::NoRegister);
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unsigned ScratchWaveOffsetReg = MFI->getScratchWaveOffsetReg();
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assert(ScratchWaveOffsetReg != AMDGPU::NoRegister);
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unsigned PreloadedScratchWaveOffsetReg = TRI->getPreloadedValue(
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MF, SIRegisterInfo::PRIVATE_SEGMENT_WAVE_BYTE_OFFSET);
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unsigned PreloadedPrivateBufferReg = AMDGPU::NoRegister;
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if (ST.isAmdHsaOS()) {
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PreloadedPrivateBufferReg = TRI->getPreloadedValue(
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MF, SIRegisterInfo::PRIVATE_SEGMENT_BUFFER);
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}
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if (MFI->hasFlatScratchInit()) {
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// We don't need this if we only have spills since there is no user facing
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// scratch.
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// TODO: If we know we don't have flat instructions earlier, we can omit
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// this from the input registers.
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//
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// TODO: We only need to know if we access scratch space through a flat
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// pointer. Because we only detect if flat instructions are used at all,
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// this will be used more often than necessary on VI.
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DebugLoc DL;
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unsigned FlatScratchInitReg
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= TRI->getPreloadedValue(MF, SIRegisterInfo::FLAT_SCRATCH_INIT);
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MRI.addLiveIn(FlatScratchInitReg);
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MBB.addLiveIn(FlatScratchInitReg);
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// Copy the size in bytes.
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unsigned FlatScrInitHi = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub1);
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BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), AMDGPU::FLAT_SCR_LO)
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.addReg(FlatScrInitHi, RegState::Kill);
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unsigned FlatScrInitLo = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub0);
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// Add wave offset in bytes to private base offset.
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// See comment in AMDKernelCodeT.h for enable_sgpr_flat_scratch_init.
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BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), FlatScrInitLo)
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.addReg(FlatScrInitLo)
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.addReg(ScratchWaveOffsetReg);
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// Convert offset to 256-byte units.
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BuildMI(MBB, I, DL, TII->get(AMDGPU::S_LSHR_B32), AMDGPU::FLAT_SCR_HI)
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.addReg(FlatScrInitLo, RegState::Kill)
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.addImm(8);
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}
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// If we reserved the original input registers, we don't need to copy to the
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// reserved registers.
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if (ScratchRsrcReg == PreloadedPrivateBufferReg) {
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// We should always reserve these 5 registers at the same time.
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assert(ScratchWaveOffsetReg == PreloadedScratchWaveOffsetReg &&
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"scratch wave offset and private segment buffer inconsistent");
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return;
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}
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// We added live-ins during argument lowering, but since they were not used
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// they were deleted. We're adding the uses now, so add them back.
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MRI.addLiveIn(PreloadedScratchWaveOffsetReg);
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MBB.addLiveIn(PreloadedScratchWaveOffsetReg);
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if (ST.isAmdHsaOS()) {
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MRI.addLiveIn(PreloadedPrivateBufferReg);
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MBB.addLiveIn(PreloadedPrivateBufferReg);
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}
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if (!ST.hasSGPRInitBug()) {
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// We reserved the last registers for this. Shift it down to the end of those
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// which were actually used.
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//
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// FIXME: It might be safer to use a pseudoregister before replacement.
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// FIXME: We should be able to eliminate unused input registers. We only
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// cannot do this for the resources required for scratch access. For now we
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// skip over user SGPRs and may leave unused holes.
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// We find the resource first because it has an alignment requirement.
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if (ScratchRsrcReg == TRI->reservedPrivateSegmentBufferReg(MF)) {
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MachineRegisterInfo &MRI = MF.getRegInfo();
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unsigned NumPreloaded = MFI->getNumPreloadedSGPRs() / 4;
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// Skip the last 2 elements because the last one is reserved for VCC, and
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// this is the 2nd to last element already.
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for (MCPhysReg Reg : getAllSGPR128().drop_back(2).slice(NumPreloaded)) {
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// Pick the first unallocated one. Make sure we don't clobber the other
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// reserved input we needed.
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if (!MRI.isPhysRegUsed(Reg)) {
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assert(MRI.isAllocatable(Reg));
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MRI.replaceRegWith(ScratchRsrcReg, Reg);
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ScratchRsrcReg = Reg;
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MFI->setScratchRSrcReg(ScratchRsrcReg);
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break;
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}
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}
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}
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if (ScratchWaveOffsetReg == TRI->reservedPrivateSegmentWaveByteOffsetReg(MF)) {
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MachineRegisterInfo &MRI = MF.getRegInfo();
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unsigned NumPreloaded = MFI->getNumPreloadedSGPRs();
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// We need to drop register from the end of the list that we cannot use
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// for the scratch wave offset.
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// + 2 s102 and s103 do not exist on VI.
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// + 2 for vcc
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// + 2 for xnack_mask
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// + 2 for flat_scratch
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// + 4 for registers reserved for scratch resource register
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// + 1 for register reserved for scratch wave offset. (By exluding this
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// register from the list to consider, it means that when this
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// register is being used for the scratch wave offset and there
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// are no other free SGPRs, then the value will stay in this register.
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// ----
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// 13
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for (MCPhysReg Reg : getAllSGPRs().drop_back(13).slice(NumPreloaded)) {
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// Pick the first unallocated SGPR. Be careful not to pick an alias of the
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// scratch descriptor, since we haven’t added its uses yet.
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if (!MRI.isPhysRegUsed(Reg)) {
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assert(MRI.isAllocatable(Reg) &&
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!TRI->isSubRegisterEq(ScratchRsrcReg, Reg));
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MRI.replaceRegWith(ScratchWaveOffsetReg, Reg);
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ScratchWaveOffsetReg = Reg;
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MFI->setScratchWaveOffsetReg(ScratchWaveOffsetReg);
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break;
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}
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}
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}
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}
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assert(!TRI->isSubRegister(ScratchRsrcReg, ScratchWaveOffsetReg));
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const MCInstrDesc &SMovB32 = TII->get(AMDGPU::S_MOV_B32);
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DebugLoc DL;
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if (PreloadedScratchWaveOffsetReg != ScratchWaveOffsetReg) {
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// Make sure we emit the copy for the offset first. We may have chosen to copy
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// the buffer resource into a register that aliases the input offset register.
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BuildMI(MBB, I, DL, SMovB32, ScratchWaveOffsetReg)
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.addReg(PreloadedScratchWaveOffsetReg, RegState::Kill);
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}
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if (ST.isAmdHsaOS()) {
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// Insert copies from argument register.
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assert(
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!TRI->isSubRegisterEq(PreloadedPrivateBufferReg, ScratchRsrcReg) &&
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!TRI->isSubRegisterEq(PreloadedPrivateBufferReg, ScratchWaveOffsetReg));
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unsigned Rsrc01 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0_sub1);
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unsigned Rsrc23 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub2_sub3);
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unsigned Lo = TRI->getSubReg(PreloadedPrivateBufferReg, AMDGPU::sub0_sub1);
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unsigned Hi = TRI->getSubReg(PreloadedPrivateBufferReg, AMDGPU::sub2_sub3);
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const MCInstrDesc &SMovB64 = TII->get(AMDGPU::S_MOV_B64);
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BuildMI(MBB, I, DL, SMovB64, Rsrc01)
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.addReg(Lo, RegState::Kill);
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BuildMI(MBB, I, DL, SMovB64, Rsrc23)
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.addReg(Hi, RegState::Kill);
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} else {
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unsigned Rsrc0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0);
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unsigned Rsrc1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1);
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unsigned Rsrc2 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub2);
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unsigned Rsrc3 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub3);
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// Use relocations to get the pointer, and setup the other bits manually.
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uint64_t Rsrc23 = TII->getScratchRsrcWords23();
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BuildMI(MBB, I, DL, SMovB32, Rsrc0)
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.addExternalSymbol("SCRATCH_RSRC_DWORD0")
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.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
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BuildMI(MBB, I, DL, SMovB32, Rsrc1)
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.addExternalSymbol("SCRATCH_RSRC_DWORD1")
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.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
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BuildMI(MBB, I, DL, SMovB32, Rsrc2)
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.addImm(Rsrc23 & 0xffffffff)
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.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
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BuildMI(MBB, I, DL, SMovB32, Rsrc3)
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.addImm(Rsrc23 >> 32)
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.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
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}
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// Make the register selected live throughout the function.
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for (MachineBasicBlock &OtherBB : MF) {
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if (&OtherBB == &MBB)
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continue;
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OtherBB.addLiveIn(ScratchRsrcReg);
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OtherBB.addLiveIn(ScratchWaveOffsetReg);
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}
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}
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void SIFrameLowering::processFunctionBeforeFrameFinalized(
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MachineFunction &MF,
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RegScavenger *RS) const {
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MachineFrameInfo *MFI = MF.getFrameInfo();
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if (!MFI->hasStackObjects())
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return;
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bool MayNeedScavengingEmergencySlot = MFI->hasStackObjects();
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assert((RS || !MayNeedScavengingEmergencySlot) &&
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"RegScavenger required if spilling");
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if (MayNeedScavengingEmergencySlot) {
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int ScavengeFI = MFI->CreateSpillStackObject(
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AMDGPU::SGPR_32RegClass.getSize(),
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AMDGPU::SGPR_32RegClass.getAlignment());
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RS->addScavengingFrameIndex(ScavengeFI);
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}
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}
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