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//===-- SIPrepareScratchRegs.cpp - Use predicates for control flow --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file
///
/// This pass loads scratch pointer and scratch offset into a register or a
/// frame index which can be used anywhere in the program. These values will
/// be used for spilling VGPRs.
///
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "AMDGPUSubtarget.h"
#include "SIDefines.h"
#include "SIInstrInfo.h"
#include "SIMachineFunctionInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/LLVMContext.h"
using namespace llvm;
namespace {
class SIPrepareScratchRegs : public MachineFunctionPass {
private:
static char ID;
public:
SIPrepareScratchRegs() : MachineFunctionPass(ID) { }
bool runOnMachineFunction(MachineFunction &MF) override;
const char *getPassName() const override {
return "SI prepare scratch registers";
}
};
} // End anonymous namespace
char SIPrepareScratchRegs::ID = 0;
FunctionPass *llvm::createSIPrepareScratchRegs() {
return new SIPrepareScratchRegs();
}
bool SIPrepareScratchRegs::runOnMachineFunction(MachineFunction &MF) {
SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
const SIInstrInfo *TII =
static_cast<const SIInstrInfo *>(MF.getSubtarget().getInstrInfo());
const SIRegisterInfo *TRI = &TII->getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
MachineFrameInfo *FrameInfo = MF.getFrameInfo();
MachineBasicBlock *Entry = MF.begin();
MachineBasicBlock::iterator I = Entry->begin();
DebugLoc DL = I->getDebugLoc();
// FIXME: If we don't have enough VGPRs for SGPR spilling we will need to
// run this pass.
if (!MFI->hasSpilledVGPRs())
return false;
unsigned ScratchPtrPreloadReg =
TRI->getPreloadedValue(MF, SIRegisterInfo::SCRATCH_PTR);
unsigned ScratchOffsetPreloadReg =
TRI->getPreloadedValue(MF, SIRegisterInfo::SCRATCH_WAVE_OFFSET);
if (!Entry->isLiveIn(ScratchPtrPreloadReg))
Entry->addLiveIn(ScratchPtrPreloadReg);
if (!Entry->isLiveIn(ScratchOffsetPreloadReg))
Entry->addLiveIn(ScratchOffsetPreloadReg);
// Load the scratch offset.
unsigned ScratchOffsetReg =
TRI->findUnusedRegister(MRI, &AMDGPU::SGPR_32RegClass);
int ScratchOffsetFI = -1;
if (ScratchOffsetReg != AMDGPU::NoRegister) {
// Found an SGPR to use
MRI.setPhysRegUsed(ScratchOffsetReg);
BuildMI(*Entry, I, DL, TII->get(AMDGPU::S_MOV_B32), ScratchOffsetReg)
.addReg(ScratchOffsetPreloadReg);
} else {
// No SGPR is available, we must spill.
ScratchOffsetFI = FrameInfo->CreateSpillStackObject(4,4);
BuildMI(*Entry, I, DL, TII->get(AMDGPU::SI_SPILL_S32_SAVE))
.addReg(ScratchOffsetPreloadReg)
.addFrameIndex(ScratchOffsetFI)
.addReg(AMDGPU::SGPR0_SGPR1_SGPR2_SGPR3, RegState::Undef)
.addReg(AMDGPU::SGPR0, RegState::Undef);
}
// Now that we have the scratch pointer and offset values, we need to
// add them to all the SI_SPILL_V* instructions.
RegScavenger RS;
unsigned ScratchRsrcFI = FrameInfo->CreateSpillStackObject(16, 4);
RS.addScavengingFrameIndex(ScratchRsrcFI);
for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
BI != BE; ++BI) {
MachineBasicBlock &MBB = *BI;
// Add the scratch offset reg as a live-in so that the register scavenger
// doesn't re-use it.
if (!MBB.isLiveIn(ScratchOffsetReg) &&
ScratchOffsetReg != AMDGPU::NoRegister)
MBB.addLiveIn(ScratchOffsetReg);
RS.enterBasicBlock(&MBB);
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
I != E; ++I) {
MachineInstr &MI = *I;
RS.forward(I);
DebugLoc DL = MI.getDebugLoc();
if (!TII->isVGPRSpill(MI.getOpcode()))
continue;
// Scratch resource
unsigned ScratchRsrcReg =
RS.scavengeRegister(&AMDGPU::SReg_128RegClass, 0);
uint64_t Rsrc23 = TII->getScratchRsrcWords23();
unsigned Rsrc0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0);
unsigned Rsrc1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1);
unsigned Rsrc2 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub2);
unsigned Rsrc3 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub3);
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), Rsrc0)
.addExternalSymbol("SCRATCH_RSRC_DWORD0")
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), Rsrc1)
.addExternalSymbol("SCRATCH_RSRC_DWORD1")
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), Rsrc2)
.addImm(Rsrc23 & 0xffffffff)
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), Rsrc3)
.addImm(Rsrc23 >> 32)
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
// Scratch Offset
if (ScratchOffsetReg == AMDGPU::NoRegister) {
ScratchOffsetReg = RS.scavengeRegister(&AMDGPU::SGPR_32RegClass, 0);
BuildMI(MBB, I, DL, TII->get(AMDGPU::SI_SPILL_S32_RESTORE),
ScratchOffsetReg)
.addFrameIndex(ScratchOffsetFI)
.addReg(AMDGPU::SGPR0_SGPR1_SGPR2_SGPR3, RegState::Undef)
.addReg(AMDGPU::SGPR0, RegState::Undef);
} else if (!MBB.isLiveIn(ScratchOffsetReg)) {
MBB.addLiveIn(ScratchOffsetReg);
}
if (ScratchRsrcReg == AMDGPU::NoRegister ||
ScratchOffsetReg == AMDGPU::NoRegister) {
LLVMContext &Ctx = MF.getFunction()->getContext();
Ctx.emitError("ran out of SGPRs for spilling VGPRs");
ScratchRsrcReg = AMDGPU::SGPR0;
ScratchOffsetReg = AMDGPU::SGPR0;
}
MI.getOperand(2).setReg(ScratchRsrcReg);
MI.getOperand(2).setIsKill(true);
MI.getOperand(2).setIsUndef(false);
MI.getOperand(3).setReg(ScratchOffsetReg);
MI.getOperand(3).setIsUndef(false);
MI.getOperand(3).setIsKill(false);
MI.addOperand(MachineOperand::CreateReg(Rsrc0, false, true, true));
MI.addOperand(MachineOperand::CreateReg(Rsrc1, false, true, true));
MI.addOperand(MachineOperand::CreateReg(Rsrc2, false, true, true));
MI.addOperand(MachineOperand::CreateReg(Rsrc3, false, true, true));
}
}
return true;
}
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