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//===-- BPFRegisterInfo.cpp - BPF Register Information ----------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains the BPF implementation of the TargetRegisterInfo class.
//
//===----------------------------------------------------------------------===//
#include "BPFRegisterInfo.h"
#include "BPFSubtarget.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#define GET_REGINFO_TARGET_DESC
#include "BPFGenRegisterInfo.inc"
using namespace llvm;
static cl::opt<int>
BPFStackSizeOption("bpf-stack-size",
cl::desc("Specify the BPF stack size limit"),
cl::init(512));
BPFRegisterInfo::BPFRegisterInfo()
: BPFGenRegisterInfo(BPF::R0) {}
const MCPhysReg *
BPFRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
return CSR_SaveList;
}
const uint32_t *
BPFRegisterInfo::getCallPreservedMask(const MachineFunction &MF,
CallingConv::ID CC) const {
switch (CC) {
default:
return CSR_RegMask;
case CallingConv::PreserveAll:
return CSR_PreserveAll_RegMask;
}
}
BitVector BPFRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
BitVector Reserved(getNumRegs());
markSuperRegs(Reserved, BPF::W10); // [W|R]10 is read only frame pointer
markSuperRegs(Reserved, BPF::W11); // [W|R]11 is pseudo stack pointer
return Reserved;
}
static void WarnSize(int Offset, MachineFunction &MF, DebugLoc& DL,
MachineBasicBlock& MBB) {
if (Offset <= -BPFStackSizeOption) {
if (!DL)
/* try harder to get some debug loc */
for (auto &I : MBB)
if (I.getDebugLoc()) {
DL = I.getDebugLoc();
break;
}
const Function &F = MF.getFunction();
F.getContext().diagnose(DiagnosticInfoUnsupported(
F,
"Looks like the BPF stack limit is exceeded. "
"Please move large on stack variables into BPF per-cpu array map. For "
"non-kernel uses, the stack can be increased using -mllvm "
"-bpf-stack-size.\n",
DL));
}
}
bool BPFRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
int SPAdj, unsigned FIOperandNum,
RegScavenger *RS) const {
assert(SPAdj == 0 && "Unexpected");
unsigned i = 0;
MachineInstr &MI = *II;
MachineBasicBlock &MBB = *MI.getParent();
MachineFunction &MF = *MBB.getParent();
DebugLoc DL = MI.getDebugLoc();
while (!MI.getOperand(i).isFI()) {
++i;
assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
}
Register FrameReg = getFrameRegister(MF);
int FrameIndex = MI.getOperand(i).getIndex();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
if (MI.getOpcode() == BPF::MOV_rr) {
int Offset = MF.getFrameInfo().getObjectOffset(FrameIndex);
WarnSize(Offset, MF, DL, MBB);
MI.getOperand(i).ChangeToRegister(FrameReg, false);
Register reg = MI.getOperand(i - 1).getReg();
BuildMI(MBB, ++II, DL, TII.get(BPF::ADD_ri), reg)
.addReg(reg)
.addImm(Offset);
return false;
}
int Offset = MF.getFrameInfo().getObjectOffset(FrameIndex) +
MI.getOperand(i + 1).getImm();
if (!isInt<32>(Offset))
llvm_unreachable("bug in frame offset");
WarnSize(Offset, MF, DL, MBB);
if (MI.getOpcode() == BPF::FI_ri) {
// architecture does not really support FI_ri, replace it with
// MOV_rr <target_reg>, frame_reg
// ADD_ri <target_reg>, imm
Register reg = MI.getOperand(i - 1).getReg();
BuildMI(MBB, ++II, DL, TII.get(BPF::MOV_rr), reg)
.addReg(FrameReg);
BuildMI(MBB, II, DL, TII.get(BPF::ADD_ri), reg)
.addReg(reg)
.addImm(Offset);
// Remove FI_ri instruction
MI.eraseFromParent();
} else {
MI.getOperand(i).ChangeToRegister(FrameReg, false);
MI.getOperand(i + 1).ChangeToImmediate(Offset);
}
return false;
}
Register BPFRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
return BPF::R10;
}
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