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//===-- BPFISelDAGToDAG.cpp - A dag to dag inst selector for BPF ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a DAG pattern matching instruction selector for BPF,
// converting from a legalized dag to a BPF dag.
//
//===----------------------------------------------------------------------===//
#include "BPF.h"
#include "BPFRegisterInfo.h"
#include "BPFSubtarget.h"
#include "BPFTargetMachine.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
#define DEBUG_TYPE "bpf-isel"
// Instruction Selector Implementation
namespace {
class BPFDAGToDAGISel : public SelectionDAGISel {
public:
explicit BPFDAGToDAGISel(BPFTargetMachine &TM) : SelectionDAGISel(TM) {}
const char *getPassName() const override {
return "BPF DAG->DAG Pattern Instruction Selection";
}
private:
// Include the pieces autogenerated from the target description.
#include "BPFGenDAGISel.inc"
SDNode *Select(SDNode *N) override;
// Complex Pattern for address selection.
bool SelectAddr(SDValue Addr, SDValue &Base, SDValue &Offset);
};
}
// ComplexPattern used on BPF Load/Store instructions
bool BPFDAGToDAGISel::SelectAddr(SDValue Addr, SDValue &Base, SDValue &Offset) {
// if Address is FI, get the TargetFrameIndex.
if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), MVT::i64);
Offset = CurDAG->getTargetConstant(0, MVT::i64);
return true;
}
if (Addr.getOpcode() == ISD::TargetExternalSymbol ||
Addr.getOpcode() == ISD::TargetGlobalAddress)
return false;
// Addresses of the form FI+const or FI|const
if (CurDAG->isBaseWithConstantOffset(Addr)) {
ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1));
if (isInt<32>(CN->getSExtValue())) {
// If the first operand is a FI, get the TargetFI Node
if (FrameIndexSDNode *FIN =
dyn_cast<FrameIndexSDNode>(Addr.getOperand(0)))
Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), MVT::i64);
else
Base = Addr.getOperand(0);
Offset = CurDAG->getTargetConstant(CN->getSExtValue(), MVT::i64);
return true;
}
}
Base = Addr;
Offset = CurDAG->getTargetConstant(0, MVT::i64);
return true;
}
SDNode *BPFDAGToDAGISel::Select(SDNode *Node) {
unsigned Opcode = Node->getOpcode();
// Dump information about the Node being selected
DEBUG(dbgs() << "Selecting: "; Node->dump(CurDAG); dbgs() << '\n');
// If we have a custom node, we already have selected!
if (Node->isMachineOpcode()) {
DEBUG(dbgs() << "== "; Node->dump(CurDAG); dbgs() << '\n');
return NULL;
}
// tablegen selection should be handled here.
switch (Opcode) {
default: break;
case ISD::UNDEF: {
errs() << "BUG: "; Node->dump(CurDAG); errs() << '\n';
report_fatal_error("shouldn't see UNDEF during Select");
break;
}
case ISD::INTRINSIC_W_CHAIN: {
unsigned IntNo = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
switch (IntNo) {
case Intrinsic::bpf_load_byte:
case Intrinsic::bpf_load_half:
case Intrinsic::bpf_load_word: {
SDLoc DL(Node);
SDValue Chain = Node->getOperand(0);
SDValue N1 = Node->getOperand(1);
SDValue Skb = Node->getOperand(2);
SDValue N3 = Node->getOperand(3);
SDValue R6Reg = CurDAG->getRegister(BPF::R6, MVT::i64);
Chain = CurDAG->getCopyToReg(Chain, DL, R6Reg, Skb, SDValue());
Node = CurDAG->UpdateNodeOperands(Node, Chain, N1, R6Reg, N3);
break;
}
}
break;
}
case ISD::FrameIndex: {
int FI = cast<FrameIndexSDNode>(Node)->getIndex();
EVT VT = Node->getValueType(0);
SDValue TFI = CurDAG->getTargetFrameIndex(FI, VT);
unsigned Opc = BPF::MOV_rr;
if (Node->hasOneUse())
return CurDAG->SelectNodeTo(Node, Opc, VT, TFI);
return CurDAG->getMachineNode(Opc, SDLoc(Node), VT, TFI);
}
}
// Select the default instruction
SDNode *ResNode = SelectCode(Node);
DEBUG(dbgs() << "=> ";
if (ResNode == nullptr || ResNode == Node)
Node->dump(CurDAG);
else
ResNode->dump(CurDAG);
dbgs() << '\n');
return ResNode;
}
FunctionPass *llvm::createBPFISelDag(BPFTargetMachine &TM) {
return new BPFDAGToDAGISel(TM);
}
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