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llvm-project/llvm/lib/Target/BPF/BPFISelLowering.cpp

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//===-- BPFISelLowering.cpp - BPF DAG Lowering Implementation ------------===//
//
// 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 defines the interfaces that BPF uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//
#include "BPFISelLowering.h"
#include "BPF.h"
#include "BPFSubtarget.h"
#include "BPFTargetMachine.h"
#include "llvm/CodeGen/CallingConvLower.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/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "bpf-lower"
static cl::opt<bool> BPFExpandMemcpyInOrder("bpf-expand-memcpy-in-order",
cl::Hidden, cl::init(false),
cl::desc("Expand memcpy into load/store pairs in order"));
static void fail(const SDLoc &DL, SelectionDAG &DAG, const Twine &Msg) {
MachineFunction &MF = DAG.getMachineFunction();
DAG.getContext()->diagnose(
DiagnosticInfoUnsupported(MF.getFunction(), Msg, DL.getDebugLoc()));
}
static void fail(const SDLoc &DL, SelectionDAG &DAG, const char *Msg,
SDValue Val) {
MachineFunction &MF = DAG.getMachineFunction();
std::string Str;
raw_string_ostream OS(Str);
OS << Msg;
Val->print(OS);
OS.flush();
DAG.getContext()->diagnose(
DiagnosticInfoUnsupported(MF.getFunction(), Str, DL.getDebugLoc()));
}
BPFTargetLowering::BPFTargetLowering(const TargetMachine &TM,
const BPFSubtarget &STI)
: TargetLowering(TM) {
// Set up the register classes.
addRegisterClass(MVT::i64, &BPF::GPRRegClass);
if (STI.getHasAlu32())
addRegisterClass(MVT::i32, &BPF::GPR32RegClass);
// Compute derived properties from the register classes
computeRegisterProperties(STI.getRegisterInfo());
setStackPointerRegisterToSaveRestore(BPF::R11);
setOperationAction(ISD::BR_CC, MVT::i64, Custom);
setOperationAction(ISD::BR_JT, MVT::Other, Expand);
setOperationAction(ISD::BRIND, MVT::Other, Expand);
setOperationAction(ISD::BRCOND, MVT::Other, Expand);
setOperationAction(ISD::GlobalAddress, MVT::i64, Custom);
setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i64, Custom);
setOperationAction(ISD::STACKSAVE, MVT::Other, Expand);
setOperationAction(ISD::STACKRESTORE, MVT::Other, Expand);
for (auto VT : { MVT::i32, MVT::i64 }) {
if (VT == MVT::i32 && !STI.getHasAlu32())
continue;
setOperationAction(ISD::SDIVREM, VT, Expand);
setOperationAction(ISD::UDIVREM, VT, Expand);
setOperationAction(ISD::SREM, VT, Expand);
setOperationAction(ISD::UREM, VT, Expand);
setOperationAction(ISD::MULHU, VT, Expand);
setOperationAction(ISD::MULHS, VT, Expand);
setOperationAction(ISD::UMUL_LOHI, VT, Expand);
setOperationAction(ISD::SMUL_LOHI, VT, Expand);
setOperationAction(ISD::ROTR, VT, Expand);
setOperationAction(ISD::ROTL, VT, Expand);
setOperationAction(ISD::SHL_PARTS, VT, Expand);
setOperationAction(ISD::SRL_PARTS, VT, Expand);
setOperationAction(ISD::SRA_PARTS, VT, Expand);
setOperationAction(ISD::CTPOP, VT, Expand);
setOperationAction(ISD::SETCC, VT, Expand);
setOperationAction(ISD::SELECT, VT, Expand);
setOperationAction(ISD::SELECT_CC, VT, Custom);
}
if (STI.getHasAlu32()) {
setOperationAction(ISD::BSWAP, MVT::i32, Promote);
setOperationAction(ISD::BR_CC, MVT::i32,
STI.getHasJmp32() ? Custom : Promote);
}
setOperationAction(ISD::CTTZ, MVT::i64, Custom);
setOperationAction(ISD::CTLZ, MVT::i64, Custom);
setOperationAction(ISD::CTTZ_ZERO_UNDEF, MVT::i64, Custom);
setOperationAction(ISD::CTLZ_ZERO_UNDEF, MVT::i64, Custom);
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i8, Expand);
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i16, Expand);
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i32, Expand);
// Extended load operations for i1 types must be promoted
for (MVT VT : MVT::integer_valuetypes()) {
setLoadExtAction(ISD::EXTLOAD, VT, MVT::i1, Promote);
setLoadExtAction(ISD::ZEXTLOAD, VT, MVT::i1, Promote);
setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i1, Promote);
setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i8, Expand);
setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i16, Expand);
setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i32, Expand);
}
setBooleanContents(ZeroOrOneBooleanContent);
// Function alignments
setMinFunctionAlignment(llvm::Align(8));
setPrefFunctionAlignment(llvm::Align(8));
if (BPFExpandMemcpyInOrder) {
// LLVM generic code will try to expand memcpy into load/store pairs at this
// stage which is before quite a few IR optimization passes, therefore the
// loads and stores could potentially be moved apart from each other which
// will cause trouble to memcpy pattern matcher inside kernel eBPF JIT
// compilers.
//
// When -bpf-expand-memcpy-in-order specified, we want to defer the expand
// of memcpy to later stage in IR optimization pipeline so those load/store
// pairs won't be touched and could be kept in order. Hence, we set
// MaxStoresPerMem* to zero to disable the generic getMemcpyLoadsAndStores
// code path, and ask LLVM to use target expander EmitTargetCodeForMemcpy.
MaxStoresPerMemset = MaxStoresPerMemsetOptSize = 0;
MaxStoresPerMemcpy = MaxStoresPerMemcpyOptSize = 0;
MaxStoresPerMemmove = MaxStoresPerMemmoveOptSize = 0;
} else {
// inline memcpy() for kernel to see explicit copy
unsigned CommonMaxStores =
STI.getSelectionDAGInfo()->getCommonMaxStoresPerMemFunc();
MaxStoresPerMemset = MaxStoresPerMemsetOptSize = CommonMaxStores;
MaxStoresPerMemcpy = MaxStoresPerMemcpyOptSize = CommonMaxStores;
MaxStoresPerMemmove = MaxStoresPerMemmoveOptSize = CommonMaxStores;
}
// CPU/Feature control
HasAlu32 = STI.getHasAlu32();
HasJmp32 = STI.getHasJmp32();
HasJmpExt = STI.getHasJmpExt();
}
bool BPFTargetLowering::isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const {
return false;
}
std::pair<unsigned, const TargetRegisterClass *>
BPFTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
StringRef Constraint,
MVT VT) const {
if (Constraint.size() == 1)
// GCC Constraint Letters
switch (Constraint[0]) {
case 'r': // GENERAL_REGS
return std::make_pair(0U, &BPF::GPRRegClass);
default:
break;
}
return TargetLowering::getRegForInlineAsmConstraint(TRI, Constraint, VT);
}
SDValue BPFTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
switch (Op.getOpcode()) {
case ISD::BR_CC:
return LowerBR_CC(Op, DAG);
case ISD::GlobalAddress:
return LowerGlobalAddress(Op, DAG);
case ISD::SELECT_CC:
return LowerSELECT_CC(Op, DAG);
default:
llvm_unreachable("unimplemented operand");
}
}
// Calling Convention Implementation
#include "BPFGenCallingConv.inc"
SDValue BPFTargetLowering::LowerFormalArguments(
SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &DL,
SelectionDAG &DAG, SmallVectorImpl<SDValue> &InVals) const {
switch (CallConv) {
default:
report_fatal_error("Unsupported calling convention");
case CallingConv::C:
case CallingConv::Fast:
break;
}
MachineFunction &MF = DAG.getMachineFunction();
MachineRegisterInfo &RegInfo = MF.getRegInfo();
// Assign locations to all of the incoming arguments.
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(CallConv, IsVarArg, MF, ArgLocs, *DAG.getContext());
CCInfo.AnalyzeFormalArguments(Ins, getHasAlu32() ? CC_BPF32 : CC_BPF64);
for (auto &VA : ArgLocs) {
if (VA.isRegLoc()) {
// Arguments passed in registers
EVT RegVT = VA.getLocVT();
MVT::SimpleValueType SimpleTy = RegVT.getSimpleVT().SimpleTy;
switch (SimpleTy) {
default: {
errs() << "LowerFormalArguments Unhandled argument type: "
<< RegVT.getEVTString() << '\n';
llvm_unreachable(0);
}
case MVT::i32:
case MVT::i64:
Register VReg = RegInfo.createVirtualRegister(
SimpleTy == MVT::i64 ? &BPF::GPRRegClass : &BPF::GPR32RegClass);
RegInfo.addLiveIn(VA.getLocReg(), VReg);
SDValue ArgValue = DAG.getCopyFromReg(Chain, DL, VReg, RegVT);
// If this is an value that has been promoted to wider types, insert an
// assert[sz]ext to capture this, then truncate to the right size.
if (VA.getLocInfo() == CCValAssign::SExt)
ArgValue = DAG.getNode(ISD::AssertSext, DL, RegVT, ArgValue,
DAG.getValueType(VA.getValVT()));
else if (VA.getLocInfo() == CCValAssign::ZExt)
ArgValue = DAG.getNode(ISD::AssertZext, DL, RegVT, ArgValue,
DAG.getValueType(VA.getValVT()));
if (VA.getLocInfo() != CCValAssign::Full)
ArgValue = DAG.getNode(ISD::TRUNCATE, DL, VA.getValVT(), ArgValue);
InVals.push_back(ArgValue);
break;
}
} else {
fail(DL, DAG, "defined with too many args");
InVals.push_back(DAG.getConstant(0, DL, VA.getLocVT()));
}
}
if (IsVarArg || MF.getFunction().hasStructRetAttr()) {
fail(DL, DAG, "functions with VarArgs or StructRet are not supported");
}
return Chain;
}
const unsigned BPFTargetLowering::MaxArgs = 5;
SDValue BPFTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
SmallVectorImpl<SDValue> &InVals) const {
SelectionDAG &DAG = CLI.DAG;
auto &Outs = CLI.Outs;
auto &OutVals = CLI.OutVals;
auto &Ins = CLI.Ins;
SDValue Chain = CLI.Chain;
SDValue Callee = CLI.Callee;
bool &IsTailCall = CLI.IsTailCall;
CallingConv::ID CallConv = CLI.CallConv;
bool IsVarArg = CLI.IsVarArg;
MachineFunction &MF = DAG.getMachineFunction();
// BPF target does not support tail call optimization.
IsTailCall = false;
switch (CallConv) {
default:
report_fatal_error("Unsupported calling convention");
case CallingConv::Fast:
case CallingConv::C:
break;
}
// Analyze operands of the call, assigning locations to each operand.
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(CallConv, IsVarArg, MF, ArgLocs, *DAG.getContext());
CCInfo.AnalyzeCallOperands(Outs, getHasAlu32() ? CC_BPF32 : CC_BPF64);
unsigned NumBytes = CCInfo.getNextStackOffset();
if (Outs.size() > MaxArgs)
fail(CLI.DL, DAG, "too many args to ", Callee);
for (auto &Arg : Outs) {
ISD::ArgFlagsTy Flags = Arg.Flags;
if (!Flags.isByVal())
continue;
fail(CLI.DL, DAG, "pass by value not supported ", Callee);
}
auto PtrVT = getPointerTy(MF.getDataLayout());
Chain = DAG.getCALLSEQ_START(Chain, NumBytes, 0, CLI.DL);
SmallVector<std::pair<unsigned, SDValue>, MaxArgs> RegsToPass;
// Walk arg assignments
for (unsigned i = 0,
e = std::min(static_cast<unsigned>(ArgLocs.size()), MaxArgs);
i != e; ++i) {
CCValAssign &VA = ArgLocs[i];
SDValue Arg = OutVals[i];
// Promote the value if needed.
switch (VA.getLocInfo()) {
default:
llvm_unreachable("Unknown loc info");
case CCValAssign::Full:
break;
case CCValAssign::SExt:
Arg = DAG.getNode(ISD::SIGN_EXTEND, CLI.DL, VA.getLocVT(), Arg);
break;
case CCValAssign::ZExt:
Arg = DAG.getNode(ISD::ZERO_EXTEND, CLI.DL, VA.getLocVT(), Arg);
break;
case CCValAssign::AExt:
Arg = DAG.getNode(ISD::ANY_EXTEND, CLI.DL, VA.getLocVT(), Arg);
break;
}
// Push arguments into RegsToPass vector
if (VA.isRegLoc())
RegsToPass.push_back(std::make_pair(VA.getLocReg(), Arg));
else
llvm_unreachable("call arg pass bug");
}
SDValue InFlag;
// Build a sequence of copy-to-reg nodes chained together with token chain and
// flag operands which copy the outgoing args into registers. The InFlag in
// necessary since all emitted instructions must be stuck together.
for (auto &Reg : RegsToPass) {
Chain = DAG.getCopyToReg(Chain, CLI.DL, Reg.first, Reg.second, InFlag);
InFlag = Chain.getValue(1);
}
// If the callee is a GlobalAddress node (quite common, every direct call is)
// turn it into a TargetGlobalAddress node so that legalize doesn't hack it.
// Likewise ExternalSymbol -> TargetExternalSymbol.
if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
Callee = DAG.getTargetGlobalAddress(G->getGlobal(), CLI.DL, PtrVT,
G->getOffset(), 0);
} else if (ExternalSymbolSDNode *E = dyn_cast<ExternalSymbolSDNode>(Callee)) {
Callee = DAG.getTargetExternalSymbol(E->getSymbol(), PtrVT, 0);
fail(CLI.DL, DAG, Twine("A call to built-in function '"
+ StringRef(E->getSymbol())
+ "' is not supported."));
}
// Returns a chain & a flag for retval copy to use.
SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
SmallVector<SDValue, 8> Ops;
Ops.push_back(Chain);
Ops.push_back(Callee);
// Add argument registers to the end of the list so that they are
// known live into the call.
for (auto &Reg : RegsToPass)
Ops.push_back(DAG.getRegister(Reg.first, Reg.second.getValueType()));
if (InFlag.getNode())
Ops.push_back(InFlag);
Chain = DAG.getNode(BPFISD::CALL, CLI.DL, NodeTys, Ops);
InFlag = Chain.getValue(1);
// Create the CALLSEQ_END node.
Chain = DAG.getCALLSEQ_END(
Chain, DAG.getConstant(NumBytes, CLI.DL, PtrVT, true),
DAG.getConstant(0, CLI.DL, PtrVT, true), InFlag, CLI.DL);
InFlag = Chain.getValue(1);
// Handle result values, copying them out of physregs into vregs that we
// return.
return LowerCallResult(Chain, InFlag, CallConv, IsVarArg, Ins, CLI.DL, DAG,
InVals);
}
SDValue
BPFTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
bool IsVarArg,
const SmallVectorImpl<ISD::OutputArg> &Outs,
const SmallVectorImpl<SDValue> &OutVals,
const SDLoc &DL, SelectionDAG &DAG) const {
unsigned Opc = BPFISD::RET_FLAG;
// CCValAssign - represent the assignment of the return value to a location
SmallVector<CCValAssign, 16> RVLocs;
MachineFunction &MF = DAG.getMachineFunction();
// CCState - Info about the registers and stack slot.
CCState CCInfo(CallConv, IsVarArg, MF, RVLocs, *DAG.getContext());
if (MF.getFunction().getReturnType()->isAggregateType()) {
fail(DL, DAG, "only integer returns supported");
return DAG.getNode(Opc, DL, MVT::Other, Chain);
}
// Analize return values.
CCInfo.AnalyzeReturn(Outs, getHasAlu32() ? RetCC_BPF32 : RetCC_BPF64);
SDValue Flag;
SmallVector<SDValue, 4> RetOps(1, Chain);
// Copy the result values into the output registers.
for (unsigned i = 0; i != RVLocs.size(); ++i) {
CCValAssign &VA = RVLocs[i];
assert(VA.isRegLoc() && "Can only return in registers!");
Chain = DAG.getCopyToReg(Chain, DL, VA.getLocReg(), OutVals[i], Flag);
// Guarantee that all emitted copies are stuck together,
// avoiding something bad.
Flag = Chain.getValue(1);
RetOps.push_back(DAG.getRegister(VA.getLocReg(), VA.getLocVT()));
}
RetOps[0] = Chain; // Update chain.
// Add the flag if we have it.
if (Flag.getNode())
RetOps.push_back(Flag);
return DAG.getNode(Opc, DL, MVT::Other, RetOps);
}
SDValue BPFTargetLowering::LowerCallResult(
SDValue Chain, SDValue InFlag, CallingConv::ID CallConv, bool IsVarArg,
const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &DL,
SelectionDAG &DAG, SmallVectorImpl<SDValue> &InVals) const {
MachineFunction &MF = DAG.getMachineFunction();
// Assign locations to each value returned by this call.
SmallVector<CCValAssign, 16> RVLocs;
CCState CCInfo(CallConv, IsVarArg, MF, RVLocs, *DAG.getContext());
if (Ins.size() >= 2) {
fail(DL, DAG, "only small returns supported");
for (unsigned i = 0, e = Ins.size(); i != e; ++i)
InVals.push_back(DAG.getConstant(0, DL, Ins[i].VT));
return DAG.getCopyFromReg(Chain, DL, 1, Ins[0].VT, InFlag).getValue(1);
}
CCInfo.AnalyzeCallResult(Ins, getHasAlu32() ? RetCC_BPF32 : RetCC_BPF64);
// Copy all of the result registers out of their specified physreg.
for (auto &Val : RVLocs) {
Chain = DAG.getCopyFromReg(Chain, DL, Val.getLocReg(),
Val.getValVT(), InFlag).getValue(1);
InFlag = Chain.getValue(2);
InVals.push_back(Chain.getValue(0));
}
return Chain;
}
static void NegateCC(SDValue &LHS, SDValue &RHS, ISD::CondCode &CC) {
switch (CC) {
default:
break;
case ISD::SETULT:
case ISD::SETULE:
case ISD::SETLT:
case ISD::SETLE:
CC = ISD::getSetCCSwappedOperands(CC);
std::swap(LHS, RHS);
break;
}
}
SDValue BPFTargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
SDValue Chain = Op.getOperand(0);
ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(1))->get();
SDValue LHS = Op.getOperand(2);
SDValue RHS = Op.getOperand(3);
SDValue Dest = Op.getOperand(4);
SDLoc DL(Op);
if (!getHasJmpExt())
NegateCC(LHS, RHS, CC);
return DAG.getNode(BPFISD::BR_CC, DL, Op.getValueType(), Chain, LHS, RHS,
DAG.getConstant(CC, DL, LHS.getValueType()), Dest);
}
SDValue BPFTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
SDValue LHS = Op.getOperand(0);
SDValue RHS = Op.getOperand(1);
SDValue TrueV = Op.getOperand(2);
SDValue FalseV = Op.getOperand(3);
ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(4))->get();
SDLoc DL(Op);
if (!getHasJmpExt())
NegateCC(LHS, RHS, CC);
SDValue TargetCC = DAG.getConstant(CC, DL, LHS.getValueType());
SDVTList VTs = DAG.getVTList(Op.getValueType(), MVT::Glue);
SDValue Ops[] = {LHS, RHS, TargetCC, TrueV, FalseV};
return DAG.getNode(BPFISD::SELECT_CC, DL, VTs, Ops);
}
const char *BPFTargetLowering::getTargetNodeName(unsigned Opcode) const {
switch ((BPFISD::NodeType)Opcode) {
case BPFISD::FIRST_NUMBER:
break;
case BPFISD::RET_FLAG:
return "BPFISD::RET_FLAG";
case BPFISD::CALL:
return "BPFISD::CALL";
case BPFISD::SELECT_CC:
return "BPFISD::SELECT_CC";
case BPFISD::BR_CC:
return "BPFISD::BR_CC";
case BPFISD::Wrapper:
return "BPFISD::Wrapper";
case BPFISD::MEMCPY:
return "BPFISD::MEMCPY";
}
return nullptr;
}
SDValue BPFTargetLowering::LowerGlobalAddress(SDValue Op,
SelectionDAG &DAG) const {
auto N = cast<GlobalAddressSDNode>(Op);
assert(N->getOffset() == 0 && "Invalid offset for global address");
SDLoc DL(Op);
const GlobalValue *GV = N->getGlobal();
SDValue GA = DAG.getTargetGlobalAddress(GV, DL, MVT::i64);
return DAG.getNode(BPFISD::Wrapper, DL, MVT::i64, GA);
}
unsigned
BPFTargetLowering::EmitSubregExt(MachineInstr &MI, MachineBasicBlock *BB,
unsigned Reg, bool isSigned) const {
const TargetInstrInfo &TII = *BB->getParent()->getSubtarget().getInstrInfo();
const TargetRegisterClass *RC = getRegClassFor(MVT::i64);
int RShiftOp = isSigned ? BPF::SRA_ri : BPF::SRL_ri;
MachineFunction *F = BB->getParent();
DebugLoc DL = MI.getDebugLoc();
MachineRegisterInfo &RegInfo = F->getRegInfo();
Register PromotedReg0 = RegInfo.createVirtualRegister(RC);
Register PromotedReg1 = RegInfo.createVirtualRegister(RC);
Register PromotedReg2 = RegInfo.createVirtualRegister(RC);
BuildMI(BB, DL, TII.get(BPF::MOV_32_64), PromotedReg0).addReg(Reg);
BuildMI(BB, DL, TII.get(BPF::SLL_ri), PromotedReg1)
.addReg(PromotedReg0).addImm(32);
BuildMI(BB, DL, TII.get(RShiftOp), PromotedReg2)
.addReg(PromotedReg1).addImm(32);
return PromotedReg2;
}
MachineBasicBlock *
BPFTargetLowering::EmitInstrWithCustomInserterMemcpy(MachineInstr &MI,
MachineBasicBlock *BB)
const {
MachineFunction *MF = MI.getParent()->getParent();
MachineRegisterInfo &MRI = MF->getRegInfo();
MachineInstrBuilder MIB(*MF, MI);
unsigned ScratchReg;
// This function does custom insertion during lowering BPFISD::MEMCPY which
// only has two register operands from memcpy semantics, the copy source
// address and the copy destination address.
//
// Because we will expand BPFISD::MEMCPY into load/store pairs, we will need
// a third scratch register to serve as the destination register of load and
// source register of store.
//
// The scratch register here is with the Define | Dead | EarlyClobber flags.
// The EarlyClobber flag has the semantic property that the operand it is
// attached to is clobbered before the rest of the inputs are read. Hence it
// must be unique among the operands to the instruction. The Define flag is
// needed to coerce the machine verifier that an Undef value isn't a problem
// as we anyway is loading memory into it. The Dead flag is needed as the
// value in scratch isn't supposed to be used by any other instruction.
ScratchReg = MRI.createVirtualRegister(&BPF::GPRRegClass);
MIB.addReg(ScratchReg,
RegState::Define | RegState::Dead | RegState::EarlyClobber);
return BB;
}
MachineBasicBlock *
BPFTargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
MachineBasicBlock *BB) const {
const TargetInstrInfo &TII = *BB->getParent()->getSubtarget().getInstrInfo();
DebugLoc DL = MI.getDebugLoc();
unsigned Opc = MI.getOpcode();
bool isSelectRROp = (Opc == BPF::Select ||
Opc == BPF::Select_64_32 ||
Opc == BPF::Select_32 ||
Opc == BPF::Select_32_64);
bool isMemcpyOp = Opc == BPF::MEMCPY;
#ifndef NDEBUG
bool isSelectRIOp = (Opc == BPF::Select_Ri ||
Opc == BPF::Select_Ri_64_32 ||
Opc == BPF::Select_Ri_32 ||
Opc == BPF::Select_Ri_32_64);
assert((isSelectRROp || isSelectRIOp || isMemcpyOp) &&
"Unexpected instr type to insert");
#endif
if (isMemcpyOp)
return EmitInstrWithCustomInserterMemcpy(MI, BB);
bool is32BitCmp = (Opc == BPF::Select_32 ||
Opc == BPF::Select_32_64 ||
Opc == BPF::Select_Ri_32 ||
Opc == BPF::Select_Ri_32_64);
// To "insert" a SELECT instruction, we actually have to insert the diamond
// control-flow pattern. The incoming instruction knows the destination vreg
// to set, the condition code register to branch on, the true/false values to
// select between, and a branch opcode to use.
const BasicBlock *LLVM_BB = BB->getBasicBlock();
MachineFunction::iterator I = ++BB->getIterator();
// ThisMBB:
// ...
// TrueVal = ...
// jmp_XX r1, r2 goto Copy1MBB
// fallthrough --> Copy0MBB
MachineBasicBlock *ThisMBB = BB;
MachineFunction *F = BB->getParent();
MachineBasicBlock *Copy0MBB = F->CreateMachineBasicBlock(LLVM_BB);
MachineBasicBlock *Copy1MBB = F->CreateMachineBasicBlock(LLVM_BB);
F->insert(I, Copy0MBB);
F->insert(I, Copy1MBB);
// Update machine-CFG edges by transferring all successors of the current
// block to the new block which will contain the Phi node for the select.
Copy1MBB->splice(Copy1MBB->begin(), BB,
std::next(MachineBasicBlock::iterator(MI)), BB->end());
Copy1MBB->transferSuccessorsAndUpdatePHIs(BB);
// Next, add the true and fallthrough blocks as its successors.
BB->addSuccessor(Copy0MBB);
BB->addSuccessor(Copy1MBB);
// Insert Branch if Flag
int CC = MI.getOperand(3).getImm();
int NewCC;
switch (CC) {
#define SET_NEWCC(X, Y) \
case ISD::X: \
if (is32BitCmp && HasJmp32) \
NewCC = isSelectRROp ? BPF::Y##_rr_32 : BPF::Y##_ri_32; \
else \
NewCC = isSelectRROp ? BPF::Y##_rr : BPF::Y##_ri; \
break
SET_NEWCC(SETGT, JSGT);
SET_NEWCC(SETUGT, JUGT);
SET_NEWCC(SETGE, JSGE);
SET_NEWCC(SETUGE, JUGE);
SET_NEWCC(SETEQ, JEQ);
SET_NEWCC(SETNE, JNE);
SET_NEWCC(SETLT, JSLT);
SET_NEWCC(SETULT, JULT);
SET_NEWCC(SETLE, JSLE);
SET_NEWCC(SETULE, JULE);
default:
report_fatal_error("unimplemented select CondCode " + Twine(CC));
}
Register LHS = MI.getOperand(1).getReg();
bool isSignedCmp = (CC == ISD::SETGT ||
CC == ISD::SETGE ||
CC == ISD::SETLT ||
CC == ISD::SETLE);
// eBPF at the moment only has 64-bit comparison. Any 32-bit comparison need
// to be promoted, however if the 32-bit comparison operands are destination
// registers then they are implicitly zero-extended already, there is no
// need of explicit zero-extend sequence for them.
//
// We simply do extension for all situations in this method, but we will
// try to remove those unnecessary in BPFMIPeephole pass.
if (is32BitCmp && !HasJmp32)
LHS = EmitSubregExt(MI, BB, LHS, isSignedCmp);
if (isSelectRROp) {
Register RHS = MI.getOperand(2).getReg();
if (is32BitCmp && !HasJmp32)
RHS = EmitSubregExt(MI, BB, RHS, isSignedCmp);
BuildMI(BB, DL, TII.get(NewCC)).addReg(LHS).addReg(RHS).addMBB(Copy1MBB);
} else {
int64_t imm32 = MI.getOperand(2).getImm();
// sanity check before we build J*_ri instruction.
assert (isInt<32>(imm32));
BuildMI(BB, DL, TII.get(NewCC))
.addReg(LHS).addImm(imm32).addMBB(Copy1MBB);
}
// Copy0MBB:
// %FalseValue = ...
// # fallthrough to Copy1MBB
BB = Copy0MBB;
// Update machine-CFG edges
BB->addSuccessor(Copy1MBB);
// Copy1MBB:
// %Result = phi [ %FalseValue, Copy0MBB ], [ %TrueValue, ThisMBB ]
// ...
BB = Copy1MBB;
BuildMI(*BB, BB->begin(), DL, TII.get(BPF::PHI), MI.getOperand(0).getReg())
.addReg(MI.getOperand(5).getReg())
.addMBB(Copy0MBB)
.addReg(MI.getOperand(4).getReg())
.addMBB(ThisMBB);
MI.eraseFromParent(); // The pseudo instruction is gone now.
return BB;
}
EVT BPFTargetLowering::getSetCCResultType(const DataLayout &, LLVMContext &,
EVT VT) const {
return getHasAlu32() ? MVT::i32 : MVT::i64;
}
MVT BPFTargetLowering::getScalarShiftAmountTy(const DataLayout &DL,
EVT VT) const {
return (getHasAlu32() && VT == MVT::i32) ? MVT::i32 : MVT::i64;
}
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