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llvm-6502/lib/Target/Mips/MipsISelDAGToDAG.cpp
Akira Hatanaka 7065b7b203 This patch eliminates redundant instructions that produce 0. 
For example, the first instruction in the code below can be eliminated if the
use of $vr0 is replaced with $zero: 

addiu $vr0, $zero, 0
add $vr2, $vr1, $vr0

add $vr2, $vr1, $zero



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152280 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-08 01:51:59 +00:00

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//===-- MipsISelDAGToDAG.cpp - A Dag to Dag Inst Selector for Mips --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines an instruction selector for the MIPS target.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "mips-isel"
#include "Mips.h"
#include "MipsAnalyzeImmediate.h"
#include "MipsMachineFunction.h"
#include "MipsRegisterInfo.h"
#include "MipsSubtarget.h"
#include "MipsTargetMachine.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "llvm/GlobalValue.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/Support/CFG.h"
#include "llvm/Type.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
//===----------------------------------------------------------------------===//
// Instruction Selector Implementation
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
// MipsDAGToDAGISel - MIPS specific code to select MIPS machine
// instructions for SelectionDAG operations.
//===----------------------------------------------------------------------===//
namespace {
class MipsDAGToDAGISel : public SelectionDAGISel {
/// TM - Keep a reference to MipsTargetMachine.
MipsTargetMachine &TM;
/// Subtarget - Keep a pointer to the MipsSubtarget around so that we can
/// make the right decision when generating code for different targets.
const MipsSubtarget &Subtarget;
public:
explicit MipsDAGToDAGISel(MipsTargetMachine &tm) :
SelectionDAGISel(tm),
TM(tm), Subtarget(tm.getSubtarget<MipsSubtarget>()) {}
// Pass Name
virtual const char *getPassName() const {
return "MIPS DAG->DAG Pattern Instruction Selection";
}
virtual bool runOnMachineFunction(MachineFunction &MF);
private:
// Include the pieces autogenerated from the target description.
#include "MipsGenDAGISel.inc"
/// getTargetMachine - Return a reference to the TargetMachine, casted
/// to the target-specific type.
const MipsTargetMachine &getTargetMachine() {
return static_cast<const MipsTargetMachine &>(TM);
}
/// getInstrInfo - Return a reference to the TargetInstrInfo, casted
/// to the target-specific type.
const MipsInstrInfo *getInstrInfo() {
return getTargetMachine().getInstrInfo();
}
SDNode *getGlobalBaseReg();
std::pair<SDNode*, SDNode*> SelectMULT(SDNode *N, unsigned Opc, DebugLoc dl,
EVT Ty, bool HasLo, bool HasHi);
SDNode *Select(SDNode *N);
// Complex Pattern.
bool SelectAddr(SDNode *Parent, SDValue N, SDValue &Base, SDValue &Offset);
// getImm - Return a target constant with the specified value.
inline SDValue getImm(const SDNode *Node, unsigned Imm) {
return CurDAG->getTargetConstant(Imm, Node->getValueType(0));
}
void ProcessFunctionAfterISel(MachineFunction &MF);
bool ReplaceUsesWithZeroReg(MachineRegisterInfo *MRI, const MachineInstr&);
void InitGlobalBaseReg(MachineFunction &MF);
virtual bool SelectInlineAsmMemoryOperand(const SDValue &Op,
char ConstraintCode,
std::vector<SDValue> &OutOps);
};
}
// Insert instructions to initialize the global base register in the
// first MBB of the function. When the ABI is O32 and the relocation model is
// PIC, the necessary instructions are emitted later to prevent optimization
// passes from moving them.
void MipsDAGToDAGISel::InitGlobalBaseReg(MachineFunction &MF) {
MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
if (!MipsFI->globalBaseRegSet())
return;
MachineBasicBlock &MBB = MF.front();
MachineBasicBlock::iterator I = MBB.begin();
MachineRegisterInfo &RegInfo = MF.getRegInfo();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
DebugLoc DL = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
unsigned V0, V1, GlobalBaseReg = MipsFI->getGlobalBaseReg();
bool FixGlobalBaseReg = MipsFI->globalBaseRegFixed();
if (Subtarget.isABI_O32() && FixGlobalBaseReg)
// $gp is the global base register.
V0 = V1 = GlobalBaseReg;
else {
const TargetRegisterClass *RC;
RC = Subtarget.isABI_N64() ?
Mips::CPU64RegsRegisterClass : Mips::CPURegsRegisterClass;
V0 = RegInfo.createVirtualRegister(RC);
V1 = RegInfo.createVirtualRegister(RC);
}
if (Subtarget.isABI_N64()) {
MF.getRegInfo().addLiveIn(Mips::T9_64);
// lui $v0, %hi(%neg(%gp_rel(fname)))
// daddu $v1, $v0, $t9
// daddiu $globalbasereg, $v1, %lo(%neg(%gp_rel(fname)))
const GlobalValue *FName = MF.getFunction();
BuildMI(MBB, I, DL, TII.get(Mips::LUi64), V0)
.addGlobalAddress(FName, 0, MipsII::MO_GPOFF_HI);
BuildMI(MBB, I, DL, TII.get(Mips::DADDu), V1).addReg(V0).addReg(Mips::T9_64);
BuildMI(MBB, I, DL, TII.get(Mips::DADDiu), GlobalBaseReg).addReg(V1)
.addGlobalAddress(FName, 0, MipsII::MO_GPOFF_LO);
} else if (MF.getTarget().getRelocationModel() == Reloc::Static) {
// Set global register to __gnu_local_gp.
//
// lui $v0, %hi(__gnu_local_gp)
// addiu $globalbasereg, $v0, %lo(__gnu_local_gp)
BuildMI(MBB, I, DL, TII.get(Mips::LUi), V0)
.addExternalSymbol("__gnu_local_gp", MipsII::MO_ABS_HI);
BuildMI(MBB, I, DL, TII.get(Mips::ADDiu), GlobalBaseReg).addReg(V0)
.addExternalSymbol("__gnu_local_gp", MipsII::MO_ABS_LO);
} else {
MF.getRegInfo().addLiveIn(Mips::T9);
if (Subtarget.isABI_N32()) {
// lui $v0, %hi(%neg(%gp_rel(fname)))
// addu $v1, $v0, $t9
// addiu $globalbasereg, $v1, %lo(%neg(%gp_rel(fname)))
const GlobalValue *FName = MF.getFunction();
BuildMI(MBB, I, DL, TII.get(Mips::LUi), V0)
.addGlobalAddress(FName, 0, MipsII::MO_GPOFF_HI);
BuildMI(MBB, I, DL, TII.get(Mips::ADDu), V1).addReg(V0).addReg(Mips::T9);
BuildMI(MBB, I, DL, TII.get(Mips::ADDiu), GlobalBaseReg).addReg(V1)
.addGlobalAddress(FName, 0, MipsII::MO_GPOFF_LO);
} else if (!MipsFI->globalBaseRegFixed()) {
assert(Subtarget.isABI_O32());
BuildMI(MBB, I, DL, TII.get(Mips::SETGP2), GlobalBaseReg)
.addReg(Mips::T9);
}
}
}
bool MipsDAGToDAGISel::ReplaceUsesWithZeroReg(MachineRegisterInfo *MRI,
const MachineInstr& MI) {
unsigned DstReg = 0, ZeroReg = 0;
// Check if MI is "addiu $dst, $zero, 0" or "daddiu $dst, $zero, 0".
if ((MI.getOpcode() == Mips::ADDiu) &&
(MI.getOperand(1).getReg() == Mips::ZERO) &&
(MI.getOperand(2).getImm() == 0)) {
DstReg = MI.getOperand(0).getReg();
ZeroReg = Mips::ZERO;
} else if ((MI.getOpcode() == Mips::DADDiu) &&
(MI.getOperand(1).getReg() == Mips::ZERO_64) &&
(MI.getOperand(2).getImm() == 0)) {
DstReg = MI.getOperand(0).getReg();
ZeroReg = Mips::ZERO_64;
}
if (!DstReg)
return false;
// Replace uses with ZeroReg.
for (MachineRegisterInfo::use_iterator U = MRI->use_begin(DstReg),
E = MRI->use_end(); U != E; ++U) {
MachineOperand &MO = U.getOperand();
MachineInstr *MI = MO.getParent();
// Do not replace if it is a phi's operand or is tied to def operand.
if (MI->isPHI() || MI->isRegTiedToDefOperand(U.getOperandNo()))
continue;
MO.setReg(ZeroReg);
}
return true;
}
void MipsDAGToDAGISel::ProcessFunctionAfterISel(MachineFunction &MF) {
InitGlobalBaseReg(MF);
MachineRegisterInfo *MRI = &MF.getRegInfo();
for (MachineFunction::iterator MFI = MF.begin(), MFE = MF.end(); MFI != MFE;
++MFI)
for (MachineBasicBlock::iterator I = MFI->begin(); I != MFI->end(); ++I)
ReplaceUsesWithZeroReg(MRI, *I);
}
bool MipsDAGToDAGISel::runOnMachineFunction(MachineFunction &MF) {
bool Ret = SelectionDAGISel::runOnMachineFunction(MF);
ProcessFunctionAfterISel(MF);
return Ret;
}
/// getGlobalBaseReg - Output the instructions required to put the
/// GOT address into a register.
SDNode *MipsDAGToDAGISel::getGlobalBaseReg() {
unsigned GlobalBaseReg = MF->getInfo<MipsFunctionInfo>()->getGlobalBaseReg();
return CurDAG->getRegister(GlobalBaseReg, TLI.getPointerTy()).getNode();
}
/// ComplexPattern used on MipsInstrInfo
/// Used on Mips Load/Store instructions
bool MipsDAGToDAGISel::
SelectAddr(SDNode *Parent, SDValue Addr, SDValue &Base, SDValue &Offset) {
EVT ValTy = Addr.getValueType();
// If Parent is an unaligned f32 load or store, select a (base + index)
// floating point load/store instruction (luxc1 or suxc1).
const LSBaseSDNode* LS = 0;
if (Parent && (LS = dyn_cast<LSBaseSDNode>(Parent))) {
EVT VT = LS->getMemoryVT();
if (VT.getSizeInBits() / 8 > LS->getAlignment()) {
assert(TLI.allowsUnalignedMemoryAccesses(VT) &&
"Unaligned loads/stores not supported for this type.");
if (VT == MVT::f32)
return false;
}
}
// if Address is FI, get the TargetFrameIndex.
if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), ValTy);
Offset = CurDAG->getTargetConstant(0, ValTy);
return true;
}
// on PIC code Load GA
if (Addr.getOpcode() == MipsISD::Wrapper) {
Base = Addr.getOperand(0);
Offset = Addr.getOperand(1);
return true;
}
if (TM.getRelocationModel() != Reloc::PIC_) {
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<16>(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(), ValTy);
else
Base = Addr.getOperand(0);
Offset = CurDAG->getTargetConstant(CN->getZExtValue(), ValTy);
return true;
}
}
// Operand is a result from an ADD.
if (Addr.getOpcode() == ISD::ADD) {
// When loading from constant pools, load the lower address part in
// the instruction itself. Example, instead of:
// lui $2, %hi($CPI1_0)
// addiu $2, $2, %lo($CPI1_0)
// lwc1 $f0, 0($2)
// Generate:
// lui $2, %hi($CPI1_0)
// lwc1 $f0, %lo($CPI1_0)($2)
if (Addr.getOperand(1).getOpcode() == MipsISD::Lo) {
SDValue LoVal = Addr.getOperand(1);
if (isa<ConstantPoolSDNode>(LoVal.getOperand(0)) ||
isa<GlobalAddressSDNode>(LoVal.getOperand(0))) {
Base = Addr.getOperand(0);
Offset = LoVal.getOperand(0);
return true;
}
}
// If an indexed floating point load/store can be emitted, return false.
if (LS && (LS->getMemoryVT() == MVT::f32 || LS->getMemoryVT() == MVT::f64) &&
Subtarget.hasMips32r2Or64())
return false;
}
Base = Addr;
Offset = CurDAG->getTargetConstant(0, ValTy);
return true;
}
/// Select multiply instructions.
std::pair<SDNode*, SDNode*>
MipsDAGToDAGISel::SelectMULT(SDNode *N, unsigned Opc, DebugLoc dl, EVT Ty,
bool HasLo, bool HasHi) {
SDNode *Lo = 0, *Hi = 0;
SDNode *Mul = CurDAG->getMachineNode(Opc, dl, MVT::Glue, N->getOperand(0),
N->getOperand(1));
SDValue InFlag = SDValue(Mul, 0);
if (HasLo) {
Lo = CurDAG->getMachineNode(Ty == MVT::i32 ? Mips::MFLO : Mips::MFLO64, dl,
Ty, MVT::Glue, InFlag);
InFlag = SDValue(Lo, 1);
}
if (HasHi)
Hi = CurDAG->getMachineNode(Ty == MVT::i32 ? Mips::MFHI : Mips::MFHI64, dl,
Ty, InFlag);
return std::make_pair(Lo, Hi);
}
/// Select instructions not customized! Used for
/// expanded, promoted and normal instructions
SDNode* MipsDAGToDAGISel::Select(SDNode *Node) {
unsigned Opcode = Node->getOpcode();
DebugLoc dl = Node->getDebugLoc();
// Dump information about the Node being selected
DEBUG(errs() << "Selecting: "; Node->dump(CurDAG); errs() << "\n");
// If we have a custom node, we already have selected!
if (Node->isMachineOpcode()) {
DEBUG(errs() << "== "; Node->dump(CurDAG); errs() << "\n");
return NULL;
}
///
// Instruction Selection not handled by the auto-generated
// tablegen selection should be handled here.
///
EVT NodeTy = Node->getValueType(0);
unsigned MultOpc;
switch(Opcode) {
default: break;
case ISD::SUBE:
case ISD::ADDE: {
SDValue InFlag = Node->getOperand(2), CmpLHS;
unsigned Opc = InFlag.getOpcode(); (void)Opc;
assert(((Opc == ISD::ADDC || Opc == ISD::ADDE) ||
(Opc == ISD::SUBC || Opc == ISD::SUBE)) &&
"(ADD|SUB)E flag operand must come from (ADD|SUB)C/E insn");
unsigned MOp;
if (Opcode == ISD::ADDE) {
CmpLHS = InFlag.getValue(0);
MOp = Mips::ADDu;
} else {
CmpLHS = InFlag.getOperand(0);
MOp = Mips::SUBu;
}
SDValue Ops[] = { CmpLHS, InFlag.getOperand(1) };
SDValue LHS = Node->getOperand(0);
SDValue RHS = Node->getOperand(1);
EVT VT = LHS.getValueType();
SDNode *Carry = CurDAG->getMachineNode(Mips::SLTu, dl, VT, Ops, 2);
SDNode *AddCarry = CurDAG->getMachineNode(Mips::ADDu, dl, VT,
SDValue(Carry,0), RHS);
return CurDAG->SelectNodeTo(Node, MOp, VT, MVT::Glue,
LHS, SDValue(AddCarry,0));
}
/// Mul with two results
case ISD::SMUL_LOHI:
case ISD::UMUL_LOHI: {
if (NodeTy == MVT::i32)
MultOpc = (Opcode == ISD::UMUL_LOHI ? Mips::MULTu : Mips::MULT);
else
MultOpc = (Opcode == ISD::UMUL_LOHI ? Mips::DMULTu : Mips::DMULT);
std::pair<SDNode*, SDNode*> LoHi = SelectMULT(Node, MultOpc, dl, NodeTy,
true, true);
if (!SDValue(Node, 0).use_empty())
ReplaceUses(SDValue(Node, 0), SDValue(LoHi.first, 0));
if (!SDValue(Node, 1).use_empty())
ReplaceUses(SDValue(Node, 1), SDValue(LoHi.second, 0));
return NULL;
}
/// Special Muls
case ISD::MUL: {
// Mips32 has a 32-bit three operand mul instruction.
if (Subtarget.hasMips32() && NodeTy == MVT::i32)
break;
return SelectMULT(Node, NodeTy == MVT::i32 ? Mips::MULT : Mips::DMULT,
dl, NodeTy, true, false).first;
}
case ISD::MULHS:
case ISD::MULHU: {
if (NodeTy == MVT::i32)
MultOpc = (Opcode == ISD::MULHU ? Mips::MULTu : Mips::MULT);
else
MultOpc = (Opcode == ISD::MULHU ? Mips::DMULTu : Mips::DMULT);
return SelectMULT(Node, MultOpc, dl, NodeTy, false, true).second;
}
// Get target GOT address.
case ISD::GLOBAL_OFFSET_TABLE:
return getGlobalBaseReg();
case ISD::ConstantFP: {
ConstantFPSDNode *CN = dyn_cast<ConstantFPSDNode>(Node);
if (Node->getValueType(0) == MVT::f64 && CN->isExactlyValue(+0.0)) {
if (Subtarget.hasMips64()) {
SDValue Zero = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl,
Mips::ZERO_64, MVT::i64);
return CurDAG->getMachineNode(Mips::DMTC1, dl, MVT::f64, Zero);
}
SDValue Zero = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl,
Mips::ZERO, MVT::i32);
return CurDAG->getMachineNode(Mips::BuildPairF64, dl, MVT::f64, Zero,
Zero);
}
break;
}
case ISD::Constant: {
const ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Node);
unsigned Size = CN->getValueSizeInBits(0);
if (Size == 32)
break;
MipsAnalyzeImmediate AnalyzeImm;
int64_t Imm = CN->getSExtValue();
const MipsAnalyzeImmediate::InstSeq &Seq =
AnalyzeImm.Analyze(Imm, Size, false);
MipsAnalyzeImmediate::InstSeq::const_iterator Inst = Seq.begin();
DebugLoc DL = CN->getDebugLoc();
SDNode *RegOpnd;
SDValue ImmOpnd = CurDAG->getTargetConstant(SignExtend64<16>(Inst->ImmOpnd),
MVT::i64);
// The first instruction can be a LUi which is different from other
// instructions (ADDiu, ORI and SLL) in that it does not have a register
// operand.
if (Inst->Opc == Mips::LUi64)
RegOpnd = CurDAG->getMachineNode(Inst->Opc, DL, MVT::i64, ImmOpnd);
else
RegOpnd =
CurDAG->getMachineNode(Inst->Opc, DL, MVT::i64,
CurDAG->getRegister(Mips::ZERO_64, MVT::i64),
ImmOpnd);
// The remaining instructions in the sequence are handled here.
for (++Inst; Inst != Seq.end(); ++Inst) {
ImmOpnd = CurDAG->getTargetConstant(SignExtend64<16>(Inst->ImmOpnd),
MVT::i64);
RegOpnd = CurDAG->getMachineNode(Inst->Opc, DL, MVT::i64,
SDValue(RegOpnd, 0), ImmOpnd);
}
return RegOpnd;
}
case MipsISD::ThreadPointer: {
EVT PtrVT = TLI.getPointerTy();
unsigned RdhwrOpc, SrcReg, DestReg;
if (PtrVT == MVT::i32) {
RdhwrOpc = Mips::RDHWR;
SrcReg = Mips::HWR29;
DestReg = Mips::V1;
} else {
RdhwrOpc = Mips::RDHWR64;
SrcReg = Mips::HWR29_64;
DestReg = Mips::V1_64;
}
SDNode *Rdhwr =
CurDAG->getMachineNode(RdhwrOpc, Node->getDebugLoc(),
Node->getValueType(0),
CurDAG->getRegister(SrcReg, PtrVT));
SDValue Chain = CurDAG->getCopyToReg(CurDAG->getEntryNode(), dl, DestReg,
SDValue(Rdhwr, 0));
SDValue ResNode = CurDAG->getCopyFromReg(Chain, dl, DestReg, PtrVT);
ReplaceUses(SDValue(Node, 0), ResNode);
return ResNode.getNode();
}
}
// Select the default instruction
SDNode *ResNode = SelectCode(Node);
DEBUG(errs() << "=> ");
if (ResNode == NULL || ResNode == Node)
DEBUG(Node->dump(CurDAG));
else
DEBUG(ResNode->dump(CurDAG));
DEBUG(errs() << "\n");
return ResNode;
}
bool MipsDAGToDAGISel::
SelectInlineAsmMemoryOperand(const SDValue &Op, char ConstraintCode,
std::vector<SDValue> &OutOps) {
assert(ConstraintCode == 'm' && "unexpected asm memory constraint");
OutOps.push_back(Op);
return false;
}
/// createMipsISelDag - This pass converts a legalized DAG into a
/// MIPS-specific DAG, ready for instruction scheduling.
FunctionPass *llvm::createMipsISelDag(MipsTargetMachine &TM) {
return new MipsDAGToDAGISel(TM);
}
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