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llvm-project/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp

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//==--- InstrEmitter.cpp - Emit MachineInstrs for the SelectionDAG class ---==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements the Emit routines for the SelectionDAG class, which creates
// MachineInstrs based on the decisions of the SelectionDAG instruction
// selection.
//
//===----------------------------------------------------------------------===//
#include "InstrEmitter.h"
#include "SDNodeDbgValue.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
using namespace llvm;
#define DEBUG_TYPE "instr-emitter"
/// MinRCSize - Smallest register class we allow when constraining virtual
/// registers. If satisfying all register class constraints would require
/// using a smaller register class, emit a COPY to a new virtual register
/// instead.
const unsigned MinRCSize = 4;
/// CountResults - The results of target nodes have register or immediate
/// operands first, then an optional chain, and optional glue operands (which do
/// not go into the resulting MachineInstr).
unsigned InstrEmitter::CountResults(SDNode *Node) {
unsigned N = Node->getNumValues();
while (N && Node->getValueType(N - 1) == MVT::Glue)
--N;
if (N && Node->getValueType(N - 1) == MVT::Other)
--N; // Skip over chain result.
return N;
}
/// countOperands - The inputs to target nodes have any actual inputs first,
/// followed by an optional chain operand, then an optional glue operand.
/// Compute the number of actual operands that will go into the resulting
/// MachineInstr.
///
/// Also count physreg RegisterSDNode and RegisterMaskSDNode operands preceding
/// the chain and glue. These operands may be implicit on the machine instr.
static unsigned countOperands(SDNode *Node, unsigned NumExpUses,
unsigned &NumImpUses) {
unsigned N = Node->getNumOperands();
while (N && Node->getOperand(N - 1).getValueType() == MVT::Glue)
--N;
if (N && Node->getOperand(N - 1).getValueType() == MVT::Other)
--N; // Ignore chain if it exists.
// Count RegisterSDNode and RegisterMaskSDNode operands for NumImpUses.
NumImpUses = N - NumExpUses;
for (unsigned I = N; I > NumExpUses; --I) {
if (isa<RegisterMaskSDNode>(Node->getOperand(I - 1)))
continue;
if (RegisterSDNode *RN = dyn_cast<RegisterSDNode>(Node->getOperand(I - 1)))
if (TargetRegisterInfo::isPhysicalRegister(RN->getReg()))
continue;
NumImpUses = N - I;
break;
}
return N;
}
/// EmitCopyFromReg - Generate machine code for an CopyFromReg node or an
/// implicit physical register output.
void InstrEmitter::
EmitCopyFromReg(SDNode *Node, unsigned ResNo, bool IsClone, bool IsCloned,
unsigned SrcReg, DenseMap<SDValue, unsigned> &VRBaseMap) {
unsigned VRBase = 0;
if (TargetRegisterInfo::isVirtualRegister(SrcReg)) {
// Just use the input register directly!
SDValue Op(Node, ResNo);
if (IsClone)
VRBaseMap.erase(Op);
bool isNew = VRBaseMap.insert(std::make_pair(Op, SrcReg)).second;
(void)isNew; // Silence compiler warning.
assert(isNew && "Node emitted out of order - early");
return;
}
// If the node is only used by a CopyToReg and the dest reg is a vreg, use
// the CopyToReg'd destination register instead of creating a new vreg.
bool MatchReg = true;
const TargetRegisterClass *UseRC = nullptr;
MVT VT = Node->getSimpleValueType(ResNo);
// Stick to the preferred register classes for legal types.
if (TLI->isTypeLegal(VT))
UseRC = TLI->getRegClassFor(VT);
if (!IsClone && !IsCloned)
for (SDNode *User : Node->uses()) {
bool Match = true;
if (User->getOpcode() == ISD::CopyToReg &&
User->getOperand(2).getNode() == Node &&
User->getOperand(2).getResNo() == ResNo) {
unsigned DestReg = cast<RegisterSDNode>(User->getOperand(1))->getReg();
if (TargetRegisterInfo::isVirtualRegister(DestReg)) {
VRBase = DestReg;
Match = false;
} else if (DestReg != SrcReg)
Match = false;
} else {
for (unsigned i = 0, e = User->getNumOperands(); i != e; ++i) {
SDValue Op = User->getOperand(i);
if (Op.getNode() != Node || Op.getResNo() != ResNo)
continue;
MVT VT = Node->getSimpleValueType(Op.getResNo());
if (VT == MVT::Other || VT == MVT::Glue)
continue;
Match = false;
if (User->isMachineOpcode()) {
const MCInstrDesc &II = TII->get(User->getMachineOpcode());
const TargetRegisterClass *RC = nullptr;
if (i+II.getNumDefs() < II.getNumOperands()) {
RC = TRI->getAllocatableClass(
TII->getRegClass(II, i+II.getNumDefs(), TRI, *MF));
}
if (!UseRC)
UseRC = RC;
else if (RC) {
const TargetRegisterClass *ComRC =
TRI->getCommonSubClass(UseRC, RC, VT.SimpleTy);
// If multiple uses expect disjoint register classes, we emit
// copies in AddRegisterOperand.
if (ComRC)
UseRC = ComRC;
}
}
}
}
MatchReg &= Match;
if (VRBase)
break;
}
const TargetRegisterClass *SrcRC = nullptr, *DstRC = nullptr;
SrcRC = TRI->getMinimalPhysRegClass(SrcReg, VT);
// Figure out the register class to create for the destreg.
if (VRBase) {
DstRC = MRI->getRegClass(VRBase);
} else if (UseRC) {
assert(TRI->isTypeLegalForClass(*UseRC, VT) &&
"Incompatible phys register def and uses!");
DstRC = UseRC;
} else {
DstRC = TLI->getRegClassFor(VT);
}
// If all uses are reading from the src physical register and copying the
// register is either impossible or very expensive, then don't create a copy.
if (MatchReg && SrcRC->getCopyCost() < 0) {
VRBase = SrcReg;
} else {
// Create the reg, emit the copy.
VRBase = MRI->createVirtualRegister(DstRC);
BuildMI(*MBB, InsertPos, Node->getDebugLoc(), TII->get(TargetOpcode::COPY),
VRBase).addReg(SrcReg);
}
SDValue Op(Node, ResNo);
if (IsClone)
VRBaseMap.erase(Op);
bool isNew = VRBaseMap.insert(std::make_pair(Op, VRBase)).second;
(void)isNew; // Silence compiler warning.
assert(isNew && "Node emitted out of order - early");
}
/// getDstOfCopyToRegUse - If the only use of the specified result number of
/// node is a CopyToReg, return its destination register. Return 0 otherwise.
unsigned InstrEmitter::getDstOfOnlyCopyToRegUse(SDNode *Node,
unsigned ResNo) const {
if (!Node->hasOneUse())
return 0;
SDNode *User = *Node->use_begin();
if (User->getOpcode() == ISD::CopyToReg &&
User->getOperand(2).getNode() == Node &&
User->getOperand(2).getResNo() == ResNo) {
unsigned Reg = cast<RegisterSDNode>(User->getOperand(1))->getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg))
return Reg;
}
return 0;
}
void InstrEmitter::CreateVirtualRegisters(SDNode *Node,
MachineInstrBuilder &MIB,
const MCInstrDesc &II,
bool IsClone, bool IsCloned,
DenseMap<SDValue, unsigned> &VRBaseMap) {
assert(Node->getMachineOpcode() != TargetOpcode::IMPLICIT_DEF &&
"IMPLICIT_DEF should have been handled as a special case elsewhere!");
unsigned NumResults = CountResults(Node);
for (unsigned i = 0; i < II.getNumDefs(); ++i) {
// If the specific node value is only used by a CopyToReg and the dest reg
// is a vreg in the same register class, use the CopyToReg'd destination
// register instead of creating a new vreg.
unsigned VRBase = 0;
const TargetRegisterClass *RC =
TRI->getAllocatableClass(TII->getRegClass(II, i, TRI, *MF));
// Always let the value type influence the used register class. The
// constraints on the instruction may be too lax to represent the value
// type correctly. For example, a 64-bit float (X86::FR64) can't live in
// the 32-bit float super-class (X86::FR32).
if (i < NumResults && TLI->isTypeLegal(Node->getSimpleValueType(i))) {
const TargetRegisterClass *VTRC =
TLI->getRegClassFor(Node->getSimpleValueType(i));
if (RC)
VTRC = TRI->getCommonSubClass(RC, VTRC);
if (VTRC)
RC = VTRC;
}
if (II.OpInfo[i].isOptionalDef()) {
// Optional def must be a physical register.
VRBase = cast<RegisterSDNode>(Node->getOperand(i-NumResults))->getReg();
assert(TargetRegisterInfo::isPhysicalRegister(VRBase));
MIB.addReg(VRBase, RegState::Define);
}
if (!VRBase && !IsClone && !IsCloned)
for (SDNode *User : Node->uses()) {
if (User->getOpcode() == ISD::CopyToReg &&
User->getOperand(2).getNode() == Node &&
User->getOperand(2).getResNo() == i) {
unsigned Reg = cast<RegisterSDNode>(User->getOperand(1))->getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
const TargetRegisterClass *RegRC = MRI->getRegClass(Reg);
if (RegRC == RC) {
VRBase = Reg;
MIB.addReg(VRBase, RegState::Define);
break;
}
}
}
}
// Create the result registers for this node and add the result regs to
// the machine instruction.
if (VRBase == 0) {
assert(RC && "Isn't a register operand!");
VRBase = MRI->createVirtualRegister(RC);
MIB.addReg(VRBase, RegState::Define);
}
// If this def corresponds to a result of the SDNode insert the VRBase into
// the lookup map.
if (i < NumResults) {
SDValue Op(Node, i);
if (IsClone)
VRBaseMap.erase(Op);
bool isNew = VRBaseMap.insert(std::make_pair(Op, VRBase)).second;
(void)isNew; // Silence compiler warning.
assert(isNew && "Node emitted out of order - early");
}
}
}
/// getVR - Return the virtual register corresponding to the specified result
/// of the specified node.
unsigned InstrEmitter::getVR(SDValue Op,
DenseMap<SDValue, unsigned> &VRBaseMap) {
if (Op.isMachineOpcode() &&
Op.getMachineOpcode() == TargetOpcode::IMPLICIT_DEF) {
// Add an IMPLICIT_DEF instruction before every use.
unsigned VReg = getDstOfOnlyCopyToRegUse(Op.getNode(), Op.getResNo());
// IMPLICIT_DEF can produce any type of result so its MCInstrDesc
// does not include operand register class info.
if (!VReg) {
const TargetRegisterClass *RC =
TLI->getRegClassFor(Op.getSimpleValueType());
VReg = MRI->createVirtualRegister(RC);
}
BuildMI(*MBB, InsertPos, Op.getDebugLoc(),
TII->get(TargetOpcode::IMPLICIT_DEF), VReg);
return VReg;
}
DenseMap<SDValue, unsigned>::iterator I = VRBaseMap.find(Op);
assert(I != VRBaseMap.end() && "Node emitted out of order - late");
return I->second;
}
/// AddRegisterOperand - Add the specified register as an operand to the
/// specified machine instr. Insert register copies if the register is
/// not in the required register class.
void
InstrEmitter::AddRegisterOperand(MachineInstrBuilder &MIB,
SDValue Op,
unsigned IIOpNum,
const MCInstrDesc *II,
DenseMap<SDValue, unsigned> &VRBaseMap,
bool IsDebug, bool IsClone, bool IsCloned) {
assert(Op.getValueType() != MVT::Other &&
Op.getValueType() != MVT::Glue &&
"Chain and glue operands should occur at end of operand list!");
// Get/emit the operand.
unsigned VReg = getVR(Op, VRBaseMap);
const MCInstrDesc &MCID = MIB->getDesc();
bool isOptDef = IIOpNum < MCID.getNumOperands() &&
MCID.OpInfo[IIOpNum].isOptionalDef();
// If the instruction requires a register in a different class, create
// a new virtual register and copy the value into it, but first attempt to
// shrink VReg's register class within reason. For example, if VReg == GR32
// and II requires a GR32_NOSP, just constrain VReg to GR32_NOSP.
if (II) {
const TargetRegisterClass *OpRC = nullptr;
if (IIOpNum < II->getNumOperands())
OpRC = TII->getRegClass(*II, IIOpNum, TRI, *MF);
if (OpRC) {
const TargetRegisterClass *ConstrainedRC
= MRI->constrainRegClass(VReg, OpRC, MinRCSize);
if (!ConstrainedRC) {
OpRC = TRI->getAllocatableClass(OpRC);
assert(OpRC && "Constraints cannot be fulfilled for allocation");
unsigned NewVReg = MRI->createVirtualRegister(OpRC);
BuildMI(*MBB, InsertPos, Op.getNode()->getDebugLoc(),
TII->get(TargetOpcode::COPY), NewVReg).addReg(VReg);
VReg = NewVReg;
} else {
assert(ConstrainedRC->isAllocatable() &&
"Constraining an allocatable VReg produced an unallocatable class?");
}
}
}
// If this value has only one use, that use is a kill. This is a
// conservative approximation. InstrEmitter does trivial coalescing
// with CopyFromReg nodes, so don't emit kill flags for them.
// Avoid kill flags on Schedule cloned nodes, since there will be
// multiple uses.
// Tied operands are never killed, so we need to check that. And that
// means we need to determine the index of the operand.
bool isKill = Op.hasOneUse() &&
Op.getNode()->getOpcode() != ISD::CopyFromReg &&
!IsDebug &&
!(IsClone || IsCloned);
if (isKill) {
unsigned Idx = MIB->getNumOperands();
while (Idx > 0 &&
MIB->getOperand(Idx-1).isReg() &&
MIB->getOperand(Idx-1).isImplicit())
--Idx;
bool isTied = MCID.getOperandConstraint(Idx, MCOI::TIED_TO) != -1;
if (isTied)
isKill = false;
}
MIB.addReg(VReg, getDefRegState(isOptDef) | getKillRegState(isKill) |
getDebugRegState(IsDebug));
}
/// AddOperand - Add the specified operand to the specified machine instr. II
/// specifies the instruction information for the node, and IIOpNum is the
/// operand number (in the II) that we are adding.
void InstrEmitter::AddOperand(MachineInstrBuilder &MIB,
SDValue Op,
unsigned IIOpNum,
const MCInstrDesc *II,
DenseMap<SDValue, unsigned> &VRBaseMap,
bool IsDebug, bool IsClone, bool IsCloned) {
if (Op.isMachineOpcode()) {
AddRegisterOperand(MIB, Op, IIOpNum, II, VRBaseMap,
IsDebug, IsClone, IsCloned);
} else if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
MIB.addImm(C->getSExtValue());
} else if (ConstantFPSDNode *F = dyn_cast<ConstantFPSDNode>(Op)) {
MIB.addFPImm(F->getConstantFPValue());
} else if (RegisterSDNode *R = dyn_cast<RegisterSDNode>(Op)) {
unsigned VReg = R->getReg();
MVT OpVT = Op.getSimpleValueType();
const TargetRegisterClass *OpRC =
TLI->isTypeLegal(OpVT) ? TLI->getRegClassFor(OpVT) : nullptr;
const TargetRegisterClass *IIRC =
II ? TRI->getAllocatableClass(TII->getRegClass(*II, IIOpNum, TRI, *MF))
: nullptr;
if (OpRC && IIRC && OpRC != IIRC &&
TargetRegisterInfo::isVirtualRegister(VReg)) {
unsigned NewVReg = MRI->createVirtualRegister(IIRC);
BuildMI(*MBB, InsertPos, Op.getNode()->getDebugLoc(),
TII->get(TargetOpcode::COPY), NewVReg).addReg(VReg);
VReg = NewVReg;
}
// Turn additional physreg operands into implicit uses on non-variadic
// instructions. This is used by call and return instructions passing
// arguments in registers.
bool Imp = II && (IIOpNum >= II->getNumOperands() && !II->isVariadic());
MIB.addReg(VReg, getImplRegState(Imp));
} else if (RegisterMaskSDNode *RM = dyn_cast<RegisterMaskSDNode>(Op)) {
MIB.addRegMask(RM->getRegMask());
} else if (GlobalAddressSDNode *TGA = dyn_cast<GlobalAddressSDNode>(Op)) {
MIB.addGlobalAddress(TGA->getGlobal(), TGA->getOffset(),
TGA->getTargetFlags());
} else if (BasicBlockSDNode *BBNode = dyn_cast<BasicBlockSDNode>(Op)) {
MIB.addMBB(BBNode->getBasicBlock());
} else if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Op)) {
MIB.addFrameIndex(FI->getIndex());
} else if (JumpTableSDNode *JT = dyn_cast<JumpTableSDNode>(Op)) {
MIB.addJumpTableIndex(JT->getIndex(), JT->getTargetFlags());
} else if (ConstantPoolSDNode *CP = dyn_cast<ConstantPoolSDNode>(Op)) {
int Offset = CP->getOffset();
unsigned Align = CP->getAlignment();
Type *Type = CP->getType();
// MachineConstantPool wants an explicit alignment.
if (Align == 0) {
Align = MF->getDataLayout().getPrefTypeAlignment(Type);
if (Align == 0) {
// Alignment of vector types. FIXME!
Align = MF->getDataLayout().getTypeAllocSize(Type);
}
}
unsigned Idx;
MachineConstantPool *MCP = MF->getConstantPool();
if (CP->isMachineConstantPoolEntry())
Idx = MCP->getConstantPoolIndex(CP->getMachineCPVal(), Align);
else
Idx = MCP->getConstantPoolIndex(CP->getConstVal(), Align);
MIB.addConstantPoolIndex(Idx, Offset, CP->getTargetFlags());
} else if (ExternalSymbolSDNode *ES = dyn_cast<ExternalSymbolSDNode>(Op)) {
MIB.addExternalSymbol(ES->getSymbol(), ES->getTargetFlags());
} else if (auto *SymNode = dyn_cast<MCSymbolSDNode>(Op)) {
MIB.addSym(SymNode->getMCSymbol());
} else if (BlockAddressSDNode *BA = dyn_cast<BlockAddressSDNode>(Op)) {
MIB.addBlockAddress(BA->getBlockAddress(),
BA->getOffset(),
BA->getTargetFlags());
} else if (TargetIndexSDNode *TI = dyn_cast<TargetIndexSDNode>(Op)) {
MIB.addTargetIndex(TI->getIndex(), TI->getOffset(), TI->getTargetFlags());
} else {
assert(Op.getValueType() != MVT::Other &&
Op.getValueType() != MVT::Glue &&
"Chain and glue operands should occur at end of operand list!");
AddRegisterOperand(MIB, Op, IIOpNum, II, VRBaseMap,
IsDebug, IsClone, IsCloned);
}
}
unsigned InstrEmitter::ConstrainForSubReg(unsigned VReg, unsigned SubIdx,
MVT VT, const DebugLoc &DL) {
const TargetRegisterClass *VRC = MRI->getRegClass(VReg);
const TargetRegisterClass *RC = TRI->getSubClassWithSubReg(VRC, SubIdx);
// RC is a sub-class of VRC that supports SubIdx. Try to constrain VReg
// within reason.
if (RC && RC != VRC)
RC = MRI->constrainRegClass(VReg, RC, MinRCSize);
// VReg has been adjusted. It can be used with SubIdx operands now.
if (RC)
return VReg;
// VReg couldn't be reasonably constrained. Emit a COPY to a new virtual
// register instead.
RC = TRI->getSubClassWithSubReg(TLI->getRegClassFor(VT), SubIdx);
assert(RC && "No legal register class for VT supports that SubIdx");
unsigned NewReg = MRI->createVirtualRegister(RC);
BuildMI(*MBB, InsertPos, DL, TII->get(TargetOpcode::COPY), NewReg)
.addReg(VReg);
return NewReg;
}
/// EmitSubregNode - Generate machine code for subreg nodes.
///
void InstrEmitter::EmitSubregNode(SDNode *Node,
DenseMap<SDValue, unsigned> &VRBaseMap,
bool IsClone, bool IsCloned) {
unsigned VRBase = 0;
unsigned Opc = Node->getMachineOpcode();
// If the node is only used by a CopyToReg and the dest reg is a vreg, use
// the CopyToReg'd destination register instead of creating a new vreg.
for (SDNode *User : Node->uses()) {
if (User->getOpcode() == ISD::CopyToReg &&
User->getOperand(2).getNode() == Node) {
unsigned DestReg = cast<RegisterSDNode>(User->getOperand(1))->getReg();
if (TargetRegisterInfo::isVirtualRegister(DestReg)) {
VRBase = DestReg;
break;
}
}
}
if (Opc == TargetOpcode::EXTRACT_SUBREG) {
// EXTRACT_SUBREG is lowered as %dst = COPY %src:sub. There are no
// constraints on the %dst register, COPY can target all legal register
// classes.
unsigned SubIdx = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
const TargetRegisterClass *TRC =
TLI->getRegClassFor(Node->getSimpleValueType(0));
unsigned Reg;
MachineInstr *DefMI;
RegisterSDNode *R = dyn_cast<RegisterSDNode>(Node->getOperand(0));
if (R && TargetRegisterInfo::isPhysicalRegister(R->getReg())) {
Reg = R->getReg();
DefMI = nullptr;
} else {
Reg = R ? R->getReg() : getVR(Node->getOperand(0), VRBaseMap);
DefMI = MRI->getVRegDef(Reg);
}
unsigned SrcReg, DstReg, DefSubIdx;
if (DefMI &&
TII->isCoalescableExtInstr(*DefMI, SrcReg, DstReg, DefSubIdx) &&
SubIdx == DefSubIdx &&
TRC == MRI->getRegClass(SrcReg)) {
// Optimize these:
// r1025 = s/zext r1024, 4
// r1026 = extract_subreg r1025, 4
// to a copy
// r1026 = copy r1024
VRBase = MRI->createVirtualRegister(TRC);
BuildMI(*MBB, InsertPos, Node->getDebugLoc(),
TII->get(TargetOpcode::COPY), VRBase).addReg(SrcReg);
MRI->clearKillFlags(SrcReg);
} else {
// Reg may not support a SubIdx sub-register, and we may need to
// constrain its register class or issue a COPY to a compatible register
// class.
if (TargetRegisterInfo::isVirtualRegister(Reg))
Reg = ConstrainForSubReg(Reg, SubIdx,
Node->getOperand(0).getSimpleValueType(),
Node->getDebugLoc());
// Create the destreg if it is missing.
if (VRBase == 0)
VRBase = MRI->createVirtualRegister(TRC);
// Create the extract_subreg machine instruction.
MachineInstrBuilder CopyMI =
BuildMI(*MBB, InsertPos, Node->getDebugLoc(),
TII->get(TargetOpcode::COPY), VRBase);
if (TargetRegisterInfo::isVirtualRegister(Reg))
CopyMI.addReg(Reg, 0, SubIdx);
else
CopyMI.addReg(TRI->getSubReg(Reg, SubIdx));
}
} else if (Opc == TargetOpcode::INSERT_SUBREG ||
Opc == TargetOpcode::SUBREG_TO_REG) {
SDValue N0 = Node->getOperand(0);
SDValue N1 = Node->getOperand(1);
SDValue N2 = Node->getOperand(2);
unsigned SubIdx = cast<ConstantSDNode>(N2)->getZExtValue();
// Figure out the register class to create for the destreg. It should be
// the largest legal register class supporting SubIdx sub-registers.
// RegisterCoalescer will constrain it further if it decides to eliminate
// the INSERT_SUBREG instruction.
//
// %dst = INSERT_SUBREG %src, %sub, SubIdx
//
// is lowered by TwoAddressInstructionPass to:
//
// %dst = COPY %src
// %dst:SubIdx = COPY %sub
//
// There is no constraint on the %src register class.
//
const TargetRegisterClass *SRC = TLI->getRegClassFor(Node->getSimpleValueType(0));
SRC = TRI->getSubClassWithSubReg(SRC, SubIdx);
assert(SRC && "No register class supports VT and SubIdx for INSERT_SUBREG");
if (VRBase == 0 || !SRC->hasSubClassEq(MRI->getRegClass(VRBase)))
VRBase = MRI->createVirtualRegister(SRC);
// Create the insert_subreg or subreg_to_reg machine instruction.
MachineInstrBuilder MIB =
BuildMI(*MF, Node->getDebugLoc(), TII->get(Opc), VRBase);
// If creating a subreg_to_reg, then the first input operand
// is an implicit value immediate, otherwise it's a register
if (Opc == TargetOpcode::SUBREG_TO_REG) {
const ConstantSDNode *SD = cast<ConstantSDNode>(N0);
MIB.addImm(SD->getZExtValue());
} else
AddOperand(MIB, N0, 0, nullptr, VRBaseMap, /*IsDebug=*/false,
IsClone, IsCloned);
// Add the subregister being inserted
AddOperand(MIB, N1, 0, nullptr, VRBaseMap, /*IsDebug=*/false,
IsClone, IsCloned);
MIB.addImm(SubIdx);
MBB->insert(InsertPos, MIB);
} else
llvm_unreachable("Node is not insert_subreg, extract_subreg, or subreg_to_reg");
SDValue Op(Node, 0);
bool isNew = VRBaseMap.insert(std::make_pair(Op, VRBase)).second;
(void)isNew; // Silence compiler warning.
assert(isNew && "Node emitted out of order - early");
}
/// EmitCopyToRegClassNode - Generate machine code for COPY_TO_REGCLASS nodes.
/// COPY_TO_REGCLASS is just a normal copy, except that the destination
/// register is constrained to be in a particular register class.
///
void
InstrEmitter::EmitCopyToRegClassNode(SDNode *Node,
DenseMap<SDValue, unsigned> &VRBaseMap) {
unsigned VReg = getVR(Node->getOperand(0), VRBaseMap);
// Create the new VReg in the destination class and emit a copy.
unsigned DstRCIdx = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
const TargetRegisterClass *DstRC =
TRI->getAllocatableClass(TRI->getRegClass(DstRCIdx));
unsigned NewVReg = MRI->createVirtualRegister(DstRC);
BuildMI(*MBB, InsertPos, Node->getDebugLoc(), TII->get(TargetOpcode::COPY),
NewVReg).addReg(VReg);
SDValue Op(Node, 0);
bool isNew = VRBaseMap.insert(std::make_pair(Op, NewVReg)).second;
(void)isNew; // Silence compiler warning.
assert(isNew && "Node emitted out of order - early");
}
/// EmitRegSequence - Generate machine code for REG_SEQUENCE nodes.
///
void InstrEmitter::EmitRegSequence(SDNode *Node,
DenseMap<SDValue, unsigned> &VRBaseMap,
bool IsClone, bool IsCloned) {
unsigned DstRCIdx = cast<ConstantSDNode>(Node->getOperand(0))->getZExtValue();
const TargetRegisterClass *RC = TRI->getRegClass(DstRCIdx);
unsigned NewVReg = MRI->createVirtualRegister(TRI->getAllocatableClass(RC));
const MCInstrDesc &II = TII->get(TargetOpcode::REG_SEQUENCE);
MachineInstrBuilder MIB = BuildMI(*MF, Node->getDebugLoc(), II, NewVReg);
unsigned NumOps = Node->getNumOperands();
assert((NumOps & 1) == 1 &&
"REG_SEQUENCE must have an odd number of operands!");
for (unsigned i = 1; i != NumOps; ++i) {
SDValue Op = Node->getOperand(i);
if ((i & 1) == 0) {
RegisterSDNode *R = dyn_cast<RegisterSDNode>(Node->getOperand(i-1));
// Skip physical registers as they don't have a vreg to get and we'll
// insert copies for them in TwoAddressInstructionPass anyway.
if (!R || !TargetRegisterInfo::isPhysicalRegister(R->getReg())) {
unsigned SubIdx = cast<ConstantSDNode>(Op)->getZExtValue();
unsigned SubReg = getVR(Node->getOperand(i-1), VRBaseMap);
const TargetRegisterClass *TRC = MRI->getRegClass(SubReg);
const TargetRegisterClass *SRC =
TRI->getMatchingSuperRegClass(RC, TRC, SubIdx);
if (SRC && SRC != RC) {
MRI->setRegClass(NewVReg, SRC);
RC = SRC;
}
}
}
AddOperand(MIB, Op, i+1, &II, VRBaseMap, /*IsDebug=*/false,
IsClone, IsCloned);
}
MBB->insert(InsertPos, MIB);
SDValue Op(Node, 0);
bool isNew = VRBaseMap.insert(std::make_pair(Op, NewVReg)).second;
(void)isNew; // Silence compiler warning.
assert(isNew && "Node emitted out of order - early");
}
/// EmitDbgValue - Generate machine instruction for a dbg_value node.
///
MachineInstr *
InstrEmitter::EmitDbgValue(SDDbgValue *SD,
DenseMap<SDValue, unsigned> &VRBaseMap) {
MDNode *Var = SD->getVariable();
MDNode *Expr = SD->getExpression();
DebugLoc DL = SD->getDebugLoc();
assert(cast<DILocalVariable>(Var)->isValidLocationForIntrinsic(DL) &&
"Expected inlined-at fields to agree");
if (SD->getKind() == SDDbgValue::FRAMEIX) {
// Stack address; this needs to be lowered in target-dependent fashion.
// EmitTargetCodeForFrameDebugValue is responsible for allocation.
auto FrameMI = BuildMI(*MF, DL, TII->get(TargetOpcode::DBG_VALUE))
.addFrameIndex(SD->getFrameIx());
if (SD->isIndirect())
// Push [fi + 0] onto the DIExpression stack.
FrameMI.addImm(0);
else
// Push fi onto the DIExpression stack.
FrameMI.addReg(0);
return FrameMI.addMetadata(Var).addMetadata(Expr);
}
// Otherwise, we're going to create an instruction here.
const MCInstrDesc &II = TII->get(TargetOpcode::DBG_VALUE);
MachineInstrBuilder MIB = BuildMI(*MF, DL, II);
if (SD->getKind() == SDDbgValue::SDNODE) {
SDNode *Node = SD->getSDNode();
SDValue Op = SDValue(Node, SD->getResNo());
// It's possible we replaced this SDNode with other(s) and therefore
// didn't generate code for it. It's better to catch these cases where
// they happen and transfer the debug info, but trying to guarantee that
// in all cases would be very fragile; this is a safeguard for any
// that were missed.
DenseMap<SDValue, unsigned>::iterator I = VRBaseMap.find(Op);
if (I==VRBaseMap.end())
MIB.addReg(0U); // undef
else
AddOperand(MIB, Op, (*MIB).getNumOperands(), &II, VRBaseMap,
/*IsDebug=*/true, /*IsClone=*/false, /*IsCloned=*/false);
} else if (SD->getKind() == SDDbgValue::VREG) {
MIB.addReg(SD->getVReg(), RegState::Debug);
} else if (SD->getKind() == SDDbgValue::CONST) {
const Value *V = SD->getConst();
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
if (CI->getBitWidth() > 64)
MIB.addCImm(CI);
else
MIB.addImm(CI->getSExtValue());
} else if (const ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
MIB.addFPImm(CF);
} else {
// Could be an Undef. In any case insert an Undef so we can see what we
// dropped.
MIB.addReg(0U);
}
} else {
// Insert an Undef so we can see what we dropped.
MIB.addReg(0U);
}
// Indirect addressing is indicated by an Imm as the second parameter.
if (SD->isIndirect())
MIB.addImm(0U);
else
MIB.addReg(0U, RegState::Debug);
MIB.addMetadata(Var);
MIB.addMetadata(Expr);
return &*MIB;
}
MachineInstr *
InstrEmitter::EmitDbgLabel(SDDbgLabel *SD) {
MDNode *Label = SD->getLabel();
DebugLoc DL = SD->getDebugLoc();
assert(cast<DILabel>(Label)->isValidLocationForIntrinsic(DL) &&
"Expected inlined-at fields to agree");
const MCInstrDesc &II = TII->get(TargetOpcode::DBG_LABEL);
MachineInstrBuilder MIB = BuildMI(*MF, DL, II);
MIB.addMetadata(Label);
return &*MIB;
}
/// EmitMachineNode - Generate machine code for a target-specific node and
/// needed dependencies.
///
void InstrEmitter::
EmitMachineNode(SDNode *Node, bool IsClone, bool IsCloned,
DenseMap<SDValue, unsigned> &VRBaseMap) {
unsigned Opc = Node->getMachineOpcode();
// Handle subreg insert/extract specially
if (Opc == TargetOpcode::EXTRACT_SUBREG ||
Opc == TargetOpcode::INSERT_SUBREG ||
Opc == TargetOpcode::SUBREG_TO_REG) {
EmitSubregNode(Node, VRBaseMap, IsClone, IsCloned);
return;
}
// Handle COPY_TO_REGCLASS specially.
if (Opc == TargetOpcode::COPY_TO_REGCLASS) {
EmitCopyToRegClassNode(Node, VRBaseMap);
return;
}
// Handle REG_SEQUENCE specially.
if (Opc == TargetOpcode::REG_SEQUENCE) {
EmitRegSequence(Node, VRBaseMap, IsClone, IsCloned);
return;
}
if (Opc == TargetOpcode::IMPLICIT_DEF)
// We want a unique VR for each IMPLICIT_DEF use.
return;
const MCInstrDesc &II = TII->get(Opc);
unsigned NumResults = CountResults(Node);
unsigned NumDefs = II.getNumDefs();
const MCPhysReg *ScratchRegs = nullptr;
// Handle STACKMAP and PATCHPOINT specially and then use the generic code.
if (Opc == TargetOpcode::STACKMAP || Opc == TargetOpcode::PATCHPOINT) {
// Stackmaps do not have arguments and do not preserve their calling
// convention. However, to simplify runtime support, they clobber the same
// scratch registers as AnyRegCC.
unsigned CC = CallingConv::AnyReg;
if (Opc == TargetOpcode::PATCHPOINT) {
CC = Node->getConstantOperandVal(PatchPointOpers::CCPos);
NumDefs = NumResults;
}
ScratchRegs = TLI->getScratchRegisters((CallingConv::ID) CC);
}
unsigned NumImpUses = 0;
unsigned NodeOperands =
countOperands(Node, II.getNumOperands() - NumDefs, NumImpUses);
bool HasPhysRegOuts = NumResults > NumDefs && II.getImplicitDefs()!=nullptr;
#ifndef NDEBUG
unsigned NumMIOperands = NodeOperands + NumResults;
if (II.isVariadic())
assert(NumMIOperands >= II.getNumOperands() &&
"Too few operands for a variadic node!");
else
assert(NumMIOperands >= II.getNumOperands() &&
NumMIOperands <= II.getNumOperands() + II.getNumImplicitDefs() +
NumImpUses &&
"#operands for dag node doesn't match .td file!");
#endif
// Create the new machine instruction.
MachineInstrBuilder MIB = BuildMI(*MF, Node->getDebugLoc(), II);
// Add result register values for things that are defined by this
// instruction.
if (NumResults) {
CreateVirtualRegisters(Node, MIB, II, IsClone, IsCloned, VRBaseMap);
// Transfer any IR flags from the SDNode to the MachineInstr
MachineInstr *MI = MIB.getInstr();
const SDNodeFlags Flags = Node->getFlags();
if (Flags.hasNoSignedZeros())
MI->setFlag(MachineInstr::MIFlag::FmNsz);
if (Flags.hasAllowReciprocal())
MI->setFlag(MachineInstr::MIFlag::FmArcp);
if (Flags.hasNoNaNs())
MI->setFlag(MachineInstr::MIFlag::FmNoNans);
if (Flags.hasNoInfs())
MI->setFlag(MachineInstr::MIFlag::FmNoInfs);
if (Flags.hasAllowContract())
MI->setFlag(MachineInstr::MIFlag::FmContract);
if (Flags.hasApproximateFuncs())
MI->setFlag(MachineInstr::MIFlag::FmAfn);
if (Flags.hasAllowReassociation())
MI->setFlag(MachineInstr::MIFlag::FmReassoc);
if (Flags.hasNoUnsignedWrap())
MI->setFlag(MachineInstr::MIFlag::NoUWrap);
if (Flags.hasNoSignedWrap())
MI->setFlag(MachineInstr::MIFlag::NoSWrap);
if (Flags.hasExact())
MI->setFlag(MachineInstr::MIFlag::IsExact);
}
// Emit all of the actual operands of this instruction, adding them to the
// instruction as appropriate.
bool HasOptPRefs = NumDefs > NumResults;
assert((!HasOptPRefs || !HasPhysRegOuts) &&
"Unable to cope with optional defs and phys regs defs!");
unsigned NumSkip = HasOptPRefs ? NumDefs - NumResults : 0;
for (unsigned i = NumSkip; i != NodeOperands; ++i)
AddOperand(MIB, Node->getOperand(i), i-NumSkip+NumDefs, &II,
VRBaseMap, /*IsDebug=*/false, IsClone, IsCloned);
// Add scratch registers as implicit def and early clobber
if (ScratchRegs)
for (unsigned i = 0; ScratchRegs[i]; ++i)
MIB.addReg(ScratchRegs[i], RegState::ImplicitDefine |
RegState::EarlyClobber);
// Set the memory reference descriptions of this instruction now that it is
// part of the function.
MIB.setMemRefs(cast<MachineSDNode>(Node)->memoperands());
// Insert the instruction into position in the block. This needs to
// happen before any custom inserter hook is called so that the
// hook knows where in the block to insert the replacement code.
MBB->insert(InsertPos, MIB);
// The MachineInstr may also define physregs instead of virtregs. These
// physreg values can reach other instructions in different ways:
//
// 1. When there is a use of a Node value beyond the explicitly defined
// virtual registers, we emit a CopyFromReg for one of the implicitly
// defined physregs. This only happens when HasPhysRegOuts is true.
//
// 2. A CopyFromReg reading a physreg may be glued to this instruction.
//
// 3. A glued instruction may implicitly use a physreg.
//
// 4. A glued instruction may use a RegisterSDNode operand.
//
// Collect all the used physreg defs, and make sure that any unused physreg
// defs are marked as dead.
SmallVector<unsigned, 8> UsedRegs;
// Additional results must be physical register defs.
if (HasPhysRegOuts) {
for (unsigned i = NumDefs; i < NumResults; ++i) {
unsigned Reg = II.getImplicitDefs()[i - NumDefs];
if (!Node->hasAnyUseOfValue(i))
continue;
// This implicitly defined physreg has a use.
UsedRegs.push_back(Reg);
EmitCopyFromReg(Node, i, IsClone, IsCloned, Reg, VRBaseMap);
}
}
// Scan the glue chain for any used physregs.
if (Node->getValueType(Node->getNumValues()-1) == MVT::Glue) {
for (SDNode *F = Node->getGluedUser(); F; F = F->getGluedUser()) {
if (F->getOpcode() == ISD::CopyFromReg) {
UsedRegs.push_back(cast<RegisterSDNode>(F->getOperand(1))->getReg());
continue;
} else if (F->getOpcode() == ISD::CopyToReg) {
// Skip CopyToReg nodes that are internal to the glue chain.
continue;
}
// Collect declared implicit uses.
const MCInstrDesc &MCID = TII->get(F->getMachineOpcode());
UsedRegs.append(MCID.getImplicitUses(),
MCID.getImplicitUses() + MCID.getNumImplicitUses());
// In addition to declared implicit uses, we must also check for
// direct RegisterSDNode operands.
for (unsigned i = 0, e = F->getNumOperands(); i != e; ++i)
if (RegisterSDNode *R = dyn_cast<RegisterSDNode>(F->getOperand(i))) {
unsigned Reg = R->getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg))
UsedRegs.push_back(Reg);
}
}
}
// Finally mark unused registers as dead.
if (!UsedRegs.empty() || II.getImplicitDefs())
MIB->setPhysRegsDeadExcept(UsedRegs, *TRI);
// Run post-isel target hook to adjust this instruction if needed.
if (II.hasPostISelHook())
TLI->AdjustInstrPostInstrSelection(*MIB, Node);
}
/// EmitSpecialNode - Generate machine code for a target-independent node and
/// needed dependencies.
void InstrEmitter::
EmitSpecialNode(SDNode *Node, bool IsClone, bool IsCloned,
DenseMap<SDValue, unsigned> &VRBaseMap) {
switch (Node->getOpcode()) {
default:
#ifndef NDEBUG
Node->dump();
#endif
llvm_unreachable("This target-independent node should have been selected!");
case ISD::EntryToken:
llvm_unreachable("EntryToken should have been excluded from the schedule!");
case ISD::MERGE_VALUES:
case ISD::TokenFactor: // fall thru
break;
case ISD::CopyToReg: {
unsigned SrcReg;
SDValue SrcVal = Node->getOperand(2);
if (RegisterSDNode *R = dyn_cast<RegisterSDNode>(SrcVal))
SrcReg = R->getReg();
else
SrcReg = getVR(SrcVal, VRBaseMap);
unsigned DestReg = cast<RegisterSDNode>(Node->getOperand(1))->getReg();
if (SrcReg == DestReg) // Coalesced away the copy? Ignore.
break;
BuildMI(*MBB, InsertPos, Node->getDebugLoc(), TII->get(TargetOpcode::COPY),
DestReg).addReg(SrcReg);
break;
}
case ISD::CopyFromReg: {
unsigned SrcReg = cast<RegisterSDNode>(Node->getOperand(1))->getReg();
EmitCopyFromReg(Node, 0, IsClone, IsCloned, SrcReg, VRBaseMap);
break;
}
case ISD::EH_LABEL:
case ISD::ANNOTATION_LABEL: {
unsigned Opc = (Node->getOpcode() == ISD::EH_LABEL)
? TargetOpcode::EH_LABEL
: TargetOpcode::ANNOTATION_LABEL;
MCSymbol *S = cast<LabelSDNode>(Node)->getLabel();
BuildMI(*MBB, InsertPos, Node->getDebugLoc(),
TII->get(Opc)).addSym(S);
break;
}
case ISD::LIFETIME_START:
case ISD::LIFETIME_END: {
unsigned TarOp = (Node->getOpcode() == ISD::LIFETIME_START) ?
TargetOpcode::LIFETIME_START : TargetOpcode::LIFETIME_END;
FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Node->getOperand(1));
BuildMI(*MBB, InsertPos, Node->getDebugLoc(), TII->get(TarOp))
.addFrameIndex(FI->getIndex());
break;
}
case ISD::INLINEASM: {
unsigned NumOps = Node->getNumOperands();
if (Node->getOperand(NumOps-1).getValueType() == MVT::Glue)
--NumOps; // Ignore the glue operand.
// Create the inline asm machine instruction.
MachineInstrBuilder MIB = BuildMI(*MF, Node->getDebugLoc(),
TII->get(TargetOpcode::INLINEASM));
// Add the asm string as an external symbol operand.
SDValue AsmStrV = Node->getOperand(InlineAsm::Op_AsmString);
const char *AsmStr = cast<ExternalSymbolSDNode>(AsmStrV)->getSymbol();
MIB.addExternalSymbol(AsmStr);
// Add the HasSideEffect, isAlignStack, AsmDialect, MayLoad and MayStore
// bits.
int64_t ExtraInfo =
cast<ConstantSDNode>(Node->getOperand(InlineAsm::Op_ExtraInfo))->
getZExtValue();
MIB.addImm(ExtraInfo);
// Remember to operand index of the group flags.
SmallVector<unsigned, 8> GroupIdx;
// Remember registers that are part of early-clobber defs.
SmallVector<unsigned, 8> ECRegs;
// Add all of the operand registers to the instruction.
for (unsigned i = InlineAsm::Op_FirstOperand; i != NumOps;) {
unsigned Flags =
cast<ConstantSDNode>(Node->getOperand(i))->getZExtValue();
const unsigned NumVals = InlineAsm::getNumOperandRegisters(Flags);
GroupIdx.push_back(MIB->getNumOperands());
MIB.addImm(Flags);
++i; // Skip the ID value.
switch (InlineAsm::getKind(Flags)) {
default: llvm_unreachable("Bad flags!");
case InlineAsm::Kind_RegDef:
for (unsigned j = 0; j != NumVals; ++j, ++i) {
unsigned Reg = cast<RegisterSDNode>(Node->getOperand(i))->getReg();
// FIXME: Add dead flags for physical and virtual registers defined.
// For now, mark physical register defs as implicit to help fast
// regalloc. This makes inline asm look a lot like calls.
MIB.addReg(Reg, RegState::Define |
getImplRegState(TargetRegisterInfo::isPhysicalRegister(Reg)));
}
break;
case InlineAsm::Kind_RegDefEarlyClobber:
case InlineAsm::Kind_Clobber:
for (unsigned j = 0; j != NumVals; ++j, ++i) {
unsigned Reg = cast<RegisterSDNode>(Node->getOperand(i))->getReg();
MIB.addReg(Reg, RegState::Define | RegState::EarlyClobber |
getImplRegState(TargetRegisterInfo::isPhysicalRegister(Reg)));
ECRegs.push_back(Reg);
}
break;
case InlineAsm::Kind_RegUse: // Use of register.
case InlineAsm::Kind_Imm: // Immediate.
case InlineAsm::Kind_Mem: // Addressing mode.
// The addressing mode has been selected, just add all of the
// operands to the machine instruction.
for (unsigned j = 0; j != NumVals; ++j, ++i)
AddOperand(MIB, Node->getOperand(i), 0, nullptr, VRBaseMap,
/*IsDebug=*/false, IsClone, IsCloned);
// Manually set isTied bits.
if (InlineAsm::getKind(Flags) == InlineAsm::Kind_RegUse) {
unsigned DefGroup = 0;
if (InlineAsm::isUseOperandTiedToDef(Flags, DefGroup)) {
unsigned DefIdx = GroupIdx[DefGroup] + 1;
unsigned UseIdx = GroupIdx.back() + 1;
for (unsigned j = 0; j != NumVals; ++j)
MIB->tieOperands(DefIdx + j, UseIdx + j);
}
}
break;
}
}
// GCC inline assembly allows input operands to also be early-clobber
// output operands (so long as the operand is written only after it's
// used), but this does not match the semantics of our early-clobber flag.
// If an early-clobber operand register is also an input operand register,
// then remove the early-clobber flag.
for (unsigned Reg : ECRegs) {
if (MIB->readsRegister(Reg, TRI)) {
MachineOperand *MO = MIB->findRegisterDefOperand(Reg, false, TRI);
assert(MO && "No def operand for clobbered register?");
MO->setIsEarlyClobber(false);
}
}
// Get the mdnode from the asm if it exists and add it to the instruction.
SDValue MDV = Node->getOperand(InlineAsm::Op_MDNode);
const MDNode *MD = cast<MDNodeSDNode>(MDV)->getMD();
if (MD)
MIB.addMetadata(MD);
MBB->insert(InsertPos, MIB);
break;
}
}
}
/// InstrEmitter - Construct an InstrEmitter and set it to start inserting
/// at the given position in the given block.
InstrEmitter::InstrEmitter(MachineBasicBlock *mbb,
MachineBasicBlock::iterator insertpos)
: MF(mbb->getParent()), MRI(&MF->getRegInfo()),
TII(MF->getSubtarget().getInstrInfo()),
TRI(MF->getSubtarget().getRegisterInfo()),
TLI(MF->getSubtarget().getTargetLowering()), MBB(mbb),
InsertPos(insertpos) {}
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