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llvm-project/llvm/lib/Target/MSP430/MSP430ISelDAGToDAG.cpp

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//===-- MSP430ISelDAGToDAG.cpp - A dag to dag inst selector for MSP430 ----===//
//
// 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 MSP430 target.
//
//===----------------------------------------------------------------------===//
#include "MSP430.h"
#include "MSP430ISelLowering.h"
#include "MSP430TargetMachine.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Intrinsics.h"
#include "llvm/CallingConv.h"
#include "llvm/Constants.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
#ifndef NDEBUG
static cl::opt<bool>
ViewRMWDAGs("view-msp430-rmw-dags", cl::Hidden,
cl::desc("Pop up a window to show isel dags after RMW preprocess"));
#else
static const bool ViewRMWDAGs = false;
#endif
STATISTIC(NumLoadMoved, "Number of loads moved below TokenFactor");
/// MSP430DAGToDAGISel - MSP430 specific code to select MSP430 machine
/// instructions for SelectionDAG operations.
///
namespace {
class MSP430DAGToDAGISel : public SelectionDAGISel {
MSP430TargetLowering &Lowering;
const MSP430Subtarget &Subtarget;
public:
MSP430DAGToDAGISel(MSP430TargetMachine &TM, CodeGenOpt::Level OptLevel)
: SelectionDAGISel(TM, OptLevel),
Lowering(*TM.getTargetLowering()),
Subtarget(*TM.getSubtargetImpl()) { }
virtual void InstructionSelect();
virtual const char *getPassName() const {
return "MSP430 DAG->DAG Pattern Instruction Selection";
}
bool IsLegalAndProfitableToFold(SDNode *N, SDNode *U,
SDNode *Root) const;
virtual bool
SelectInlineAsmMemoryOperand(const SDValue &Op, char ConstraintCode,
std::vector<SDValue> &OutOps);
// Include the pieces autogenerated from the target description.
#include "MSP430GenDAGISel.inc"
private:
DenseMap<SDNode*, SDNode*> RMWStores;
void PreprocessForRMW();
SDNode *Select(SDValue Op);
bool SelectAddr(SDValue Op, SDValue Addr, SDValue &Base, SDValue &Disp);
#ifndef NDEBUG
unsigned Indent;
#endif
};
} // end anonymous namespace
/// createMSP430ISelDag - This pass converts a legalized DAG into a
/// MSP430-specific DAG, ready for instruction scheduling.
///
FunctionPass *llvm::createMSP430ISelDag(MSP430TargetMachine &TM,
CodeGenOpt::Level OptLevel) {
return new MSP430DAGToDAGISel(TM, OptLevel);
}
// FIXME: This is pretty dummy routine and needs to be rewritten in the future.
bool MSP430DAGToDAGISel::SelectAddr(SDValue Op, SDValue Addr,
SDValue &Base, SDValue &Disp) {
// Try to match frame address first.
if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), MVT::i16);
Disp = CurDAG->getTargetConstant(0, MVT::i16);
return true;
}
switch (Addr.getOpcode()) {
case ISD::ADD:
// Operand is a result from ADD with constant operand which fits into i16.
if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1))) {
uint64_t CVal = CN->getZExtValue();
// Offset should fit into 16 bits.
if (((CVal << 48) >> 48) == CVal) {
SDValue N0 = Addr.getOperand(0);
if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>(N0))
Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), MVT::i16);
else
Base = N0;
Disp = CurDAG->getTargetConstant(CVal, MVT::i16);
return true;
}
}
break;
case MSP430ISD::Wrapper:
SDValue N0 = Addr.getOperand(0);
if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(N0)) {
Base = CurDAG->getTargetGlobalAddress(G->getGlobal(),
MVT::i16, G->getOffset());
Disp = CurDAG->getTargetConstant(0, MVT::i16);
return true;
} else if (ExternalSymbolSDNode *E = dyn_cast<ExternalSymbolSDNode>(N0)) {
Base = CurDAG->getTargetExternalSymbol(E->getSymbol(), MVT::i16);
Disp = CurDAG->getTargetConstant(0, MVT::i16);
}
break;
};
Base = Addr;
Disp = CurDAG->getTargetConstant(0, MVT::i16);
return true;
}
bool MSP430DAGToDAGISel::
SelectInlineAsmMemoryOperand(const SDValue &Op, char ConstraintCode,
std::vector<SDValue> &OutOps) {
SDValue Op0, Op1;
switch (ConstraintCode) {
default: return true;
case 'm': // memory
if (!SelectAddr(Op, Op, Op0, Op1))
return true;
break;
}
OutOps.push_back(Op0);
OutOps.push_back(Op1);
return false;
}
bool MSP430DAGToDAGISel::IsLegalAndProfitableToFold(SDNode *N, SDNode *U,
SDNode *Root) const {
if (OptLevel == CodeGenOpt::None) return false;
/// RMW preprocessing creates the following code:
/// [Load1]
/// ^ ^
/// / |
/// / |
/// [Load2] |
/// ^ ^ |
/// | | |
/// | \-|
/// | |
/// | [Op]
/// | ^
/// | |
/// \ /
/// \ /
/// [Store]
///
/// The path Store => Load2 => Load1 is via chain. Note that in general it is
/// not allowed to fold Load1 into Op (and Store) since it will creates a
/// cycle. However, this is perfectly legal for the loads moved below the
/// TokenFactor by PreprocessForRMW. Query the map Store => Load1 (created
/// during preprocessing) to determine whether it's legal to introduce such
/// "cycle" for a moment.
DenseMap<SDNode*, SDNode*>::iterator I = RMWStores.find(Root);
if (I != RMWStores.end() && I->second == N)
return true;
// Proceed to 'generic' cycle finder code
return SelectionDAGISel::IsLegalAndProfitableToFold(N, U, Root);
}
/// MoveBelowTokenFactor - Replace TokenFactor operand with load's chain operand
/// and move load below the TokenFactor. Replace store's chain operand with
/// load's chain result.
static void MoveBelowTokenFactor(SelectionDAG *CurDAG, SDValue Load,
SDValue Store, SDValue TF) {
SmallVector<SDValue, 4> Ops;
for (unsigned i = 0, e = TF.getNode()->getNumOperands(); i != e; ++i)
if (Load.getNode() == TF.getOperand(i).getNode())
Ops.push_back(Load.getOperand(0));
else
Ops.push_back(TF.getOperand(i));
SDValue NewTF = CurDAG->UpdateNodeOperands(TF, &Ops[0], Ops.size());
SDValue NewLoad = CurDAG->UpdateNodeOperands(Load, NewTF,
Load.getOperand(1),
Load.getOperand(2));
CurDAG->UpdateNodeOperands(Store, NewLoad.getValue(1), Store.getOperand(1),
Store.getOperand(2), Store.getOperand(3));
}
/// MoveBelowTokenFactor2 - Replace TokenFactor operand with load's chain operand
/// and move load below the TokenFactor. Replace store's chain operand with
/// load's chain result. This a version which sinks two loads below token factor.
/// Look into PreprocessForRMW comments for explanation of transform.
static void MoveBelowTokenFactor2(SelectionDAG *CurDAG,
SDValue Load1, SDValue Load2,
SDValue Store, SDValue TF) {
SmallVector<SDValue, 4> Ops;
for (unsigned i = 0, e = TF.getNode()->getNumOperands(); i != e; ++i) {
SDNode* N = TF.getOperand(i).getNode();
if (Load2.getNode() == N)
Ops.push_back(Load2.getOperand(0));
else if (Load1.getNode() != N)
Ops.push_back(TF.getOperand(i));
}
SDValue NewTF = SDValue(CurDAG->MorphNodeTo(TF.getNode(),
TF.getOpcode(),
TF.getNode()->getVTList(),
&Ops[0], Ops.size()), TF.getResNo());
SDValue NewLoad2 = CurDAG->UpdateNodeOperands(Load2, NewTF,
Load2.getOperand(1),
Load2.getOperand(2));
SDValue NewLoad1 = CurDAG->UpdateNodeOperands(Load1, NewLoad2.getValue(1),
Load1.getOperand(1),
Load1.getOperand(2));
CurDAG->UpdateNodeOperands(Store,
NewLoad1.getValue(1),
Store.getOperand(1),
Store.getOperand(2), Store.getOperand(3));
}
/// isAllowedToSink - return true if N a load which can be moved below token
/// factor. Basically, the load should be non-volatile and has single use.
static bool isLoadAllowedToSink(SDValue N, SDValue Chain) {
if (N.getOpcode() == ISD::BIT_CONVERT)
N = N.getOperand(0);
LoadSDNode *LD = dyn_cast<LoadSDNode>(N);
if (!LD || LD->isVolatile())
return false;
if (LD->getAddressingMode() != ISD::UNINDEXED)
return false;
ISD::LoadExtType ExtType = LD->getExtensionType();
if (ExtType != ISD::NON_EXTLOAD && ExtType != ISD::EXTLOAD)
return false;
return (N.hasOneUse() &&
LD->hasNUsesOfValue(1, 1) &&
LD->isOperandOf(Chain.getNode()));
}
/// isRMWLoad - Return true if N is a load that's part of RMW sub-DAG.
/// The chain produced by the load must only be used by the store's chain
/// operand, otherwise this may produce a cycle in the DAG.
static bool isRMWLoad(SDValue N, SDValue Chain, SDValue Address,
SDValue &Load) {
if (isLoadAllowedToSink(N, Chain) &&
N.getOperand(1) == Address) {
Load = N;
return true;
}
return false;
}
/// PreprocessForRMW - Preprocess the DAG to make instruction selection better.
/// This is only run if not in -O0 mode.
/// This allows the instruction selector to pick more read-modify-write
/// instructions. This is a common case:
///
/// [Load chain]
/// ^
/// |
/// [Load]
/// ^ ^
/// | |
/// / \-
/// / |
/// [TokenFactor] [Op]
/// ^ ^
/// | |
/// \ /
/// \ /
/// [Store]
///
/// The fact the store's chain operand != load's chain will prevent the
/// (store (op (load))) instruction from being selected. We can transform it to:
///
/// [Load chain]
/// ^
/// |
/// [TokenFactor]
/// ^
/// |
/// [Load]
/// ^ ^
/// | |
/// | \-
/// | |
/// | [Op]
/// | ^
/// | |
/// \ /
/// \ /
/// [Store]
///
/// We also recognize the case where second operand of Op is load as well and
/// move it below token factor as well creating DAG as follows:
///
/// [Load chain]
/// ^
/// |
/// [TokenFactor]
/// ^
/// |
/// [Load1]
/// ^ ^
/// / |
/// / |
/// [Load2] |
/// ^ ^ |
/// | | |
/// | \-|
/// | |
/// | [Op]
/// | ^
/// | |
/// \ /
/// \ /
/// [Store]
///
/// This allows selection of mem-mem instructions. Yay!
void MSP430DAGToDAGISel::PreprocessForRMW() {
for (SelectionDAG::allnodes_iterator I = CurDAG->allnodes_begin(),
E = CurDAG->allnodes_end(); I != E; ++I) {
if (!ISD::isNON_TRUNCStore(I))
continue;
SDValue Chain = I->getOperand(0);
if (Chain.getNode()->getOpcode() != ISD::TokenFactor)
continue;
SDValue N1 = I->getOperand(1);
SDValue N2 = I->getOperand(2);
if ((N1.getValueType().isFloatingPoint() &&
!N1.getValueType().isVector()) ||
!N1.hasOneUse())
continue;
unsigned RModW = 0;
SDValue Load1, Load2;
unsigned Opcode = N1.getNode()->getOpcode();
switch (Opcode) {
case ISD::ADD:
case ISD::AND:
case ISD::OR:
case ISD::XOR:
case ISD::ADDC:
case ISD::ADDE: {
SDValue N10 = N1.getOperand(0);
SDValue N11 = N1.getOperand(1);
if (isRMWLoad(N10, Chain, N2, Load1)) {
if (isLoadAllowedToSink(N11, Chain)) {
Load2 = N11;
RModW = 2;
} else
RModW = 1;
} else if (isRMWLoad(N11, Chain, N2, Load1)) {
if (isLoadAllowedToSink(N10, Chain)) {
Load2 = N10;
RModW = 2;
} else
RModW = 1;
}
break;
}
case ISD::SUB:
case ISD::SUBC:
case ISD::SUBE: {
SDValue N10 = N1.getOperand(0);
SDValue N11 = N1.getOperand(1);
if (isRMWLoad(N10, Chain, N2, Load1)) {
if (isLoadAllowedToSink(N11, Chain)) {
Load2 = N11;
RModW = 2;
} else
RModW = 1;
}
break;
}
}
NumLoadMoved += RModW;
if (RModW == 1)
MoveBelowTokenFactor(CurDAG, Load1, SDValue(I, 0), Chain);
else if (RModW == 2) {
MoveBelowTokenFactor2(CurDAG, Load1, Load2, SDValue(I, 0), Chain);
SDNode* Store = I;
RMWStores[Store] = Load2.getNode();
}
}
}
/// InstructionSelect - This callback is invoked by
/// SelectionDAGISel when it has created a SelectionDAG for us to codegen.
void MSP430DAGToDAGISel::InstructionSelect() {
std::string BlockName;
if (ViewRMWDAGs)
BlockName = MF->getFunction()->getNameStr() + ":" +
BB->getBasicBlock()->getNameStr();
PreprocessForRMW();
if (ViewRMWDAGs) CurDAG->viewGraph("RMW preprocessed:" + BlockName);
DEBUG(errs() << "Selection DAG after RMW preprocessing:\n");
DEBUG(CurDAG->dump());
DEBUG(BB->dump());
// Codegen the basic block.
DEBUG(errs() << "===== Instruction selection begins:\n");
DEBUG(Indent = 0);
SelectRoot(*CurDAG);
DEBUG(errs() << "===== Instruction selection ends:\n");
CurDAG->RemoveDeadNodes();
RMWStores.clear();
}
SDNode *MSP430DAGToDAGISel::Select(SDValue Op) {
SDNode *Node = Op.getNode();
DebugLoc dl = Op.getDebugLoc();
// Dump information about the Node being selected
DEBUG(errs().indent(Indent) << "Selecting: ");
DEBUG(Node->dump(CurDAG));
DEBUG(errs() << "\n");
DEBUG(Indent += 2);
// If we have a custom node, we already have selected!
if (Node->isMachineOpcode()) {
DEBUG(errs().indent(Indent-2) << "== ";
Node->dump(CurDAG);
errs() << "\n");
DEBUG(Indent -= 2);
return NULL;
}
// Few custom selection stuff.
switch (Node->getOpcode()) {
default: break;
case ISD::FrameIndex: {
assert(Op.getValueType() == MVT::i16);
int FI = cast<FrameIndexSDNode>(Node)->getIndex();
SDValue TFI = CurDAG->getTargetFrameIndex(FI, MVT::i16);
if (Node->hasOneUse())
return CurDAG->SelectNodeTo(Node, MSP430::ADD16ri, MVT::i16,
TFI, CurDAG->getTargetConstant(0, MVT::i16));
return CurDAG->getMachineNode(MSP430::ADD16ri, dl, MVT::i16,
TFI, CurDAG->getTargetConstant(0, MVT::i16));
}
}
// Select the default instruction
SDNode *ResNode = SelectCode(Op);
DEBUG(errs() << std::string(Indent-2, ' ') << "=> ");
if (ResNode == NULL || ResNode == Op.getNode())
DEBUG(Op.getNode()->dump(CurDAG));
else
DEBUG(ResNode->dump(CurDAG));
DEBUG(errs() << "\n");
DEBUG(Indent -= 2);
return ResNode;
}
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