llvm-6502/include/llvm/Target/TargetLowering.h

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//===-- llvm/Target/TargetLowering.h - Target Lowering Info -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file describes how to lower LLVM code to machine code. This has two
// main components:
//
// 1. Which ValueTypes are natively supported by the target.
// 2. Which operations are supported for supported ValueTypes.
// 3. Cost thresholds for alternative implementations of certain operations.
//
// In addition it has a few other components, like information about FP
// immediates.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TARGET_TARGETLOWERING_H
#define LLVM_TARGET_TARGETLOWERING_H
#include "llvm/Type.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/Support/DataTypes.h"
#include <vector>
namespace llvm {
class Value;
class Function;
class TargetMachine;
class TargetData;
class TargetRegisterClass;
class SDNode;
class SDOperand;
class SelectionDAG;
class MachineBasicBlock;
class MachineInstr;
//===----------------------------------------------------------------------===//
/// TargetLowering - This class defines information used to lower LLVM code to
/// legal SelectionDAG operators that the target instruction selector can accept
/// natively.
///
/// This class also defines callbacks that targets must implement to lower
/// target-specific constructs to SelectionDAG operators.
///
class TargetLowering {
public:
/// LegalizeAction - This enum indicates whether operations are valid for a
/// target, and if not, what action should be used to make them valid.
enum LegalizeAction {
Legal, // The target natively supports this operation.
Promote, // This operation should be executed in a larger type.
Expand, // Try to expand this to other ops, otherwise use a libcall.
Custom, // Use the LowerOperation hook to implement custom lowering.
};
enum OutOfRangeShiftAmount {
Undefined, // Oversized shift amounts are undefined (default).
Mask, // Shift amounts are auto masked (anded) to value size.
Extend, // Oversized shift pulls in zeros or sign bits.
};
enum SetCCResultValue {
UndefinedSetCCResult, // SetCC returns a garbage/unknown extend.
ZeroOrOneSetCCResult, // SetCC returns a zero extended result.
ZeroOrNegativeOneSetCCResult, // SetCC returns a sign extended result.
};
TargetLowering(TargetMachine &TM);
virtual ~TargetLowering();
TargetMachine &getTargetMachine() const { return TM; }
const TargetData &getTargetData() const { return TD; }
bool isLittleEndian() const { return IsLittleEndian; }
MVT::ValueType getPointerTy() const { return PointerTy; }
MVT::ValueType getShiftAmountTy() const { return ShiftAmountTy; }
OutOfRangeShiftAmount getShiftAmountFlavor() const {return ShiftAmtHandling; }
/// isSetCCExpensive - Return true if the setcc operation is expensive for
/// this target.
bool isSetCCExpensive() const { return SetCCIsExpensive; }
/// isIntDivCheap() - Return true if integer divide is usually cheaper than
/// a sequence of several shifts, adds, and multiplies for this target.
bool isIntDivCheap() const { return IntDivIsCheap; }
/// isPow2DivCheap() - Return true if pow2 div is cheaper than a chain of
/// srl/add/sra.
bool isPow2DivCheap() const { return Pow2DivIsCheap; }
/// getSetCCResultTy - Return the ValueType of the result of setcc operations.
///
MVT::ValueType getSetCCResultTy() const { return SetCCResultTy; }
/// getSetCCResultContents - For targets without boolean registers, this flag
/// returns information about the contents of the high-bits in the setcc
/// result register.
SetCCResultValue getSetCCResultContents() const { return SetCCResultContents;}
/// getRegClassFor - Return the register class that should be used for the
/// specified value type. This may only be called on legal types.
TargetRegisterClass *getRegClassFor(MVT::ValueType VT) const {
TargetRegisterClass *RC = RegClassForVT[VT];
assert(RC && "This value type is not natively supported!");
return RC;
}
/// isTypeLegal - Return true if the target has native support for the
/// specified value type. This means that it has a register that directly
/// holds it without promotions or expansions.
bool isTypeLegal(MVT::ValueType VT) const {
return RegClassForVT[VT] != 0;
}
/// getTypeAction - Return how we should legalize values of this type, either
/// it is already legal (return 'Legal') or we need to promote it to a larger
/// type (return 'Promote'), or we need to expand it into multiple registers
/// of smaller integer type (return 'Expand'). 'Custom' is not an option.
LegalizeAction getTypeAction(MVT::ValueType VT) const {
return (LegalizeAction)((ValueTypeActions >> (2*VT)) & 3);
}
unsigned long long getValueTypeActions() const { return ValueTypeActions; }
/// getTypeToTransformTo - For types supported by the target, this is an
/// identity function. For types that must be promoted to larger types, this
/// returns the larger type to promote to. For types that are larger than the
/// largest integer register, this contains one step in the expansion to get
/// to the smaller register.
MVT::ValueType getTypeToTransformTo(MVT::ValueType VT) const {
return TransformToType[VT];
}
typedef std::vector<double>::const_iterator legal_fpimm_iterator;
legal_fpimm_iterator legal_fpimm_begin() const {
return LegalFPImmediates.begin();
}
legal_fpimm_iterator legal_fpimm_end() const {
return LegalFPImmediates.end();
}
/// getOperationAction - Return how this operation should be treated: either
/// it is legal, needs to be promoted to a larger size, needs to be
/// expanded to some other code sequence, or the target has a custom expander
/// for it.
LegalizeAction getOperationAction(unsigned Op, MVT::ValueType VT) const {
return (LegalizeAction)((OpActions[Op] >> (2*VT)) & 3);
}
/// isOperationLegal - Return true if the specified operation is legal on this
/// target.
bool isOperationLegal(unsigned Op, MVT::ValueType VT) const {
return getOperationAction(Op, VT) == Legal;
}
/// getTypeToPromoteTo - If the action for this operation is to promote, this
/// method returns the ValueType to promote to.
MVT::ValueType getTypeToPromoteTo(unsigned Op, MVT::ValueType VT) const {
assert(getOperationAction(Op, VT) == Promote &&
"This operation isn't promoted!");
MVT::ValueType NVT = VT;
do {
NVT = (MVT::ValueType)(NVT+1);
assert(MVT::isInteger(NVT) == MVT::isInteger(VT) && NVT != MVT::isVoid &&
"Didn't find type to promote to!");
} while (!isTypeLegal(NVT) ||
getOperationAction(Op, NVT) == Promote);
return NVT;
}
/// getValueType - Return the MVT::ValueType corresponding to this LLVM type.
/// This is fixed by the LLVM operations except for the pointer size.
MVT::ValueType getValueType(const Type *Ty) const {
switch (Ty->getTypeID()) {
default: assert(0 && "Unknown type!");
case Type::VoidTyID: return MVT::isVoid;
case Type::BoolTyID: return MVT::i1;
case Type::UByteTyID:
case Type::SByteTyID: return MVT::i8;
case Type::ShortTyID:
case Type::UShortTyID: return MVT::i16;
case Type::IntTyID:
case Type::UIntTyID: return MVT::i32;
case Type::LongTyID:
case Type::ULongTyID: return MVT::i64;
case Type::FloatTyID: return MVT::f32;
case Type::DoubleTyID: return MVT::f64;
case Type::PointerTyID: return PointerTy;
case Type::PackedTyID: return MVT::Vector;
}
}
/// getNumElements - Return the number of registers that this ValueType will
/// eventually require. This is always one for all non-integer types, is
/// one for any types promoted to live in larger registers, but may be more
/// than one for types (like i64) that are split into pieces.
unsigned getNumElements(MVT::ValueType VT) const {
return NumElementsForVT[VT];
}
/// This function returns the maximum number of store operations permitted
/// to replace a call to llvm.memset. The value is set by the target at the
/// performance threshold for such a replacement.
/// @brief Get maximum # of store operations permitted for llvm.memset
unsigned getMaxStoresPerMemSet() const { return maxStoresPerMemSet; }
/// This function returns the maximum number of store operations permitted
/// to replace a call to llvm.memcpy. The value is set by the target at the
/// performance threshold for such a replacement.
/// @brief Get maximum # of store operations permitted for llvm.memcpy
unsigned getMaxStoresPerMemCpy() const { return maxStoresPerMemCpy; }
/// This function returns the maximum number of store operations permitted
/// to replace a call to llvm.memmove. The value is set by the target at the
/// performance threshold for such a replacement.
/// @brief Get maximum # of store operations permitted for llvm.memmove
unsigned getMaxStoresPerMemMove() const { return maxStoresPerMemMove; }
/// This function returns true if the target allows unaligned memory accesses.
/// This is used, for example, in situations where an array copy/move/set is
/// converted to a sequence of store operations. It's use helps to ensure that
/// such replacements don't generate code that causes an alignment error
/// (trap) on the target machine.
/// @brief Determine if the target supports unaligned memory accesses.
bool allowsUnalignedMemoryAccesses() const
{ return allowUnalignedMemoryAccesses; }
/// usesUnderscoreSetJmpLongJmp - Determine if we should use _setjmp or setjmp
/// to implement llvm.setjmp.
bool usesUnderscoreSetJmpLongJmp() const {
return UseUnderscoreSetJmpLongJmp;
}
/// getStackPointerRegisterToSaveRestore - If a physical register, this
/// specifies the register that llvm.savestack/llvm.restorestack should save
/// and restore.
unsigned getStackPointerRegisterToSaveRestore() const {
return StackPointerRegisterToSaveRestore;
}
//===--------------------------------------------------------------------===//
// TargetLowering Configuration Methods - These methods should be invoked by
// the derived class constructor to configure this object for the target.
//
protected:
/// setShiftAmountType - Describe the type that should be used for shift
/// amounts. This type defaults to the pointer type.
void setShiftAmountType(MVT::ValueType VT) { ShiftAmountTy = VT; }
/// setSetCCResultType - Describe the type that shoudl be used as the result
/// of a setcc operation. This defaults to the pointer type.
void setSetCCResultType(MVT::ValueType VT) { SetCCResultTy = VT; }
/// setSetCCResultContents - Specify how the target extends the result of a
/// setcc operation in a register.
void setSetCCResultContents(SetCCResultValue Ty) { SetCCResultContents = Ty; }
/// setShiftAmountFlavor - Describe how the target handles out of range shift
/// amounts.
void setShiftAmountFlavor(OutOfRangeShiftAmount OORSA) {
ShiftAmtHandling = OORSA;
}
/// setUseUnderscoreSetJmpLongJmp - Indicate whether this target prefers to
/// use _setjmp and _longjmp to or implement llvm.setjmp/llvm.longjmp or
/// the non _ versions. Defaults to false.
void setUseUnderscoreSetJmpLongJmp(bool Val) {
UseUnderscoreSetJmpLongJmp = Val;
}
/// setStackPointerRegisterToSaveRestore - If set to a physical register, this
/// specifies the register that llvm.savestack/llvm.restorestack should save
/// and restore.
void setStackPointerRegisterToSaveRestore(unsigned R) {
StackPointerRegisterToSaveRestore = R;
}
/// setSetCCIxExpensive - This is a short term hack for targets that codegen
/// setcc as a conditional branch. This encourages the code generator to fold
/// setcc operations into other operations if possible.
void setSetCCIsExpensive() { SetCCIsExpensive = true; }
/// setIntDivIsCheap - Tells the code generator that integer divide is
/// expensive, and if possible, should be replaced by an alternate sequence
/// of instructions not containing an integer divide.
void setIntDivIsCheap(bool isCheap = true) { IntDivIsCheap = isCheap; }
/// setPow2DivIsCheap - Tells the code generator that it shouldn't generate
/// srl/add/sra for a signed divide by power of two, and let the target handle
/// it.
void setPow2DivIsCheap(bool isCheap = true) { Pow2DivIsCheap = isCheap; }
/// addRegisterClass - Add the specified register class as an available
/// regclass for the specified value type. This indicates the selector can
/// handle values of that class natively.
void addRegisterClass(MVT::ValueType VT, TargetRegisterClass *RC) {
AvailableRegClasses.push_back(std::make_pair(VT, RC));
RegClassForVT[VT] = RC;
}
/// computeRegisterProperties - Once all of the register classes are added,
/// this allows us to compute derived properties we expose.
void computeRegisterProperties();
/// setOperationAction - Indicate that the specified operation does not work
/// with the specified type and indicate what to do about it.
void setOperationAction(unsigned Op, MVT::ValueType VT,
LegalizeAction Action) {
assert(VT < 16 && Op < sizeof(OpActions)/sizeof(OpActions[0]) &&
"Table isn't big enough!");
OpActions[Op] |= Action << VT*2;
}
/// addLegalFPImmediate - Indicate that this target can instruction select
/// the specified FP immediate natively.
void addLegalFPImmediate(double Imm) {
LegalFPImmediates.push_back(Imm);
}
public:
//===--------------------------------------------------------------------===//
// Lowering methods - These methods must be implemented by targets so that
// the SelectionDAGLowering code knows how to lower these.
//
/// LowerArguments - This hook must be implemented to indicate how we should
/// lower the arguments for the specified function, into the specified DAG.
virtual std::vector<SDOperand>
LowerArguments(Function &F, SelectionDAG &DAG) = 0;
/// LowerCallTo - This hook lowers an abstract call to a function into an
/// actual call. This returns a pair of operands. The first element is the
/// return value for the function (if RetTy is not VoidTy). The second
/// element is the outgoing token chain.
typedef std::vector<std::pair<SDOperand, const Type*> > ArgListTy;
virtual std::pair<SDOperand, SDOperand>
LowerCallTo(SDOperand Chain, const Type *RetTy, bool isVarArg,
unsigned CallingConv, bool isTailCall, SDOperand Callee,
ArgListTy &Args, SelectionDAG &DAG) = 0;
/// LowerReturnTo - This hook lowers a return instruction into the appropriate
/// legal ISD::RET node for the target's current ABI. This method is optional
/// and is intended for targets that need non-standard behavior.
virtual SDOperand LowerReturnTo(SDOperand Chain, SDOperand Op,
SelectionDAG &DAG);
/// LowerVAStart - This lowers the llvm.va_start intrinsic. If not
/// implemented, this method prints a message and aborts. This method should
/// return the modified chain value. Note that VAListPtr* correspond to the
/// llvm.va_start operand.
virtual SDOperand LowerVAStart(SDOperand Chain, SDOperand VAListP,
Value *VAListV, SelectionDAG &DAG);
/// LowerVAEnd - This lowers llvm.va_end and returns the resultant chain. If
/// not implemented, this defaults to a noop.
virtual SDOperand LowerVAEnd(SDOperand Chain, SDOperand LP, Value *LV,
SelectionDAG &DAG);
/// LowerVACopy - This lowers llvm.va_copy and returns the resultant chain.
/// If not implemented, this defaults to loading a pointer from the input and
/// storing it to the output.
virtual SDOperand LowerVACopy(SDOperand Chain, SDOperand SrcP, Value *SrcV,
SDOperand DestP, Value *DestV,
SelectionDAG &DAG);
/// LowerVAArg - This lowers the vaarg instruction. If not implemented, this
/// prints a message and aborts.
virtual std::pair<SDOperand,SDOperand>
LowerVAArg(SDOperand Chain, SDOperand VAListP, Value *VAListV,
const Type *ArgTy, SelectionDAG &DAG);
/// LowerFrameReturnAddress - This hook lowers a call to llvm.returnaddress or
/// llvm.frameaddress (depending on the value of the first argument). The
/// return values are the result pointer and the resultant token chain. If
/// not implemented, both of these intrinsics will return null.
virtual std::pair<SDOperand, SDOperand>
LowerFrameReturnAddress(bool isFrameAddr, SDOperand Chain, unsigned Depth,
SelectionDAG &DAG);
/// LowerOperation - For operations that are unsupported by the target, and
/// which are registered to use 'custom' lowering. This callback is invoked.
/// If the target has no operations that require custom lowering, it need not
/// implement this. The default implementation of this aborts.
virtual SDOperand LowerOperation(SDOperand Op, SelectionDAG &DAG);
/// getTargetNodeName() - This method returns the name of a target specific
/// DAG node.
virtual const char *getTargetNodeName(unsigned Opcode) const;
/// isMaskedValueZeroForTargetNode - Return true if 'Op & Mask' is known to
/// be zero. Op is expected to be a target specific node. Used by DAG
/// combiner.
virtual bool isMaskedValueZeroForTargetNode(const SDOperand &Op,
uint64_t Mask) const;
//===--------------------------------------------------------------------===//
// Scheduler hooks
//
// InsertAtEndOfBasicBlock - This method should be implemented by targets that
// mark instructions with the 'usesCustomDAGSchedInserter' flag. These
// instructions are special in various ways, which require special support to
// insert. The specified MachineInstr is created but not inserted into any
// basic blocks, and the scheduler passes ownership of it to this method.
virtual MachineBasicBlock *InsertAtEndOfBasicBlock(MachineInstr *MI,
MachineBasicBlock *MBB);
private:
TargetMachine &TM;
const TargetData &TD;
/// IsLittleEndian - True if this is a little endian target.
///
bool IsLittleEndian;
/// PointerTy - The type to use for pointers, usually i32 or i64.
///
MVT::ValueType PointerTy;
/// ShiftAmountTy - The type to use for shift amounts, usually i8 or whatever
/// PointerTy is.
MVT::ValueType ShiftAmountTy;
OutOfRangeShiftAmount ShiftAmtHandling;
/// SetCCIsExpensive - This is a short term hack for targets that codegen
/// setcc as a conditional branch. This encourages the code generator to fold
/// setcc operations into other operations if possible.
bool SetCCIsExpensive;
/// IntDivIsCheap - Tells the code generator not to expand integer divides by
/// constants into a sequence of muls, adds, and shifts. This is a hack until
/// a real cost model is in place. If we ever optimize for size, this will be
/// set to true unconditionally.
bool IntDivIsCheap;
/// Pow2DivIsCheap - Tells the code generator that it shouldn't generate
/// srl/add/sra for a signed divide by power of two, and let the target handle
/// it.
bool Pow2DivIsCheap;
/// SetCCResultTy - The type that SetCC operations use. This defaults to the
/// PointerTy.
MVT::ValueType SetCCResultTy;
/// SetCCResultContents - Information about the contents of the high-bits in
/// the result of a setcc comparison operation.
SetCCResultValue SetCCResultContents;
/// UseUnderscoreSetJmpLongJmp - This target prefers to use _setjmp and
/// _longjmp to implement llvm.setjmp/llvm.longjmp. Defaults to false.
bool UseUnderscoreSetJmpLongJmp;
/// StackPointerRegisterToSaveRestore - If set to a physical register, this
/// specifies the register that llvm.savestack/llvm.restorestack should save
/// and restore.
unsigned StackPointerRegisterToSaveRestore;
/// RegClassForVT - This indicates the default register class to use for
/// each ValueType the target supports natively.
TargetRegisterClass *RegClassForVT[MVT::LAST_VALUETYPE];
unsigned char NumElementsForVT[MVT::LAST_VALUETYPE];
/// ValueTypeActions - This is a bitvector that contains two bits for each
/// value type, where the two bits correspond to the LegalizeAction enum.
/// This can be queried with "getTypeAction(VT)".
unsigned long long ValueTypeActions;
/// TransformToType - For any value types we are promoting or expanding, this
/// contains the value type that we are changing to. For Expanded types, this
/// contains one step of the expand (e.g. i64 -> i32), even if there are
/// multiple steps required (e.g. i64 -> i16). For types natively supported
/// by the system, this holds the same type (e.g. i32 -> i32).
MVT::ValueType TransformToType[MVT::LAST_VALUETYPE];
/// OpActions - For each operation and each value type, keep a LegalizeAction
/// that indicates how instruction selection should deal with the operation.
/// Most operations are Legal (aka, supported natively by the target), but
/// operations that are not should be described. Note that operations on
/// non-legal value types are not described here.
unsigned OpActions[128];
std::vector<double> LegalFPImmediates;
std::vector<std::pair<MVT::ValueType,
TargetRegisterClass*> > AvailableRegClasses;
protected:
/// When lowering %llvm.memset this field specifies the maximum number of
/// store operations that may be substituted for the call to memset. Targets
/// must set this value based on the cost threshold for that target. Targets
/// should assume that the memset will be done using as many of the largest
/// store operations first, followed by smaller ones, if necessary, per
/// alignment restrictions. For example, storing 9 bytes on a 32-bit machine
/// with 16-bit alignment would result in four 2-byte stores and one 1-byte
/// store. This only applies to setting a constant array of a constant size.
/// @brief Specify maximum number of store instructions per memset call.
unsigned maxStoresPerMemSet;
/// When lowering %llvm.memcpy this field specifies the maximum number of
/// store operations that may be substituted for a call to memcpy. Targets
/// must set this value based on the cost threshold for that target. Targets
/// should assume that the memcpy will be done using as many of the largest
/// store operations first, followed by smaller ones, if necessary, per
/// alignment restrictions. For example, storing 7 bytes on a 32-bit machine
/// with 32-bit alignment would result in one 4-byte store, a one 2-byte store
/// and one 1-byte store. This only applies to copying a constant array of
/// constant size.
/// @brief Specify maximum bytes of store instructions per memcpy call.
unsigned maxStoresPerMemCpy;
/// When lowering %llvm.memmove this field specifies the maximum number of
/// store instructions that may be substituted for a call to memmove. Targets
/// must set this value based on the cost threshold for that target. Targets
/// should assume that the memmove will be done using as many of the largest
/// store operations first, followed by smaller ones, if necessary, per
/// alignment restrictions. For example, moving 9 bytes on a 32-bit machine
/// with 8-bit alignment would result in nine 1-byte stores. This only
/// applies to copying a constant array of constant size.
/// @brief Specify maximum bytes of store instructions per memmove call.
unsigned maxStoresPerMemMove;
/// This field specifies whether the target machine permits unaligned memory
/// accesses. This is used, for example, to determine the size of store
/// operations when copying small arrays and other similar tasks.
/// @brief Indicate whether the target permits unaligned memory accesses.
bool allowUnalignedMemoryAccesses;
};
} // end llvm namespace
#endif