//===- FastISel.h - Definition of the FastISel class ------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file defines the FastISel class.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_FASTISEL_H
#define LLVM_CODEGEN_FASTISEL_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/Support/MachineValueType.h"
#include <cstdint>
#include <utility>
namespace llvm {
class AllocaInst;
class Instruction;
class IntrinsicInst;
class BasicBlock;
class CallInst;
class Constant;
class ConstantFP;
class DataLayout;
class FunctionLoweringInfo;
class LoadInst;
class MachineConstantPool;
class MachineFrameInfo;
class MachineFunction;
class MachineInstr;
class MachineMemOperand;
class MachineOperand;
class MachineRegisterInfo;
class MCContext;
class MCInstrDesc;
class MCSymbol;
class TargetInstrInfo;
class TargetLibraryInfo;
class TargetMachine;
class TargetRegisterClass;
class TargetRegisterInfo;
class Type;
class User;
class Value;
/// This is a fast-path instruction selection class that generates poor
/// code and doesn't support illegal types or non-trivial lowering, but runs
/// quickly.
class FastISel {
public:
using ArgListEntry = TargetLoweringBase::ArgListEntry;
using ArgListTy = TargetLoweringBase::ArgListTy;
struct CallLoweringInfo {
Type *RetTy = nullptr;
bool RetSExt : 1;
bool RetZExt : 1;
bool IsVarArg : 1;
bool IsInReg : 1;
bool DoesNotReturn : 1;
bool IsReturnValueUsed : 1;
bool IsPatchPoint : 1;
// IsTailCall Should be modified by implementations of FastLowerCall
// that perform tail call conversions.
bool IsTailCall = false;
unsigned NumFixedArgs = -1;
CallingConv::ID CallConv = CallingConv::C;
const Value *Callee = nullptr;
MCSymbol *Symbol = nullptr;
ArgListTy Args;
const CallBase *CB = nullptr;
MachineInstr *Call = nullptr;
Register ResultReg;
unsigned NumResultRegs = 0;
SmallVector<Value *, 16> OutVals;
SmallVector<ISD::ArgFlagsTy, 16> OutFlags;
SmallVector<Register, 16> OutRegs;
SmallVector<ISD::InputArg, 4> Ins;
SmallVector<Register, 4> InRegs;
CallLoweringInfo()
: RetSExt(false), RetZExt(false), IsVarArg(false), IsInReg(false),
DoesNotReturn(false), IsReturnValueUsed(true), IsPatchPoint(false) {}
CallLoweringInfo &setCallee(Type *ResultTy, FunctionType *FuncTy,
const Value *Target, ArgListTy &&ArgsList,
const CallBase &Call) {
RetTy = ResultTy;
Callee = Target;
IsInReg = Call.hasRetAttr(Attribute::InReg);
DoesNotReturn = Call.doesNotReturn();
IsVarArg = FuncTy->isVarArg();
IsReturnValueUsed = !Call.use_empty();
RetSExt = Call.hasRetAttr(Attribute::SExt);
RetZExt = Call.hasRetAttr(Attribute::ZExt);
CallConv = Call.getCallingConv();
Args = std::move(ArgsList);
NumFixedArgs = FuncTy->getNumParams();
CB = &Call;
return *this;
}
CallLoweringInfo &setCallee(Type *ResultTy, FunctionType *FuncTy,
MCSymbol *Target, ArgListTy &&ArgsList,
const CallBase &Call,
unsigned FixedArgs = ~0U) {
RetTy = ResultTy;
Callee = Call.getCalledOperand();
Symbol = Target;
IsInReg = Call.hasRetAttr(Attribute::InReg);
DoesNotReturn = Call.doesNotReturn();
IsVarArg = FuncTy->isVarArg();
IsReturnValueUsed = !Call.use_empty();
RetSExt = Call.hasRetAttr(Attribute::SExt);
RetZExt = Call.hasRetAttr(Attribute::ZExt);
CallConv = Call.getCallingConv();
Args = std::move(ArgsList);
NumFixedArgs = (FixedArgs == ~0U) ? FuncTy->getNumParams() : FixedArgs;
CB = &Call;
return *this;
}
CallLoweringInfo &setCallee(CallingConv::ID CC, Type *ResultTy,
const Value *Target, ArgListTy &&ArgsList,
unsigned FixedArgs = ~0U) {
RetTy = ResultTy;
Callee = Target;
CallConv = CC;
Args = std::move(ArgsList);
NumFixedArgs = (FixedArgs == ~0U) ? Args.size() : FixedArgs;
return *this;
}
CallLoweringInfo &setCallee(const DataLayout &DL, MCContext &Ctx,
CallingConv::ID CC, Type *ResultTy,
StringRef Target, ArgListTy &&ArgsList,
unsigned FixedArgs = ~0U);
CallLoweringInfo &setCallee(CallingConv::ID CC, Type *ResultTy,
MCSymbol *Target, ArgListTy &&ArgsList,
unsigned FixedArgs = ~0U) {
RetTy = ResultTy;
Symbol = Target;
CallConv = CC;
Args = std::move(ArgsList);
NumFixedArgs = (FixedArgs == ~0U) ? Args.size() : FixedArgs;
return *this;
}
CallLoweringInfo &setTailCall(bool Value = true) {
IsTailCall = Value;
return *this;
}
CallLoweringInfo &setIsPatchPoint(bool Value = true) {
IsPatchPoint = Value;
return *this;
}
ArgListTy &getArgs() { return Args; }
void clearOuts() {
OutVals.clear();
OutFlags.clear();
OutRegs.clear();
}
void clearIns() {
Ins.clear();
InRegs.clear();
}
};
protected:
DenseMap<const Value *, Register> LocalValueMap;
FunctionLoweringInfo &FuncInfo;
MachineFunction *MF;
MachineRegisterInfo &MRI;
MachineFrameInfo &MFI;
MachineConstantPool &MCP;
MIMetadata MIMD;
const TargetMachine &TM;
const DataLayout &DL;
const TargetInstrInfo &TII;
const TargetLowering &TLI;
const TargetRegisterInfo &TRI;
const TargetLibraryInfo *LibInfo;
bool SkipTargetIndependentISel;
/// The position of the last instruction for materializing constants
/// for use in the current block. It resets to EmitStartPt when it makes sense
/// (for example, it's usually profitable to avoid function calls between the
/// definition and the use)
MachineInstr *LastLocalValue = nullptr;
/// The top most instruction in the current block that is allowed for
/// emitting local variables. LastLocalValue resets to EmitStartPt when it
/// makes sense (for example, on function calls)
MachineInstr *EmitStartPt = nullptr;
public:
virtual ~FastISel();
/// Return the position of the last instruction emitted for
/// materializing constants for use in the current block.
MachineInstr *getLastLocalValue() { return LastLocalValue; }
/// Update the position of the last instruction emitted for
/// materializing constants for use in the current block.
void setLastLocalValue(MachineInstr *I) {
EmitStartPt = I;
LastLocalValue = I;
}
/// Set the current block to which generated machine instructions will
/// be appended.
void startNewBlock();
/// Flush the local value map.
void finishBasicBlock();
/// Return current debug location information.
DebugLoc getCurDebugLoc() const { return MIMD.getDL(); }
/// Do "fast" instruction selection for function arguments and append
/// the machine instructions to the current block. Returns true when
/// successful.
bool lowerArguments();
/// Do "fast" instruction selection for the given LLVM IR instruction
/// and append the generated machine instructions to the current block.
/// Returns true if selection was successful.
bool selectInstruction(const Instruction *I);
/// Do "fast" instruction selection for the given LLVM IR operator
/// (Instruction or ConstantExpr), and append generated machine instructions
/// to the current block. Return true if selection was successful.
bool selectOperator(const User *I, unsigned Opcode);
/// Create a virtual register and arrange for it to be assigned the
/// value for the given LLVM value.
Register getRegForValue(const Value *V);
/// Look up the value to see if its value is already cached in a
/// register. It may be defined by instructions across blocks or defined
/// locally.
Register lookUpRegForValue(const Value *V);
/// This is a wrapper around getRegForValue that also takes care of
/// truncating or sign-extending the given getelementptr index value.
Register getRegForGEPIndex(const Value *Idx);
/// We're checking to see if we can fold \p LI into \p FoldInst. Note
/// that we could have a sequence where multiple LLVM IR instructions are
/// folded into the same machineinstr. For example we could have:
///
/// A: x = load i32 *P
/// B: y = icmp A, 42
/// C: br y, ...
///
/// In this scenario, \p LI is "A", and \p FoldInst is "C". We know about "B"
/// (and any other folded instructions) because it is between A and C.
///
/// If we succeed folding, return true.
bool tryToFoldLoad(const LoadInst *LI, const Instruction *FoldInst);
/// The specified machine instr operand is a vreg, and that vreg is
/// being provided by the specified load instruction. If possible, try to
/// fold the load as an operand to the instruction, returning true if
/// possible.
///
/// This method should be implemented by targets.
virtual bool tryToFoldLoadIntoMI(MachineInstr * /*MI*/, unsigned /*OpNo*/,
const LoadInst * /*LI*/) {
return false;
}
/// Reset InsertPt to prepare for inserting instructions into the
/// current block.
void recomputeInsertPt();
/// Remove all dead instructions between the I and E.
void removeDeadCode(MachineBasicBlock::iterator I,
MachineBasicBlock::iterator E);
using SavePoint = MachineBasicBlock::iterator;
/// Prepare InsertPt to begin inserting instructions into the local
/// value area and return the old insert position.
SavePoint enterLocalValueArea();
/// Reset InsertPt to the given old insert position.
void leaveLocalValueArea(SavePoint Old);
protected:
explicit FastISel(FunctionLoweringInfo &FuncInfo,
const TargetLibraryInfo *LibInfo,
bool SkipTargetIndependentISel = false);
/// This method is called by target-independent code when the normal
/// FastISel process fails to select an instruction. This gives targets a
/// chance to emit code for anything that doesn't fit into FastISel's
/// framework. It returns true if it was successful.
virtual bool fastSelectInstruction(const Instruction *I) = 0;
/// This method is called by target-independent code to do target-
/// specific argument lowering. It returns true if it was successful.
virtual bool fastLowerArguments();
/// This method is called by target-independent code to do target-
/// specific call lowering. It returns true if it was successful.
virtual bool fastLowerCall(CallLoweringInfo &CLI);
/// This method is called by target-independent code to do target-
/// specific intrinsic lowering. It returns true if it was successful.
virtual bool fastLowerIntrinsicCall(const IntrinsicInst *II);
/// This method is called by target-independent code to request that an
/// instruction with the given type and opcode be emitted.
virtual unsigned fastEmit_(MVT VT, MVT RetVT, unsigned Opcode);
/// This method is called by target-independent code to request that an
/// instruction with the given type, opcode, and register operand be emitted.
virtual unsigned fastEmit_r(MVT VT, MVT RetVT, unsigned Opcode, unsigned Op0);
/// This method is called by target-independent code to request that an
/// instruction with the given type, opcode, and register operands be emitted.
virtual unsigned fastEmit_rr(MVT VT, MVT RetVT, unsigned Opcode, unsigned Op0,
unsigned Op1);
/// This method is called by target-independent code to request that an
/// instruction with the given type, opcode, and register and immediate
/// operands be emitted.
virtual unsigned fastEmit_ri(MVT VT, MVT RetVT, unsigned Opcode, unsigned Op0,
uint64_t Imm);
/// This method is a wrapper of fastEmit_ri.
///
/// It first tries to emit an instruction with an immediate operand using
/// fastEmit_ri. If that fails, it materializes the immediate into a register
/// and try fastEmit_rr instead.
Register fastEmit_ri_(MVT VT, unsigned Opcode, unsigned Op0, uint64_t Imm,
MVT ImmType);
/// This method is called by target-independent code to request that an
/// instruction with the given type, opcode, and immediate operand be emitted.
virtual unsigned fastEmit_i(MVT VT, MVT RetVT, unsigned Opcode, uint64_t Imm);
/// This method is called by target-independent code to request that an
/// instruction with the given type, opcode, and floating-point immediate
/// operand be emitted.
virtual unsigned fastEmit_f(MVT VT, MVT RetVT, unsigned Opcode,
const ConstantFP *FPImm);
/// Emit a MachineInstr with no operands and a result register in the
/// given register class.
Register fastEmitInst_(unsigned MachineInstOpcode,
const TargetRegisterClass *RC);
/// Emit a MachineInstr with one register operand and a result register
/// in the given register class.
Register fastEmitInst_r(unsigned MachineInstOpcode,
const TargetRegisterClass *RC, unsigned Op0);
/// Emit a MachineInstr with two register operands and a result
/// register in the given register class.
Register fastEmitInst_rr(unsigned MachineInstOpcode,
const TargetRegisterClass *RC, unsigned Op0,
unsigned Op1);
/// Emit a MachineInstr with three register operands and a result
/// register in the given register class.
Register fastEmitInst_rrr(unsigned MachineInstOpcode,
const TargetRegisterClass *RC, unsigned Op0,
unsigned Op1, unsigned Op2);
/// Emit a MachineInstr with a register operand, an immediate, and a
/// result register in the given register class.
Register fastEmitInst_ri(unsigned MachineInstOpcode,
const TargetRegisterClass *RC, unsigned Op0,
uint64_t Imm);
/// Emit a MachineInstr with one register operand and two immediate
/// operands.
Register fastEmitInst_rii(unsigned MachineInstOpcode,
const TargetRegisterClass *RC, unsigned Op0,
uint64_t Imm1, uint64_t Imm2);
/// Emit a MachineInstr with a floating point immediate, and a result
/// register in the given register class.
Register fastEmitInst_f(unsigned MachineInstOpcode,
const TargetRegisterClass *RC,
const ConstantFP *FPImm);
/// Emit a MachineInstr with two register operands, an immediate, and a
/// result register in the given register class.
Register fastEmitInst_rri(unsigned MachineInstOpcode,
const TargetRegisterClass *RC, unsigned Op0,
unsigned Op1, uint64_t Imm);
/// Emit a MachineInstr with a single immediate operand, and a result
/// register in the given register class.
Register fastEmitInst_i(unsigned MachineInstOpcode,
const TargetRegisterClass *RC, uint64_t Imm);
/// Emit a MachineInstr for an extract_subreg from a specified index of
/// a superregister to a specified type.
Register fastEmitInst_extractsubreg(MVT RetVT, unsigned Op0, uint32_t Idx);
/// Emit MachineInstrs to compute the value of Op with all but the
/// least significant bit set to zero.
Register fastEmitZExtFromI1(MVT VT, unsigned Op0);
/// Emit an unconditional branch to the given block, unless it is the
/// immediate (fall-through) successor, and update the CFG.
void fastEmitBranch(MachineBasicBlock *MSucc, const DebugLoc &DbgLoc);
/// Emit an unconditional branch to \p FalseMBB, obtains the branch weight
/// and adds TrueMBB and FalseMBB to the successor list.
void finishCondBranch(const BasicBlock *BranchBB, MachineBasicBlock *TrueMBB,
MachineBasicBlock *FalseMBB);
/// Update the value map to include the new mapping for this
/// instruction, or insert an extra copy to get the result in a previous
/// determined register.
///
/// NOTE: This is only necessary because we might select a block that uses a
/// value before we select the block that defines the value. It might be
/// possible to fix this by selecting blocks in reverse postorder.
void updateValueMap(const Value *I, Register Reg, unsigned NumRegs = 1);
Register createResultReg(const TargetRegisterClass *RC);
/// Try to constrain Op so that it is usable by argument OpNum of the
/// provided MCInstrDesc. If this fails, create a new virtual register in the
/// correct class and COPY the value there.
Register constrainOperandRegClass(const MCInstrDesc &II, Register Op,
unsigned OpNum);
/// Emit a constant in a register using target-specific logic, such as
/// constant pool loads.
virtual unsigned fastMaterializeConstant(const Constant *C) { return 0; }
/// Emit an alloca address in a register using target-specific logic.
virtual unsigned fastMaterializeAlloca(const AllocaInst *C) { return 0; }
/// Emit the floating-point constant +0.0 in a register using target-
/// specific logic.
virtual unsigned fastMaterializeFloatZero(const ConstantFP *CF) {
return 0;
}
/// Check if \c Add is an add that can be safely folded into \c GEP.
///
/// \c Add can be folded into \c GEP if:
/// - \c Add is an add,
/// - \c Add's size matches \c GEP's,
/// - \c Add is in the same basic block as \c GEP, and
/// - \c Add has a constant operand.
bool canFoldAddIntoGEP(const User *GEP, const Value *Add);
/// Create a machine mem operand from the given instruction.
MachineMemOperand *createMachineMemOperandFor(const Instruction *I) const;
CmpInst::Predicate optimizeCmpPredicate(const CmpInst *CI) const;
bool lowerCallTo(const CallInst *CI, MCSymbol *Symbol, unsigned NumArgs);
bool lowerCallTo(const CallInst *CI, const char *SymName,
unsigned NumArgs);
bool lowerCallTo(CallLoweringInfo &CLI);
bool lowerCall(const CallInst *I);
/// Select and emit code for a binary operator instruction, which has
/// an opcode which directly corresponds to the given ISD opcode.
bool selectBinaryOp(const User *I, unsigned ISDOpcode);
bool selectFNeg(const User *I, const Value *In);
bool selectGetElementPtr(const User *I);
bool selectStackmap(const CallInst *I);
bool selectPatchpoint(const CallInst *I);
bool selectCall(const User *I);
bool selectIntrinsicCall(const IntrinsicInst *II);
bool selectBitCast(const User *I);
bool selectFreeze(const User *I);
bool selectCast(const User *I, unsigned Opcode);
bool selectExtractValue(const User *U);
bool selectXRayCustomEvent(const CallInst *II);
bool selectXRayTypedEvent(const CallInst *II);
bool shouldOptForSize(const MachineFunction *MF) const {
// TODO: Implement PGSO.
return MF->getFunction().hasOptSize();
}
private:
/// Handle PHI nodes in successor blocks.
///
/// Emit code to ensure constants are copied into registers when needed.
/// Remember the virtual registers that need to be added to the Machine PHI
/// nodes as input. We cannot just directly add them, because expansion might
/// result in multiple MBB's for one BB. As such, the start of the BB might
/// correspond to a different MBB than the end.
bool handlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB);
/// Helper for materializeRegForValue to materialize a constant in a
/// target-independent way.
Register materializeConstant(const Value *V, MVT VT);
/// Helper for getRegForVale. This function is called when the value
/// isn't already available in a register and must be materialized with new
/// instructions.
Register materializeRegForValue(const Value *V, MVT VT);
/// Clears LocalValueMap and moves the area for the new local variables
/// to the beginning of the block. It helps to avoid spilling cached variables
/// across heavy instructions like calls.
void flushLocalValueMap();
/// Removes dead local value instructions after SavedLastLocalvalue.
void removeDeadLocalValueCode(MachineInstr *SavedLastLocalValue);
/// Insertion point before trying to select the current instruction.
MachineBasicBlock::iterator SavedInsertPt;
/// Add a stackmap or patchpoint intrinsic call's live variable
/// operands to a stackmap or patchpoint machine instruction.
bool addStackMapLiveVars(SmallVectorImpl<MachineOperand> &Ops,
const CallInst *CI, unsigned StartIdx);
bool lowerCallOperands(const CallInst *CI, unsigned ArgIdx, unsigned NumArgs,
const Value *Callee, bool ForceRetVoidTy,
CallLoweringInfo &CLI);
};
} // end namespace llvm
#endif // LLVM_CODEGEN_FASTISEL_H