//===- llvm/CodeGen/GlobalISel/GISelKnownBits.h ---------------*- 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 /// Provides analysis for querying information about KnownBits during GISel /// passes. /// //===----------------------------------------------------------------------===// #ifndef LLVM_CODEGEN_GLOBALISEL_GISELKNOWNBITS_H #define LLVM_CODEGEN_GLOBALISEL_GISELKNOWNBITS_H #include "llvm/ADT/DenseMap.h" #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/Register.h" #include "llvm/InitializePasses.h" #include "llvm/Support/KnownBits.h" namespace llvm { class TargetLowering; class DataLayout; class GISelKnownBits : public GISelChangeObserver { MachineFunction &MF; MachineRegisterInfo &MRI; const TargetLowering &TL; const DataLayout &DL; unsigned MaxDepth; /// Cache maintained during a computeKnownBits request. SmallDenseMap ComputeKnownBitsCache; void computeKnownBitsMin(Register Src0, Register Src1, KnownBits &Known, const APInt &DemandedElts, unsigned Depth = 0); unsigned computeNumSignBitsMin(Register Src0, Register Src1, const APInt &DemandedElts, unsigned Depth = 0); public: GISelKnownBits(MachineFunction &MF, unsigned MaxDepth = 6); virtual ~GISelKnownBits() = default; const MachineFunction &getMachineFunction() const { return MF; } const DataLayout &getDataLayout() const { return DL; } virtual void computeKnownBitsImpl(Register R, KnownBits &Known, const APInt &DemandedElts, unsigned Depth = 0); unsigned computeNumSignBits(Register R, const APInt &DemandedElts, unsigned Depth = 0); unsigned computeNumSignBits(Register R, unsigned Depth = 0); // KnownBitsAPI KnownBits getKnownBits(Register R); KnownBits getKnownBits(Register R, const APInt &DemandedElts, unsigned Depth = 0); // Calls getKnownBits for first operand def of MI. KnownBits getKnownBits(MachineInstr &MI); APInt getKnownZeroes(Register R); APInt getKnownOnes(Register R); /// \return true if 'V & Mask' is known to be zero in DemandedElts. We use /// this predicate to simplify operations downstream. /// Mask is known to be zero for bits that V cannot have. bool maskedValueIsZero(Register Val, const APInt &Mask) { return Mask.isSubsetOf(getKnownBits(Val).Zero); } /// \return true if the sign bit of Op is known to be zero. We use this /// predicate to simplify operations downstream. bool signBitIsZero(Register Op); static void computeKnownBitsForAlignment(KnownBits &Known, Align Alignment) { // The low bits are known zero if the pointer is aligned. Known.Zero.setLowBits(Log2(Alignment)); } /// \return The known alignment for the pointer-like value \p R. Align computeKnownAlignment(Register R, unsigned Depth = 0); // Observer API. No-op for non-caching implementation. void erasingInstr(MachineInstr &MI) override {} void createdInstr(MachineInstr &MI) override {} void changingInstr(MachineInstr &MI) override {} void changedInstr(MachineInstr &MI) override {} protected: unsigned getMaxDepth() const { return MaxDepth; } }; /// To use KnownBitsInfo analysis in a pass, /// KnownBitsInfo &Info = getAnalysis().get(MF); /// Add to observer if the Info is caching. /// WrapperObserver.addObserver(Info); /// Eventually add other features such as caching/ser/deserializing /// to MIR etc. Those implementations can derive from GISelKnownBits /// and override computeKnownBitsImpl. class GISelKnownBitsAnalysis : public MachineFunctionPass { std::unique_ptr Info; public: static char ID; GISelKnownBitsAnalysis() : MachineFunctionPass(ID) { initializeGISelKnownBitsAnalysisPass(*PassRegistry::getPassRegistry()); } GISelKnownBits &get(MachineFunction &MF); void getAnalysisUsage(AnalysisUsage &AU) const override; bool runOnMachineFunction(MachineFunction &MF) override; void releaseMemory() override { Info.reset(); } }; } // namespace llvm #endif // LLVM_CODEGEN_GLOBALISEL_GISELKNOWNBITS_H