1 //===- llvm/CodeGen/GlobalISel/GISelKnownBits.h ---------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 /// Provides analysis for querying information about KnownBits during GISel 10 /// passes. 11 // 12 //===----------------------------------------------------------------------===// 13 #ifndef LLVM_CODEGEN_GLOBALISEL_KNOWNBITSINFO_H 14 #define LLVM_CODEGEN_GLOBALISEL_KNOWNBITSINFO_H 15 16 #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h" 17 #include "llvm/CodeGen/MachineFunctionPass.h" 18 #include "llvm/CodeGen/Register.h" 19 #include "llvm/IR/PassManager.h" 20 #include "llvm/InitializePasses.h" 21 #include "llvm/Pass.h" 22 #include "llvm/Support/KnownBits.h" 23 24 namespace llvm { 25 26 class TargetLowering; 27 class DataLayout; 28 29 class GISelKnownBits : public GISelChangeObserver { 30 MachineFunction &MF; 31 MachineRegisterInfo &MRI; 32 const TargetLowering &TL; 33 const DataLayout &DL; 34 35 public: 36 GISelKnownBits(MachineFunction &MF); 37 virtual ~GISelKnownBits() = default; 38 void setMF(MachineFunction &MF); 39 virtual void computeKnownBitsImpl(Register R, KnownBits &Known, 40 const APInt &DemandedElts, 41 unsigned Depth = 0); 42 43 unsigned computeNumSignBits(Register R, const APInt &DemandedElts, 44 unsigned Depth = 0); 45 unsigned computeNumSignBits(Register R, unsigned Depth = 0); 46 47 // KnownBitsAPI 48 KnownBits getKnownBits(Register R); 49 // Calls getKnownBits for first operand def of MI. 50 KnownBits getKnownBits(MachineInstr &MI); 51 APInt getKnownZeroes(Register R); 52 APInt getKnownOnes(Register R); 53 54 /// \return true if 'V & Mask' is known to be zero in DemandedElts. We use 55 /// this predicate to simplify operations downstream. 56 /// Mask is known to be zero for bits that V cannot have. 57 bool maskedValueIsZero(Register Val, const APInt &Mask) { 58 return Mask.isSubsetOf(getKnownBits(Val).Zero); 59 } 60 61 /// \return true if the sign bit of Op is known to be zero. We use this 62 /// predicate to simplify operations downstream. 63 bool signBitIsZero(Register Op); 64 65 // FIXME: Is this the right place for G_FRAME_INDEX? Should it be in 66 // TargetLowering? 67 void computeKnownBitsForFrameIndex(Register R, KnownBits &Known, 68 const APInt &DemandedElts, 69 unsigned Depth = 0); 70 static Align inferAlignmentForFrameIdx(int FrameIdx, int Offset, 71 const MachineFunction &MF); 72 static void computeKnownBitsForAlignment(KnownBits &Known, 73 MaybeAlign Alignment); 74 75 // Try to infer alignment for MI. 76 static MaybeAlign inferPtrAlignment(const MachineInstr &MI); 77 78 // Observer API. No-op for non-caching implementation. 79 void erasingInstr(MachineInstr &MI) override{}; 80 void createdInstr(MachineInstr &MI) override{}; 81 void changingInstr(MachineInstr &MI) override{}; 82 void changedInstr(MachineInstr &MI) override{}; 83 84 protected: 85 unsigned getMaxDepth() const { return 6; } 86 }; 87 88 /// To use KnownBitsInfo analysis in a pass, 89 /// KnownBitsInfo &Info = getAnalysis<GISelKnownBitsInfoAnalysis>().get(MF); 90 /// Add to observer if the Info is caching. 91 /// WrapperObserver.addObserver(Info); 92 93 /// Eventually add other features such as caching/ser/deserializing 94 /// to MIR etc. Those implementations can derive from GISelKnownBits 95 /// and override computeKnownBitsImpl. 96 class GISelKnownBitsAnalysis : public MachineFunctionPass { 97 std::unique_ptr<GISelKnownBits> Info; 98 99 public: 100 static char ID; 101 GISelKnownBitsAnalysis() : MachineFunctionPass(ID) { 102 initializeGISelKnownBitsAnalysisPass(*PassRegistry::getPassRegistry()); 103 } 104 GISelKnownBits &get(MachineFunction &MF) { 105 if (!Info) 106 Info = std::make_unique<GISelKnownBits>(MF); 107 return *Info.get(); 108 } 109 void getAnalysisUsage(AnalysisUsage &AU) const override; 110 bool runOnMachineFunction(MachineFunction &MF) override; 111 void releaseMemory() override { Info.reset(); } 112 }; 113 } // namespace llvm 114 115 #endif // ifdef 116