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| 14 | pmbaty | 1 | //===- llvm/CodeGen/GlobalISel/GISelKnownBits.h ---------------*- C++ -*-===// |
| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | /// \file |
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| 9 | /// Provides analysis for querying information about KnownBits during GISel |
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| 10 | /// passes. |
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| 11 | /// |
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| 12 | //===----------------------------------------------------------------------===// |
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| 13 | |||
| 14 | #ifndef LLVM_CODEGEN_GLOBALISEL_GISELKNOWNBITS_H |
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| 15 | #define LLVM_CODEGEN_GLOBALISEL_GISELKNOWNBITS_H |
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| 16 | |||
| 17 | #include "llvm/ADT/DenseMap.h" |
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| 18 | #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h" |
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| 19 | #include "llvm/CodeGen/MachineFunctionPass.h" |
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| 20 | #include "llvm/CodeGen/Register.h" |
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| 21 | #include "llvm/InitializePasses.h" |
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| 22 | #include "llvm/Support/KnownBits.h" |
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| 23 | |||
| 24 | namespace llvm { |
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| 25 | |||
| 26 | class TargetLowering; |
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| 27 | class DataLayout; |
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| 28 | |||
| 29 | class GISelKnownBits : public GISelChangeObserver { |
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| 30 | MachineFunction &MF; |
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| 31 | MachineRegisterInfo &MRI; |
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| 32 | const TargetLowering &TL; |
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| 33 | const DataLayout &DL; |
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| 34 | unsigned MaxDepth; |
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| 35 | /// Cache maintained during a computeKnownBits request. |
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| 36 | SmallDenseMap<Register, KnownBits, 16> ComputeKnownBitsCache; |
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| 37 | |||
| 38 | void computeKnownBitsMin(Register Src0, Register Src1, KnownBits &Known, |
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| 39 | const APInt &DemandedElts, |
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| 40 | unsigned Depth = 0); |
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| 41 | |||
| 42 | unsigned computeNumSignBitsMin(Register Src0, Register Src1, |
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| 43 | const APInt &DemandedElts, unsigned Depth = 0); |
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| 44 | |||
| 45 | public: |
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| 46 | GISelKnownBits(MachineFunction &MF, unsigned MaxDepth = 6); |
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| 47 | virtual ~GISelKnownBits() = default; |
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| 48 | |||
| 49 | const MachineFunction &getMachineFunction() const { |
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| 50 | return MF; |
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| 51 | } |
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| 52 | |||
| 53 | const DataLayout &getDataLayout() const { |
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| 54 | return DL; |
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| 55 | } |
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| 56 | |||
| 57 | virtual void computeKnownBitsImpl(Register R, KnownBits &Known, |
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| 58 | const APInt &DemandedElts, |
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| 59 | unsigned Depth = 0); |
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| 60 | |||
| 61 | unsigned computeNumSignBits(Register R, const APInt &DemandedElts, |
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| 62 | unsigned Depth = 0); |
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| 63 | unsigned computeNumSignBits(Register R, unsigned Depth = 0); |
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| 64 | |||
| 65 | // KnownBitsAPI |
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| 66 | KnownBits getKnownBits(Register R); |
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| 67 | KnownBits getKnownBits(Register R, const APInt &DemandedElts, |
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| 68 | unsigned Depth = 0); |
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| 69 | |||
| 70 | // Calls getKnownBits for first operand def of MI. |
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| 71 | KnownBits getKnownBits(MachineInstr &MI); |
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| 72 | APInt getKnownZeroes(Register R); |
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| 73 | APInt getKnownOnes(Register R); |
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| 74 | |||
| 75 | /// \return true if 'V & Mask' is known to be zero in DemandedElts. We use |
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| 76 | /// this predicate to simplify operations downstream. |
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| 77 | /// Mask is known to be zero for bits that V cannot have. |
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| 78 | bool maskedValueIsZero(Register Val, const APInt &Mask) { |
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| 79 | return Mask.isSubsetOf(getKnownBits(Val).Zero); |
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| 80 | } |
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| 81 | |||
| 82 | /// \return true if the sign bit of Op is known to be zero. We use this |
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| 83 | /// predicate to simplify operations downstream. |
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| 84 | bool signBitIsZero(Register Op); |
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| 85 | |||
| 86 | static void computeKnownBitsForAlignment(KnownBits &Known, |
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| 87 | Align Alignment) { |
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| 88 | // The low bits are known zero if the pointer is aligned. |
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| 89 | Known.Zero.setLowBits(Log2(Alignment)); |
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| 90 | } |
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| 91 | |||
| 92 | /// \return The known alignment for the pointer-like value \p R. |
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| 93 | Align computeKnownAlignment(Register R, unsigned Depth = 0); |
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| 94 | |||
| 95 | // Observer API. No-op for non-caching implementation. |
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| 96 | void erasingInstr(MachineInstr &MI) override{}; |
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| 97 | void createdInstr(MachineInstr &MI) override{}; |
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| 98 | void changingInstr(MachineInstr &MI) override{}; |
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| 99 | void changedInstr(MachineInstr &MI) override{}; |
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| 100 | |||
| 101 | protected: |
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| 102 | unsigned getMaxDepth() const { return MaxDepth; } |
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| 103 | }; |
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| 104 | |||
| 105 | /// To use KnownBitsInfo analysis in a pass, |
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| 106 | /// KnownBitsInfo &Info = getAnalysis<GISelKnownBitsInfoAnalysis>().get(MF); |
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| 107 | /// Add to observer if the Info is caching. |
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| 108 | /// WrapperObserver.addObserver(Info); |
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| 109 | |||
| 110 | /// Eventually add other features such as caching/ser/deserializing |
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| 111 | /// to MIR etc. Those implementations can derive from GISelKnownBits |
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| 112 | /// and override computeKnownBitsImpl. |
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| 113 | class GISelKnownBitsAnalysis : public MachineFunctionPass { |
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| 114 | std::unique_ptr<GISelKnownBits> Info; |
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| 115 | |||
| 116 | public: |
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| 117 | static char ID; |
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| 118 | GISelKnownBitsAnalysis() : MachineFunctionPass(ID) { |
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| 119 | initializeGISelKnownBitsAnalysisPass(*PassRegistry::getPassRegistry()); |
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| 120 | } |
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| 121 | GISelKnownBits &get(MachineFunction &MF) { |
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| 122 | if (!Info) |
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| 123 | Info = std::make_unique<GISelKnownBits>(MF); |
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| 124 | return *Info.get(); |
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| 125 | } |
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| 126 | void getAnalysisUsage(AnalysisUsage &AU) const override; |
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| 127 | bool runOnMachineFunction(MachineFunction &MF) override; |
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| 128 | void releaseMemory() override { Info.reset(); } |
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| 129 | }; |
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| 130 | } // namespace llvm |
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| 131 | |||
| 132 | #endif // LLVM_CODEGEN_GLOBALISEL_GISELKNOWNBITS_H |