132 lines
4.6 KiB
C++
132 lines
4.6 KiB
C++
//===- llvm/CodeGen/GlobalISel/GISelKnownBits.h ---------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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/// Provides analysis for querying information about KnownBits during GISel
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/// passes.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_GLOBALISEL_KNOWNBITSINFO_H
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#define LLVM_CODEGEN_GLOBALISEL_KNOWNBITSINFO_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/Register.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Support/KnownBits.h"
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namespace llvm {
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class TargetLowering;
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class DataLayout;
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class GISelKnownBits : public GISelChangeObserver {
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MachineFunction &MF;
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MachineRegisterInfo &MRI;
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const TargetLowering &TL;
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const DataLayout &DL;
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unsigned MaxDepth;
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/// Cache maintained during a computeKnownBits request.
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SmallDenseMap<Register, KnownBits, 16> ComputeKnownBitsCache;
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void computeKnownBitsMin(Register Src0, Register Src1, KnownBits &Known,
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const APInt &DemandedElts,
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unsigned Depth = 0);
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unsigned computeNumSignBitsMin(Register Src0, Register Src1,
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const APInt &DemandedElts, unsigned Depth = 0);
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public:
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GISelKnownBits(MachineFunction &MF, unsigned MaxDepth = 6);
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virtual ~GISelKnownBits() = default;
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const MachineFunction &getMachineFunction() const {
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return MF;
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}
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const DataLayout &getDataLayout() const {
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return DL;
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}
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virtual void computeKnownBitsImpl(Register R, KnownBits &Known,
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const APInt &DemandedElts,
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unsigned Depth = 0);
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unsigned computeNumSignBits(Register R, const APInt &DemandedElts,
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unsigned Depth = 0);
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unsigned computeNumSignBits(Register R, unsigned Depth = 0);
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// KnownBitsAPI
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KnownBits getKnownBits(Register R);
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KnownBits getKnownBits(Register R, const APInt &DemandedElts,
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unsigned Depth = 0);
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// Calls getKnownBits for first operand def of MI.
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KnownBits getKnownBits(MachineInstr &MI);
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APInt getKnownZeroes(Register R);
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APInt getKnownOnes(Register R);
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/// \return true if 'V & Mask' is known to be zero in DemandedElts. We use
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/// this predicate to simplify operations downstream.
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/// Mask is known to be zero for bits that V cannot have.
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bool maskedValueIsZero(Register Val, const APInt &Mask) {
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return Mask.isSubsetOf(getKnownBits(Val).Zero);
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}
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/// \return true if the sign bit of Op is known to be zero. We use this
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/// predicate to simplify operations downstream.
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bool signBitIsZero(Register Op);
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static void computeKnownBitsForAlignment(KnownBits &Known,
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Align Alignment) {
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// The low bits are known zero if the pointer is aligned.
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Known.Zero.setLowBits(Log2(Alignment));
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}
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/// \return The known alignment for the pointer-like value \p R.
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Align computeKnownAlignment(Register R, unsigned Depth = 0);
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// Observer API. No-op for non-caching implementation.
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void erasingInstr(MachineInstr &MI) override{};
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void createdInstr(MachineInstr &MI) override{};
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void changingInstr(MachineInstr &MI) override{};
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void changedInstr(MachineInstr &MI) override{};
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protected:
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unsigned getMaxDepth() const { return MaxDepth; }
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};
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/// To use KnownBitsInfo analysis in a pass,
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/// KnownBitsInfo &Info = getAnalysis<GISelKnownBitsInfoAnalysis>().get(MF);
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/// Add to observer if the Info is caching.
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/// WrapperObserver.addObserver(Info);
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/// Eventually add other features such as caching/ser/deserializing
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/// to MIR etc. Those implementations can derive from GISelKnownBits
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/// and override computeKnownBitsImpl.
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class GISelKnownBitsAnalysis : public MachineFunctionPass {
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std::unique_ptr<GISelKnownBits> Info;
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public:
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static char ID;
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GISelKnownBitsAnalysis() : MachineFunctionPass(ID) {
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initializeGISelKnownBitsAnalysisPass(*PassRegistry::getPassRegistry());
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}
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GISelKnownBits &get(MachineFunction &MF) {
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if (!Info)
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Info = std::make_unique<GISelKnownBits>(MF);
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return *Info.get();
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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bool runOnMachineFunction(MachineFunction &MF) override;
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void releaseMemory() override { Info.reset(); }
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};
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} // namespace llvm
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#endif // ifdef
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