src/third_party/mozjs-45/js/src/jit/shared/Lowering-shared.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef jit_shared_Lowering_shared_h
#define jit_shared_Lowering_shared_h

// This file declares the structures that are used for attaching LIR to a
// MIRGraph.

#include "jit/LIR.h"
#include "jit/MIRGenerator.h"

namespace js {
namespace jit {

class MIRGenerator;
class MIRGraph;
class MDefinition;
class MInstruction;
class LOsiPoint;

class LIRGeneratorShared : public MDefinitionVisitor
{
  protected:
    MIRGenerator* gen;
    MIRGraph& graph;
    LIRGraph& lirGraph_;
    LBlock* current;
    MResumePoint* lastResumePoint_;
    LRecoverInfo* cachedRecoverInfo_;
    LOsiPoint* osiPoint_;

  public:
    LIRGeneratorShared(MIRGenerator* gen, MIRGraph& graph, LIRGraph& lirGraph)
      : gen(gen),
        graph(graph),
        lirGraph_(lirGraph),
        lastResumePoint_(nullptr),
        cachedRecoverInfo_(nullptr),
        osiPoint_(nullptr)
    { }

    MIRGenerator* mir() {
        return gen;
    }

  protected:

    static void ReorderCommutative(MDefinition** lhsp, MDefinition** rhsp, MInstruction* ins);
    static bool ShouldReorderCommutative(MDefinition* lhs, MDefinition* rhs, MInstruction* ins);

    // A backend can decide that an instruction should be emitted at its uses,
    // rather than at its definition. To communicate this, set the
    // instruction's virtual register set to 0. When using the instruction,
    // its virtual register is temporarily reassigned. To know to clear it
    // after constructing the use information, the worklist bit is temporarily
    // unset.
    //
    // The backend can use the worklist bit to determine whether or not a
    // definition should be created.
    inline void emitAtUses(MInstruction* mir);

    // The lowest-level calls to use, those that do not wrap another call to
    // use(), must prefix grabbing virtual register IDs by these calls.
    inline void ensureDefined(MDefinition* mir);

    // These all create a use of a virtual register, with an optional
    // allocation policy.
    //
    // Some of these use functions have atStart variants.
    // - non-atStart variants will tell the register allocator that the input
    // allocation must be different from any Temp or Definition also needed for
    // this LInstruction.
    // - atStart variants relax that restriction and allow the input to be in
    // the same register as any Temp or output Definition used by the
    // LInstruction. Note that it doesn't *imply* this will actually happen,
    // but gives a hint to the register allocator that it can do it.
    //
    // TL;DR: Use non-atStart variants only if you need the input value after
    // writing to any temp or definitions, during code generation of this
    // LInstruction. Otherwise, use atStart variants, which will lower register
    // pressure.
    inline LUse use(MDefinition* mir, LUse policy);
    inline LUse use(MDefinition* mir);
    inline LUse useAtStart(MDefinition* mir);
    inline LUse useRegister(MDefinition* mir);
    inline LUse useRegisterAtStart(MDefinition* mir);
    inline LUse useFixed(MDefinition* mir, Register reg);
    inline LUse useFixed(MDefinition* mir, FloatRegister reg);
    inline LUse useFixed(MDefinition* mir, AnyRegister reg);
    inline LUse useFixedAtStart(MDefinition* mir, Register reg);
    inline LAllocation useOrConstant(MDefinition* mir);
    inline LAllocation useOrConstantAtStart(MDefinition* mir);
    // "Any" is architecture dependent, and will include registers and stack
    // slots on X86, and only registers on ARM.
    inline LAllocation useAny(MDefinition* mir);
    inline LAllocation useAnyOrConstant(MDefinition* mir);
    // "Storable" is architecture dependend, and will include registers and
    // constants on X86 and only registers on ARM.  This is a generic "things
    // we can expect to write into memory in 1 instruction".
    inline LAllocation useStorable(MDefinition* mir);
    inline LAllocation useStorableAtStart(MDefinition* mir);
    inline LAllocation useKeepalive(MDefinition* mir);
    inline LAllocation useKeepaliveOrConstant(MDefinition* mir);
    inline LAllocation useRegisterOrConstant(MDefinition* mir);
    inline LAllocation useRegisterOrConstantAtStart(MDefinition* mir);
    inline LAllocation useRegisterOrZeroAtStart(MDefinition* mir);
    inline LAllocation useRegisterOrNonDoubleConstant(MDefinition* mir);

    inline LUse useRegisterForTypedLoad(MDefinition* mir, MIRType type);

#ifdef JS_NUNBOX32
    inline LUse useType(MDefinition* mir, LUse::Policy policy);
    inline LUse usePayload(MDefinition* mir, LUse::Policy policy);
    inline LUse usePayloadAtStart(MDefinition* mir, LUse::Policy policy);
    inline LUse usePayloadInRegisterAtStart(MDefinition* mir);

    // Adds a box input to an instruction, setting operand |n| to the type and
    // |n+1| to the payload. Does not modify the operands, instead expecting a
    // policy to already be set.
    inline void fillBoxUses(LInstruction* lir, size_t n, MDefinition* mir);
#endif

    // These create temporary register requests.
    inline LDefinition temp(LDefinition::Type type = LDefinition::GENERAL,
                            LDefinition::Policy policy = LDefinition::REGISTER);
    inline LDefinition tempFloat32();
    inline LDefinition tempDouble();
    inline LDefinition tempCopy(MDefinition* input, uint32_t reusedInput);

    // Note that the fixed register has a GENERAL type.
    inline LDefinition tempFixed(Register reg);

    template <size_t Ops, size_t Temps>
    inline void defineFixed(LInstructionHelper<1, Ops, Temps>* lir, MDefinition* mir,
                            const LAllocation& output);

    template <size_t Ops, size_t Temps>
    inline void defineBox(LInstructionHelper<BOX_PIECES, Ops, Temps>* lir, MDefinition* mir,
                          LDefinition::Policy policy = LDefinition::REGISTER);

    template <size_t Ops, size_t Temps>
    inline void defineSinCos(LInstructionHelper<2, Ops, Temps> *lir, MDefinition *mir,
                             LDefinition::Policy policy = LDefinition::REGISTER);

    inline void defineSharedStubReturn(LInstruction* lir, MDefinition* mir);
    inline void defineReturn(LInstruction* lir, MDefinition* mir);

    template <size_t X>
    inline void define(details::LInstructionFixedDefsTempsHelper<1, X>* lir, MDefinition* mir,
                       LDefinition::Policy policy = LDefinition::REGISTER);
    template <size_t X>
    inline void define(details::LInstructionFixedDefsTempsHelper<1, X>* lir, MDefinition* mir,
                       const LDefinition& def);

    template <size_t Ops, size_t Temps>
    inline void defineReuseInput(LInstructionHelper<1, Ops, Temps>* lir, MDefinition* mir, uint32_t operand);

    // Adds a use at operand |n| of a value-typed insturction.
    inline void useBox(LInstruction* lir, size_t n, MDefinition* mir,
                       LUse::Policy policy = LUse::REGISTER, bool useAtStart = false);

    // Adds a use at operand |n|. The use is either typed, a Value, or a
    // constant (if useConstant is true).
    inline void useBoxOrTypedOrConstant(LInstruction* lir, size_t n, MDefinition* mir,
                                        bool useConstant);

    // Rather than defining a new virtual register, sets |ins| to have the same
    // virtual register as |as|.
    inline void redefine(MDefinition* ins, MDefinition* as);

    // Redefine a sin/cos call to sincos.
    inline void redefine(MDefinition* def, MDefinition* as, MMathFunction::Function func);

    TempAllocator& alloc() const {
        return graph.alloc();
    }

    uint32_t getVirtualRegister() {
        uint32_t vreg = lirGraph_.getVirtualRegister();

        // If we run out of virtual registers, mark code generation as having
        // failed and return a dummy vreg. Include a + 1 here for NUNBOX32
        // platforms that expect Value vregs to be adjacent.
        if (vreg + 1 >= MAX_VIRTUAL_REGISTERS) {
            gen->abort("max virtual registers");
            return 1;
        }
        return vreg;
    }

    template <typename T> void annotate(T* ins);
    template <typename T> void add(T* ins, MInstruction* mir = nullptr);

    void lowerTypedPhiInput(MPhi* phi, uint32_t inputPosition, LBlock* block, size_t lirIndex);
    void defineTypedPhi(MPhi* phi, size_t lirIndex);

    LOsiPoint* popOsiPoint() {
        LOsiPoint* tmp = osiPoint_;
        osiPoint_ = nullptr;
        return tmp;
    }

    LRecoverInfo* getRecoverInfo(MResumePoint* rp);
    LSnapshot* buildSnapshot(LInstruction* ins, MResumePoint* rp, BailoutKind kind);
    bool assignPostSnapshot(MInstruction* mir, LInstruction* ins);

    // Marks this instruction as fallible, meaning that before it performs
    // effects (if any), it may check pre-conditions and bailout if they do not
    // hold. This function informs the register allocator that it will need to
    // capture appropriate state.
    void assignSnapshot(LInstruction* ins, BailoutKind kind);

    // Marks this instruction as needing to call into either the VM or GC. This
    // function may build a snapshot that captures the result of its own
    // instruction, and as such, should generally be called after define*().
    void assignSafepoint(LInstruction* ins, MInstruction* mir,
                         BailoutKind kind = Bailout_DuringVMCall);

  public:
    void lowerConstantDouble(double d, MInstruction* mir) {
        define(new(alloc()) LDouble(d), mir);
    }
    void lowerConstantFloat32(float f, MInstruction* mir) {
        define(new(alloc()) LFloat32(f), mir);
    }

    void visitConstant(MConstant* ins);

    // Whether to generate typed reads for element accesses with hole checks.
    static bool allowTypedElementHoleCheck() {
        return false;
    }

    // Whether to generate typed array accesses on statically known objects.
    static bool allowStaticTypedArrayAccesses() {
        return false;
    }

};

} // namespace jit
} // namespace js

#endif /* jit_shared_Lowering_shared_h */