mozjs_sys 0.67.1

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * 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_CompileInfo_h
#define jit_CompileInfo_h

#include "mozilla/Maybe.h"

#include "jit/JitAllocPolicy.h"
#include "jit/JitFrames.h"
#include "jit/Registers.h"
#include "vm/EnvironmentObject.h"
#include "vm/JSFunction.h"

namespace js {
namespace jit {

class TrackedOptimizations;

inline unsigned StartArgSlot(JSScript* script) {
  // Reserved slots:
  // Slot 0: Environment chain.
  // Slot 1: Return value.

  // When needed:
  // Slot 2: Argumentsobject.

  // Note: when updating this, please also update the assert in
  // SnapshotWriter::startFrame
  return 2 + (script->argumentsHasVarBinding() ? 1 : 0);
}

inline unsigned CountArgSlots(JSScript* script, JSFunction* fun) {
  // Slot x + 0: This value.
  // Slot x + 1: Argument 1.
  // ...
  // Slot x + n: Argument n.

  // Note: when updating this, please also update the assert in
  // SnapshotWriter::startFrame
  return StartArgSlot(script) + (fun ? fun->nargs() + 1 : 0);
}

// The compiler at various points needs to be able to store references to the
// current inline path (the sequence of scripts and call-pcs that lead to the
// current function being inlined).
//
// To support this, the top-level IonBuilder keeps a tree that records the
// inlinings done during compilation.
class InlineScriptTree {
  // InlineScriptTree for the caller
  InlineScriptTree* caller_;

  // PC in the caller corresponding to this script.
  jsbytecode* callerPc_;

  // Script for this entry.
  JSScript* script_;

  // Child entries (linked together by nextCallee pointer)
  InlineScriptTree* children_;
  InlineScriptTree* nextCallee_;

 public:
  InlineScriptTree(InlineScriptTree* caller, jsbytecode* callerPc,
                   JSScript* script)
      : caller_(caller),
        callerPc_(callerPc),
        script_(script),
        children_(nullptr),
        nextCallee_(nullptr) {}

  static InlineScriptTree* New(TempAllocator* allocator,
                               InlineScriptTree* caller, jsbytecode* callerPc,
                               JSScript* script);

  InlineScriptTree* addCallee(TempAllocator* allocator, jsbytecode* callerPc,
                              JSScript* calleeScript);

  InlineScriptTree* caller() const { return caller_; }

  bool isOutermostCaller() const { return caller_ == nullptr; }
  bool hasCaller() const { return caller_ != nullptr; }
  InlineScriptTree* outermostCaller() {
    if (isOutermostCaller()) {
      return this;
    }
    return caller_->outermostCaller();
  }

  jsbytecode* callerPc() const { return callerPc_; }

  JSScript* script() const { return script_; }

  bool hasChildren() const { return children_ != nullptr; }
  InlineScriptTree* firstChild() const {
    MOZ_ASSERT(hasChildren());
    return children_;
  }

  bool hasNextCallee() const { return nextCallee_ != nullptr; }
  InlineScriptTree* nextCallee() const {
    MOZ_ASSERT(hasNextCallee());
    return nextCallee_;
  }

  unsigned depth() const {
    if (isOutermostCaller()) {
      return 1;
    }
    return 1 + caller_->depth();
  }
};

class BytecodeSite : public TempObject {
  // InlineScriptTree identifying innermost active function at site.
  InlineScriptTree* tree_;

  // Bytecode address within innermost active function.
  jsbytecode* pc_;

  // Optimization information at the pc.
  TrackedOptimizations* optimizations_;

 public:
  BytecodeSite() : tree_(nullptr), pc_(nullptr), optimizations_(nullptr) {}

  BytecodeSite(InlineScriptTree* tree, jsbytecode* pc)
      : tree_(tree), pc_(pc), optimizations_(nullptr) {
    MOZ_ASSERT(tree_ != nullptr);
    MOZ_ASSERT(pc_ != nullptr);
  }

  InlineScriptTree* tree() const { return tree_; }

  jsbytecode* pc() const { return pc_; }

  JSScript* script() const { return tree_ ? tree_->script() : nullptr; }

  bool hasOptimizations() const { return !!optimizations_; }

  TrackedOptimizations* optimizations() const {
    MOZ_ASSERT(hasOptimizations());
    return optimizations_;
  }

  void setOptimizations(TrackedOptimizations* optimizations) {
    optimizations_ = optimizations;
  }
};

enum AnalysisMode {
  /* JavaScript execution, not analysis. */
  Analysis_None,

  /*
   * MIR analysis performed when invoking 'new' on a script, to determine
   * definite properties. Used by the optimizing JIT.
   */
  Analysis_DefiniteProperties,

  /*
   * MIR analysis performed when executing a script which uses its arguments,
   * when it is not known whether a lazy arguments value can be used.
   */
  Analysis_ArgumentsUsage
};

// Contains information about the compilation source for IR being generated.
class CompileInfo {
 public:
  CompileInfo(CompileRuntime* runtime, JSScript* script, JSFunction* fun,
              jsbytecode* osrPc, AnalysisMode analysisMode,
              bool scriptNeedsArgsObj, InlineScriptTree* inlineScriptTree)
      : script_(script),
        fun_(fun),
        osrPc_(osrPc),
        analysisMode_(analysisMode),
        scriptNeedsArgsObj_(scriptNeedsArgsObj),
        hadOverflowBailout_(script->hadOverflowBailout()),
        hadFrequentBailouts_(script->hadFrequentBailouts()),
        mayReadFrameArgsDirectly_(script->mayReadFrameArgsDirectly()),
        trackRecordReplayProgress_(script->trackRecordReplayProgress()),
        inlineScriptTree_(inlineScriptTree) {
    MOZ_ASSERT_IF(osrPc, JSOp(*osrPc) == JSOP_LOOPENTRY);

    // The function here can flow in from anywhere so look up the canonical
    // function to ensure that we do not try to embed a nursery pointer in
    // jit-code. Precisely because it can flow in from anywhere, it's not
    // guaranteed to be non-lazy. Hence, don't access its script!
    if (fun_) {
      fun_ = fun_->nonLazyScript()->functionNonDelazifying();
      MOZ_ASSERT(fun_->isTenured());
    }

    nimplicit_ = StartArgSlot(script) /* env chain and argument obj */
                 + (fun ? 1 : 0);     /* this */
    nargs_ = fun ? fun->nargs() : 0;
    nlocals_ = script->nfixed();

    // An extra slot is needed for global scopes because INITGLEXICAL (stack
    // depth 1) is compiled as a SETPROP (stack depth 2) on the global lexical
    // scope.
    uint32_t extra = script->isGlobalCode() ? 1 : 0;
    nstack_ =
        Max<unsigned>(script->nslots() - script->nfixed(), MinJITStackSize) +
        extra;
    nslots_ = nimplicit_ + nargs_ + nlocals_ + nstack_;

    // For derived class constructors, find and cache the frame slot for
    // the .this binding. This slot is assumed to be always
    // observable. See isObservableFrameSlot.
    if (script->isDerivedClassConstructor()) {
      MOZ_ASSERT(script->functionHasThisBinding());
      for (BindingIter bi(script); bi; bi++) {
        if (bi.name() != runtime->names().dotThis) {
          continue;
        }
        BindingLocation loc = bi.location();
        if (loc.kind() == BindingLocation::Kind::Frame) {
          thisSlotForDerivedClassConstructor_ =
              mozilla::Some(localSlot(loc.slot()));
          break;
        }
      }
    }

    // If the script uses an environment in body, the environment chain
    // will need to be observable.
    needsBodyEnvironmentObject_ = script->needsBodyEnvironment();
    funNeedsSomeEnvironmentObject_ =
        fun ? fun->needsSomeEnvironmentObject() : false;
  }

  explicit CompileInfo(unsigned nlocals)
      : script_(nullptr),
        fun_(nullptr),
        osrPc_(nullptr),
        analysisMode_(Analysis_None),
        scriptNeedsArgsObj_(false),
        hadOverflowBailout_(false),
        hadFrequentBailouts_(false),
        mayReadFrameArgsDirectly_(false),
        trackRecordReplayProgress_(false),
        inlineScriptTree_(nullptr),
        needsBodyEnvironmentObject_(false),
        funNeedsSomeEnvironmentObject_(false) {
    nimplicit_ = 0;
    nargs_ = 0;
    nlocals_ = nlocals;
    nstack_ = 1; /* For FunctionCompiler::pushPhiInput/popPhiOutput */
    nslots_ = nlocals_ + nstack_;
  }

  JSScript* script() const { return script_; }
  bool compilingWasm() const { return script() == nullptr; }
  JSFunction* funMaybeLazy() const { return fun_; }
  ModuleObject* module() const { return script_->module(); }
  jsbytecode* osrPc() const { return osrPc_; }
  InlineScriptTree* inlineScriptTree() const { return inlineScriptTree_; }

  bool hasOsrAt(jsbytecode* pc) const {
    MOZ_ASSERT(JSOp(*pc) == JSOP_LOOPENTRY);
    return pc == osrPc();
  }

  jsbytecode* startPC() const { return script_->code(); }
  jsbytecode* limitPC() const { return script_->codeEnd(); }

  const char* filename() const { return script_->filename(); }

  unsigned lineno() const { return script_->lineno(); }
  unsigned lineno(jsbytecode* pc) const { return PCToLineNumber(script_, pc); }

  // Script accessors based on PC.

  JSAtom* getAtom(jsbytecode* pc) const {
    return script_->getAtom(GET_UINT32_INDEX(pc));
  }

  PropertyName* getName(jsbytecode* pc) const {
    return script_->getName(GET_UINT32_INDEX(pc));
  }

  inline RegExpObject* getRegExp(jsbytecode* pc) const;

  JSObject* getObject(jsbytecode* pc) const {
    return script_->getObject(GET_UINT32_INDEX(pc));
  }

  inline JSFunction* getFunction(jsbytecode* pc) const;

  const Value& getConst(jsbytecode* pc) const {
    return script_->getConst(GET_UINT32_INDEX(pc));
  }

  jssrcnote* getNote(GSNCache& gsn, jsbytecode* pc) const {
    return GetSrcNote(gsn, script(), pc);
  }

  // Total number of slots: args, locals, and stack.
  unsigned nslots() const { return nslots_; }

  // Number of slots needed for env chain, return value,
  // maybe argumentsobject and this value.
  unsigned nimplicit() const { return nimplicit_; }
  // Number of arguments (without counting this value).
  unsigned nargs() const { return nargs_; }
  // Number of slots needed for all local variables.  This includes "fixed
  // vars" (see above) and also block-scoped locals.
  unsigned nlocals() const { return nlocals_; }
  unsigned ninvoke() const { return nslots_ - nstack_; }

  uint32_t environmentChainSlot() const {
    MOZ_ASSERT(script());
    return 0;
  }
  uint32_t returnValueSlot() const {
    MOZ_ASSERT(script());
    return 1;
  }
  uint32_t argsObjSlot() const {
    MOZ_ASSERT(hasArguments());
    return 2;
  }
  uint32_t thisSlot() const {
    MOZ_ASSERT(funMaybeLazy());
    MOZ_ASSERT(nimplicit_ > 0);
    return nimplicit_ - 1;
  }
  uint32_t firstArgSlot() const { return nimplicit_; }
  uint32_t argSlotUnchecked(uint32_t i) const {
    // During initialization, some routines need to get at arg
    // slots regardless of how regular argument access is done.
    MOZ_ASSERT(i < nargs_);
    return nimplicit_ + i;
  }
  uint32_t argSlot(uint32_t i) const {
    // This should only be accessed when compiling functions for
    // which argument accesses don't need to go through the
    // argument object.
    MOZ_ASSERT(!argsObjAliasesFormals());
    return argSlotUnchecked(i);
  }
  uint32_t firstLocalSlot() const { return nimplicit_ + nargs_; }
  uint32_t localSlot(uint32_t i) const { return firstLocalSlot() + i; }
  uint32_t firstStackSlot() const { return firstLocalSlot() + nlocals(); }
  uint32_t stackSlot(uint32_t i) const { return firstStackSlot() + i; }

  uint32_t startArgSlot() const {
    MOZ_ASSERT(script());
    return StartArgSlot(script());
  }
  uint32_t endArgSlot() const {
    MOZ_ASSERT(script());
    return CountArgSlots(script(), funMaybeLazy());
  }

  uint32_t totalSlots() const {
    MOZ_ASSERT(script() && funMaybeLazy());
    return nimplicit() + nargs() + nlocals();
  }

  bool isSlotAliased(uint32_t index) const {
    MOZ_ASSERT(index >= startArgSlot());
    uint32_t arg = index - firstArgSlot();
    if (arg < nargs()) {
      return script()->formalIsAliased(arg);
    }
    return false;
  }

  bool hasArguments() const { return script()->argumentsHasVarBinding(); }
  bool argumentsAliasesFormals() const {
    return script()->argumentsAliasesFormals();
  }
  bool needsArgsObj() const { return scriptNeedsArgsObj_; }
  bool argsObjAliasesFormals() const {
    return scriptNeedsArgsObj_ && script()->hasMappedArgsObj();
  }

  AnalysisMode analysisMode() const { return analysisMode_; }

  bool isAnalysis() const { return analysisMode_ != Analysis_None; }

  bool needsBodyEnvironmentObject() const {
    return needsBodyEnvironmentObject_;
  }

  // Returns true if a slot can be observed out-side the current frame while
  // the frame is active on the stack.  This implies that these definitions
  // would have to be executed and that they cannot be removed even if they
  // are unused.
  inline bool isObservableSlot(uint32_t slot) const {
    if (slot >= firstLocalSlot()) {
      // The |this| slot for a derived class constructor is a local slot.
      if (thisSlotForDerivedClassConstructor_) {
        return *thisSlotForDerivedClassConstructor_ == slot;
      }
      return false;
    }

    if (slot < firstArgSlot()) {
      return isObservableFrameSlot(slot);
    }

    return isObservableArgumentSlot(slot);
  }

  bool isObservableFrameSlot(uint32_t slot) const {
    // The |envChain| value must be preserved if environments are added
    // after the prologue.
    if (needsBodyEnvironmentObject() && slot == environmentChainSlot()) {
      return true;
    }

    if (!funMaybeLazy()) {
      return false;
    }

    // The |this| value must always be observable.
    if (slot == thisSlot()) {
      return true;
    }

    // The |this| frame slot in derived class constructors should never be
    // optimized out, as a Debugger might need to perform TDZ checks on it
    // via, e.g., an exceptionUnwind handler. The TDZ check is required
    // for correctness if the handler decides to continue execution.
    if (thisSlotForDerivedClassConstructor_ &&
        *thisSlotForDerivedClassConstructor_ == slot) {
      return true;
    }

    if (funNeedsSomeEnvironmentObject_ && slot == environmentChainSlot()) {
      return true;
    }

    // If the function may need an arguments object, then make sure to
    // preserve the env chain, because it may be needed to construct the
    // arguments object during bailout. If we've already created an
    // arguments object (or got one via OSR), preserve that as well.
    if (hasArguments() &&
        (slot == environmentChainSlot() || slot == argsObjSlot())) {
      return true;
    }

    return false;
  }

  bool isObservableArgumentSlot(uint32_t slot) const {
    if (!funMaybeLazy()) {
      return false;
    }

    // Function.arguments can be used to access all arguments in non-strict
    // scripts, so we can't optimize out any arguments.
    if ((hasArguments() || !script()->strict()) && firstArgSlot() <= slot &&
        slot - firstArgSlot() < nargs()) {
      return true;
    }

    return false;
  }

  // Returns true if a slot can be recovered before or during a bailout.  A
  // definition which can be observed and recovered, implies that this
  // definition can be optimized away as long as we can compute its values.
  bool isRecoverableOperand(uint32_t slot) const {
    // The |envChain| value cannot be recovered if environments can be
    // added in body (after the prologue).
    if (needsBodyEnvironmentObject() && slot == environmentChainSlot()) {
      return false;
    }

    if (!funMaybeLazy()) {
      return true;
    }

    // The |this| and the |envChain| values can be recovered.
    if (slot == thisSlot() || slot == environmentChainSlot()) {
      return true;
    }

    if (isObservableFrameSlot(slot)) {
      return false;
    }

    if (needsArgsObj() && isObservableArgumentSlot(slot)) {
      return false;
    }

    return true;
  }

  // Check previous bailout states to prevent doing the same bailout in the
  // next compilation.
  bool hadOverflowBailout() const { return hadOverflowBailout_; }
  bool hadFrequentBailouts() const { return hadFrequentBailouts_; }
  bool mayReadFrameArgsDirectly() const { return mayReadFrameArgsDirectly_; }
  bool trackRecordReplayProgress() const { return trackRecordReplayProgress_; }

 private:
  unsigned nimplicit_;
  unsigned nargs_;
  unsigned nlocals_;
  unsigned nstack_;
  unsigned nslots_;
  mozilla::Maybe<unsigned> thisSlotForDerivedClassConstructor_;
  JSScript* script_;
  JSFunction* fun_;
  jsbytecode* osrPc_;
  AnalysisMode analysisMode_;

  // Whether a script needs an arguments object is unstable over compilation
  // since the arguments optimization could be marked as failed on the active
  // thread, so cache a value here and use it throughout for consistency.
  bool scriptNeedsArgsObj_;

  // Record the state of previous bailouts in order to prevent compiling the
  // same function identically the next time.
  bool hadOverflowBailout_;
  bool hadFrequentBailouts_;

  bool mayReadFrameArgsDirectly_;
  bool trackRecordReplayProgress_;

  InlineScriptTree* inlineScriptTree_;

  // Whether a script needs environments within its body. This informs us
  // that the environment chain is not easy to reconstruct.
  bool needsBodyEnvironmentObject_;
  bool funNeedsSomeEnvironmentObject_;
};

}  // namespace jit
}  // namespace js

#endif /* jit_CompileInfo_h */