tor-browser

StencilEnums.h (13149B)

---

/* -*- 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 vm_StencilEnums_h
#define vm_StencilEnums_h

#include <stdint.h>  // uint8_t

//
// Enum definitions shared between frontend, stencil, and the VM.
//

namespace js {

// [SMDOC] Try Notes
//
// Trynotes are attached to regions that are involved with
// exception unwinding. They can be broken up into four categories:
//
// 1. Catch and Finally: Basic exception handling. A Catch trynote
//    covers the range of the associated try. A Finally trynote covers
//    the try and the catch.
//
// 2. ForIn and Destructuring: These operations create an iterator
//    which must be cleaned up (by calling IteratorClose) during
//    exception unwinding.
//
// 3. ForOf and ForOfIterclose: For-of loops handle unwinding using
//    catch blocks. These trynotes are used for for-of breaks/returns,
//    which create regions that are lexically within a for-of block,
//    but logically outside of it. See TryNoteIter::settle for more
//    details.
//
// 4. Loop: This represents normal for/while/do-while loops. It is
//    unnecessary for exception unwinding, but storing the boundaries
//    of loops here is helpful for heuristics that need to know
//    whether a given op is inside a loop.
enum class TryNoteKind : uint8_t {
 Catch,
 Finally,
 ForIn,
 Destructuring,
 ForOf,
 ForOfIterClose,
 Loop
};

// [SMDOC] Script Flags
//
// Interpreted scripts represented by the BaseScript type use two flag words to
// encode an assortment of conditions and attributes about the script.
//
// The "immutable" flags are a combination of input flags describing aspects of
// the execution context that affect parsing (such as if we are an ES module or
// normal script), and flags derived from source text. These flags are preserved
// during cloning and serializing. As well, they should never change after the
// BaseScript is created (although there are currently a few exceptions for
// de-/re-lazification that remain).
//
// The "mutable" flags are temporary flags that are used by subsystems in the
// engine such as the debugger or JITs. These flags are not preserved through
// serialization or cloning since the attributes are generally associated with
// one specific instance of a BaseScript.

enum class ImmutableScriptFlagsEnum : uint32_t {
 // Input Flags
 //
 // These flags are from CompileOptions or the Parser entry point. They
 // generally cannot be derived from the source text alone.
 // ----

 // A script may have one of the following kinds: Global, Eval, Module,
 // Function. At most one flag can be set, with a default of Global.
 IsForEval = 1 << 0,
 IsModule = 1 << 1,
 IsFunction = 1 << 2,

 // The script is compiled as engine-internal self-hosted JavaScript. This mode
 // is used to implement certain library functions and has special parse,
 // bytecode, and runtime behaviour that differs from normal script.
 SelfHosted = 1 << 3,

 // The script was compiled with the default mode set to strict mode. Note that
 // this tracks the default value, while the actual mode used (after processing
 // source and its directives) is the `Strict` flag below.
 ForceStrict = 1 << 4,

 // The script has a non-syntactic scope on its environment chain. That is,
 // there may be objects about which we know nothing between the outermost
 // syntactic scope and the global.
 HasNonSyntacticScope = 1 << 5,

 // The script return value will not be used and simplified code will be
 // generated. This can only be applied to top-level scripts. The value this
 // script returns will be UndefinedValue instead of what the spec normally
 // prescribes.
 NoScriptRval = 1 << 6,

 // TreatAsRunOnce roughly indicates that a script is expected to be run no
 // more than once. This affects optimizations and heuristics.
 //
 // On top-level global/eval/module scripts, this is set when the embedding
 // ensures this script will not be re-used. In this case, parser literals may
 // be exposed directly instead of being cloned.
 TreatAsRunOnce = 1 << 7,
 // ----

 // Parser Flags
 //
 // Flags computed by the Parser from the source text and input flags.
 // ----

 // Generated code will execute in strict mode. This is due to either the
 // ForceStrict flag being specified above, or due to source text itself (such
 // as "use strict" directives).
 Strict = 1 << 8,

 // Script is parsed with a top-level goal of Module. This may be a top-level
 // or an inner-function script.
 HasModuleGoal = 1 << 9,

 // Script contains inner functions.
 //
 // Note: This prevents relazification since inner function close-over the
 // current scripts scopes.
 HasInnerFunctions = 1 << 10,

 // There is a direct eval statement in this script OR in any of its inner
 // functions.
 //
 // Note: This prevents relazification since it can introduce inner functions.
 HasDirectEval = 1 << 11,

 // The (static) bindings of this script must support dynamic name access for
 // read/write. The environment chain is used to do these dynamic lookups and
 // optimizations to avoid allocating environments are suppressed.
 //
 // This includes direct-eval, `with`, and `delete` in this script OR in any of
 // its inner functions.
 //
 // Note: Access through the arguments object is not considered dynamic binding
 // access since it does not go through the normal name lookup mechanism.
 BindingsAccessedDynamically = 1 << 12,

 // A tagged template exists in the body (which will use JSOp::CallSiteObj in
 // bytecode).
 //
 // Note: This prevents relazification since the template's object is
 // observable to the user and cannot be recreated.
 HasCallSiteObj = 1 << 13,

 // Parser Flags for Functions
 // ----

 // This function's initial prototype is one of Function, GeneratorFunction,
 // AsyncFunction, or AsyncGeneratorFunction as indicated by these flags.
 //
 // If either of these flags is set, the script may suspend and resume as it
 // executes. Stack frames for this script also have a generator object.
 IsAsync = 1 << 14,
 IsGenerator = 1 << 15,

 // This function's body serves as the `var` environment for a non-strict
 // direct eval. This matters because it's the only way bindings can be
 // dynamically added to a local environment, possibly shadowing other
 // variables.
 FunHasExtensibleScope = 1 << 16,

 // This function has an internal .this binding and we need to emit
 // JSOp::FunctionThis in the prologue to initialize it. This binding may be
 // used directly for "this", or indirectly (such as class constructors).
 FunctionHasThisBinding = 1 << 17,

 // This function is a class method that must uses an internal [[HomeObject]]
 // slot. This slot is initialized when the class definition is executed in the
 // enclosing function.
 NeedsHomeObject = 1 << 18,

 // This function is a constructor for a derived class. This is a class that
 // uses the `extends` syntax.
 IsDerivedClassConstructor = 1 << 19,

 // This function is synthesized by the Parser. This is used for field
 // initializer lambdas and missing constructors for classes. These functions
 // have unusual source coordinates and may be hidden from things like
 // Reflect.parse.
 IsSyntheticFunction = 1 << 20,

 // This function is a class constructor that has MemberInitializer data
 // associated with it.
 UseMemberInitializers = 1 << 21,

 // This function has a rest (`...`) parameter.
 HasRest = 1 << 22,

 // This function needs a call object or named lambda environment to be created
 // in order to execute the function. This is done in the Stack or JIT frame
 // setup code _before_ the bytecode prologue starts.
 NeedsFunctionEnvironmentObjects = 1 << 23,

 // An extra VarScope is used as the body scope instead of the normal
 // FunctionScope. This is needed when parameter expressions are used AND the
 // function has var bindings or a sloppy-direct-eval. For example,
 //    `function(x = eval("")) { var y; }`
 FunctionHasExtraBodyVarScope = 1 << 24,

 // This function must define the implicit `arguments` binding on the function
 // scope. If there are no free uses or an appropriate explicit binding exists,
 // then this flag is unset.
 //
 // Note: Parameter expressions will not see an explicit `var arguments;`
 // binding in the body and an implicit binding on the function-scope must
 // still be used in that case.
 ShouldDeclareArguments = 1 << 25,

 // This function has a local (implicit or explicit) `arguments` binding. This
 // binding is initialized by the JSOp::Arguments bytecode.
 //
 // Technically, every function has a binding named `arguments`. Internally,
 // this binding is only added when `arguments` is mentioned by the function
 // body.
 //
 // Examples:
 //   ```
 //    // Explicit definition
 //    function f() { var arguments; return arguments; }
 //
 //    // Implicit use
 //    function f() { return arguments; }
 //
 //    // Implicit use in arrow function
 //    function f() { return () => arguments; }
 //
 //    // Implicit use in parameter expression
 //    function f(a = arguments) { return a; }
 //   ```
 NeedsArgsObj = 1 << 26,

 // This function must use the "mapped" form of an arguments object. This flag
 // is set independently of whether we actually use an `arguments` binding. The
 // conditions are specified in the ECMAScript spec.
 HasMappedArgsObj = 1 << 27,

 // Large self-hosted methods that should be inlined anyway by the JIT for
 // performance reasons can be marked with this flag.
 IsInlinableLargeFunction = 1 << 28,

 // This function has an internal .newTarget binding and we need to emit
 // JSOp::NewTarget in the prologue to initialize it. This binding may be
 // used directly for "new.target", or indirectly (e.g. in super() calls).
 FunctionHasNewTargetBinding = 1 << 29,

 // Whether this is a self-hosted function that uses the ArgumentsLength or
 // GetArgument intrinsic.
 UsesArgumentsIntrinsics = 1 << 30,
};

enum class MutableScriptFlagsEnum : uint32_t {
 // Number of times the |warmUpCount| was forcibly discarded. The counter is
 // reset when a script is successfully jit-compiled.
 WarmupResets_MASK = 0xFF,

 // If treatAsRunOnce, whether script has executed.
 HasRunOnce = 1 << 8,

 // Script has been reused for a clone.
 HasBeenCloned = 1 << 9,

 // Script has an entry in Realm::scriptCountsMap.
 HasScriptCounts = 1 << 10,

 // Script has an entry in Realm::debugScriptMap.
 HasDebugScript = 1 << 11,

 // (1 << 12) is unused.
 // (1 << 13) is unused.

 // Script supports relazification where it releases bytecode and gcthings to
 // save memory. This process is opt-in since various complexities may disallow
 // this for some scripts.
 // NOTE: Must check for isRelazifiable() before setting this flag.
 AllowRelazify = 1 << 14,

 // Set if the script has opted into spew.
 SpewEnabled = 1 << 15,

 // Set if we care about a script's final warmup count.
 NeedsFinalWarmUpCount = 1 << 16,

 //
 // IonMonkey compilation hints.
 //

 // Whether Baseline or Ion compilation has been disabled for this script.
 // IonDisabled is equivalent to |jitScript->canIonCompile() == false| but
 // JitScript can be discarded on GC and we don't want this to affect
 // observable behavior (see ArgumentsGetterImpl comment).
 BaselineDisabled = 1 << 17,
 IonDisabled = 1 << 18,

 // This script should not be inlined into others. This happens after inlining
 // has failed.
 Uninlineable = 1 << 19,

 // Indicates that this script has no eager baseline hint available
 // in the cache, used to prevent further lookups.
 NoEagerBaselineHint = 1 << 20,

 // *****************************************************************
 // The flags below are set when we bail out and invalidate a script.
 // When we recompile, we will be more conservative.
 // *****************************************************************

 // A hoisted bounds check bailed out.
 FailedBoundsCheck = 1 << 21,

 // An instruction hoisted by LICM bailed out.
 HadLICMInvalidation = 1 << 22,

 // An instruction hoisted by InstructionReordering bailed out.
 HadReorderingBailout = 1 << 23,

 // An instruction inserted or truncated by Range Analysis bailed out.
 HadEagerTruncationBailout = 1 << 24,

 // A lexical check bailed out.
 FailedLexicalCheck = 1 << 25,

 // A guard inserted by phi specialization bailed out.
 HadSpeculativePhiBailout = 1 << 26,

 // An unbox folded with a load bailed out.
 HadUnboxFoldingBailout = 1 << 27,
};

// Retrievable source can be retrieved using the source hook (and therefore
// need not be XDR'd, can be discarded if desired because it can always be
// reconstituted later, etc.).
enum class SourceRetrievable { No = 0, Yes };

}  // namespace js

#endif /* vm_StencilEnums_h */