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+/* -*- 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 js_experimental_JitInfo_h
+#define js_experimental_JitInfo_h
+
+#include "mozilla/Assertions.h" // MOZ_ASSERT
+
+#include <stddef.h> // size_t
+#include <stdint.h> // uint16_t, uint32_t
+
+#include "js/CallArgs.h" // JS::CallArgs, JS::detail::CallArgsBase, JSNative
+#include "js/RootingAPI.h" // JS::{,Mutable}Handle, JS::Rooted
+#include "js/Value.h" // JS::Value, JSValueType
+
+namespace js {
+
+namespace jit {
+
+enum class InlinableNative : uint16_t;
+
+} // namespace jit
+
+} // namespace js
+
+/**
+ * A class, expected to be passed by value, which represents the CallArgs for a
+ * JSJitGetterOp.
+ */
+class JSJitGetterCallArgs : protected JS::MutableHandle<JS::Value> {
+ public:
+ explicit JSJitGetterCallArgs(const JS::CallArgs& args)
+ : JS::MutableHandle<JS::Value>(args.rval()) {}
+
+ explicit JSJitGetterCallArgs(JS::Rooted<JS::Value>* rooted)
+ : JS::MutableHandle<JS::Value>(rooted) {}
+
+ explicit JSJitGetterCallArgs(JS::MutableHandle<JS::Value> handle)
+ : JS::MutableHandle<JS::Value>(handle) {}
+
+ JS::MutableHandle<JS::Value> rval() { return *this; }
+};
+
+/**
+ * A class, expected to be passed by value, which represents the CallArgs for a
+ * JSJitSetterOp.
+ */
+class JSJitSetterCallArgs : protected JS::MutableHandle<JS::Value> {
+ public:
+ explicit JSJitSetterCallArgs(const JS::CallArgs& args)
+ : JS::MutableHandle<JS::Value>(args[0]) {}
+
+ explicit JSJitSetterCallArgs(JS::Rooted<JS::Value>* rooted)
+ : JS::MutableHandle<JS::Value>(rooted) {}
+
+ JS::MutableHandle<JS::Value> operator[](unsigned i) {
+ MOZ_ASSERT(i == 0);
+ return *this;
+ }
+
+ unsigned length() const { return 1; }
+
+ // Add get() or maybe hasDefined() as needed
+};
+
+struct JSJitMethodCallArgsTraits;
+
+/**
+ * A class, expected to be passed by reference, which represents the CallArgs
+ * for a JSJitMethodOp.
+ */
+class JSJitMethodCallArgs
+ : protected JS::detail::CallArgsBase<JS::detail::NoUsedRval> {
+ private:
+ using Base = JS::detail::CallArgsBase<JS::detail::NoUsedRval>;
+ friend struct JSJitMethodCallArgsTraits;
+
+ public:
+ explicit JSJitMethodCallArgs(const JS::CallArgs& args) {
+ argv_ = args.array();
+ argc_ = args.length();
+ }
+
+ JS::MutableHandle<JS::Value> rval() const { return Base::rval(); }
+
+ unsigned length() const { return Base::length(); }
+
+ JS::MutableHandle<JS::Value> operator[](unsigned i) const {
+ return Base::operator[](i);
+ }
+
+ bool hasDefined(unsigned i) const { return Base::hasDefined(i); }
+
+ JSObject& callee() const {
+ // We can't use Base::callee() because that will try to poke at
+ // this->usedRval_, which we don't have.
+ return argv_[-2].toObject();
+ }
+
+ JS::Handle<JS::Value> get(unsigned i) const { return Base::get(i); }
+
+ bool requireAtLeast(JSContext* cx, const char* fnname,
+ unsigned required) const {
+ // Can just forward to Base, since it only needs the length and we
+ // forward that already.
+ return Base::requireAtLeast(cx, fnname, required);
+ }
+};
+
+struct JSJitMethodCallArgsTraits {
+ static constexpr size_t offsetOfArgv = offsetof(JSJitMethodCallArgs, argv_);
+ static constexpr size_t offsetOfArgc = offsetof(JSJitMethodCallArgs, argc_);
+};
+
+using JSJitGetterOp = bool (*)(JSContext*, JS::Handle<JSObject*>, void*,
+ JSJitGetterCallArgs);
+using JSJitSetterOp = bool (*)(JSContext*, JS::Handle<JSObject*>, void*,
+ JSJitSetterCallArgs);
+using JSJitMethodOp = bool (*)(JSContext*, JS::Handle<JSObject*>, void*,
+ const JSJitMethodCallArgs&);
+
+/**
+ * This struct contains metadata passed from the DOM to the JS Engine for JIT
+ * optimizations on DOM property accessors.
+ *
+ * Eventually, this should be made available to general JSAPI users as *not*
+ * experimental and *not* a friend API, but we're not ready to do so yet.
+ */
+class JSJitInfo {
+ public:
+ enum OpType {
+ Getter,
+ Setter,
+ Method,
+ StaticMethod,
+ InlinableNative,
+ IgnoresReturnValueNative,
+ // Must be last
+ OpTypeCount
+ };
+
+ enum ArgType {
+ // Basic types
+ String = (1 << 0),
+ Integer = (1 << 1), // Only 32-bit or less
+ Double = (1 << 2), // Maybe we want to add Float sometime too
+ Boolean = (1 << 3),
+ Object = (1 << 4),
+ Null = (1 << 5),
+
+ // And derived types
+ Numeric = Integer | Double,
+ // Should "Primitive" use the WebIDL definition, which
+ // excludes string and null, or the typical JS one that includes them?
+ Primitive = Numeric | Boolean | Null | String,
+ ObjectOrNull = Object | Null,
+ Any = ObjectOrNull | Primitive,
+
+ // Our sentinel value.
+ ArgTypeListEnd = (1 << 31)
+ };
+
+ static_assert(Any & String, "Any must include String");
+ static_assert(Any & Integer, "Any must include Integer");
+ static_assert(Any & Double, "Any must include Double");
+ static_assert(Any & Boolean, "Any must include Boolean");
+ static_assert(Any & Object, "Any must include Object");
+ static_assert(Any & Null, "Any must include Null");
+
+ /**
+ * An enum that describes what this getter/setter/method aliases. This
+ * determines what things can be hoisted past this call, and if this
+ * call is movable what it can be hoisted past.
+ */
+ enum AliasSet {
+ /**
+ * Alias nothing: a constant value, getting it can't affect any other
+ * values, nothing can affect it.
+ */
+ AliasNone,
+
+ /**
+ * Alias things that can modify the DOM but nothing else. Doing the
+ * call can't affect the behavior of any other function.
+ */
+ AliasDOMSets,
+
+ /**
+ * Alias the world. Calling this can change arbitrary values anywhere
+ * in the system. Most things fall in this bucket.
+ */
+ AliasEverything,
+
+ /** Must be last. */
+ AliasSetCount
+ };
+
+ bool needsOuterizedThisObject() const {
+ return type() != Getter && type() != Setter;
+ }
+
+ bool isTypedMethodJitInfo() const { return isTypedMethod; }
+
+ OpType type() const { return OpType(type_); }
+
+ AliasSet aliasSet() const { return AliasSet(aliasSet_); }
+
+ JSValueType returnType() const { return JSValueType(returnType_); }
+
+ union {
+ JSJitGetterOp getter;
+ JSJitSetterOp setter;
+ JSJitMethodOp method;
+ /** A DOM static method, used for Promise wrappers */
+ JSNative staticMethod;
+ JSNative ignoresReturnValueMethod;
+ };
+
+ static unsigned offsetOfIgnoresReturnValueNative() {
+ return offsetof(JSJitInfo, ignoresReturnValueMethod);
+ }
+
+ union {
+ uint16_t protoID;
+ js::jit::InlinableNative inlinableNative;
+ };
+
+ union {
+ uint16_t depth;
+
+ // Additional opcode for some InlinableNative functions.
+ uint16_t nativeOp;
+ };
+
+ // These fields are carefully packed to take up 4 bytes. If you need more
+ // bits for whatever reason, please see if you can steal bits from existing
+ // fields before adding more members to this structure.
+ static constexpr size_t OpTypeBits = 4;
+ static constexpr size_t AliasSetBits = 4;
+ static constexpr size_t ReturnTypeBits = 8;
+ static constexpr size_t SlotIndexBits = 10;
+
+ /** The OpType that says what sort of function we are. */
+ uint32_t type_ : OpTypeBits;
+
+ /**
+ * The alias set for this op. This is a _minimal_ alias set; in
+ * particular for a method it does not include whatever argument
+ * conversions might do. That's covered by argTypes and runtime
+ * analysis of the actual argument types being passed in.
+ */
+ uint32_t aliasSet_ : AliasSetBits;
+
+ /** The return type tag. Might be JSVAL_TYPE_UNKNOWN. */
+ uint32_t returnType_ : ReturnTypeBits;
+
+ static_assert(OpTypeCount <= (1 << OpTypeBits),
+ "Not enough space for OpType");
+ static_assert(AliasSetCount <= (1 << AliasSetBits),
+ "Not enough space for AliasSet");
+ static_assert((sizeof(JSValueType) * 8) <= ReturnTypeBits,
+ "Not enough space for JSValueType");
+
+ /** Is op fallible? False in setters. */
+ uint32_t isInfallible : 1;
+
+ /**
+ * Is op movable? To be movable the op must
+ * not AliasEverything, but even that might
+ * not be enough (e.g. in cases when it can
+ * throw or is explicitly not movable).
+ */
+ uint32_t isMovable : 1;
+
+ /**
+ * Can op be dead-code eliminated? Again, this
+ * depends on whether the op can throw, in
+ * addition to the alias set.
+ */
+ uint32_t isEliminatable : 1;
+
+ // XXXbz should we have a JSValueType for the type of the member?
+ /**
+ * True if this is a getter that can always
+ * get the value from a slot of the "this" object.
+ */
+ uint32_t isAlwaysInSlot : 1;
+
+ /**
+ * True if this is a getter that can sometimes (if the slot doesn't contain
+ * UndefinedValue()) get the value from a slot of the "this" object.
+ */
+ uint32_t isLazilyCachedInSlot : 1;
+
+ /** True if this is an instance of JSTypedMethodJitInfo. */
+ uint32_t isTypedMethod : 1;
+
+ /**
+ * If isAlwaysInSlot or isSometimesInSlot is true,
+ * the index of the slot to get the value from.
+ * Otherwise 0.
+ */
+ uint32_t slotIndex : SlotIndexBits;
+
+ static constexpr size_t maxSlotIndex = (1 << SlotIndexBits) - 1;
+};
+
+static_assert(sizeof(JSJitInfo) == (sizeof(void*) + 2 * sizeof(uint32_t)),
+ "There are several thousand instances of JSJitInfo stored in "
+ "a binary. Please don't increase its space requirements without "
+ "verifying that there is no other way forward (better packing, "
+ "smaller datatypes for fields, subclassing, etc.).");
+
+struct JSTypedMethodJitInfo {
+ // We use C-style inheritance here, rather than C++ style inheritance
+ // because not all compilers support brace-initialization for non-aggregate
+ // classes. Using C++ style inheritance and constructors instead of
+ // brace-initialization would also force the creation of static
+ // constructors (on some compilers) when JSJitInfo and JSTypedMethodJitInfo
+ // structures are declared. Since there can be several thousand of these
+ // structures present and we want to have roughly equivalent performance
+ // across a range of compilers, we do things manually.
+ JSJitInfo base;
+
+ const JSJitInfo::ArgType* const argTypes; /* For a method, a list of sets of
+ types that the function
+ expects. This can be used,
+ for example, to figure out
+ when argument coercions can
+ have side-effects. */
+};
+
+#endif // js_experimental_JitInfo_h