/* * Copyright (C) 2016 Apple Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #ifndef B3Kind_h #define B3Kind_h #if ENABLE(B3_JIT) #include "B3Opcode.h" #include <wtf/HashTable.h> #include <wtf/PrintStream.h> namespace JSC { namespace B3 { // A Kind is a terse summary of what a Value does. There is a fixed number of possible // Kinds. Kind is a tuple of Opcode (see B3Opcode.h) and some extra bits. Most opcodes don't // get any extra bits, and those bits must remain zero if the Kind's opcode field is set to // one of those opcodes. The purpose of Kind is to be like an opcode in other IRs, but to // be multidimensional. For example, a Load has many dimensions of customization that we may // eventually implement. A Load can have different alignments, alignment failure modes, // temporality modes, trapping modes, ordering modes, etc. It's fine to put such flags into // subclasses of Value, but in some cases that would be overkill, particularly since if you // did that for a pure value then you'd also have to thread it through ValueKey. It's much // easier to put it in Kind, and then your extra bit will get carried around by everyone who // knows how to carry around Kinds. Most importantly, putting flags into Kind allows you to // use them as part of B3::Value's dynamic cast facility. For example we could have a // trapping Load that uses a Value subclass that has a stackmap while non-trapping Loads // continue to use the normal MemoryValue. // // Note that any code in the compiler that transcribes IR (like a strength reduction that // replaces an Add with a different Add, or even with a different opcode entirely) will // probably drop unknown bits by default. This is definitely not correct for many bits (like // isChill for Div/Mod and all of the envisioned Load/Store flags), so if you add a new bit // you will probably have to audit the compiler to make sure that phases that transcribe // your opcode do the right thing with your bit. class Kind { public: Kind(Opcode opcode) : m_opcode(opcode) , m_isChill(false) , m_traps(false) { } Kind() : Kind(Oops) { } Opcode opcode() const { return m_opcode; } void setOpcode(Opcode opcode) { m_opcode = opcode; } bool hasExtraBits() const { return m_isChill || m_traps; } // Chill bit. This applies to division-based arithmetic ops, which may trap on some // platforms or exhibit bizarre behavior when passed certain inputs. The non-chill // version will behave as unpredictably as it wants. For example, it's legal to // constant-fold Div(x, 0) to any value or to replace it with any effectful operation. // But when it's chill, that means that the semantics when it would have trapped are // the JS semantics. For example, Div<Chill>(@a, @b) means: // // ((a | 0) / (b | 0)) | 0 // // And Mod<Chill>(a, b) means: // // ((a | 0) % (b | 0)) | 0 // // Note that Div<Chill> matches exactly how ARM handles integer division. bool hasIsChill() const { switch (m_opcode) { case Div: case Mod: return true; default: return false; } } bool isChill() const { return m_isChill; } void setIsChill(bool isChill) { ASSERT(hasIsChill()); m_isChill = isChill; } // Traps bit. This applies to memory access ops. It means that the instruction could // trap as part of some check it performs, and that we mean to make this observable. This // currently only applies to memory accesses (loads and stores). You don't get to find out where // in the Procedure the trap happened. If you try to work it out using Origin, you'll have a bad // time because the instruction selector is too sloppy with Origin(). // FIXME: https://bugs.webkit.org/show_bug.cgi?id=162688 bool hasTraps() const { switch (m_opcode) { case Load8Z: case Load8S: case Load16Z: case Load16S: case Load: case Store8: case Store16: case Store: return true; default: return false; } } bool traps() const { return m_traps; } void setTraps(bool traps) { ASSERT(hasTraps()); m_traps = traps; } // Rules for adding new properties: // - Put the accessors here. // - hasBlah() should check if the opcode allows for your property. // - blah() returns a default value if !hasBlah() // - setBlah() asserts if !hasBlah() // - Try not to increase the size of Kind too much. But it wouldn't be the end of the // world if it bloated to 64 bits. bool operator==(const Kind& other) const { return m_opcode == other.m_opcode && m_isChill == other.m_isChill && m_traps == other.m_traps; } bool operator!=(const Kind& other) const { return !(*this == other); } void dump(PrintStream&) const; unsigned hash() const { // It's almost certainly more important that this hash function is cheap to compute than // anything else. We can live with some kind hash collisions. return m_opcode + (static_cast<unsigned>(m_isChill) << 16) + (static_cast<unsigned>(m_traps) << 7); } Kind(WTF::HashTableDeletedValueType) : m_opcode(Oops) , m_isChill(true) , m_traps(false) { } bool isHashTableDeletedValue() const { return *this == Kind(WTF::HashTableDeletedValue); } private: Opcode m_opcode; bool m_isChill : 1; bool m_traps : 1; }; // For every flag 'foo' you add, it's customary to create a Kind B3::foo(Kind) function that makes // a kind with the flag set. For example, for chill, this lets us say: // // block->appendNew<Value>(m_proc, chill(Mod), Origin(), a, b); // // I like to make the flag name fill in the sentence "Mod _____" (like "isChill" or "traps") while // the flag constructor fills in the phrase "_____ Mod" (like "chill" or "trapping"). inline Kind chill(Kind kind) { kind.setIsChill(true); return kind; } inline Kind trapping(Kind kind) { kind.setTraps(true); return kind; } struct KindHash { static unsigned hash(const Kind& key) { return key.hash(); } static bool equal(const Kind& a, const Kind& b) { return a == b; } static const bool safeToCompareToEmptyOrDeleted = true; }; } } // namespace JSC::B3 namespace WTF { template<typename T> struct DefaultHash; template<> struct DefaultHash<JSC::B3::Kind> { typedef JSC::B3::KindHash Hash; }; template<typename T> struct HashTraits; template<> struct HashTraits<JSC::B3::Kind> : public SimpleClassHashTraits<JSC::B3::Kind> { static const bool emptyValueIsZero = false; }; } // namespace WTF #endif // ENABLE(B3_JIT) #endif // B3Kind_h