Source/JavaScriptCore/b3/B3Kind.h - WebKit - Git at Google

 /*
  * 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
	/*
	* 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