Source/JavaScriptCore/b3/B3Opcode.h - WebKit - Git at Google

 /*
  * Copyright (C) 2015-2017 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.
  */

 #pragma once

 #if ENABLE(B3_JIT)

 #include "B3Type.h"
 #include "B3Width.h"
 #include <wtf/Optional.h>
 #include <wtf/StdLibExtras.h>

 namespace JSC { namespace B3 {

 // Warning: In B3, an Opcode is just one part of a Kind. Kind is used the way that an opcode
 // would be used in simple IRs. See B3Kind.h.

 enum Opcode : uint8_t {
     // A no-op that returns Void, useful for when you want to remove a value.
     Nop,

     // Polymorphic identity, usable with any value type.
     Identity,

     // This is an identity, but we prohibit the compiler from realizing this until the bitter end. This can
     // be used to block reassociation and other compiler reasoning, if we find that it's wrong or
     // unprofitable and we need an escape hatch.
     Opaque,

     // Constants. Use the ConstValue* classes. Constants exist in the control flow, so that we can
     // reason about where we would construct them. Large constants are expensive to create.
     Const32,
     Const64,
     ConstDouble,
     ConstFloat,

     // B3 supports non-SSA variables. These are accessed using Get and Set opcodes. Use the
     // VariableValue class. It's a good idea to run fixSSA() to turn these into SSA. The
     // optimizer will do that eventually, but if your input tends to use these opcodes, you
     // should run fixSSA() directly before launching the optimizer.
     Set,
     Get,

     // Gets the base address of a StackSlot.
     SlotBase,

     // The magical argument register. This is viewed as executing at the top of the program
     // regardless of where in control flow you put it, and the compiler takes care to ensure that we
     // don't clobber the value by register allocation or calls (either by saving the argument to the
     // stack or preserving it in a callee-save register). Use the ArgumentRegValue class. The return
     // type is either pointer() (for GPRs) or Double (for FPRs).
     ArgumentReg,

     // The frame pointer. You can put this anywhere in control flow but it will always yield the
     // frame pointer, with a caveat: if our compiler changes the frame pointer temporarily for some
     // silly reason, the FramePointer intrinsic will return where the frame pointer *should* be not
     // where it happens to be right now.
     FramePointer,

     // Polymorphic math, usable with any value type.
     Add,
     Sub,
     Mul,
     Div, // All bets are off as to what will happen when you execute this for -2^31/-1 and x/0.
     UDiv,
     Mod, // All bets are off as to what will happen when you execute this for -2^31%-1 and x%0.
     UMod,

     // Polymorphic negation. Note that we only need this for floating point, since integer negation
     // is exactly like Sub(0, x). But that's not true for floating point. Sub(0, 0) is 0, while
     // Neg(0) is -0. Also, we canonicalize Sub(0, x) into Neg(x) in case of integers.
     Neg,

     // Integer math.
     BitAnd,
     BitOr,
     BitXor,
     Shl,
     SShr, // Arithmetic Shift.
     ZShr, // Logical Shift.
     RotR, // Rotate Right.
     RotL, // Rotate Left.
     Clz, // Count leading zeros.

     // Floating point math.
     Abs,
     Ceil,
     Floor,
     Sqrt,

     // Casts and such.
     // Bitwise Cast of Double->Int64 or Int64->Double
     BitwiseCast,
     // Takes and returns Int32:
     SExt8,
     SExt16,
     // Takes Int32 and returns Int64:
     SExt32,
     ZExt32,
     // Does a bitwise truncation of Int64->Int32 and Double->Float:
     Trunc,
     // Takes ints and returns floating point value. Note that we don't currently provide the opposite operation,
     // because double-to-int conversions have weirdly different semantics on different platforms. Use
     // a patchpoint if you need to do that.
     IToD,
     IToF,
     // Convert between double and float.
     FloatToDouble,
     DoubleToFloat,

     // Polymorphic comparisons, usable with any value type. Returns int32 0 or 1. Note that "Not"
     // is just Equal(x, 0), and "ToBoolean" is just NotEqual(x, 0).
     Equal,
     NotEqual,
     LessThan,
     GreaterThan,
     LessEqual,
     GreaterEqual,

     // Integer comparisons. Returns int32 0 or 1.
     Above,
     Below,
     AboveEqual,
     BelowEqual,

     // Unordered floating point compare: values are equal or either one is NaN.
     EqualOrUnordered,

     // SSA form of conditional move. The first child is evaluated for truthiness. If true, the second child
     // is returned. Otherwise, the third child is returned.
     Select,

     // Memory loads. Opcode indicates how we load and the loaded type. These use MemoryValue.
     // These return Int32:
     Load8Z,
     Load8S,
     Load16Z,
     Load16S,
     // This returns whatever the return type is:
     Load,

     // Memory stores. Opcode indicates how the value is stored. These use MemoryValue.
     // These take an Int32 value:
     Store8,
     Store16,
     // This is a polymorphic store for Int32, Int64, Float, and Double.
     Store,

     // Atomic compare and swap that returns a boolean. May choose to do nothing and return false. You can
     // usually assume that this is faster and results in less code than AtomicStrongCAS, though that's
     // not necessarily true on Intel, if instruction selection does its job. Imagine that this opcode is
     // as if you did this atomically:
     //
     // template<typename T>
     // bool AtomicWeakCAS(T expectedValue, T newValue, T* ptr)
     // {
     //     if (!rand())
     //         return false; // Real world example of this: context switch on ARM while doing CAS.
     //     if (*ptr != expectedValue)
     //         return false;
     //     *ptr = newValue;
     //     return true;
     // }
     //
     // Note that all atomics put the pointer last to be consistent with how loads and stores work. This
     // is a goofy tradition, but it's harmless, and better than being inconsistent.
     //
     // Note that weak CAS has no fencing guarantees when it fails. This means that the following
     // transformation is always valid:
     //
     // Before:
     //
     //         Branch(AtomicWeakCAS(expected, new, ptr))
     //       Successors: Then:#success, Else:#fail
     //
     // After:
     //
     //         Branch(Equal(Load(ptr), expected))
     //       Successors: Then:#attempt, Else:#fail
     //     BB#attempt:
     //         Branch(AtomicWeakCAS(expected, new, ptr))
     //       Successors: Then:#success, Else:#fail
     //
     // Both kinds of CAS for non-canonical widths (Width8 and Width16) ignore the irrelevant bits of the
     // input.
     AtomicWeakCAS,

     // Atomic compare and swap that returns the old value. Does not have the nondeterminism of WeakCAS.
     // This is a bit more code and a bit slower in some cases, though not by a lot. Imagine that this
     // opcode is as if you did this atomically:
     //
     // template<typename T>
     // T AtomicStrongCAS(T expectedValue, T newValue, T* ptr)
     // {
     //     T oldValue = *ptr;
     //     if (oldValue == expectedValue)
     //         *ptr = newValue;
     //     return oldValue
     // }
     //
     // AtomicStrongCAS sign-extends its result for subwidth operations.
     //
     // Note that AtomicWeakCAS and AtomicStrongCAS sort of have this kind of equivalence:
     //
     // AtomicWeakCAS(@exp, @new, @ptr) == Equal(AtomicStrongCAS(@exp, @new, @ptr), @exp)
     //
     // Assuming that the WeakCAS does not spuriously fail, of course.
     AtomicStrongCAS,

     // Atomically ___ a memory location and return the old value. Syntax:
     //
     // @oldValue = AtomicXchg___(@operand, @ptr)
     //
     // For non-canonical widths (Width8 and Width16), these return sign-extended results and ignore the
     // irrelevant bits of their inputs.
     AtomicXchgAdd,
     AtomicXchgAnd,
     AtomicXchgOr,
     AtomicXchgSub,
     AtomicXchgXor,

     // FIXME: Maybe we should have AtomicXchgNeg.
     // https://bugs.webkit.org/show_bug.cgi?id=169252

     // Atomically exchange a value with a memory location. Syntax:
     //
     // @oldValue = AtomicXchg(@newValue, @ptr)
     AtomicXchg,

     // Introduce an invisible dependency for blocking motion of loads with respect to each other. Syntax:
     //
     // @result = Depend(@phantom)
     //
     // This is eventually codegenerated to have local semantics as if we did:
     //
     // @result = $0
     //
     // But it ensures that the users of @result cannot execute until @phantom is computed.
     //
     // The compiler is not allowed to reason about the fact that Depend codegenerates this way. Any kind
     // of transformation or analysis that relies on the insight that Depend is really zero is unsound,
     // because it unlocks reordering of users of @result and @phantom.
     //
     // On X86, this is lowered to a load-load fence and @result folds to zero.
     //
     // On ARM, this is lowered as if like:
     //
     // @result = BitXor(@phantom, @phantom)
     //
     // Except that the compiler never gets an opportunity to simplify out the BitXor.
     Depend,

     // This is used to compute the actual address of a Wasm memory operation. It takes an IntPtr
     // and a pinned register then computes the appropriate IntPtr address. For the use-case of
     // Wasm it is important that the first child initially be a ZExt32 so the top bits are cleared.
     // We do WasmAddress(ZExt32(ptr), ...) so that we can avoid generating extraneous moves in Air.
     WasmAddress,

     // This is used to represent standalone fences - i.e. fences that are not part of other
     // instructions. It's expressive enough to expose mfence on x86 and dmb ish/ishst on ARM. On
     // x86, it also acts as a compiler store-store fence in those cases where it would have been a
     // dmb ishst on ARM.
     Fence,

     // This is a regular ordinary C function call, using the system C calling convention. Make sure
     // that the arguments are passed using the right types. The first argument is the callee.
     CCall,

     // This is a patchpoint. Use the PatchpointValue class. This is viewed as behaving like a call,
     // but only emits code via a code generation callback. That callback gets to emit code inline.
     // You can pass a stackmap along with constraints on how each stackmap argument must be passed.
     // It's legal to request that a stackmap argument is in some register and it's legal to request
     // that a stackmap argument is at some offset from the top of the argument passing area on the
     // stack.
     Patchpoint,

     // This is a projection out of a tuple. Currently only Patchpoints, Get, and Phi can produce tuples.
     // It's assumumed that each entry in a tuple has a fixed Numeric B3 Type (i.e. not Void or Tuple).
     Extract,

     // Checked math. Use the CheckValue class. Like a Patchpoint, this takes a code generation
     // callback. That callback gets to emit some code after the epilogue, and gets to link the jump
     // from the check, and the choice of registers. You also get to supply a stackmap. Note that you
     // are not allowed to jump back into the mainline code from your slow path, since the compiler
     // will assume that the execution of these instructions proves that overflow didn't happen. For
     // example, if you have two CheckAdd's:
     //
     // a = CheckAdd(x, y)
     // b = CheckAdd(x, y)
     //
     // Then it's valid to change this to:
     //
     // a = CheckAdd(x, y)
     // b = Identity(a)
     //
     // This is valid regardless of the callbacks used by the two CheckAdds. They may have different
     // callbacks. Yet, this transformation is valid even if they are different because we know that
     // after the first CheckAdd executes, the second CheckAdd could not have possibly taken slow
     // path. Therefore, the second CheckAdd's callback is irrelevant.
     //
     // Note that the first two children of these operations have ValueRep's as input constraints but do
     // not have output constraints.
     CheckAdd,
     CheckSub,
     CheckMul,

     // Check that side-exits. Use the CheckValue class. Like CheckAdd and friends, this has a
     // stackmap with a generation callback. This takes an int argument that this branches on, with
     // full branch fusion in the instruction selector. A true value jumps to the generator's slow
     // path. Note that the predicate child is has both an input ValueRep. The input constraint must be
     // WarmAny. It will not have an output constraint.
     Check,

     // Special Wasm opcode that takes a Int32, a special pinned gpr and an offset. This node exists
     // to allow us to CSE WasmBoundsChecks if both use the same pointer and one dominates the other.
     // Without some such node B3 would not have enough information about the inner workings of wasm
     // to be able to perform such optimizations.
     WasmBoundsCheck,

     // SSA support, in the style of DFG SSA.
     Upsilon, // This uses the UpsilonValue class.
     Phi,

     // Jump.
     Jump,

     // Polymorphic branch, usable with any integer type. Branches if not equal to zero. The 0-index
     // successor is the true successor.
     Branch,

     // Switch. Switches over either Int32 or Int64. Uses the SwitchValue class.
     Switch,

     // Multiple entrypoints are supported via the EntrySwitch operation. Place this in the root
     // block and list the entrypoints as the successors. All blocks backwards-reachable from
     // EntrySwitch are duplicated for each entrypoint.
     EntrySwitch,

     // Return. Note that B3 procedures don't know their return type, so this can just return any
     // type.
     Return,

     // This is a terminal that indicates that we will never get here.
     Oops
 };

 inline bool isCheckMath(Opcode opcode)
 {
     switch (opcode) {
     case CheckAdd:
     case CheckSub:
     case CheckMul:
         return true;
     default:
         return false;
     }
 }

 Optional<Opcode> invertedCompare(Opcode, Type);

 inline Opcode constPtrOpcode()
 {
     if (is64Bit())
         return Const64;
     return Const32;
 }

 inline bool isConstant(Opcode opcode)
 {
     switch (opcode) {
     case Const32:
     case Const64:
     case ConstDouble:
     case ConstFloat:
         return true;
     default:
         return false;
     }
 }

 inline Opcode opcodeForConstant(Type type)
 {
     switch (type.kind()) {
     case Int32: return Const32;
     case Int64: return Const64;
     case Float: return ConstFloat;
     case Double: return ConstDouble;
     default:
         RELEASE_ASSERT_NOT_REACHED();
     }
 }

 inline bool isDefinitelyTerminal(Opcode opcode)
 {
     switch (opcode) {
     case Jump:
     case Branch:
     case Switch:
     case Oops:
     case Return:
         return true;
     default:
         return false;
     }
 }

 inline bool isLoad(Opcode opcode)
 {
     switch (opcode) {
     case Load8Z:
     case Load8S:
     case Load16Z:
     case Load16S:
     case Load:
         return true;
     default:
         return false;
     }
 }

 inline bool isStore(Opcode opcode)
 {
     switch (opcode) {
     case Store8:
     case Store16:
     case Store:
         return true;
     default:
         return false;
     }
 }

 inline bool isLoadStore(Opcode opcode)
 {
     switch (opcode) {
     case Load8Z:
     case Load8S:
     case Load16Z:
     case Load16S:
     case Load:
     case Store8:
     case Store16:
     case Store:
         return true;
     default:
         return false;
     }
 }

 inline bool isAtom(Opcode opcode)
 {
     switch (opcode) {
     case AtomicWeakCAS:
     case AtomicStrongCAS:
     case AtomicXchgAdd:
     case AtomicXchgAnd:
     case AtomicXchgOr:
     case AtomicXchgSub:
     case AtomicXchgXor:
     case AtomicXchg:
         return true;
     default:
         return false;
     }
 }

 inline bool isAtomicCAS(Opcode opcode)
 {
     switch (opcode) {
     case AtomicWeakCAS:
     case AtomicStrongCAS:
         return true;
     default:
         return false;
     }
 }

 inline bool isAtomicXchg(Opcode opcode)
 {
     switch (opcode) {
     case AtomicXchgAdd:
     case AtomicXchgAnd:
     case AtomicXchgOr:
     case AtomicXchgSub:
     case AtomicXchgXor:
     case AtomicXchg:
         return true;
     default:
         return false;
     }
 }

 inline bool isMemoryAccess(Opcode opcode)
 {
     return isAtom(opcode) || isLoadStore(opcode);
 }

 inline Opcode signExtendOpcode(Width width)
 {
     switch (width) {
     case Width8:
         return SExt8;
     case Width16:
         return SExt16;
     default:
         RELEASE_ASSERT_NOT_REACHED();
         return Oops;
     }
 }

 JS_EXPORT_PRIVATE Opcode storeOpcode(Bank bank, Width width);

 } } // namespace JSC::B3

 namespace WTF {

 class PrintStream;

 JS_EXPORT_PRIVATE void printInternal(PrintStream&, JSC::B3::Opcode);

 } // namespace WTF

 #endif // ENABLE(B3_JIT)
	/*
	* Copyright (C) 2015-2017 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.
	*/

	#pragma once

	#if ENABLE(B3_JIT)

	#include "B3Type.h"
	#include "B3Width.h"
	#include <wtf/Optional.h>
	#include <wtf/StdLibExtras.h>

	namespace JSC { namespace B3 {

	// Warning: In B3, an Opcode is just one part of a Kind. Kind is used the way that an opcode
	// would be used in simple IRs. See B3Kind.h.

	enum Opcode : uint8_t {
	// A no-op that returns Void, useful for when you want to remove a value.
	Nop,

	// Polymorphic identity, usable with any value type.
	Identity,

	// This is an identity, but we prohibit the compiler from realizing this until the bitter end. This can
	// be used to block reassociation and other compiler reasoning, if we find that it's wrong or
	// unprofitable and we need an escape hatch.
	Opaque,

	// Constants. Use the ConstValue* classes. Constants exist in the control flow, so that we can
	// reason about where we would construct them. Large constants are expensive to create.
	Const32,
	Const64,
	ConstDouble,
	ConstFloat,

	// B3 supports non-SSA variables. These are accessed using Get and Set opcodes. Use the
	// VariableValue class. It's a good idea to run fixSSA() to turn these into SSA. The
	// optimizer will do that eventually, but if your input tends to use these opcodes, you
	// should run fixSSA() directly before launching the optimizer.
	Set,
	Get,

	// Gets the base address of a StackSlot.
	SlotBase,

	// The magical argument register. This is viewed as executing at the top of the program
	// regardless of where in control flow you put it, and the compiler takes care to ensure that we
	// don't clobber the value by register allocation or calls (either by saving the argument to the
	// stack or preserving it in a callee-save register). Use the ArgumentRegValue class. The return
	// type is either pointer() (for GPRs) or Double (for FPRs).
	ArgumentReg,

	// The frame pointer. You can put this anywhere in control flow but it will always yield the
	// frame pointer, with a caveat: if our compiler changes the frame pointer temporarily for some
	// silly reason, the FramePointer intrinsic will return where the frame pointer should be not
	// where it happens to be right now.
	FramePointer,

	// Polymorphic math, usable with any value type.
	Add,
	Sub,
	Mul,
	Div, // All bets are off as to what will happen when you execute this for -2^31/-1 and x/0.
	UDiv,
	Mod, // All bets are off as to what will happen when you execute this for -2^31%-1 and x%0.
	UMod,

	// Polymorphic negation. Note that we only need this for floating point, since integer negation
	// is exactly like Sub(0, x). But that's not true for floating point. Sub(0, 0) is 0, while
	// Neg(0) is -0. Also, we canonicalize Sub(0, x) into Neg(x) in case of integers.
	Neg,

	// Integer math.
	BitAnd,
	BitOr,
	BitXor,
	Shl,
	SShr, // Arithmetic Shift.
	ZShr, // Logical Shift.
	RotR, // Rotate Right.
	RotL, // Rotate Left.
	Clz, // Count leading zeros.

	// Floating point math.
	Abs,
	Ceil,
	Floor,
	Sqrt,

	// Casts and such.
	// Bitwise Cast of Double->Int64 or Int64->Double
	BitwiseCast,
	// Takes and returns Int32:
	SExt8,
	SExt16,
	// Takes Int32 and returns Int64:
	SExt32,
	ZExt32,
	// Does a bitwise truncation of Int64->Int32 and Double->Float:
	Trunc,
	// Takes ints and returns floating point value. Note that we don't currently provide the opposite operation,
	// because double-to-int conversions have weirdly different semantics on different platforms. Use
	// a patchpoint if you need to do that.
	IToD,
	IToF,
	// Convert between double and float.
	FloatToDouble,
	DoubleToFloat,

	// Polymorphic comparisons, usable with any value type. Returns int32 0 or 1. Note that "Not"
	// is just Equal(x, 0), and "ToBoolean" is just NotEqual(x, 0).
	Equal,
	NotEqual,
	LessThan,
	GreaterThan,
	LessEqual,
	GreaterEqual,

	// Integer comparisons. Returns int32 0 or 1.
	Above,
	Below,
	AboveEqual,
	BelowEqual,

	// Unordered floating point compare: values are equal or either one is NaN.
	EqualOrUnordered,

	// SSA form of conditional move. The first child is evaluated for truthiness. If true, the second child
	// is returned. Otherwise, the third child is returned.
	Select,

	// Memory loads. Opcode indicates how we load and the loaded type. These use MemoryValue.
	// These return Int32:
	Load8Z,
	Load8S,
	Load16Z,
	Load16S,
	// This returns whatever the return type is:
	Load,

	// Memory stores. Opcode indicates how the value is stored. These use MemoryValue.
	// These take an Int32 value:
	Store8,
	Store16,
	// This is a polymorphic store for Int32, Int64, Float, and Double.
	Store,

	// Atomic compare and swap that returns a boolean. May choose to do nothing and return false. You can
	// usually assume that this is faster and results in less code than AtomicStrongCAS, though that's
	// not necessarily true on Intel, if instruction selection does its job. Imagine that this opcode is
	// as if you did this atomically:
	//
	// template<typename T>
	// bool AtomicWeakCAS(T expectedValue, T newValue, T* ptr)
	// {
	// if (!rand())
	// return false; // Real world example of this: context switch on ARM while doing CAS.
	// if (*ptr != expectedValue)
	// return false;
	// *ptr = newValue;
	// return true;
	// }
	//
	// Note that all atomics put the pointer last to be consistent with how loads and stores work. This
	// is a goofy tradition, but it's harmless, and better than being inconsistent.
	//
	// Note that weak CAS has no fencing guarantees when it fails. This means that the following
	// transformation is always valid:
	//
	// Before:
	//
	// Branch(AtomicWeakCAS(expected, new, ptr))
	// Successors: Then:#success, Else:#fail
	//
	// After:
	//
	// Branch(Equal(Load(ptr), expected))
	// Successors: Then:#attempt, Else:#fail
	// BB#attempt:
	// Branch(AtomicWeakCAS(expected, new, ptr))
	// Successors: Then:#success, Else:#fail
	//
	// Both kinds of CAS for non-canonical widths (Width8 and Width16) ignore the irrelevant bits of the
	// input.
	AtomicWeakCAS,

	// Atomic compare and swap that returns the old value. Does not have the nondeterminism of WeakCAS.
	// This is a bit more code and a bit slower in some cases, though not by a lot. Imagine that this
	// opcode is as if you did this atomically:
	//
	// template<typename T>
	// T AtomicStrongCAS(T expectedValue, T newValue, T* ptr)
	// {
	// T oldValue = *ptr;
	// if (oldValue == expectedValue)
	// *ptr = newValue;
	// return oldValue
	// }
	//
	// AtomicStrongCAS sign-extends its result for subwidth operations.
	//
	// Note that AtomicWeakCAS and AtomicStrongCAS sort of have this kind of equivalence:
	//
	// AtomicWeakCAS(@exp, @new, @ptr) == Equal(AtomicStrongCAS(@exp, @new, @ptr), @exp)
	//
	// Assuming that the WeakCAS does not spuriously fail, of course.
	AtomicStrongCAS,

	// Atomically ___ a memory location and return the old value. Syntax:
	//
	// @oldValue = AtomicXchg___(@operand, @ptr)
	//
	// For non-canonical widths (Width8 and Width16), these return sign-extended results and ignore the
	// irrelevant bits of their inputs.
	AtomicXchgAdd,
	AtomicXchgAnd,
	AtomicXchgOr,
	AtomicXchgSub,
	AtomicXchgXor,

	// FIXME: Maybe we should have AtomicXchgNeg.
	// https://bugs.webkit.org/show_bug.cgi?id=169252

	// Atomically exchange a value with a memory location. Syntax:
	//
	// @oldValue = AtomicXchg(@newValue, @ptr)
	AtomicXchg,

	// Introduce an invisible dependency for blocking motion of loads with respect to each other. Syntax:
	//
	// @result = Depend(@phantom)
	//
	// This is eventually codegenerated to have local semantics as if we did:
	//
	// @result = $0
	//
	// But it ensures that the users of @result cannot execute until @phantom is computed.
	//
	// The compiler is not allowed to reason about the fact that Depend codegenerates this way. Any kind
	// of transformation or analysis that relies on the insight that Depend is really zero is unsound,
	// because it unlocks reordering of users of @result and @phantom.
	//
	// On X86, this is lowered to a load-load fence and @result folds to zero.
	//
	// On ARM, this is lowered as if like:
	//
	// @result = BitXor(@phantom, @phantom)
	//
	// Except that the compiler never gets an opportunity to simplify out the BitXor.
	Depend,

	// This is used to compute the actual address of a Wasm memory operation. It takes an IntPtr
	// and a pinned register then computes the appropriate IntPtr address. For the use-case of
	// Wasm it is important that the first child initially be a ZExt32 so the top bits are cleared.
	// We do WasmAddress(ZExt32(ptr), ...) so that we can avoid generating extraneous moves in Air.
	WasmAddress,

	// This is used to represent standalone fences - i.e. fences that are not part of other
	// instructions. It's expressive enough to expose mfence on x86 and dmb ish/ishst on ARM. On
	// x86, it also acts as a compiler store-store fence in those cases where it would have been a
	// dmb ishst on ARM.
	Fence,

	// This is a regular ordinary C function call, using the system C calling convention. Make sure
	// that the arguments are passed using the right types. The first argument is the callee.
	CCall,

	// This is a patchpoint. Use the PatchpointValue class. This is viewed as behaving like a call,
	// but only emits code via a code generation callback. That callback gets to emit code inline.
	// You can pass a stackmap along with constraints on how each stackmap argument must be passed.
	// It's legal to request that a stackmap argument is in some register and it's legal to request
	// that a stackmap argument is at some offset from the top of the argument passing area on the
	// stack.
	Patchpoint,

	// This is a projection out of a tuple. Currently only Patchpoints, Get, and Phi can produce tuples.
	// It's assumumed that each entry in a tuple has a fixed Numeric B3 Type (i.e. not Void or Tuple).
	Extract,

	// Checked math. Use the CheckValue class. Like a Patchpoint, this takes a code generation
	// callback. That callback gets to emit some code after the epilogue, and gets to link the jump
	// from the check, and the choice of registers. You also get to supply a stackmap. Note that you
	// are not allowed to jump back into the mainline code from your slow path, since the compiler
	// will assume that the execution of these instructions proves that overflow didn't happen. For
	// example, if you have two CheckAdd's:
	//
	// a = CheckAdd(x, y)
	// b = CheckAdd(x, y)
	//
	// Then it's valid to change this to:
	//
	// a = CheckAdd(x, y)
	// b = Identity(a)
	//
	// This is valid regardless of the callbacks used by the two CheckAdds. They may have different
	// callbacks. Yet, this transformation is valid even if they are different because we know that
	// after the first CheckAdd executes, the second CheckAdd could not have possibly taken slow
	// path. Therefore, the second CheckAdd's callback is irrelevant.
	//
	// Note that the first two children of these operations have ValueRep's as input constraints but do
	// not have output constraints.
	CheckAdd,
	CheckSub,
	CheckMul,

	// Check that side-exits. Use the CheckValue class. Like CheckAdd and friends, this has a
	// stackmap with a generation callback. This takes an int argument that this branches on, with
	// full branch fusion in the instruction selector. A true value jumps to the generator's slow
	// path. Note that the predicate child is has both an input ValueRep. The input constraint must be
	// WarmAny. It will not have an output constraint.
	Check,

	// Special Wasm opcode that takes a Int32, a special pinned gpr and an offset. This node exists
	// to allow us to CSE WasmBoundsChecks if both use the same pointer and one dominates the other.
	// Without some such node B3 would not have enough information about the inner workings of wasm
	// to be able to perform such optimizations.
	WasmBoundsCheck,

	// SSA support, in the style of DFG SSA.
	Upsilon, // This uses the UpsilonValue class.
	Phi,

	// Jump.
	Jump,

	// Polymorphic branch, usable with any integer type. Branches if not equal to zero. The 0-index
	// successor is the true successor.
	Branch,

	// Switch. Switches over either Int32 or Int64. Uses the SwitchValue class.
	Switch,

	// Multiple entrypoints are supported via the EntrySwitch operation. Place this in the root
	// block and list the entrypoints as the successors. All blocks backwards-reachable from
	// EntrySwitch are duplicated for each entrypoint.
	EntrySwitch,

	// Return. Note that B3 procedures don't know their return type, so this can just return any
	// type.
	Return,

	// This is a terminal that indicates that we will never get here.
	Oops
	};

	inline bool isCheckMath(Opcode opcode)
	{
	switch (opcode) {
	case CheckAdd:
	case CheckSub:
	case CheckMul:
	return true;
	default:
	return false;
	}
	}

	Optional<Opcode> invertedCompare(Opcode, Type);

	inline Opcode constPtrOpcode()
	{
	if (is64Bit())
	return Const64;
	return Const32;
	}

	inline bool isConstant(Opcode opcode)
	{
	switch (opcode) {
	case Const32:
	case Const64:
	case ConstDouble:
	case ConstFloat:
	return true;
	default:
	return false;
	}
	}

	inline Opcode opcodeForConstant(Type type)
	{
	switch (type.kind()) {
	case Int32: return Const32;
	case Int64: return Const64;
	case Float: return ConstFloat;
	case Double: return ConstDouble;
	default:
	RELEASE_ASSERT_NOT_REACHED();
	}
	}

	inline bool isDefinitelyTerminal(Opcode opcode)
	{
	switch (opcode) {
	case Jump:
	case Branch:
	case Switch:
	case Oops:
	case Return:
	return true;
	default:
	return false;
	}
	}

	inline bool isLoad(Opcode opcode)
	{
	switch (opcode) {
	case Load8Z:
	case Load8S:
	case Load16Z:
	case Load16S:
	case Load:
	return true;
	default:
	return false;
	}
	}

	inline bool isStore(Opcode opcode)
	{
	switch (opcode) {
	case Store8:
	case Store16:
	case Store:
	return true;
	default:
	return false;
	}
	}

	inline bool isLoadStore(Opcode opcode)
	{
	switch (opcode) {
	case Load8Z:
	case Load8S:
	case Load16Z:
	case Load16S:
	case Load:
	case Store8:
	case Store16:
	case Store:
	return true;
	default:
	return false;
	}
	}

	inline bool isAtom(Opcode opcode)
	{
	switch (opcode) {
	case AtomicWeakCAS:
	case AtomicStrongCAS:
	case AtomicXchgAdd:
	case AtomicXchgAnd:
	case AtomicXchgOr:
	case AtomicXchgSub:
	case AtomicXchgXor:
	case AtomicXchg:
	return true;
	default:
	return false;
	}
	}

	inline bool isAtomicCAS(Opcode opcode)
	{
	switch (opcode) {
	case AtomicWeakCAS:
	case AtomicStrongCAS:
	return true;
	default:
	return false;
	}
	}

	inline bool isAtomicXchg(Opcode opcode)
	{
	switch (opcode) {
	case AtomicXchgAdd:
	case AtomicXchgAnd:
	case AtomicXchgOr:
	case AtomicXchgSub:
	case AtomicXchgXor:
	case AtomicXchg:
	return true;
	default:
	return false;
	}
	}

	inline bool isMemoryAccess(Opcode opcode)
	{
	return isAtom(opcode) \|\| isLoadStore(opcode);
	}

	inline Opcode signExtendOpcode(Width width)
	{
	switch (width) {
	case Width8:
	return SExt8;
	case Width16:
	return SExt16;
	default:
	RELEASE_ASSERT_NOT_REACHED();
	return Oops;
	}
	}

	JS_EXPORT_PRIVATE Opcode storeOpcode(Bank bank, Width width);

	} } // namespace JSC::B3

	namespace WTF {

	class PrintStream;

	JS_EXPORT_PRIVATE void printInternal(PrintStream&, JSC::B3::Opcode);

	} // namespace WTF

	#endif // ENABLE(B3_JIT)