/// <summary>
/// Tells if syntactically equivalent instances of a particular intrinsic
/// are semantically equivalent.
/// </summary>
/// <param name="intrinsic">An intrinsic to consider.</param>
/// <returns>
/// <c>true</c> if syntactically equivalent instances of
/// <paramref name="intrinsic"/> are semantically equivalent;
/// otherwise, <c>false</c>.
/// </returns>
private static bool IsCopyableIntrinsic(IntrinsicPrototype intrinsic)
{
return(ArithmeticIntrinsics.IsArithmeticIntrinsicPrototype(intrinsic) ||
ArrayIntrinsics.Namespace.IsIntrinsicPrototype(intrinsic, ArrayIntrinsics.Operators.GetLength) ||
ArrayIntrinsics.Namespace.IsIntrinsicPrototype(intrinsic, ArrayIntrinsics.Operators.GetElementPointer) ||
ExceptionIntrinsics.Namespace.IsIntrinsicPrototype(intrinsic, ExceptionIntrinsics.Operators.GetCapturedException));
}
private static bool IsLeftToRightReassociable(
IntrinsicPrototype prototype,
out IntrinsicPrototype rightPrototype)
{
string op;
string rightOp;
bool isChecked;
if (ArithmeticIntrinsics.TryParseArithmeticIntrinsicName(prototype.Name, out op, out isChecked) &&
!isChecked &&
intArithLeftToRight.TryGetValue(op, out rightOp) &&
prototype.ParameterTypes.All(x => x.IsIntegerType()))
{
rightPrototype = ArithmeticIntrinsics.CreatePrototype(
rightOp,
isChecked,
prototype.ResultType,
prototype.ParameterTypes);
return(true);
}
else
{
rightPrototype = null;
return(false);
}
}
/// <summary>
/// Creates an arithmetic intrinsic.
/// </summary>
/// <param name="operatorName">
/// The name of the arithmetic operator to apply.
/// </param>
/// <param name="resultType">
/// The type of value produced by the intrinsic.
/// </param>
/// <param name="parameterTypes">
/// The parameter types taken by the intrinsic.
/// </param>
/// <param name="arguments">
/// The argument list to pass to the instruction.
/// </param>
/// <returns>
/// An arithmetic intrinsic.
/// </returns>
public static Instruction CreateArithmeticIntrinsic(
string operatorName,
IType resultType,
IReadOnlyList <IType> parameterTypes,
IReadOnlyList <ValueTag> arguments)
{
return(ArithmeticIntrinsics.CreatePrototype(
operatorName,
resultType,
parameterTypes).Instantiate(arguments));
}
private static bool IsAssociative(IntrinsicPrototype prototype)
{
string op;
bool isChecked;
if (ArithmeticIntrinsics.TryParseArithmeticIntrinsicName(prototype.Name, out op, out isChecked) &&
!isChecked &&
assocIntArith.Contains(op))
{
return(prototype.ParameterTypes.All(x => x.IsIntegerType()));
}
else
{
return(false);
}
}
/// <summary>
/// The default constant instruction evaluation function.
/// </summary>
/// <param name="prototype">
/// The prorotype of the instruction to evaluate.
/// </param>
/// <param name="arguments">
/// A list of arguments to the instruction, all of which
/// must be constants.
/// </param>
/// <returns>
/// <c>null</c> if the instruction cannot be evaluated; otherwise, the constant
/// to which the instruction evaluates.
/// </returns>
public static Constant EvaluateDefault(
InstructionPrototype prototype,
IReadOnlyList <Constant> arguments)
{
if (prototype is CopyPrototype ||
prototype is ReinterpretCastPrototype)
{
return(arguments[0]);
}
else if (prototype is ConstantPrototype)
{
var constProto = (ConstantPrototype)prototype;
if (constProto.Value is DefaultConstant)
{
// Try to specialize 'default' constants.
var intSpec = constProto.ResultType.GetIntegerSpecOrNull();
if (intSpec != null)
{
return(new IntegerConstant(0, intSpec));
}
}
return(constProto.Value);
}
else if (prototype is IntrinsicPrototype)
{
string arithOp;
Constant result;
if (ArithmeticIntrinsics.TryParseArithmeticIntrinsicName(
((IntrinsicPrototype)prototype).Name,
out arithOp) &&
ArithmeticIntrinsics.TryEvaluate(
arithOp,
prototype.ResultType,
arguments,
out result))
{
return(result);
}
}
return(null);
}
/// <summary>
/// Looks for an instruction that is semantically
/// equivalent to a given instruction but minimizes
/// the number of layers of indirection erected by
/// copies.
/// </summary>
/// <param name="instruction">
/// The instruction to simplify.
/// </param>
/// <param name="graph">
/// The graph that defines the instruction.
/// </param>
/// <returns>
/// A semantically equivalent instruction.</returns>
private static Instruction SimplifyInstruction(
Instruction instruction,
FlowGraph graph)
{
if (instruction.Prototype is CopyPrototype)
{
var copyProto = (CopyPrototype)instruction.Prototype;
var copiedVal = copyProto.GetCopiedValue(instruction);
if (graph.ContainsInstruction(copiedVal))
{
var copiedInsn = graph.GetInstruction(copiedVal).Instruction;
// Only simplify copies of arithmetic intriniscs and constants.
// Those are the only instructions we're actually
// interested in and they don't have any "funny" behavior.
if (copiedInsn.Prototype is ConstantPrototype ||
copiedInsn.Prototype is CopyPrototype ||
ArithmeticIntrinsics.IsArithmeticIntrinsicPrototype(copiedInsn.Prototype))
{
return(SimplifyInstruction(copiedInsn, graph));
}
}
}
return(instruction);
}
static RuleBasedPrototypeExceptionSpecs()
{
Default = new RuleBasedPrototypeExceptionSpecs();
// Instruction prototypes that never throw.
Default.Register <AllocaArrayPrototype>(ExceptionSpecification.NoThrow);
Default.Register <AllocaPrototype>(ExceptionSpecification.NoThrow);
Default.Register <BoxPrototype>(ExceptionSpecification.NoThrow);
Default.Register <ConstantPrototype>(ExceptionSpecification.NoThrow);
Default.Register <CopyPrototype>(ExceptionSpecification.NoThrow);
Default.Register <DynamicCastPrototype>(ExceptionSpecification.NoThrow);
Default.Register <GetStaticFieldPointerPrototype>(ExceptionSpecification.NoThrow);
Default.Register <LoadPrototype>(ExceptionSpecification.NoThrow);
Default.Register <ReinterpretCastPrototype>(ExceptionSpecification.NoThrow);
Default.Register <StorePrototype>(ExceptionSpecification.NoThrow);
// Instruction prototypes that may throw because of implicit null checks.
Default.Register <GetFieldPointerPrototype>(
new NullCheckExceptionSpecification(0, ExceptionSpecification.ThrowAny));
Default.Register <NewDelegatePrototype>(
proto => proto.Lookup == MethodLookup.Virtual
? new NullCheckExceptionSpecification(0, ExceptionSpecification.ThrowAny)
: ExceptionSpecification.NoThrow);
Default.Register <UnboxPrototype>(
new NullCheckExceptionSpecification(0, ExceptionSpecification.ThrowAny));
// Call-like instruction prototypes.
Default.Register <CallPrototype>(
proto => proto.Lookup == MethodLookup.Static
? proto.Callee.GetExceptionSpecification()
: ExceptionSpecification.ThrowAny);
Default.Register <NewObjectPrototype>(
proto => proto.Constructor.GetExceptionSpecification());
Default.Register <IndirectCallPrototype>(ExceptionSpecification.ThrowAny);
// Unchecked arithmetic intrinsics never throw.
foreach (var name in ArithmeticIntrinsics.Operators.All)
{
Default.Register(
ArithmeticIntrinsics.GetArithmeticIntrinsicName(name, false),
ExceptionSpecification.NoThrow);
}
// Array intrinsics are a little more complicated.
// TODO: model bounds checks somehow.
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.GetElementPointer),
ExceptionSpecification.ThrowAny);
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.LoadElement),
ExceptionSpecification.ThrowAny);
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.StoreElement),
ExceptionSpecification.ThrowAny);
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.GetLength),
new NullCheckExceptionSpecification(0, ExceptionSpecification.ThrowAny));
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.NewArray),
ExceptionSpecification.NoThrow);
// Exception intrinsics.
Default.Register(
ExceptionIntrinsics.Namespace.GetIntrinsicName(ExceptionIntrinsics.Operators.Capture),
ExceptionSpecification.NoThrow);
Default.Register(
ExceptionIntrinsics.Namespace.GetIntrinsicName(ExceptionIntrinsics.Operators.GetCapturedException),
ExceptionSpecification.NoThrow);
Default.Register(
ExceptionIntrinsics.Namespace.GetIntrinsicName(ExceptionIntrinsics.Operators.Rethrow),
ExceptionSpecification.ThrowAny);
Default.Register(
ExceptionIntrinsics.Namespace.GetIntrinsicName(ExceptionIntrinsics.Operators.Throw),
proto => ExceptionSpecification.Exact.Create(proto.ParameterTypes[0]));
// Object intrinsics.
// TODO: model exception thrown by type check.
Default.Register(
ObjectIntrinsics.Namespace.GetIntrinsicName(ObjectIntrinsics.Operators.UnboxAny),
ExceptionSpecification.ThrowAny);
// Memory intrinsics.
Default.Register(
MemoryIntrinsics.Namespace.GetIntrinsicName(MemoryIntrinsics.Operators.AllocaPinned),
ExceptionSpecification.NoThrow);
}
static RuleBasedPrototypeMemorySpecs()
{
Default = new RuleBasedPrototypeMemorySpecs();
Default.Register <AllocaArrayPrototype>(MemorySpecification.Nothing);
Default.Register <AllocaPrototype>(MemorySpecification.Nothing);
Default.Register <BoxPrototype>(MemorySpecification.Nothing);
Default.Register <ConstantPrototype>(MemorySpecification.Nothing);
Default.Register <CopyPrototype>(MemorySpecification.Nothing);
Default.Register <DynamicCastPrototype>(MemorySpecification.Nothing);
Default.Register <GetStaticFieldPointerPrototype>(MemorySpecification.Nothing);
Default.Register <ReinterpretCastPrototype>(MemorySpecification.Nothing);
Default.Register <GetFieldPointerPrototype>(MemorySpecification.Nothing);
Default.Register <NewDelegatePrototype>(MemorySpecification.Nothing);
Default.Register <UnboxPrototype>(MemorySpecification.Nothing);
// Mark volatile loads and stores as unknown to ensure that they are never reordered
// with regard to other memory operations.
// TODO: is this really how we should represent volatility?
Default.Register <LoadPrototype>(proto =>
proto.IsVolatile ? MemorySpecification.Unknown : MemorySpecification.ArgumentRead.Create(0));
Default.Register <StorePrototype>(proto =>
proto.IsVolatile ? MemorySpecification.Unknown : MemorySpecification.ArgumentWrite.Create(0));
// Call-like instruction prototypes.
Default.Register <CallPrototype>(
proto => proto.Lookup == MethodLookup.Static
? proto.Callee.GetMemorySpecification()
: MemorySpecification.Unknown);
Default.Register <NewObjectPrototype>(
proto => proto.Constructor.GetMemorySpecification());
Default.Register <IndirectCallPrototype>(MemorySpecification.Unknown);
// Arithmetic intrinsics never read or write.
foreach (var name in ArithmeticIntrinsics.Operators.All)
{
Default.Register(
ArithmeticIntrinsics.GetArithmeticIntrinsicName(name, false),
MemorySpecification.Nothing);
Default.Register(
ArithmeticIntrinsics.GetArithmeticIntrinsicName(name, true),
MemorySpecification.Nothing);
}
// Array intrinsics.
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.GetElementPointer),
MemorySpecification.Nothing);
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.LoadElement),
MemorySpecification.UnknownRead);
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.StoreElement),
MemorySpecification.UnknownWrite);
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.GetLength),
MemorySpecification.Nothing);
Default.Register(
ArrayIntrinsics.Namespace.GetIntrinsicName(ArrayIntrinsics.Operators.NewArray),
MemorySpecification.Nothing);
// Exception intrinsics.
Default.Register(
ExceptionIntrinsics.Namespace.GetIntrinsicName(ExceptionIntrinsics.Operators.GetCapturedException),
MemorySpecification.UnknownRead);
// Object intrinsics.
Default.Register(
ObjectIntrinsics.Namespace.GetIntrinsicName(ObjectIntrinsics.Operators.UnboxAny),
MemorySpecification.UnknownRead);
// Memory intrinsics.
Default.Register(
MemoryIntrinsics.Namespace.GetIntrinsicName(MemoryIntrinsics.Operators.AllocaPinned),
MemorySpecification.Nothing);
}
private static BlockFlow SimplifySwitchFlow(SwitchFlow flow, FlowGraph graph)
{
var value = SimplifyInstruction(flow.SwitchValue, graph);
if (value.Prototype is ConstantPrototype)
{
// Turn the switch into a jump.
var constant = ((ConstantPrototype)value.Prototype).Value;
var valuesToBranches = flow.ValueToBranchMap;
return(new JumpFlow(
valuesToBranches.ContainsKey(constant)
? valuesToBranches[constant]
: flow.DefaultBranch));
}
else if (ArithmeticIntrinsics.IsArithmeticIntrinsicPrototype(value.Prototype))
{
var proto = (IntrinsicPrototype)value.Prototype;
var intrinsicName = ArithmeticIntrinsics.ParseArithmeticIntrinsicName(proto.Name);
if (intrinsicName == ArithmeticIntrinsics.Operators.Convert &&
proto.ParameterCount == 1 &&
flow.IsIntegerSwitch)
{
// We can eliminate instructions that extend integers
// by changing the values in the list of cases.
var operand = proto.GetArgumentList(value).Single();
var operandType = graph.GetValueType(operand);
var convType = proto.ResultType;
var operandSpec = operandType.GetIntegerSpecOrNull();
if (operandSpec == null)
{
// The operand of the conversion intrinsic is not an
// integer.
return(flow);
}
var convSpec = convType.GetIntegerSpecOrNull();
if (operandSpec.Size > convSpec.Size)
{
// We can't handle this case. To handle it anyway
// would require us to introduce additional cases
// and that's costly.
return(flow);
}
var caseList = new List <SwitchCase>();
foreach (var switchCase in flow.Cases)
{
// Retain only those switch cases that have values
// that are in the range of the conversion function.
var values = ImmutableHashSet.CreateBuilder <Constant>();
foreach (var val in switchCase.Values.Cast <IntegerConstant>())
{
var opVal = val.Cast(operandSpec);
if (opVal.Cast(convSpec).Equals(val))
{
values.Add(opVal);
}
}
if (values.Count > 0)
{
caseList.Add(new SwitchCase(values.ToImmutableHashSet(), switchCase.Branch));
}
}
return(SimplifySwitchFlow(
new SwitchFlow(
Instruction.CreateCopy(
operandType,
operand),
caseList,
flow.DefaultBranch),
graph));
}
else if (intrinsicName == ArithmeticIntrinsics.Operators.IsEqualTo &&
proto.ParameterCount == 2 &&
proto.ResultType.IsIntegerType())
{
var args = proto.GetArgumentList(value);
var lhs = args[0];
var rhs = args[1];
Constant constant;
ValueTag operand;
if (TryExtractConstantAndValue(lhs, rhs, graph, out constant, out operand))
{
// The 'arith.eq' intrinsic always either produces '0' or '1'.
// Because of that property, we can safely rewrite switches
// like so:
//
// switch arith.eq(value, constant)
// 0 -> zeroBranch
// 1 -> oneBranch
// default -> defaultBranch
//
// -->
//
// switch value
// constant -> oneBranch ?? defaultBranch
// default -> zeroBranch ?? defaultBranch
//
var resultSpec = proto.ResultType.GetIntegerSpecOrNull();
var zeroVal = new IntegerConstant(0, resultSpec);
var oneVal = new IntegerConstant(1, resultSpec);
var valuesToBranches = flow.ValueToBranchMap;
var zeroBranch = valuesToBranches.ContainsKey(zeroVal)
? valuesToBranches[zeroVal]
: flow.DefaultBranch;
var oneBranch = valuesToBranches.ContainsKey(oneVal)
? valuesToBranches[oneVal]
: flow.DefaultBranch;
return(SimplifySwitchFlow(
new SwitchFlow(
Instruction.CreateCopy(
graph.GetValueType(operand),
operand),
new[] { new SwitchCase(ImmutableHashSet.Create(constant), oneBranch) },
zeroBranch),
graph));
}
}
}
return(flow);
}
