/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
foreach (var insn in builder.NamedInstructions)
{
ValueTag array;
ClrFieldDefinition pseudoField;
if (IsArrayInit(insn, out array, out pseudoField))
{
array = ElideReinterpretCasts(array, builder.ToImmutable());
var arrayType = TypeHelpers.UnboxIfPossible(graph.GetValueType(array));
IType elementType;
IReadOnlyList <Constant> data;
int rank;
if (ClrArrayType.TryGetArrayElementType(arrayType, out elementType) &&
ClrArrayType.TryGetArrayRank(arrayType, out rank) &&
rank == 1 &&
TryDecodePseudoFieldData(pseudoField, elementType, out data))
{
// Generate instructions to fill the array.
FillWith(array, data, elementType, insn);
// Neuter the old array init function.
insn.Instruction = Instruction.CreateConstant(DefaultConstant.Instance, insn.ResultType);
}
}
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
BasicBlockTag entryThunk = null;
foreach (var block in builder.BasicBlocks)
{
var flow = block.Flow;
foreach (var branch in block.Flow.Branches)
{
if (branch.Target == graph.EntryPointTag)
{
if (entryThunk == null)
{
entryThunk = CreateEntryPointThunk(builder);
break;
}
}
}
if (entryThunk != null)
{
break;
}
}
if (entryThunk != null)
{
builder.EntryPointTag = entryThunk;
}
return(builder.ToImmutable());
}
/// <summary>
/// Propagates copies in a flow graph.
/// </summary>
/// <param name="graph">
/// The graph to transform.
/// </param>
/// <returns>
/// A transformed graph.
/// </returns>
public override FlowGraph Apply(FlowGraph graph)
{
// We'll first create a mapping of values to the
// values they copy. Then we'll use that to
// rewrite uses.
var copyMap = FindCopies(graph);
var graphBuilder = graph.ToBuilder();
// Undefined values are encoded as `null` values.
// We will first materialize them as `default`
// constants and then replace uses.
var entryPoint = graphBuilder.GetBasicBlock(graphBuilder.EntryPointTag);
var materializedReplacements = new Dictionary <ValueTag, ValueTag>();
foreach (var pair in copyMap)
{
if (pair.Value == null)
{
materializedReplacements[pair.Key] = entryPoint.InsertInstruction(
0,
Instruction.CreateDefaultConstant(graphBuilder.GetValueType(pair.Key)),
pair.Key.Name);
}
else
{
materializedReplacements[pair.Key] = pair.Value;
}
}
graphBuilder.ReplaceUses(materializedReplacements);
return(graphBuilder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
foreach (var block in builder.BasicBlocks)
{
var instruction = block.NamedInstructions.FirstOrDefault();
while (instruction != null)
{
ReassociateNonAssociative(instruction);
instruction = instruction.NextInstructionOrNull;
}
}
foreach (var block in builder.BasicBlocks)
{
var instruction = block.NamedInstructions.LastOrDefault();
while (instruction != null)
{
ReassociateReduction(instruction);
instruction = instruction.PreviousInstructionOrNull;
}
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var ordering = graph.GetAnalysisResult <InstructionOrdering>();
var builder = graph.ToBuilder();
foreach (var block in builder.BasicBlocks)
{
// Create a linked list that contains all instructions.
var schedule = new LinkedList <ValueTag>(block.InstructionTags);
// Plus a dummy node for the block's flow.
schedule.AddLast((ValueTag)null);
// Reorder branch arguments.
foreach (var branch in block.Flow.Branches.Reverse())
{
ReorderArguments(
branch.Arguments
.Select(arg => arg.ValueOrNull)
.Where(arg => arg != null),
block,
schedule.Last,
ordering,
builder.ImmutableGraph);
}
// Reorder anonymous instruction arguments.
foreach (var instruction in block.Flow.Instructions.Reverse())
{
ReorderArguments(instruction, block, schedule.Last, ordering, builder.ImmutableGraph);
}
// Reorder named instruction arguments in reverse.
var finger = schedule.Last.Previous;
while (finger != null)
{
var instruction = graph.GetInstruction(finger.Value);
ReorderArguments(instruction.Instruction, block, finger, ordering, builder.ImmutableGraph);
finger = finger.Previous;
}
// Materialize the new schedule.
int index = 0;
foreach (var value in schedule)
{
if (value == null)
{
continue;
}
var instruction = builder.GetInstruction(value);
instruction.MoveTo(index, block);
index++;
}
}
return(builder.ToImmutable());
}
/// <summary>
/// Simplifies switches in a particular flow graph.
/// </summary>
/// <param name="graph">The graph to transform.</param>
/// <returns>A transformed graph.</returns>
public override FlowGraph Apply(FlowGraph graph)
{
var graphBuilder = graph.ToBuilder();
foreach (var block in graphBuilder.BasicBlocks)
{
TrySimplifySwitchFlow(block);
}
return(graphBuilder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
foreach (var instruction in builder.Instructions)
{
TrySimplify(instruction);
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
// Figure out which blocks contain nothing but a return.
var candidatesToValues = new Dictionary <BasicBlockTag, ValueTag>();
foreach (var block in graph.BasicBlocks)
{
if (block.InstructionTags.Count == 0)
{
var flow = block.Flow as ReturnFlow;
if (flow != null)
{
var retInsn = flow.ReturnValue;
var retProto = retInsn.Prototype as CopyPrototype;
if (retProto != null)
{
candidatesToValues[block] = retProto.GetCopiedValue(retInsn);
}
}
}
}
if (candidatesToValues.Count == 0)
{
return(graph);
}
else
{
// Rewrite blocks if we found any candidates.
var builder = graph.ToBuilder();
foreach (var block in builder.BasicBlocks)
{
var flow = block.Flow as JumpFlow;
ValueTag retValue;
if (flow != null &&
candidatesToValues.TryGetValue(flow.Branch.Target, out retValue))
{
foreach (var pair in flow.Branch.ZipArgumentsWithParameters(builder.ToImmutable()))
{
if (pair.Key == retValue)
{
retValue = pair.Value.ValueOrNull;
}
}
block.Flow = new ReturnFlow(
Instruction.CreateCopy(
builder.GetValueType(retValue),
retValue));
}
}
return(builder.ToImmutable());
}
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
// Compute the value numbering for the graph.
var numbering = graph.GetAnalysisResult <ValueNumbering>();
// Partition the set of all instructions into equivalence classes.
var equivValues = new Dictionary <Instruction, HashSet <ValueTag> >(
new ValueNumberingInstructionComparer(numbering));
foreach (var insn in graph.NamedInstructions)
{
HashSet <ValueTag> valueSet;
if (!equivValues.TryGetValue(insn.Instruction, out valueSet))
{
equivValues[insn.Instruction] = valueSet = new HashSet <ValueTag>();
}
valueSet.Add(insn);
}
// Compute the dominator tree for the graph.
var domTree = graph.GetAnalysisResult <DominatorTree>();
// Replace instructions with copies to your heart's content.
var builder = graph.ToBuilder();
foreach (var insn in builder.Instructions)
{
// An instruction can be replaced with another instruction
// if it is equivalent to that instruction and it is strictly
// dominated by the other instruction.
HashSet <ValueTag> valueSet;
if (!equivValues.TryGetValue(insn.Instruction, out valueSet))
{
continue;
}
foreach (var equivValue in valueSet)
{
if (domTree.IsStrictlyDominatedBy(insn, equivValue))
{
insn.Instruction = Instruction.CreateCopy(insn.Instruction.ResultType, equivValue);
break;
}
}
}
return(builder.ToImmutable());
}
/// <summary>
/// Removes dead blocks from a particular graph.
/// </summary>
/// <param name="graph">The graph to rewrite.</param>
/// <returns>A rewritten flow graph.</returns>
public override FlowGraph Apply(FlowGraph graph)
{
var reachability = graph.GetAnalysisResult<BlockReachability>();
var deadBlocks = new HashSet<BasicBlockTag>(graph.BasicBlockTags);
deadBlocks.Remove(graph.EntryPointTag);
deadBlocks.ExceptWith(
reachability.GetStrictlyReachableBlocks(
graph.EntryPointTag));
var graphBuilder = graph.ToBuilder();
foreach (var tag in deadBlocks)
{
graphBuilder.RemoveBasicBlock(tag);
}
return graphBuilder.ToImmutable();
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
// This transform does the following things:
// 1. It figures out which values need materializing.
// 2. It delays the materialization of aggregates that cannot
// be fully replaced by scalars.
// 3. It runs the regular scalar replacement pass.
var builder = graph.ToBuilder();
var analysisResults = new MaterializationAnalysis().Analyze(graph);
DelayMaterialization(builder, analysisResults.BlockResults);
builder.Transform(new ScalarReplacement(CanReplaceByScalars));
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
foreach (var instruction in builder.Instructions)
{
var proto = instruction.Prototype;
if (proto is BoxPrototype)
{
var boxProto = (BoxPrototype)proto;
if (boxProto.ElementType.IsReferenceType())
{
LowerReferenceTypeBox(instruction, boxProto.ElementType);
}
}
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
var ordering = graph.GetAnalysisResult <InstructionOrdering>();
foreach (var block in builder.BasicBlocks)
{
if (block.Flow is ReturnFlow)
{
var retFlow = (ReturnFlow)block.Flow;
TryReplaceWithBranchToEntry(
block,
retFlow.ReturnValue,
builder,
ordering);
}
}
return(builder.ToImmutable());
}
// This transform is based on the algorithm described by M. Braun et al
// in Simple and Efficient Construction of Static Single Assignment Form
// (https://pp.info.uni-karlsruhe.de/uploads/publikationen/braun13cc.pdf).
/// <summary>
/// Applies the alloca to register transformation to a flow graph.
/// </summary>
/// <param name="graph">
/// A flow graph to transform.
/// </param>
/// <returns>
/// A transformed flow graph.
/// </returns>
public override FlowGraph Apply(FlowGraph graph)
{
// Our first order of business is to identify
// all `alloca` instructions that we *cannot*
// replace with SSA magic.
//
// To keep things simple, we'll just blacklist
// any `alloca` that is used by instructions other
// than `load` and `store`.
var eligibleAllocas = GetAllocasWithoutIdentity(graph);
// We now have a set of all blacklisted `alloca` instructions.
// All we need to do now is actually apply the SSA construction
// algorithm.
var graphBuilder = graph.ToBuilder();
var algo = new SSAConstructionAlgorithm(graphBuilder, eligibleAllocas);
algo.Run();
return(graphBuilder.ToImmutable());
}
/// <summary>
/// Lowers general switch flow in a particular flow graph.
/// </summary>
/// <param name="graph">The flow graph to rewrite.</param>
/// <returns>A rewritten flow graph.</returns>
public override FlowGraph Apply(FlowGraph graph)
{
var graphBuilder = graph.ToBuilder();
foreach (var block in graphBuilder.BasicBlocks)
{
var flow = block.Flow;
if (flow is SwitchFlow)
{
var switchFlow = (SwitchFlow)flow;
if (switchFlow.IsIfElseFlow)
{
// If-else flow is its own optimal lowering.
continue;
}
var value = block.AppendInstruction(switchFlow.SwitchValue, "switchval");
block.Flow = GetSwitchFlowLowering(switchFlow)
.Emit(graphBuilder, value);
}
}
return(graphBuilder.ToImmutable());
}
/// <summary>
/// Applies the jump threading optimization to a flow graph.
/// </summary>
/// <param name="graph">The flow graph to rewrite.</param>
/// <returns>An optimized flow graph.</returns>
public override FlowGraph Apply(FlowGraph graph)
{
var graphBuilder = graph.ToBuilder();
// Ensure that the graph is in register forwarding form.
// Jump threading will work even if it isn't, but register
// forwarding form will allow jump threading to make more
// aggressive simplifications.
graphBuilder.Transform(ForwardRegisters.Instance);
// Suggest exception spec analyses if the graph doesn't have any yet.
if (!graphBuilder.HasAnalysisFor <PrototypeExceptionSpecs>())
{
graphBuilder.AddAnalysis(
new ConstantAnalysis <PrototypeExceptionSpecs>(
RuleBasedPrototypeExceptionSpecs.Default));
}
if (!graphBuilder.HasAnalysisFor <InstructionExceptionSpecs>())
{
graphBuilder.AddAnalysis(
new ConstantAnalysis <InstructionExceptionSpecs>(
new TrivialInstructionExceptionSpecs(
graphBuilder.GetAnalysisResult <PrototypeExceptionSpecs>())));
}
var finished = new HashSet <BasicBlockTag>();
foreach (var block in graphBuilder.BasicBlocks)
{
ThreadJumps(block, finished);
}
// Move out of register forwarding form by applying copy propagation
// and dead code elimination.
graphBuilder.Transform(CopyPropagation.Instance, DeadValueElimination.Instance, DeadBlockElimination.Instance);
return(graphBuilder.ToImmutable());
}
/// <summary>
/// Applies the jump threading optimization to a flow graph.
/// </summary>
/// <param name="graph">The flow graph to rewrite.</param>
/// <returns>An optimized flow graph.</returns>
public override FlowGraph Apply(FlowGraph graph)
{
var graphBuilder = graph.ToBuilder();
// Ensure that the graph is in register forwarding form.
// Jump threading will work even if it isn't, but register
// forwarding form will allow jump threading to make more
// aggressive simplifications.
graphBuilder.Transform(ForwardRegisters.Instance);
var finished = new HashSet <BasicBlockTag>();
foreach (var block in graphBuilder.BasicBlocks)
{
ThreadJumps(block, finished);
}
// Move out of register forwarding form by applying copy propagation
// and dead code elimination.
graphBuilder.Transform(CopyPropagation.Instance, DeadValueElimination.Instance, DeadBlockElimination.Instance);
return(graphBuilder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var uses = graph.GetAnalysisResult <ValueUses>();
// Figure out which unbox instructions are eligible.
// TODO: implement a proper escape analysis.
var nonescapingUnboxInstructions = new HashSet <ValueTag>();
foreach (var instruction in graph.NamedInstructions)
{
if (instruction.Prototype is UnboxPrototype &&
uses.GetFlowUses(instruction).Count == 0 &&
!uses.GetInstructionUses(instruction).Any(
tag => AllowsEscape(tag, instruction, graph)))
{
nonescapingUnboxInstructions.Add(instruction);
}
}
var builder = graph.ToBuilder();
// Rewrite box and unbox instructions.
var unboxReplacements = new Dictionary <ValueTag, ValueTag>();
foreach (var instruction in builder.NamedInstructions)
{
var boxProto = instruction.Prototype as BoxPrototype;
if (boxProto != null &&
uses.GetFlowUses(instruction).Count == 0 &&
uses.GetInstructionUses(instruction).IsSubsetOf(
nonescapingUnboxInstructions))
{
var boxedValue = boxProto.GetBoxedValue(instruction.Instruction);
// Replace the box with an alloca.
instruction.Instruction = Instruction.CreateAlloca(boxProto.ElementType);
// Initialize the alloca with the boxed value.
instruction.InsertAfter(
Instruction.CreateStore(
boxProto.ElementType,
instruction,
boxedValue));
// Record which unbox instructions wrap to which
// alloca instructions.
foreach (var use in uses.GetInstructionUses(instruction))
{
unboxReplacements[use] = instruction;
}
}
}
// Replace all unbox instructions that use the box with
// references to alloca instructions. Delete the unbox
// instructions themselves.
builder.ReplaceUses(unboxReplacements);
builder.RemoveInstructionDefinitions(unboxReplacements.Keys);
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
// Figure out which aggregates can be replaced by scalars.
var eligible = FindEligibleAllocas(graph);
var builder = graph.ToBuilder();
// Create allocas for fields.
var replacements = new Dictionary <ValueTag, Dictionary <IField, ValueTag> >();
foreach (var allocaTag in eligible)
{
var allocaInstruction = builder.GetInstruction(allocaTag);
var elementType = ((PointerType)allocaInstruction.ResultType).ElementType;
var fieldSlots = new Dictionary <IField, ValueTag>();
foreach (var field in elementType.GetAllInstanceFields())
{
fieldSlots[field] = allocaInstruction.InsertAfter(
Instruction.CreateAlloca(field.FieldType),
allocaTag.Name + ".scalarrepl.field." + field.Name);
}
replacements[allocaTag] = fieldSlots;
}
// Rewrite instructions.
foreach (var instruction in builder.NamedInstructions)
{
var proto = instruction.Prototype;
if (proto is GetFieldPointerPrototype)
{
var gfpProto = (GetFieldPointerPrototype)proto;
var basePointer = gfpProto.GetBasePointer(instruction.Instruction);
if (eligible.Contains(basePointer))
{
instruction.Instruction = Instruction.CreateCopy(
instruction.Instruction.ResultType,
replacements[basePointer][gfpProto.Field]);
}
}
else if (IsDefaultInitialization(instruction.Instruction, graph))
{
var storeProto = (StorePrototype)proto;
var pointer = storeProto.GetPointer(instruction.Instruction);
if (eligible.Contains(pointer))
{
foreach (var pair in replacements[pointer])
{
// Initialize each field with
//
// c = const(#default, field_type)();
// _ = store(field_pointer, c);
//
var constant = instruction.InsertAfter(
Instruction.CreateDefaultConstant(pair.Key.FieldType));
constant.InsertAfter(
Instruction.CreateStore(
pair.Key.FieldType,
pair.Value,
constant));
}
// Replace the store with a copy, in case someone is
// using the value it returns.
instruction.Instruction = Instruction.CreateCopy(
instruction.Instruction.ResultType,
storeProto.GetValue(instruction.Instruction));
}
}
else if (proto is StorePrototype)
{
TryRewriteStore(instruction, replacements);
}
}
var uses = builder.GetAnalysisResult <ValueUses>();
var killList = new HashSet <ValueTag>(eligible);
// In a second pass, also rewrite load instructions. It is crucial
// that they are handled *after* stores are handled, because the
// lowering for stores is a whole lot better if we don't lower the
// load to something convoluted first.
foreach (var instruction in builder.NamedInstructions)
{
var proto = instruction.Prototype;
if (proto is LoadPrototype)
{
if (uses.GetUseCount(instruction) == 0)
{
// Delete dead load. Loads may die during the loop above; we
// don't want to create lots of garbage code.
killList.Add(instruction);
continue;
}
var loadProto = (LoadPrototype)proto;
var pointer = loadProto.GetPointer(instruction.Instruction);
if (eligible.Contains(pointer))
{
// Looks like we're going to have to materialize a scalarrepl'ed
// value. Create a temporary, fill it, and load it.
var temporary = instruction.Graph.EntryPoint.InsertInstruction(
0,
Instruction.CreateAlloca(loadProto.ResultType));
var insertionPoint = instruction;
foreach (var pair in replacements[pointer].Reverse())
{
// Copy each field as follows:
//
// val = load(field_type)(field_replacement);
// field_ptr = get_field_pointer(field)(temp);
// _ = store(field_ptr, val);
//
var value = insertionPoint.InsertBefore(
Instruction.CreateLoad(pair.Key.FieldType, pair.Value));
var fieldPointer = value.InsertAfter(
Instruction.CreateGetFieldPointer(pair.Key, temporary));
insertionPoint = fieldPointer.InsertAfter(
Instruction.CreateStore(pair.Key.FieldType, fieldPointer, value));
}
instruction.Instruction = loadProto.Instantiate(temporary);
}
}
}
// Delete the replaced allocas.
builder.RemoveInstructionDefinitions(killList);
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
// Analyze all local value definitions and find imported values.
var definitions = new Dictionary <BasicBlockTag, Dictionary <ValueTag, ValueTag> >();
var extraArgs = new Dictionary <BasicBlockTag, List <ValueTag> >();
var imports = new Dictionary <BasicBlockTag, HashSet <ValueTag> >();
foreach (var block in builder.BasicBlocks)
{
var localDefs = new Dictionary <ValueTag, ValueTag>();
var localImports = new HashSet <ValueTag>();
foreach (var parameter in block.ParameterTags)
{
localDefs[parameter] = parameter;
}
foreach (var instruction in block.NamedInstructions)
{
localDefs[instruction] = instruction;
localImports.UnionWith(instruction.Arguments);
}
foreach (var instruction in block.Flow.Instructions)
{
localImports.UnionWith(instruction.Arguments);
}
foreach (var branch in block.Flow.Branches)
{
foreach (var arg in branch.Arguments)
{
if (arg.IsValue)
{
localImports.Add(arg.ValueOrNull);
}
}
}
definitions[block] = localDefs;
imports[block] = localImports;
extraArgs[block] = new List <ValueTag>();
}
var predecessors = graph.GetAnalysisResult <BasicBlockPredecessors>();
// Now import definitions until we reach a fixpoint.
var worklist = new HashSet <BasicBlockTag>(builder.BasicBlockTags);
while (worklist.Count > 0)
{
var block = builder.GetBasicBlock(worklist.First());
worklist.Remove(block);
var blockDefs = definitions[block];
var blockArgs = extraArgs[block];
var blockImports = imports[block];
blockImports.ExceptWith(blockDefs.Keys);
imports[block] = new HashSet <ValueTag>();
foreach (var value in blockImports)
{
var rffName = value.Name + ".rff." + block.Tag.Name;
NamedInstruction valueInstruction;
if (graph.TryGetInstruction(value, out valueInstruction) &&
valueInstruction.Prototype is ConstantPrototype)
{
// Create duplicate definitions of constants instead of
// importing them using phis.
blockDefs[value] = block.InsertInstruction(0, valueInstruction.Instruction, rffName);
continue;
}
// Import a definition by introducing a new parameter and recursively
// importing it the value in predecessor blocks.
blockDefs[value] = block.AppendParameter(
builder.GetValueType(value),
rffName);
blockArgs.Add(value);
foreach (var pred in predecessors.GetPredecessorsOf(block))
{
if (!definitions[pred].ContainsKey(value))
{
imports[pred].Add(value);
worklist.Add(pred);
}
}
}
}
// We have introduced basic block parameters and know which values are
// used by blocks. We finish by replacing value uses and appending
// branch arguments.
foreach (var block in builder.BasicBlocks)
{
var blockDefs = definitions[block];
foreach (var insn in block.NamedInstructions)
{
insn.Instruction = insn.Instruction.MapArguments(blockDefs);
}
block.Flow = block.Flow
.MapValues(blockDefs)
.MapBranches(branch =>
{
var args = new List <BranchArgument>(branch.Arguments);
foreach (var arg in extraArgs[branch.Target])
{
args.Add(BranchArgument.FromValue(blockDefs[arg]));
}
return(branch.WithArguments(args));
});
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
IEnumerable <BasicBlockTag> liveBlocks;
// Do the fancy analysis.
var cells = FillCells(graph, out liveBlocks);
// Get ready to rewrite the flow graph.
var graphBuilder = graph.ToBuilder();
// Eliminate switch cases whenever possible.
SimplifySwitches(graphBuilder, cells);
// Replace instructions with constants.
foreach (var selection in graphBuilder.NamedInstructions)
{
LatticeCell cell;
if (cells.TryGetValue(selection, out cell) &&
cell.IsConstant)
{
selection.Instruction = Instruction.CreateConstant(
cell.Value,
selection.Instruction.ResultType);
}
}
// Replace block parameters with constants if possible.
var phiReplacements = new Dictionary <ValueTag, ValueTag>();
var entryPoint = graphBuilder.GetBasicBlock(graphBuilder.EntryPointTag);
foreach (var block in graphBuilder.BasicBlocks)
{
foreach (var param in block.Parameters)
{
LatticeCell cell;
if (cells.TryGetValue(param.Tag, out cell) &&
cell.IsConstant)
{
phiReplacements[param.Tag] = entryPoint.InsertInstruction(
0,
Instruction.CreateConstant(cell.Value, param.Type));
}
}
var flowInstructions = block.Flow.Instructions;
var newFlowInstructions = new Instruction[flowInstructions.Count];
bool anyChanged = false;
for (int i = 0; i < newFlowInstructions.Length; i++)
{
var cell = EvaluateInstruction(flowInstructions[i], cells, graph);
if (cell.IsConstant)
{
anyChanged = true;
newFlowInstructions[i] = Instruction.CreateConstant(
cell.Value,
flowInstructions[i].ResultType);
}
else
{
newFlowInstructions[i] = flowInstructions[i];
}
}
if (anyChanged)
{
block.Flow = block.Flow.WithInstructions(newFlowInstructions);
}
}
graphBuilder.ReplaceUses(phiReplacements);
graphBuilder.RemoveDefinitions(phiReplacements.Keys);
// Remove all instructions from dead blocks and mark the blocks
// themselves as unreachable.
foreach (var tag in graphBuilder.BasicBlockTags.Except(liveBlocks).ToArray())
{
var block = graphBuilder.GetBasicBlock(tag);
// Turn the block's flow into unreachable flow.
block.Flow = UnreachableFlow.Instance;
// Delete the block's instructions.
graphBuilder.RemoveInstructionDefinitions(block.InstructionTags);
}
return(graphBuilder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
foreach (var instruction in builder.NamedInstructions)
{
var proto = instruction.Prototype;
if (proto is CallPrototype)
{
// CIL delegates are called using a (virtual) call to the
// delegate's 'Invoke' method. However, in Flame IR we want
// to make indirect function calls explicit using a specialized
// opcode.
var callProto = (CallPrototype)proto;
var delegateType = callProto.Callee.ParentType;
IMethod invokeMethod;
if (TypeHelpers.TryGetDelegateInvokeMethod(delegateType, out invokeMethod) &&
invokeMethod == callProto.Callee)
{
instruction.Instruction = Instruction.CreateIndirectCall(
callProto.ResultType,
callProto.Callee.Parameters.EagerSelect(p => p.Type),
callProto.GetThisArgument(instruction.Instruction),
callProto.GetArgumentList(instruction.Instruction).ToArray());
}
}
else if (proto is NewObjectPrototype && proto.ParameterCount == 2)
{
// Delegates are created by the 'newobj' opcode, but we want
// to use Flame IR's delegate-creation instructions, which better
// communicate what is going on to the optimizer.
var newobjProto = (NewObjectPrototype)proto;
var argList = newobjProto.GetArgumentList(instruction.Instruction);
var boundObject = argList[0];
var functionPointer = argList[1];
if (!builder.ContainsInstruction(functionPointer))
{
continue;
}
var functionPointerInstruction = builder.GetInstruction(functionPointer);
var functionPointerProto = functionPointerInstruction.Prototype as NewDelegatePrototype;
if (functionPointerProto == null)
{
continue;
}
var callee = functionPointerProto.Callee;
var delegateType = TypeHelpers.UnboxIfPossible(newobjProto.ResultType);
IMethod invokeMethod;
if (TypeHelpers.TryGetDelegateInvokeMethod(delegateType, out invokeMethod))
{
if (functionPointerProto.Lookup == MethodLookup.Static)
{
// We're dealing with a static method lookup. These are actually
// slightly tricky because CIL has zany rules that allow for either
// a 'this' pointer or a first parameter to be captured by the
// delegate itself.
bool hasThisParameter = !callee.IsStatic ||
invokeMethod.Parameters.Count == callee.Parameters.Count - 1;
instruction.Instruction = Instruction.CreateNewDelegate(
delegateType,
callee,
hasThisParameter
? ConvertThisArgument(
boundObject,
callee.IsStatic
? callee.Parameters[0].Type
: TypeHelpers.BoxIfReferenceType(callee.ParentType),
instruction)
: null,
MethodLookup.Static);
}
else
{
// We're dealing with a virtual method lookup. These are actually fairly
// easy to handle.
var thisArg = functionPointerProto.GetThisArgument(functionPointerInstruction.Instruction);
if (boundObject == thisArg)
{
instruction.Instruction = Instruction.CreateNewDelegate(
delegateType,
callee,
ConvertThisArgument(
thisArg,
TypeHelpers.BoxIfReferenceType(callee.ParentType),
instruction),
MethodLookup.Virtual);
}
}
}
}
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
// Build a mapping of blocks to their predecessors.
var predecessors = graph.GetAnalysisResult <BasicBlockPredecessors>();
// Figure out which blocks jump unconditionally to a block
// with only one predecessor.
var fusible = new HashSet <BasicBlockTag>();
foreach (var block in graph.BasicBlockTags)
{
BasicBlockTag tail;
if (TryGetFusibleTail(block, graph, predecessors, out tail))
{
fusible.Add(block);
}
}
// Start editing the graph.
var builder = graph.ToBuilder();
// Maintain a dictionary of values that need to be
// replaced with other values.
var replacements = new Dictionary <ValueTag, ValueTag>();
// Maintain a set of blocks to delete.
var deadBlocks = new HashSet <BasicBlockTag>();
// Fuse fusible blocks.
while (fusible.Count > 0)
{
// Pop an item from the worklist.
var tag = fusible.First();
// Grab the block to edit.
var block = builder.GetBasicBlock(tag);
// Grab the successor block to which the block jumps.
var branch = ((JumpFlow)block.Flow).Branch;
var successor = builder.GetBasicBlock(branch.Target);
// Update the worklist.
if (!fusible.Remove(successor))
{
fusible.Remove(tag);
}
// Replace branch parameters.
foreach (var pair in branch.ZipArgumentsWithParameters(builder))
{
replacements.Add(pair.Key, pair.Value.ValueOrNull);
}
// Move instructions around.
foreach (var instruction in successor.NamedInstructions)
{
instruction.MoveTo(block);
}
// Update the block's flow.
block.Flow = successor.Flow;
}
// Replace instruction uses.
builder.ReplaceUses(replacements);
// Delete dead blocks.
foreach (var tag in deadBlocks)
{
builder.RemoveBasicBlock(tag);
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var builder = graph.ToBuilder();
foreach (var instruction in builder.Instructions)
{
var proto = instruction.Prototype;
if (proto is IndirectCallPrototype)
{
// Flame IR has dedicated instructions for delegate calls,
// but in CIL they are implemented by a virtual call to
// a magic 'Invoke' method.
var callProto = (IndirectCallPrototype)proto;
var calleeValue = callProto.GetCallee(instruction.Instruction);
var delegateType = TypeHelpers.UnboxIfPossible(graph.GetValueType(calleeValue));
IMethod invokeMethod;
if (TypeHelpers.TryGetDelegateInvokeMethod(delegateType, out invokeMethod))
{
instruction.Instruction = Instruction.CreateCall(
invokeMethod,
MethodLookup.Virtual,
calleeValue,
callProto.GetArgumentList(instruction.Instruction).ToArray());
}
}
else if (proto is NewDelegatePrototype && instruction is NamedInstructionBuilder)
{
// TODO: also lower NewDelegatePrototype for anonymous instructions!
// CIL delegates are created by first loading a function pointer
// onto the stack (using either `ldftn` or `ldvirtftn`) and then
// constructing the actual delegate using a `newobj` opcode.
var newDelegateProto = (NewDelegatePrototype)proto;
var delegateType = TypeHelpers.UnboxIfPossible(newDelegateProto.ResultType);
IMethod invokeMethod;
if (!TypeHelpers.TryGetDelegateInvokeMethod(delegateType, out invokeMethod))
{
continue;
}
var constructor = delegateType.Methods.Single(method => method.IsConstructor);
bool isVirtual = newDelegateProto.Lookup == MethodLookup.Virtual;
// First create an instruction that loads the function pointer.
var namedInstruction = (NamedInstructionBuilder)instruction;
var functionPointer = namedInstruction.InsertBefore(
Instruction.CreateNewDelegate(
constructor.Parameters[1].Type,
newDelegateProto.Callee,
isVirtual
? newDelegateProto.GetThisArgument(instruction.Instruction)
: null,
newDelegateProto.Lookup),
namedInstruction.Tag.Name + "_fptr");
// CLR delegate constructors always take two parameters: a function
// pointer and a 'this' argument (of type 'Object *box').
// The latter can be somewhat tricky to get right:
//
// * if the delegate has a 'this' argument then that 'this' argument
// should be reinterpreted as an instance of 'Object *box'.
//
// * if the delegate does not have a 'this' argument, then we pass
// a `null` constant as 'this' argument.
ValueTag thisArgument;
if (newDelegateProto.HasThisArgument)
{
thisArgument = newDelegateProto.GetThisArgument(instruction.Instruction);
var thisType = builder.GetValueType(thisArgument);
var expectedThisType = constructor.Parameters[0].Type;
if (thisType != expectedThisType)
{
thisArgument = functionPointer.InsertBefore(
Instruction.CreateReinterpretCast(
(PointerType)expectedThisType,
thisArgument));
}
}
else
{
thisArgument = functionPointer.InsertBefore(
Instruction.CreateConstant(
NullConstant.Instance,
constructor.Parameters[0].Type));
}
// And then create the actual delegate. To do so we must use the
// delegate type's constructor. This constructor will always take
// two parameters: a bound object (of type System.Object) and a
// function pointer (of type natural int).
instruction.Instruction = Instruction.CreateNewObject(
constructor,
new[]
{
thisArgument,
functionPointer
});
}
}
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
// Figure out which aggregates can be replaced by scalars.
var eligible = FindEligibleAllocas(graph);
var builder = graph.ToBuilder();
// Create allocas for fields.
var replacements = new Dictionary <ValueTag, Dictionary <IField, ValueTag> >();
foreach (var allocaTag in eligible)
{
var allocaInstruction = builder.GetInstruction(allocaTag);
var allocaProto = (AllocaPrototype)allocaInstruction.Prototype;
var fieldSlots = new Dictionary <IField, ValueTag>();
foreach (var field in allocaProto.ElementType.Fields)
{
fieldSlots[field] = allocaInstruction.InsertAfter(
Instruction.CreateAlloca(field.FieldType),
allocaTag.Name + "_field_" + field.Name);
}
replacements[allocaTag] = fieldSlots;
}
// Rewrite instructions.
foreach (var instruction in builder.NamedInstructions)
{
var proto = instruction.Prototype;
if (proto is GetFieldPointerPrototype)
{
var gfpProto = (GetFieldPointerPrototype)proto;
var basePointer = gfpProto.GetBasePointer(instruction.Instruction);
if (eligible.Contains(basePointer))
{
instruction.Instruction = Instruction.CreateCopy(
instruction.Instruction.ResultType,
replacements[basePointer][gfpProto.Field]);
}
}
else if (IsDefaultInitialization(instruction.ToImmutable()))
{
var storeProto = (StorePrototype)proto;
var pointer = storeProto.GetPointer(instruction.Instruction);
if (eligible.Contains(pointer))
{
foreach (var pair in replacements[pointer])
{
// Initialize each field with
//
// c = const(#default, field_type)();
// _ = store(field_pointer, c);
//
var constant = instruction.InsertAfter(
Instruction.CreateDefaultConstant(pair.Key.FieldType));
constant.InsertAfter(
Instruction.CreateStore(
pair.Key.FieldType,
pair.Value,
constant));
}
// Replace the store with a copy, in case someone is
// using the value it returns.
instruction.Instruction = Instruction.CreateCopy(
instruction.Instruction.ResultType,
storeProto.GetValue(instruction.Instruction));
}
}
}
// Delete the replaced allocas.
builder.RemoveInstructionDefinitions(eligible);
return(builder.ToImmutable());
}
/// <inheritdoc/>
public override FlowGraph Apply(FlowGraph graph)
{
var memSSA = graph.GetAnalysisResult <MemorySSA>();
var aliasing = graph.GetAnalysisResult <AliasAnalysisResult>();
var effectfulness = graph.GetAnalysisResult <EffectfulInstructions>();
var builder = graph.ToBuilder();
// First try and eliminate loads and stores based on their memory SSA
// states.
foreach (var instruction in builder.NamedInstructions)
{
var proto = instruction.Prototype;
if (proto is LoadPrototype)
{
// Loads can be eliminated if we know the memory contents.
var loadProto = (LoadPrototype)proto;
var state = memSSA.GetMemoryAfter(instruction);
ValueTag value;
if (state.TryGetValueAt(
loadProto.GetPointer(instruction.Instruction),
graph,
out value))
{
instruction.Instruction = Instruction.CreateCopy(
instruction.ResultType,
value);
}
}
else if (proto is StorePrototype)
{
// Stores can be eliminated if they don't affect the memory state.
var storeProto = (StorePrototype)proto;
var stateBefore = memSSA.GetMemoryBefore(instruction);
var stateAfter = memSSA.GetMemoryAfter(instruction);
if (stateBefore == stateAfter)
{
EliminateStore(instruction);
}
}
}
// Then try to coalesce stores by iterating through basic blocks.
foreach (var block in builder.BasicBlocks)
{
var pendingStores = new List <NamedInstructionBuilder>();
foreach (var instruction in block.NamedInstructions)
{
var proto = instruction.Prototype;
if (proto is StorePrototype)
{
var storeProto = (StorePrototype)proto;
var pointer = storeProto.GetPointer(instruction.Instruction);
var newPending = new List <NamedInstructionBuilder>();
foreach (var pending in pendingStores)
{
var pendingProto = (StorePrototype)pending.Prototype;
var pendingPointer = pendingProto.GetPointer(pending.Instruction);
var aliasState = aliasing.GetAliasing(pointer, pendingPointer);
if (aliasState == Aliasing.MustAlias)
{
// Yes, do it. Delete the pending store.
EliminateStore(pending);
}
else if (aliasState == Aliasing.NoAlias)
{
// We can't eliminate the pending store, but we can keep it
// in the pending list.
newPending.Add(pending);
}
}
pendingStores = newPending;
// Add this store to the list of pending stores as well.
pendingStores.Add(instruction);
}
else if (proto is LoadPrototype || proto is CopyPrototype)
{
// Loads are perfectly benign. They *may* be effectful in the sense
// that they can trigger a segfault and make the program blow up, but
// there's no way we can catch that anyway. We'll just allow store
// coalescing across load boundaries.
//
// We also want to test for copy instructions here because our effectfulness
// analysis is slightly outdated and we may have turned loads/stores into copies.
}
else if (effectfulness.Instructions.Contains(instruction))
{
// Effectful instructions are a barrier for store coalescing.
pendingStores.Clear();
}
}
}
return(builder.ToImmutable());
}
