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flow.ts
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/**
* @fileoverview A concurrent code flow analyzer.
*
* Flows keep track of compilation state and can be queried for various
* conditions, like whether the current branch always terminates, whether
* a local is known to be non-null or whether an expression has possibly
* overflown its value range.
*
* To accomplish this, compilation of each function begins with a clean
* flow populated with initial local states etc. While compilation
* progresses, statements and expressions update flow state while control
* constructs fork, potentially add scoped locals and later merge these
* forked branches as necessary.
*
* @license Apache-2.0
*/
import {
Type,
TypeFlags,
TypeKind
} from "./types";
import {
Local,
Function,
Element,
ElementKind,
Global
} from "./program";
import {
NativeType,
ExpressionId,
ExpressionRef,
BinaryOp,
UnaryOp,
getExpressionId,
getLocalGetIndex,
isLocalTee,
getLocalSetValue,
getGlobalGetName,
getBinaryOp,
getBinaryLeft,
getConstValueI32,
getBinaryRight,
getUnaryOp,
getExpressionType,
getConstValueI64Low,
getConstValueF32,
getConstValueF64,
getLoadBytes,
isLoadSigned,
getBlockName,
getBlockChildCount,
getBlockChild,
getIfTrue,
getIfFalse,
getSelectThen,
getSelectElse,
getCallTarget,
getLocalSetIndex,
getIfCondition,
getConstValueI64High,
getUnaryValue,
getCallOperand,
traverse
} from "./module";
import {
CommonFlags
} from "./common";
import {
DiagnosticCode
} from "./diagnostics";
import {
Node
} from "./ast";
/** Control flow flags indicating specific conditions. */
export const enum FlowFlags {
/** No specific conditions. */
NONE = 0,
// categorical
/** This flow always returns. */
RETURNS = 1 << 0,
/** This flow always returns a wrapped value. */
RETURNS_WRAPPED = 1 << 1,
/** This flow always returns a non-null value. */
RETURNS_NONNULL = 1 << 2,
/** This flow always throws. */
THROWS = 1 << 3,
/** This flow always breaks. */
BREAKS = 1 << 4,
/** This flow always continues. */
CONTINUES = 1 << 5,
/** This flow always allocates. Constructors only. */
ALLOCATES = 1 << 6,
/** This flow always calls super. Constructors only. */
CALLS_SUPER = 1 << 7,
/** This flow always terminates (returns, throws or continues). */
TERMINATES = 1 << 8, // Note that this doesn't cover BREAKS, which is separate
// conditional
/** This flow conditionally returns in a child flow. */
CONDITIONALLY_RETURNS = 1 << 9,
/** This flow conditionally throws in a child flow. */
CONDITIONALLY_THROWS = 1 << 10,
/** This flow conditionally breaks in a child flow. */
CONDITIONALLY_BREAKS = 1 << 11,
/** This flow conditionally continues in a child flow. */
CONDITIONALLY_CONTINUES = 1 << 12,
/** This flow conditionally allocates in a child flow. Constructors only. */
CONDITIONALLY_ALLOCATES = 1 << 13,
// other
/** This is a flow with explicitly disabled bounds checking. */
UNCHECKED_CONTEXT = 1 << 15,
// masks
/** Any categorical flag. */
ANY_CATEGORICAL = FlowFlags.RETURNS
| FlowFlags.RETURNS_WRAPPED
| FlowFlags.RETURNS_NONNULL
| FlowFlags.THROWS
| FlowFlags.BREAKS
| FlowFlags.CONTINUES
| FlowFlags.ALLOCATES
| FlowFlags.CALLS_SUPER
| FlowFlags.TERMINATES,
/** Any conditional flag. */
ANY_CONDITIONAL = FlowFlags.CONDITIONALLY_RETURNS
| FlowFlags.CONDITIONALLY_THROWS
| FlowFlags.CONDITIONALLY_BREAKS
| FlowFlags.CONDITIONALLY_CONTINUES
| FlowFlags.CONDITIONALLY_ALLOCATES
}
/** Flags indicating the current state of a local. */
export enum LocalFlags {
/** No specific conditions. */
NONE = 0,
/** Local is constant. */
CONSTANT = 1 << 0,
/** Local is properly wrapped. Relevant for small integers. */
WRAPPED = 1 << 1,
/** Local is non-null. */
NONNULL = 1 << 2,
/** Local is initialized. */
INITIALIZED = 1 << 3,
/** Local is retained. */
RETAINED = 1 << 4,
/** Local must be conditionally retained. */
CONDITIONALLY_RETAINED = 1 << 5,
/** Any retained flag. */
ANY_RETAINED = RETAINED
| CONDITIONALLY_RETAINED
}
/** Flags indicating the current state of an instance field. */
export enum FieldFlags {
NONE = 1,
INITIALIZED = 1 << 1,
}
/** Condition kinds. */
export const enum ConditionKind {
/** Outcome of the condition is unknown */
UNKNOWN,
/** Condition is always true. */
TRUE,
/** Condition is always false. */
FALSE
}
/** A control flow evaluator. */
export class Flow {
/** Parent flow. */
parent: Flow | null;
/** Flow flags indicating specific conditions. */
flags: FlowFlags;
/** Function this flow belongs to. */
parentFunction: Function;
/** The label we break to when encountering a continue statement. */
continueLabel: string | null;
/** The label we break to when encountering a break statement. */
breakLabel: string | null;
/** The current return type. */
returnType: Type;
/** The current contextual type arguments. */
contextualTypeArguments: Map<string,Type> | null;
/** Scoped local variables. */
scopedLocals: Map<string,Local> | null = null;
/** Local flags. */
localFlags: LocalFlags[];
/** Field flags. */
fieldFlags: Map<string, FieldFlags> | null = null;
/** Function being inlined, when inlining. */
inlineFunction: Function | null;
/** The label we break to when encountering a return statement, when inlining. */
inlineReturnLabel: string | null;
/** Creates the parent flow of the specified function. */
static create(parentFunction: Function): Flow {
var flow = new Flow();
flow.parent = null;
flow.flags = FlowFlags.NONE;
flow.parentFunction = parentFunction;
flow.continueLabel = null;
flow.breakLabel = null;
flow.returnType = parentFunction.signature.returnType;
flow.contextualTypeArguments = parentFunction.contextualTypeArguments;
flow.localFlags = [];
if (parentFunction.is(CommonFlags.CONSTRUCTOR)) {
flow.fieldFlags = new Map();
}
flow.inlineFunction = null;
flow.inlineReturnLabel = null;
return flow;
}
/** Creates an inline flow within `parentFunction`. */
static createInline(parentFunction: Function, inlineFunction: Function): Flow {
var flow = Flow.create(parentFunction);
flow.inlineFunction = inlineFunction;
flow.inlineReturnLabel = inlineFunction.internalName + "|inlined." + (inlineFunction.nextInlineId++).toString();
flow.returnType = inlineFunction.signature.returnType;
flow.contextualTypeArguments = inlineFunction.contextualTypeArguments;
return flow;
}
private constructor() { }
/** Tests if this is an inline flow. */
get isInline(): bool {
return this.inlineFunction !== null;
}
/** Gets the actual function being compiled, The inlined function when inlining, otherwise the parent function. */
get actualFunction(): Function {
var inlineFunction = this.inlineFunction;
if (inlineFunction) return inlineFunction;
return this.parentFunction;
}
/** Tests if this flow has the specified flag or flags. */
is(flag: FlowFlags): bool { return (this.flags & flag) == flag; }
/** Tests if this flow has one of the specified flags. */
isAny(flag: FlowFlags): bool { return (this.flags & flag) != 0; }
/** Sets the specified flag or flags. */
set(flag: FlowFlags): void { this.flags |= flag; }
/** Unsets the specified flag or flags. */
unset(flag: FlowFlags): void { this.flags &= ~flag; }
/** Forks this flow to a child flow. */
fork(resetBreakContext: bool = false): Flow {
var branch = new Flow();
branch.parent = this;
branch.parentFunction = this.parentFunction;
if (resetBreakContext) {
branch.flags = this.flags & ~(
FlowFlags.BREAKS |
FlowFlags.CONDITIONALLY_BREAKS |
FlowFlags.CONTINUES |
FlowFlags.CONDITIONALLY_CONTINUES
);
} else {
branch.flags = this.flags;
branch.continueLabel = this.continueLabel;
branch.breakLabel = this.breakLabel;
}
branch.returnType = this.returnType;
branch.contextualTypeArguments = this.contextualTypeArguments;
branch.localFlags = this.localFlags.slice();
branch.inlineFunction = this.inlineFunction;
branch.inlineReturnLabel = this.inlineReturnLabel;
if (branch.parentFunction.is(CommonFlags.CONSTRUCTOR)) {
branch.fieldFlags = new Map(this.fieldFlags!);
}
return branch;
}
/** Gets a free temporary local of the specified type. */
getTempLocal(type: Type, except: Set<i32> | null = null): Local {
var parentFunction = this.parentFunction;
var temps: Local[] | null;
switch (type.toNativeType()) {
case NativeType.I32: { temps = parentFunction.tempI32s; break; }
case NativeType.I64: { temps = parentFunction.tempI64s; break; }
case NativeType.F32: { temps = parentFunction.tempF32s; break; }
case NativeType.F64: { temps = parentFunction.tempF64s; break; }
case NativeType.V128: { temps = parentFunction.tempV128s; break; }
case NativeType.Anyref: { temps = parentFunction.tempAnyrefs; break; }
case NativeType.Exnref: { temps = parentFunction.tempExnrefs; break; }
default: throw new Error("concrete type expected");
}
var local: Local;
if (except) {
if (temps !== null && temps.length > 0) {
for (let i = 0, k = temps.length; i < k; ++i) {
if (!except.has(temps[i].index)) {
local = temps[i];
let k = temps.length - 1;
while (i < k) unchecked(temps[i] = temps[i++ + 1]);
temps.length = k;
local.type = type;
local.flags = CommonFlags.NONE;
this.unsetLocalFlag(local.index, ~0);
return local;
}
}
}
local = parentFunction.addLocal(type);
} else {
if (temps !== null && temps.length > 0) {
local = assert(temps.pop());
local.type = type;
local.flags = CommonFlags.NONE;
} else {
local = parentFunction.addLocal(type);
}
}
this.unsetLocalFlag(local.index, ~0);
return local;
}
/** Gets a local that sticks around until this flow is exited, and then released. */
getAutoreleaseLocal(type: Type, except: Set<i32> | null = null): Local {
var local = this.getTempLocal(type, except);
local.set(CommonFlags.SCOPED);
var scopedLocals = this.scopedLocals;
if (!scopedLocals) this.scopedLocals = scopedLocals = new Map();
scopedLocals.set("~auto" + (this.parentFunction.nextAutoreleaseId++).toString(), local);
this.setLocalFlag(local.index, LocalFlags.RETAINED);
return local;
}
/** Frees the temporary local for reuse. */
freeTempLocal(local: Local): void {
if (local.is(CommonFlags.INLINED)) return;
assert(local.index >= 0);
var parentFunction = this.parentFunction;
var temps: Local[];
assert(local.type != null); // internal error
switch (local.type.toNativeType()) {
case NativeType.I32: {
let tempI32s = parentFunction.tempI32s;
if (tempI32s) temps = tempI32s;
else parentFunction.tempI32s = temps = [];
break;
}
case NativeType.I64: {
let tempI64s = parentFunction.tempI64s;
if (tempI64s) temps = tempI64s;
else parentFunction.tempI64s = temps = [];
break;
}
case NativeType.F32: {
let tempF32s = parentFunction.tempF32s;
if (tempF32s) temps = tempF32s;
else parentFunction.tempF32s = temps = [];
break;
}
case NativeType.F64: {
let tempF64s = parentFunction.tempF64s;
if (tempF64s) temps = tempF64s;
else parentFunction.tempF64s = temps = [];
break;
}
case NativeType.V128: {
let tempV128s = parentFunction.tempV128s;
if (tempV128s) temps = tempV128s;
else parentFunction.tempV128s = temps = [];
break;
}
case NativeType.Anyref: {
let tempAnyrefs = parentFunction.tempAnyrefs;
if (tempAnyrefs) temps = tempAnyrefs;
else parentFunction.tempAnyrefs = temps = [];
break;
}
case NativeType.Exnref: {
let tempExnrefs = parentFunction.tempExnrefs;
if (tempExnrefs) temps = tempExnrefs;
else parentFunction.tempExnrefs = temps = [];
break;
}
default: throw new Error("concrete type expected");
}
assert(local.index >= 0);
temps.push(local);
}
/** Gets the scoped local of the specified name. */
getScopedLocal(name: string): Local | null {
var scopedLocals = this.scopedLocals;
if (scopedLocals !== null && scopedLocals.has(name)) return assert(scopedLocals.get(name));
return null;
}
/** Adds a new scoped local of the specified name. */
addScopedLocal(name: string, type: Type, except: Set<i32> | null = null): Local {
var scopedLocal = this.getTempLocal(type, except);
var scopedLocals = this.scopedLocals;
if (!scopedLocals) this.scopedLocals = scopedLocals = new Map();
else assert(!scopedLocals.has(name));
scopedLocal.set(CommonFlags.SCOPED);
scopedLocals.set(name, scopedLocal);
return scopedLocal;
}
/** Adds a new scoped alias for the specified local. For example `super` aliased to the `this` local. */
addScopedAlias(name: string, type: Type, index: i32, reportNode: Node | null = null): Local {
if (!this.scopedLocals) this.scopedLocals = new Map();
else {
let existingLocal = this.scopedLocals.get(name);
if (existingLocal) {
if (reportNode) {
if (!existingLocal.declaration.range.source.isNative) {
this.parentFunction.program.errorRelated(
DiagnosticCode.Duplicate_identifier_0,
reportNode.range,
existingLocal.declaration.name.range,
name
);
} else {
this.parentFunction.program.error(
DiagnosticCode.Duplicate_identifier_0,
reportNode.range, name
);
}
}
return existingLocal;
}
}
assert(index < this.parentFunction.localsByIndex.length);
var scopedAlias = new Local(name, index, type, this.parentFunction);
// not flagged as SCOPED as it must not be free'd when the flow is finalized
this.scopedLocals.set(name, scopedAlias);
return scopedAlias;
}
/** Tests if this flow has any scoped locals that must be free'd. */
get hasScopedLocals(): bool {
var scopedLocals = this.scopedLocals;
if (scopedLocals) {
// TODO: for (let local of scopedLocals.values()) {
for (let _values = Map_values(scopedLocals), i = 0, k = _values.length; i < k; ++i) {
let local = unchecked(_values[i]);
if (local.is(CommonFlags.SCOPED)) { // otherwise an alias
return true;
}
}
}
return false;
}
/** Frees this flow's scoped variables and returns its parent flow. */
freeScopedLocals(): void {
var scopedLocals = this.scopedLocals;
if (scopedLocals) {
// TODO: for (let local of scopedLocals.values()) {
for (let _values = Map_values(scopedLocals), i = 0, k = _values.length; i < k; ++i) {
let local = unchecked(_values[i]);
if (local.is(CommonFlags.SCOPED)) { // otherwise an alias
this.freeTempLocal(local);
}
}
this.scopedLocals = null;
}
}
/** Looks up the local of the specified name in the current scope. */
lookupLocal(name: string): Local | null {
var current: Flow | null = this;
do {
let scope = current.scopedLocals;
if (scope !== null && scope.has(name)) return assert(scope.get(name));
current = current.parent;
} while (current);
var localsByName = this.parentFunction.localsByName;
if (localsByName.has(name)) return assert(localsByName.get(name));
return null;
}
/** Looks up the element with the specified name relative to the scope of this flow. */
lookup(name: string): Element | null {
var element = this.lookupLocal(name);
if (element) return element;
return this.actualFunction.lookup(name);
}
/** Tests if the local at the specified index has the specified flag or flags. */
isLocalFlag(index: i32, flag: LocalFlags, defaultIfInlined: bool = true): bool {
if (index < 0) return defaultIfInlined;
var localFlags = this.localFlags;
return index < localFlags.length && (unchecked(localFlags[index]) & flag) == flag;
}
/** Tests if the local at the specified index has any of the specified flags. */
isAnyLocalFlag(index: i32, flag: LocalFlags, defaultIfInlined: bool = true): bool {
if (index < 0) return defaultIfInlined;
var localFlags = this.localFlags;
return index < localFlags.length && (unchecked(localFlags[index]) & flag) != 0;
}
/** Sets the specified flag or flags on the local at the specified index. */
setLocalFlag(index: i32, flag: LocalFlags): void {
if (index < 0) return;
var localFlags = this.localFlags;
var flags = index < localFlags.length ? unchecked(localFlags[index]) : 0;
localFlags[index] = flags | flag;
}
/** Unsets the specified flag or flags on the local at the specified index. */
unsetLocalFlag(index: i32, flag: LocalFlags): void {
if (index < 0) return;
var localFlags = this.localFlags;
var flags = index < localFlags.length ? unchecked(localFlags[index]) : 0;
localFlags[index] = flags & ~flag;
}
setFieldFlag(name: string, flag: FieldFlags): void {
let fieldFlags = this.fieldFlags;
if (fieldFlags) {
const flags = fieldFlags.has(name) ? assert(fieldFlags.get(name)) : FieldFlags.NONE;
fieldFlags.set(name, flags | flag);
}
}
isFieldFlag(name: string, flag: FieldFlags): bool {
const fieldFlags = this.fieldFlags;
if (fieldFlags && fieldFlags.has(name)) {
const flags = assert(fieldFlags.get(name));
return (flags & flag) == flag;
}
return false;
}
/** Pushes a new break label to the stack, for example when entering a loop that one can `break` from. */
pushBreakLabel(): string {
var parentFunction = this.parentFunction;
var id = parentFunction.nextBreakId++;
var stack = parentFunction.breakStack;
if (!stack) parentFunction.breakStack = [ id ];
else stack.push(id);
var label = id.toString();
parentFunction.breakLabel = label;
return label;
}
/** Pops the most recent break label from the stack. */
popBreakLabel(): void {
var parentFunction = this.parentFunction;
var stack = assert(parentFunction.breakStack);
var length = assert(stack.length);
stack.pop();
if (length > 1) {
parentFunction.breakLabel = stack[length - 2].toString();
} else {
parentFunction.breakLabel = null;
parentFunction.breakStack = null;
}
}
/** Inherits flags of another flow into this one, i.e. a finished inner block. */
inherit(other: Flow): void {
assert(other.parentFunction == this.parentFunction);
assert(other.parent == this); // currently the case, but might change
var otherFlags = other.flags;
// respective inner flags are irrelevant if contexts differ
if (this.breakLabel != other.breakLabel) {
if (otherFlags & (FlowFlags.BREAKS | FlowFlags.CONDITIONALLY_BREAKS)) {
otherFlags &= ~FlowFlags.TERMINATES;
}
otherFlags &= ~(FlowFlags.BREAKS | FlowFlags.CONDITIONALLY_BREAKS);
}
if (this.continueLabel != other.continueLabel) {
otherFlags &= ~(FlowFlags.CONTINUES | FlowFlags.CONDITIONALLY_CONTINUES);
}
this.flags = this.flags | otherFlags; // what happens before is still true
this.localFlags = other.localFlags;
}
/** Inherits flags of a conditional branch joining again with this one, i.e. then without else. */
inheritBranch(other: Flow, conditionKind: ConditionKind = ConditionKind.UNKNOWN): void {
assert(other.parentFunction == this.parentFunction);
switch (conditionKind) {
case ConditionKind.TRUE: this.inherit(other); // always executes
case ConditionKind.FALSE: return; // never executes
}
// Note that flags in `this` flow have already happened. For instance,
// a return cannot be undone no matter what'd happen in subsequent branches,
// but an allocation, which doesn't terminate, can become conditional. Not
// all flags have a corresponding conditional flag that's tracked.
var thisFlags = this.flags;
var otherFlags = other.flags;
var newFlags = FlowFlags.NONE;
if (thisFlags & FlowFlags.RETURNS) { // nothing can change that
newFlags |= FlowFlags.RETURNS;
} else if (otherFlags & FlowFlags.RETURNS) {
newFlags |= FlowFlags.CONDITIONALLY_RETURNS;
} else {
newFlags |= (thisFlags | otherFlags) & FlowFlags.CONDITIONALLY_RETURNS;
}
// must be the case in both
newFlags |= thisFlags & otherFlags & FlowFlags.RETURNS_WRAPPED;
newFlags |= thisFlags & otherFlags & FlowFlags.RETURNS_NONNULL;
if (thisFlags & FlowFlags.THROWS) { // nothing can change that
newFlags |= FlowFlags.THROWS;
} else if (otherFlags & FlowFlags.THROWS) {
newFlags |= FlowFlags.CONDITIONALLY_THROWS;
} else {
newFlags |= (thisFlags | otherFlags) & FlowFlags.CONDITIONALLY_THROWS;
}
if (thisFlags & FlowFlags.BREAKS) { // nothing can change that
newFlags |= FlowFlags.BREAKS;
} else if (other.breakLabel == this.breakLabel) {
if (otherFlags & FlowFlags.BREAKS) {
newFlags |= FlowFlags.CONDITIONALLY_BREAKS;
} else {
newFlags |= (thisFlags | otherFlags) & FlowFlags.CONDITIONALLY_BREAKS;
}
} else {
newFlags |= thisFlags & FlowFlags.CONDITIONALLY_BREAKS;
}
if (thisFlags & FlowFlags.CONTINUES) { // nothing can change that
newFlags |= FlowFlags.CONTINUES;
} else if (other.continueLabel === this.continueLabel) {
if (otherFlags & FlowFlags.CONTINUES) {
newFlags |= FlowFlags.CONDITIONALLY_CONTINUES;
} else {
newFlags |= (thisFlags | otherFlags) & FlowFlags.CONDITIONALLY_CONTINUES;
}
} else {
newFlags |= thisFlags & FlowFlags.CONDITIONALLY_CONTINUES;
}
if (thisFlags & FlowFlags.ALLOCATES) { // can become conditional
if (otherFlags & FlowFlags.ALLOCATES) {
newFlags |= FlowFlags.ALLOCATES;
} else {
newFlags |= FlowFlags.CONDITIONALLY_ALLOCATES;
}
} else if (otherFlags & FlowFlags.ALLOCATES) {
newFlags |= FlowFlags.CONDITIONALLY_ALLOCATES;
}
// must be the case in both
newFlags |= thisFlags & otherFlags & FlowFlags.CALLS_SUPER;
if (thisFlags & FlowFlags.TERMINATES) { // nothing can change that
newFlags |= FlowFlags.TERMINATES;
}
this.flags = newFlags | (thisFlags & FlowFlags.UNCHECKED_CONTEXT);
var thisLocalFlags = this.localFlags;
var numThisLocalFlags = thisLocalFlags.length;
var otherLocalFlags = other.localFlags;
var numOtherLocalFlags = otherLocalFlags.length;
var maxLocalFlags = max(numThisLocalFlags, numOtherLocalFlags);
for (let i = 0; i < maxLocalFlags; ++i) {
let thisFlags = i < numThisLocalFlags ? thisLocalFlags[i] : 0;
let otherFlags = i < numOtherLocalFlags ? otherLocalFlags[i] : 0;
let newFlags = thisFlags & otherFlags & (
LocalFlags.CONSTANT |
LocalFlags.WRAPPED |
LocalFlags.NONNULL |
LocalFlags.INITIALIZED
);
if (thisFlags & LocalFlags.RETAINED) {
if (otherFlags & LocalFlags.RETAINED) {
newFlags |= LocalFlags.RETAINED;
} else {
newFlags |= LocalFlags.CONDITIONALLY_RETAINED;
}
} else if (otherFlags & LocalFlags.RETAINED) {
newFlags |= LocalFlags.CONDITIONALLY_RETAINED;
} else {
newFlags |= (thisFlags | otherFlags) & LocalFlags.CONDITIONALLY_RETAINED;
}
thisLocalFlags[i] = newFlags;
}
}
/** Inherits mutual flags of two alternate branches becoming this one, i.e. then with else. */
inheritMutual(left: Flow, right: Flow): void {
assert(left.parentFunction == right.parentFunction);
assert(left.parentFunction == this.parentFunction);
// This differs from the previous method in that no flags are guaranteed
// to happen unless it is the case in both flows.
var leftFlags = left.flags;
var rightFlags = right.flags;
var newFlags = FlowFlags.NONE;
if (leftFlags & FlowFlags.RETURNS) {
if (rightFlags & FlowFlags.RETURNS) {
newFlags |= FlowFlags.RETURNS;
} else {
newFlags |= FlowFlags.CONDITIONALLY_RETURNS;
}
} else if (rightFlags & FlowFlags.RETURNS) {
newFlags |= FlowFlags.CONDITIONALLY_RETURNS;
} else {
newFlags |= (leftFlags | rightFlags) & FlowFlags.CONDITIONALLY_RETURNS;
}
if ((leftFlags & FlowFlags.RETURNS_WRAPPED) && (rightFlags & FlowFlags.RETURNS_WRAPPED)) {
newFlags |= FlowFlags.RETURNS_WRAPPED;
}
if ((leftFlags & FlowFlags.RETURNS_NONNULL) && (rightFlags & FlowFlags.RETURNS_NONNULL)) {
newFlags |= FlowFlags.RETURNS_NONNULL;
}
if (leftFlags & FlowFlags.THROWS) {
if (rightFlags & FlowFlags.THROWS) {
newFlags |= FlowFlags.THROWS;
} else {
newFlags |= FlowFlags.CONDITIONALLY_THROWS;
}
} else if (rightFlags & FlowFlags.THROWS) {
newFlags |= FlowFlags.CONDITIONALLY_THROWS;
} else {
newFlags |= (leftFlags | rightFlags) & FlowFlags.CONDITIONALLY_THROWS;
}
if (leftFlags & FlowFlags.BREAKS) {
if (rightFlags & FlowFlags.BREAKS) {
newFlags |= FlowFlags.BREAKS;
} else {
newFlags |= FlowFlags.CONDITIONALLY_BREAKS;
}
} else if (rightFlags & FlowFlags.BREAKS) {
newFlags |= FlowFlags.CONDITIONALLY_BREAKS;
} else {
newFlags |= (leftFlags | rightFlags) & FlowFlags.CONDITIONALLY_BREAKS;
}
if (leftFlags & FlowFlags.CONTINUES) {
if (rightFlags & FlowFlags.CONTINUES) {
newFlags |= FlowFlags.CONTINUES;
} else {
newFlags |= FlowFlags.CONDITIONALLY_CONTINUES;
}
} else if (rightFlags & FlowFlags.CONTINUES) {
newFlags |= FlowFlags.CONDITIONALLY_CONTINUES;
} else {
newFlags |= (leftFlags | rightFlags) & FlowFlags.CONDITIONALLY_CONTINUES;
}
if (leftFlags & FlowFlags.ALLOCATES) {
if (rightFlags & FlowFlags.ALLOCATES) {
newFlags |= FlowFlags.ALLOCATES;
} else {
newFlags |= FlowFlags.CONDITIONALLY_ALLOCATES;
}
} else if (rightFlags & FlowFlags.ALLOCATES) {
newFlags |= FlowFlags.CONDITIONALLY_ALLOCATES;
} else {
newFlags |= (leftFlags | rightFlags) & FlowFlags.CONDITIONALLY_ALLOCATES;
}
if ((leftFlags & FlowFlags.CALLS_SUPER) && (rightFlags & FlowFlags.CALLS_SUPER)) {
newFlags |= FlowFlags.CALLS_SUPER;
}
if ((leftFlags & FlowFlags.TERMINATES) && (rightFlags & FlowFlags.TERMINATES)) {
newFlags |= FlowFlags.TERMINATES;
}
this.flags = newFlags | (this.flags & FlowFlags.UNCHECKED_CONTEXT);
var thisLocalFlags = this.localFlags;
if (leftFlags & FlowFlags.TERMINATES) {
if (!(rightFlags & FlowFlags.TERMINATES)) {
let rightLocalFlags = right.localFlags;
for (let i = 0, k = rightLocalFlags.length; i < k; ++i) {
thisLocalFlags[i] = rightLocalFlags[i];
}
}
} else if (rightFlags & FlowFlags.TERMINATES) {
let leftLocalFlags = left.localFlags;
for (let i = 0, k = leftLocalFlags.length; i < k; ++i) {
thisLocalFlags[i] = leftLocalFlags[i];
}
} else {
let leftLocalFlags = left.localFlags;
let numLeftLocalFlags = leftLocalFlags.length;
let rightLocalFlags = right.localFlags;
let numRightLocalFlags = rightLocalFlags.length;
let maxLocalFlags = max(numLeftLocalFlags, numRightLocalFlags);
for (let i = 0; i < maxLocalFlags; ++i) {
let leftFlags = i < numLeftLocalFlags ? leftLocalFlags[i] : 0;
let rightFlags = i < numRightLocalFlags ? rightLocalFlags[i] : 0;
let newFlags = leftFlags & rightFlags & (
LocalFlags.CONSTANT |
LocalFlags.WRAPPED |
LocalFlags.NONNULL |
LocalFlags.INITIALIZED
);
if (leftFlags & LocalFlags.RETAINED) {
if (rightFlags & LocalFlags.RETAINED) {
newFlags |= LocalFlags.RETAINED;
} else {
newFlags |= LocalFlags.CONDITIONALLY_RETAINED;
}
} else if (rightFlags & LocalFlags.RETAINED) {
newFlags |= LocalFlags.CONDITIONALLY_RETAINED;
} else {
newFlags |= (leftFlags | rightFlags) & LocalFlags.CONDITIONALLY_RETAINED;
}
thisLocalFlags[i] = newFlags;
}
}
if (left.fieldFlags && right.fieldFlags && right.fieldFlags.size > 0) {
const rightFieldFlags = right.fieldFlags;
const rightKeys = Map_keys(rightFieldFlags);
const rightValues = Map_values(rightFieldFlags);
const leftFieldFlags = left.fieldFlags;
for (let i = 0, k = rightValues.length; i < k; ++i) {
const rightValue = unchecked(rightValues[i]);
const rightKey = unchecked(rightKeys[i]);
const leftValue = leftFieldFlags.has(rightKey) ? assert(leftFieldFlags.get(rightKey)) : FieldFlags.NONE;
if ((rightValue & FieldFlags.INITIALIZED) && (leftValue & FieldFlags.INITIALIZED)) {
this.setFieldFlag(rightKey, FieldFlags.INITIALIZED);
}
}
}
}
/** Tests if the specified flows have differing local states. */
static hasIncompatibleLocalStates(before: Flow, after: Flow): bool {
var numThisLocalFlags = before.localFlags.length;
var numOtherLocalFlags = after.localFlags.length;
var parentFunction = before.parentFunction;
assert(parentFunction === after.parentFunction);
var localsByIndex = parentFunction.localsByIndex;
assert(localsByIndex === after.parentFunction.localsByIndex);
for (let i = 0, k = min<i32>(numThisLocalFlags, numOtherLocalFlags); i < k; ++i) {
let local = localsByIndex[i];
let type = local.type;
if (type.is(TypeFlags.SHORT | TypeFlags.INTEGER)) {
if (before.isLocalFlag(i, LocalFlags.WRAPPED) && !after.isLocalFlag(i, LocalFlags.WRAPPED)) {
return true;
}
}
if (type.is(TypeFlags.REFERENCE)) {
if (before.isLocalFlag(i, LocalFlags.NONNULL) && !after.isLocalFlag(i, LocalFlags.NONNULL)) {
return true;
}
}
}
return false;
}
/** Unifies local flags between this and the other flow. */
unifyLocalFlags(other: Flow): void {
var numThisLocalFlags = this.localFlags.length;
var numOtherLocalFlags = other.localFlags.length;
for (let i = 0, k = min<i32>(numThisLocalFlags, numOtherLocalFlags); i < k; ++i) {
if (this.isLocalFlag(i, LocalFlags.WRAPPED) != other.isLocalFlag(i, LocalFlags.WRAPPED)) {
this.unsetLocalFlag(i, LocalFlags.WRAPPED); // assume not wrapped
}
if (this.isLocalFlag(i, LocalFlags.NONNULL) != other.isLocalFlag(i, LocalFlags.NONNULL)) {
this.unsetLocalFlag(i, LocalFlags.NONNULL); // assume possibly null
}
assert(
// having different retain states would be a problem because the compiler
// either can't release a retained local or would release a non-retained local
this.isAnyLocalFlag(i, LocalFlags.ANY_RETAINED) == other.isAnyLocalFlag(i, LocalFlags.ANY_RETAINED)
);
}
}
/** Checks if an expression of the specified type is known to be non-null, even if the type might be nullable. */
isNonnull(expr: ExpressionRef, type: Type): bool {
if (!type.is(TypeFlags.NULLABLE)) return true;
// below, only teeLocal/getLocal are relevant because these are the only expressions that
// depend on a dynamic nullable state (flag = LocalFlags.NONNULL), while everything else
// has already been handled by the nullable type check above.
switch (getExpressionId(expr)) {
case ExpressionId.LocalSet: {
if (!isLocalTee(expr)) break;
let local = this.parentFunction.localsByIndex[getLocalSetIndex(expr)];
return !local.type.is(TypeFlags.NULLABLE) || this.isLocalFlag(local.index, LocalFlags.NONNULL, false);
}
case ExpressionId.LocalGet: {
let local = this.parentFunction.localsByIndex[getLocalGetIndex(expr)];
return !local.type.is(TypeFlags.NULLABLE) || this.isLocalFlag(local.index, LocalFlags.NONNULL, false);
}
}
return false;
}
/** Updates local states to reflect that this branch is only taken when `expr` is true-ish. */
inheritNonnullIfTrue(
/** Expression being true. */
expr: ExpressionRef,
/** If specified, only set the flag if also nonnull in this flow. */
iff: Flow | null = null
): void {
// A: `expr` is true-ish -> Q: how did that happen?
// The iff argument is useful in situations like
//
// if (!ref) {
// ref = new Ref();
// }
// // inheritNonnullIfFalse(`!ref`, thenFlow) -> ref != null
//
switch (getExpressionId(expr)) {
case ExpressionId.LocalSet: {
if (!isLocalTee(expr)) break;
let local = this.parentFunction.localsByIndex[getLocalSetIndex(expr)];
if (!iff || iff.isLocalFlag(local.index, LocalFlags.NONNULL)) {
this.setLocalFlag(local.index, LocalFlags.NONNULL);
}
this.inheritNonnullIfTrue(getLocalSetValue(expr), iff); // must have been true-ish as well
break;
}
case ExpressionId.LocalGet: {
let local = this.parentFunction.localsByIndex[getLocalGetIndex(expr)];
if (!iff || iff.isLocalFlag(local.index, LocalFlags.NONNULL)) {
this.setLocalFlag(local.index, LocalFlags.NONNULL);
}
break;
}
case ExpressionId.If: {
let ifFalse = getIfFalse(expr);
if (!ifFalse) break;
if (getExpressionId(ifFalse) == ExpressionId.Const) {
// Logical AND: (if (condition ifTrue 0))
// the only way this had become true is if condition and ifTrue are true
if (
(getExpressionType(ifFalse) == NativeType.I32 && getConstValueI32(ifFalse) == 0) ||
(getExpressionType(ifFalse) == NativeType.I64 && getConstValueI64Low(ifFalse) == 0 && getConstValueI64High(ifFalse) == 0)
) {
this.inheritNonnullIfTrue(getIfCondition(expr), iff);
this.inheritNonnullIfTrue(getIfTrue(expr), iff);
}
}
break;
}
case ExpressionId.Unary: {
switch (getUnaryOp(expr)) {
case UnaryOp.EqzI32:
case UnaryOp.EqzI64: {
this.inheritNonnullIfFalse(getUnaryValue(expr), iff); // !value -> value must have been false
break;
}
}
break;
}
case ExpressionId.Binary: {
switch (getBinaryOp(expr)) {
case BinaryOp.EqI32: {
let left = getBinaryLeft(expr);
let right = getBinaryRight(expr);
if (getExpressionId(left) == ExpressionId.Const && getConstValueI32(left) != 0) {
this.inheritNonnullIfTrue(right, iff); // TRUE == right -> right must have been true
} else if (getExpressionId(right) == ExpressionId.Const && getConstValueI32(right) != 0) {
this.inheritNonnullIfTrue(left, iff); // left == TRUE -> left must have been true
}
break;
}
case BinaryOp.EqI64: {
let left = getBinaryLeft(expr);
let right = getBinaryRight(expr);