Skip to content

Use proper flows when compiling switch statements #2573

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 2 commits into from
Closed

Use proper flows when compiling switch statements #2573

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
746b3b7
Use proper flows when compiling switch statements
dcodeIO Nov 22, 2022
66ff862
breaking flows are mutual
dcodeIO Nov 22, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
39 changes: 20 additions & 19 deletions src/compiler.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2825,15 +2825,16 @@ export class Compiler extends DiagnosticEmitter {

// nest blocks in order
let currentBlock = module.block(`case0|${context}`, breaks, TypeRef.None);
let commonCategorical = FlowFlags.AnyCategorical;
let commonConditional = 0;
let fallThroughFlow: Flow | null = null;
let mutualBreakingFlow: Flow | null = null;
for (let i = 0; i < numCases; ++i) {
let case_ = cases[i];
let statements = case_.statements;
let numStatements = statements.length;

// Each switch case initiates a new branch
// Can get here by matching the case or by fall-through
let innerFlow = outerFlow.fork();
if (fallThroughFlow) innerFlow.inheritBranch(fallThroughFlow);
this.currentFlow = innerFlow;
let breakLabel = `break|${context}`;
innerFlow.breakLabel = breakLabel;
Expand All @@ -2843,38 +2844,38 @@ export class Compiler extends DiagnosticEmitter {
let stmts = new Array<ExpressionRef>(1 + numStatements);
stmts[0] = currentBlock;
let count = 1;
let terminates = false;
let possiblyFallsThrough = true;
for (let j = 0; j < numStatements; ++j) {
let stmt = this.compileStatement(statements[j]);
if (getExpressionId(stmt) != ExpressionId.Nop) {
stmts[count++] = stmt;
}
if (innerFlow.isAny(FlowFlags.Terminates | FlowFlags.Breaks)) {
if (innerFlow.is(FlowFlags.Terminates)) terminates = true;
possiblyFallsThrough = false;
break;
}
}
stmts.length = count;
if (terminates || isLast || innerFlow.isAny(FlowFlags.Breaks | FlowFlags.ConditionallyBreaks)) {
commonCategorical &= innerFlow.flags;
fallThroughFlow = possiblyFallsThrough ? innerFlow : null;
let possiblyBreaks = innerFlow.isAny(FlowFlags.Breaks | FlowFlags.ConditionallyBreaks);
innerFlow.unset(FlowFlags.Breaks | FlowFlags.ConditionallyBreaks); // clear
if (possiblyBreaks || (isLast && possiblyFallsThrough)) {
if (mutualBreakingFlow) mutualBreakingFlow.inheritMutual(mutualBreakingFlow, innerFlow);
else mutualBreakingFlow = innerFlow;
}

commonConditional |= innerFlow.deriveConditionalFlags();

// Switch back to the parent flow
innerFlow.unset(
FlowFlags.Breaks |
FlowFlags.ConditionallyBreaks
);
this.currentFlow = outerFlow;
currentBlock = module.block(nextLabel, stmts, TypeRef.None); // must be a labeled block
}
outerFlow.popBreakLabel();

// If the switch has a default (guaranteed to handle any value), propagate common flags
if (defaultIndex >= 0) outerFlow.flags |= commonCategorical & ~FlowFlags.Breaks;
outerFlow.flags |= commonConditional & ~FlowFlags.ConditionallyBreaks;
// TODO: what about local states?
// If the switch has a default, we only get past through any breaking flow
if (defaultIndex >= 0) {
if (mutualBreakingFlow) outerFlow.inherit(mutualBreakingFlow);
else outerFlow.set(FlowFlags.Terminates);
// Otherwise either skipping or any breaking flow can get past
} else if (mutualBreakingFlow) {
outerFlow.inheritBranch(mutualBreakingFlow);
}
return currentBlock;
}

Expand Down