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[Parser] Preserve try labels #6505

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Merged
tlively merged 1 commit into from
Apr 17, 2024
Merged

[Parser] Preserve try labels #6505

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23 changes: 17 additions & 6 deletions src/wasm-ir-builder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -298,6 +298,10 @@ class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {

// The branch label name for this scope. Always fresh, never shadowed.
Name label;
// For Try/Catch/CatchAll scopes, we need to separately track a label used
// for branches, since the normal label is only used for delegates.
Name branchLabel;

bool labelUsed = false;

std::vector<Expression*> exprStack;
Expand All @@ -308,6 +312,8 @@ class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {
ScopeCtx() : scope(NoScope{}) {}
ScopeCtx(Scope scope) : scope(scope) {}
ScopeCtx(Scope scope, Name label) : scope(scope), label(label) {}
ScopeCtx(Scope scope, Name label, Name branchLabel)
: scope(scope), label(label), branchLabel(branchLabel) {}

static ScopeCtx makeFunc(Function* func) {
return ScopeCtx(FuncScope{func});
Expand All @@ -325,11 +331,13 @@ class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {
static ScopeCtx makeTry(Try* tryy, Name originalLabel = {}) {
return ScopeCtx(TryScope{tryy, originalLabel});
}
static ScopeCtx makeCatch(Try* tryy, Name originalLabel, Name label) {
return ScopeCtx(CatchScope{tryy, originalLabel}, label);
static ScopeCtx
makeCatch(Try* tryy, Name originalLabel, Name label, Name branchLabel) {
return ScopeCtx(CatchScope{tryy, originalLabel}, label, branchLabel);
}
static ScopeCtx makeCatchAll(Try* tryy, Name originalLabel, Name label) {
return ScopeCtx(CatchAllScope{tryy, originalLabel}, label);
static ScopeCtx
makeCatchAll(Try* tryy, Name originalLabel, Name label, Name branchLabel) {
return ScopeCtx(CatchAllScope{tryy, originalLabel}, label, branchLabel);
}
static ScopeCtx makeTryTable(TryTable* trytable, Name originalLabel = {}) {
return ScopeCtx(TryTableScope{trytable, originalLabel});
Expand Down Expand Up @@ -507,8 +515,11 @@ class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {
// `block`, but otherwise we will have to allocate a new block.
Result<Expression*> finishScope(Block* block = nullptr);

[[nodiscard]] Result<Name> getLabelName(Index label);
[[nodiscard]] Result<Name> getDelegateLabelName(Index label);
[[nodiscard]] Result<Name> getLabelName(Index label,
bool forDelegate = false);
[[nodiscard]] Result<Name> getDelegateLabelName(Index label) {
return getLabelName(label, true);
}
[[nodiscard]] Result<Index> addScratchLocal(Type);

struct HoistedVal {
Expand Down
63 changes: 26 additions & 37 deletions src/wasm/wasm-ir-builder.cpp
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Expand Up @@ -235,6 +235,10 @@ void IRBuilder::dump() {
std::cerr << " (label: " << scope.label << ")";
}

if (scope.branchLabel) {
std::cerr << " (branch label: " << scope.branchLabel << ")";
}

if (scope.unreachable) {
std::cerr << " (unreachable)";
}
Expand Down Expand Up @@ -703,9 +707,6 @@ Result<> IRBuilder::visitLoopStart(Loop* loop) {

Result<> IRBuilder::visitTryStart(Try* tryy, Name label) {
applyDebugLoc(tryy);
// The delegate label will be regenerated if we need it. See
// `getDelegateLabelName` for details.
tryy->name = Name();
pushScope(ScopeCtx::makeTry(tryy, label));
return Ok{};
}
Expand Down Expand Up @@ -829,6 +830,7 @@ Result<> IRBuilder::visitCatch(Name tag) {
}
auto originalLabel = scope.getOriginalLabel();
auto label = scope.label;
auto branchLabel = scope.branchLabel;
auto expr = finishScope();
CHECK_ERR(expr);
if (wasTry) {
Expand All @@ -837,7 +839,7 @@ Result<> IRBuilder::visitCatch(Name tag) {
tryy->catchBodies.push_back(*expr);
}
tryy->catchTags.push_back(tag);
pushScope(ScopeCtx::makeCatch(tryy, originalLabel, label));
pushScope(ScopeCtx::makeCatch(tryy, originalLabel, label, branchLabel));
// Push a pop for the exception payload.
auto params = wasm.getTag(tag)->sig.params;
if (params != Type::none) {
Expand All @@ -859,44 +861,18 @@ Result<> IRBuilder::visitCatchAll() {
}
auto originalLabel = scope.getOriginalLabel();
auto label = scope.label;
auto branchLabel = scope.branchLabel;
auto expr = finishScope();
CHECK_ERR(expr);
if (wasTry) {
tryy->body = *expr;
} else {
tryy->catchBodies.push_back(*expr);
}
pushScope(ScopeCtx::makeCatchAll(tryy, originalLabel, label));
pushScope(ScopeCtx::makeCatchAll(tryy, originalLabel, label, branchLabel));
return Ok{};
}

Result<Name> IRBuilder::getDelegateLabelName(Index label) {
if (label >= scopeStack.size()) {
return Err{"invalid label: " + std::to_string(label)};
}
auto& scope = scopeStack[scopeStack.size() - label - 1];
auto* delegateTry = scope.getTry();
if (!delegateTry) {
delegateTry = scope.getCatch();
}
if (!delegateTry) {
delegateTry = scope.getCatchAll();
}
if (!delegateTry) {
return Err{"expected try scope at label " + std::to_string(label)};
}
// Only delegate and rethrow can reference the try name in Binaryen IR, so
// trys might need two labels: one for delegate/rethrow and one for all
// other control flow. These labels must be different to satisfy the
// Binaryen validator. To keep this complexity contained within the
// handling of trys and delegates, pretend there is just the single normal
// label and add a prefix to it to generate the delegate label.
auto delegateName =
Name(std::string("__delegate__") + getLabelName(label)->toString());
delegateTry->name = delegateName;
return delegateName;
}

Result<> IRBuilder::visitDelegate(Index label) {
auto& scope = getScope();
auto* tryy = scope.getTry();
Expand Down Expand Up @@ -946,8 +922,10 @@ Result<> IRBuilder::visitEnd() {
// type of the scope expression.
auto originalScopeType = scope.getResultType();
auto maybeWrapForLabel = [&](Expression* curr) -> Expression* {
if (scope.label) {
return builder.makeBlock(scope.label,
bool isTry = scope.getTry() || scope.getCatch() || scope.getCatchAll();
auto& label = isTry ? scope.branchLabel : scope.label;
if (label) {
return builder.makeBlock(label,
{curr},
scope.labelUsed ? originalScopeType
: scope.getResultType());
Expand Down Expand Up @@ -981,11 +959,13 @@ Result<> IRBuilder::visitEnd() {
push(maybeWrapForLabel(iff));
} else if (auto* tryy = scope.getTry()) {
tryy->body = *expr;
tryy->name = scope.label;
tryy->finalize(tryy->type);
push(maybeWrapForLabel(tryy));
} else if (Try * tryy;
(tryy = scope.getCatch()) || (tryy = scope.getCatchAll())) {
tryy->catchBodies.push_back(*expr);
tryy->name = scope.label;
tryy->finalize(tryy->type);
push(maybeWrapForLabel(tryy));
} else if (auto* trytable = scope.getTryTable()) {
Expand Down Expand Up @@ -1029,10 +1009,17 @@ Result<Index> IRBuilder::getLabelIndex(Name label, bool inDelegate) {
return index;
}

Result<Name> IRBuilder::getLabelName(Index label) {
Result<Name> IRBuilder::getLabelName(Index label, bool forDelegate) {
auto scope = getScope(label);
CHECK_ERR(scope);
auto& scopeLabel = (*scope)->label;

// For normal branches to try blocks, we need to use the secondary label.
bool useTryBranchLabel =
!forDelegate &&
((*scope)->getTry() || (*scope)->getCatch() || (*scope)->getCatchAll());
auto& scopeLabel =
useTryBranchLabel ? (*scope)->branchLabel : (*scope)->label;

if (!scopeLabel) {
// The scope does not already have a name, so we need to create one.
if ((*scope)->getBlock()) {
Expand All @@ -1041,7 +1028,9 @@ Result<Name> IRBuilder::getLabelName(Index label) {
scopeLabel = makeFresh("label");
}
}
(*scope)->labelUsed = true;
if (!forDelegate) {
(*scope)->labelUsed = true;
}
return scopeLabel;
}

Expand Down
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