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[MakeSharedObjects] Wrap externref global imports #9141

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[MakeSharedObjects] Wrap externref global imports #9141

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114 changes: 77 additions & 37 deletions src/passes/MakeSharedObjects.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,8 @@ struct LazyTable {
// The names of conversion functions, if ever used.
Name refToIndexName;
Name indexToRefName;
// Initial elements used to populate the table via an active element segment.
std::vector<Expression*> init;

LazyTable(Name base, Type type) : base(base), type(type) {}

Expand Down Expand Up @@ -190,28 +192,36 @@ struct LazyTable {
wasm->addFunction(std::move(func));
}

// Returns true if the table was added. (If it is never used, it will not be
// added.)
bool maybeAdd(Address initial, Address max) {
// Add the table, conversion functions, and active element segment if the
// table was ever used.
void maybeAdd(Address max) {
assert(wasm);
if (!name) {
return false;
return;
}
Table* table = wasm->addTable(Builder::makeTable(name));
table->type = type;
table->initial = initial;
table->initial = init.size();
table->max = max;
if (refToIndexName) {
addRefToIndexFunction();
}
if (indexToRefName) {
addIndexToRefFunction();
}
return true;
if (!init.empty()) {
Builder builder(*wasm);
Name segName = Names::getValidElementSegmentName(*wasm, base);
auto* offset = builder.makeConst(Literal(int32_t(0)));
auto* segment = wasm->addElementSegment(
Builder::makeElementSegment(segName, name, offset));
segment->type = type;
segment->data = std::move(init);
}
}

bool isTableType(Type t) const {
return t.isRef() && Type::isSubType(t, type);
return t.isRef() && !t.isNull() && Type::isSubType(t, type);
}

bool hasTableType(Type t) const {
Expand Down Expand Up @@ -264,10 +274,16 @@ struct MakeSharedObjects
Type funcref = Type(HeapTypes::func, Nullable);
Type externref = Type(HeapTypes::ext, Nullable);

// Tables storing unshared funcrefs and externrefs that are lowered to shared
// i31ref indices inside the module.
LazyTable funcTable{"funcs", funcref};
LazyTable externTable{"externs", externref};
std::vector<Name> funcs;

// Map from function name to index in `funcTable`.
std::unordered_map<Name, Index> funcIndices;

// Imported helper functions used to lower `extern.convert_any` and
// `any.convert_extern`, if needed.
Name anyToExternName;
Name externToAnyName;

Expand All @@ -287,10 +303,11 @@ struct MakeSharedObjects
return externToAnyName;
}

Index getIndex(Name func) {
auto [it, inserted] = funcIndices.insert({func, funcs.size()});
Index getIndex(RefFunc* curr) {
auto [it, inserted] =
funcIndices.insert({curr->func, funcTable.init.size()});
if (inserted) {
funcs.push_back(func);
funcTable.init.push_back(curr);
}
return it->second;
}
Expand Down Expand Up @@ -488,8 +505,8 @@ struct MakeSharedObjects

void visitRefFunc(RefFunc* curr) {
Builder builder(*getModule());
replaceCurrent(builder.makeRefI31(
builder.makeConst(Literal(getIndex(curr->func))), Shared));
replaceCurrent(
builder.makeRefI31(builder.makeConst(Literal(getIndex(curr))), Shared));
}

std::unordered_map<CallRef*, HeapType> callRefTypes;
Expand Down Expand Up @@ -718,7 +735,47 @@ struct MakeSharedObjects

void visitElementSegment(ElementSegment* curr) { updateType(curr->type); }

void visitGlobal(Global* curr) { updateType(curr->type); }
// Create a new imported global with the original externref type and add it
// to the externref table at instantiation time. The original global ceases to
// be an import and is initialized to the shared i31 table index so internal
// uses of the global receive the table index.
void wrapGlobalImport(Global* global, Type origType) {
Builder builder(*getModule());
Name origName = global->name;
Name importName =
Names::getValidGlobalName(*getModule(), origName.toString() + "$import");

auto importGlobal = std::make_unique<Global>();
importGlobal->name = importName;
importGlobal->module = global->module;
importGlobal->base = global->base;
importGlobal->type = origType;
importGlobal->mutable_ = false;
importGlobal->hasExplicitName = true;

Index index = externTable.init.size();
externTable.init.push_back(builder.makeGlobalGet(importName, origType));

global->module = Name();
global->base = Name();
global->init =
builder.makeRefI31(builder.makeConst(Literal(int32_t(index))), Shared);

getModule()->addGlobal(std::move(importGlobal));
}

struct GlobalImportToWrap {
Global* global;
Type origType;
};
std::vector<GlobalImportToWrap> globalImportsToWrap;

void visitGlobal(Global* curr) {
if (curr->imported() && externTable.isTableType(curr->type)) {
globalImportsToWrap.push_back({curr, curr->type});
}
updateType(curr->type);
}

void doWalkModule(Module* wasm) {
funcTable.wasm = wasm;
Expand Down Expand Up @@ -759,6 +816,9 @@ struct MakeSharedObjects

rewriteTypes();

for (auto& info : globalImportsToWrap) {
wrapGlobalImport(info.global, info.origType);
}
for (auto& info : importsToWrap) {
wrapImport(info.func, info.origType);
}
Expand All @@ -773,9 +833,10 @@ struct MakeSharedObjects
}
}

addFunctionTable();
funcTable.maybeAdd(funcTable.init.size());
addExternTable();
ReFinalize().run(getPassRunner(), wasm);
ReFinalize().walkModuleCode(wasm);
}

void rewriteTypes() {
Expand Down Expand Up @@ -822,27 +883,6 @@ struct MakeSharedObjects
rewriter.mapTypeNamesAndIndices(oldToNew);
}

void addFunctionTable() {
if (!funcTable.maybeAdd(funcs.size(), funcs.size())) {
return;
}
if (funcs.empty()) {
return;
}
Builder builder(*getModule());
Name segName = Names::getValidElementSegmentName(*getModule(), "funcs");
auto* offset = builder.makeConst(Literal(int32_t(0)));
auto* segment = getModule()->addElementSegment(
Builder::makeElementSegment(segName, funcTable.getName(), offset));
segment->type = funcTable.type;

segment->data.reserve(funcs.size());
for (auto func : funcs) {
segment->data.push_back(
builder.makeRefFunc(func, getModule()->getFunction(func)->type));
}
}

void addAnyToExternFunction() {
Type sharedAnyNullable = Type(HeapTypes::any.getBasic(Shared), Nullable);
Type externrefNullable = Type(HeapTypes::ext, Nullable);
Expand All @@ -866,7 +906,7 @@ struct MakeSharedObjects
}

void addExternTable() {
externTable.maybeAdd(0, Table::kUnlimitedSize);
externTable.maybeAdd(Table::kUnlimitedSize);
if (anyToExternName) {
addAnyToExternFunction();
}
Expand Down
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