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wasm-merge: Avoid quadratic time in validation [NFC] #7845

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Merged
merged 3 commits into from
Aug 20, 2025
Merged

wasm-merge: Avoid quadratic time in validation [NFC] #7845

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kripken Aug 19, 2025
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kripken Aug 19, 2025
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kripken Aug 19, 2025
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168 changes: 95 additions & 73 deletions src/tools/wasm-merge.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,11 @@
// merged, and at the end we traverse the entire merged module once to fuse
// imports and exports.
//
// Debugging: Set BINARYEN_PASS_DEBUG=1 in the env to get validation after each
// merging of a module (like pass-debug mode for the pass runner, this does
// expensive work after each incremental operation). This can take quadratic
// time, so we do not do it by default.
//

#include "ir/module-utils.h"
#include "ir/names.h"
Expand Down Expand Up @@ -418,7 +423,7 @@ void checkLimit(bool& valid, const char* kind, T* export_, T* import) {

// Find pairs of matching imports and exports, and make uses of the import refer
// to the exported item (which has been merged into the module).
void fuseImportsAndExports() {
void fuseImportsAndExports(const PassOptions& options) {
// First, scan the exports and build a map. We build a map of [module name] to
// [export name => internal name]. For example, consider this module:
//
Expand Down Expand Up @@ -466,80 +471,86 @@ void fuseImportsAndExports() {
}
});

// Make sure that the export types match the import types.
bool valid = true;
ModuleUtils::iterImportedFunctions(merged, [&](Function* import) {
auto internalName = kindModuleExportMaps[ExternalKind::Function]
[import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getFunction(internalName);
if (!HeapType::isSubType(export_->type, import->type)) {
reportTypeMismatch(valid, "function", import);
std::cerr << "type " << export_->type << " is not a subtype of "
<< import->type << ".\n";
}
}
});
ModuleUtils::iterImportedTables(merged, [&](Table* import) {
auto internalName =
kindModuleExportMaps[ExternalKind::Table][import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getTable(internalName);
checkLimit(valid, "table", export_, import);
if (export_->type != import->type) {
reportTypeMismatch(valid, "table", import);
std::cerr << "export type " << export_->type
<< " is different from import type " << import->type << ".\n";
}
}
});
ModuleUtils::iterImportedMemories(merged, [&](Memory* import) {
auto internalName =
kindModuleExportMaps[ExternalKind::Memory][import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getMemory(internalName);
if (export_->is64() != import->is64()) {
reportTypeMismatch(valid, "memory", import);
std::cerr << "index type should match.\n";
if (options.validate) {
// Make sure that the export types match the import types.
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This seems pretty important, since you could have linking problems even if each module were independently valid. Is there a way to make this validation of the linked types fast enough to run by default?

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We validate by default, so this does run by default.

It is reasonably fast - not significant in time compared to validating an entire huge module, at least.

bool valid = true;
ModuleUtils::iterImportedFunctions(merged, [&](Function* import) {
auto internalName = kindModuleExportMaps[ExternalKind::Function]
[import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getFunction(internalName);
if (!HeapType::isSubType(export_->type, import->type)) {
reportTypeMismatch(valid, "function", import);
std::cerr << "type " << export_->type << " is not a subtype of "
<< import->type << ".\n";
}
}
checkLimit(valid, "memory", export_, import);
}
});
ModuleUtils::iterImportedGlobals(merged, [&](Global* import) {
auto internalName =
kindModuleExportMaps[ExternalKind::Global][import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getGlobal(internalName);
if (export_->mutable_ != import->mutable_) {
reportTypeMismatch(valid, "global", import);
std::cerr << "mutability should match.\n";
});
ModuleUtils::iterImportedTables(merged, [&](Table* import) {
auto internalName =
kindModuleExportMaps[ExternalKind::Table][import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getTable(internalName);
checkLimit(valid, "table", export_, import);
if (export_->type != import->type) {
reportTypeMismatch(valid, "table", import);
std::cerr << "export type " << export_->type
<< " is different from import type " << import->type
<< ".\n";
}
}
if (export_->mutable_ && export_->type != import->type) {
reportTypeMismatch(valid, "global", import);
std::cerr << "export type " << export_->type
<< " is different from import type " << import->type << ".\n";
});
ModuleUtils::iterImportedMemories(merged, [&](Memory* import) {
auto internalName = kindModuleExportMaps[ExternalKind::Memory]
[import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getMemory(internalName);
if (export_->is64() != import->is64()) {
reportTypeMismatch(valid, "memory", import);
std::cerr << "index type should match.\n";
}
checkLimit(valid, "memory", export_, import);
}
if (!export_->mutable_ && !Type::isSubType(export_->type, import->type)) {
reportTypeMismatch(valid, "global", import);
std::cerr << "type " << export_->type << " is not a subtype of "
<< import->type << ".\n";
});
ModuleUtils::iterImportedGlobals(merged, [&](Global* import) {
auto internalName = kindModuleExportMaps[ExternalKind::Global]
[import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getGlobal(internalName);
if (export_->mutable_ != import->mutable_) {
reportTypeMismatch(valid, "global", import);
std::cerr << "mutability should match.\n";
}
if (export_->mutable_ && export_->type != import->type) {
reportTypeMismatch(valid, "global", import);
std::cerr << "export type " << export_->type
<< " is different from import type " << import->type
<< ".\n";
}
if (!export_->mutable_ &&
!Type::isSubType(export_->type, import->type)) {
reportTypeMismatch(valid, "global", import);
std::cerr << "type " << export_->type << " is not a subtype of "
<< import->type << ".\n";
}
}
}
});
ModuleUtils::iterImportedTags(merged, [&](Tag* import) {
auto internalName =
kindModuleExportMaps[ExternalKind::Tag][import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getTag(internalName);
if (export_->type != import->type) {
reportTypeMismatch(valid, "tag", import);
std::cerr << "export type " << export_->type
<< " is different from import type " << import->type << ".\n";
});
ModuleUtils::iterImportedTags(merged, [&](Tag* import) {
auto internalName =
kindModuleExportMaps[ExternalKind::Tag][import->module][import->base];
if (internalName.is()) {
auto* export_ = merged.getTag(internalName);
if (export_->type != import->type) {
reportTypeMismatch(valid, "tag", import);
std::cerr << "export type " << export_->type
<< " is different from import type " << import->type
<< ".\n";
}
}
});
if (!valid) {
Fatal() << "import/export mismatches";
}
});
if (!valid) {
Fatal() << "import/export mismatches";
}

// Update the things we found.
Expand Down Expand Up @@ -730,18 +741,29 @@ Input source maps can be specified by adding an -ism option right after the modu
// This is a later module: do a full merge.
mergeInto(*currModule, inputFileName);

if (options.passOptions.validate) {
if (!WasmValidator().validate(merged)) {
// Validate after each merged module, when we are in pass-debug mode
// (this can be quadratic time).
if (PassRunner::getPassDebug()) {
std::cerr << "[WasmMerge] merged : " << inputFile << '\n';
if (options.passOptions.validate && !WasmValidator().validate(merged)) {
std::cout << merged << '\n';
Fatal() << "error in validating merged after: " << inputFile;
Fatal() << "error in validating after: " << inputFile;
}
}
}
}

// If we didn't validate after each merged module, validate once at the very
// end. This won't catch problems at the earliest point, but is still useful.
if (!PassRunner::getPassDebug() && options.passOptions.validate &&
!WasmValidator().validate(merged)) {
std::cout << merged << '\n';
Fatal() << "error in validating final merged";
}

// Fuse imports and exports now that everything is all together in the merged
// module.
fuseImportsAndExports();
fuseImportsAndExports(options.passOptions);

{
PassRunner passRunner(&merged);
Expand Down
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