[jspi] Remove module splitting changes. (#8529)

Emscripten has changed to use the regular way of splitting with a Proxy
and no longer needs this.

emscripten-core/emscripten#26396

Fixes #8424

Author: brendandahl

src/ir/module-splitting.cpp

@@ -73,7 +73,6 @@
 //      from the IR before splitting.
 //
 #include "ir/module-splitting.h"
-#include "asmjs/shared-constants.h"
 #include "ir/export-utils.h"
 #include "ir/find_all.h"
 #include "ir/module-utils.h"
@@ -87,8 +86,6 @@ namespace wasm::ModuleSplitting {
 
 namespace {
 
-static const Name LOAD_SECONDARY_STATUS = "load_secondary_module_status";
-
 template<class F> void forEachElement(Module& module, F f) {
   ModuleUtils::iterActiveElementSegments(module, [&](ElementSegment* segment) {
     Name base = "";
@@ -328,12 +325,10 @@ struct ModuleSplitter {
 
   // Other helpers
   void exportImportFunction(Name func, const std::set<Module*>& modules);
-  Expression* maybeLoadSecondary(Builder& builder, Expression* callIndirect);
   Name getTrampoline(Name funcName);
 
   // Main splitting steps
   void classifyFunctions();
-  void setupJSPI();
   void moveSecondaryFunctions();
   void thunkExportedSecondaryFunctions();
   void indirectReferencesToSecondaryFunctions();
@@ -346,9 +341,6 @@ struct ModuleSplitter {
     : config(config), primary(primary), tableManager(primary),
       exportedPrimaryFuncs(initExportedPrimaryFuncs(primary)) {
     classifyFunctions();
-    if (config.jspi) {
-      setupJSPI();
-    }
     moveSecondaryFunctions();
     thunkExportedSecondaryFunctions();
     indirectReferencesToSecondaryFunctions();
@@ -359,25 +351,6 @@ struct ModuleSplitter {
   }
 };
 
-void ModuleSplitter::setupJSPI() {
-  // Add an imported function to load the secondary module.
-  auto import = Builder::makeFunction(
-    ModuleSplitting::LOAD_SECONDARY_MODULE,
-    Type(Signature(Type::none, Type::none), NonNullable, Inexact),
-    {});
-  import->module = ENV;
-  import->base = ModuleSplitting::LOAD_SECONDARY_MODULE;
-  primary.addFunction(std::move(import));
-  Builder builder(primary);
-  // Add a global to track whether the secondary module has been loaded yet.
-  primary.addGlobal(builder.makeGlobal(LOAD_SECONDARY_STATUS,
-                                       Type::i32,
-                                       builder.makeConst(int32_t(0)),
-                                       Builder::Mutable));
-  primary.addExport(builder.makeExport(
-    LOAD_SECONDARY_STATUS, LOAD_SECONDARY_STATUS, ExternalKind::Global));
-}
-
 std::unique_ptr<Module> ModuleSplitter::initSecondary(const Module& primary) {
   // Create the secondary module and copy trivial properties.
   auto secondary = std::make_unique<Module>();
@@ -449,12 +422,7 @@ void ModuleSplitter::classifyFunctions() {
     configSecondaryFuncs.insert(funcs.begin(), funcs.end());
   }
   for (auto& func : primary.functions) {
-    // In JSPI mode exported functions cannot be moved to the secondary
-    // module since that would make them async when they may not have the JSPI
-    // wrapper. Exported JSPI functions can still benefit from splitting though
-    // since only the JSPI wrapper stub will remain in the primary module.
     if (func->imported() || !configSecondaryFuncs.count(func->name) ||
-        (config.jspi && ExportUtils::isExported(primary, *func)) ||
         segmentReferrers.count(func->name)) {
       primaryFuncs.insert(func->name);
     } else {
@@ -571,20 +539,6 @@ void ModuleSplitter::thunkExportedSecondaryFunctions() {
   }
 }
 
-Expression* ModuleSplitter::maybeLoadSecondary(Builder& builder,
-                                               Expression* callIndirect) {
-  if (!config.jspi) {
-    return callIndirect;
-  }
-  // Check if the secondary module is loaded and if it isn't, call the
-  // function to load it.
-  auto* loadSecondary = builder.makeIf(
-    builder.makeUnary(EqZInt32,
-                      builder.makeGlobalGet(LOAD_SECONDARY_STATUS, Type::i32)),
-    builder.makeCall(ModuleSplitting::LOAD_SECONDARY_MODULE, {}, Type::none));
-  return builder.makeSequence(loadSecondary, callIndirect);
-}
-
 // Helper to walk expressions in segments but NOT in globals.
 template<typename Walker>
 static void walkSegments(Walker& walker, Module* module) {
@@ -720,13 +674,12 @@ void ModuleSplitter::indirectCallsToSecondaryFunctions() {
       auto tableSlot =
         parent.tableManager.getSlot(curr->target, func->type.getHeapType());
 
-      replaceCurrent(parent.maybeLoadSecondary(
-        builder,
+      replaceCurrent(
         builder.makeCallIndirect(tableSlot.tableName,
                                  tableSlot.makeExpr(parent.primary),
                                  curr->operands,
                                  func->type.getHeapType(),
-                                 curr->isReturn)));
+                                 curr->isReturn));
     }
   };
   CallIndirector callIndirector(*this);

src/ir/module-splitting.h

@@ -48,8 +48,6 @@
 
 namespace wasm::ModuleSplitting {
 
-static const Name LOAD_SECONDARY_MODULE("__load_secondary_module");
-
 struct Config {
   // A vector of set of functions to split into that secondary. Each function
   // set belongs to a single secondary module. All others are kept in the
@@ -77,9 +75,6 @@ struct Config {
   // false, the original function names will be used (after `newExportPrefix`)
   // as the new export names.
   bool minimizeNewExportNames = false;
-  // When JSPI support is enabled the secondary module loading is handled by an
-  // imported function.
-  bool jspi = false;
 };
 
 struct Results {

src/tools/wasm-split/split-options.cpp

@@ -256,14 +256,6 @@ WasmSplitOptions::WasmSplitOptions()
          [&](Options* o, const std::string& argument) {
            placeholderNamespacePrefix = argument;
          })
-    .add("--jspi",
-         "",
-         "Transform the module to support asynchronously loading the secondary "
-         "module before any placeholder functions have been called.",
-         WasmSplitOption,
-         {Mode::Split},
-         Options::Arguments::Zero,
-         [&](Options* o, const std::string& argument) { jspi = true; })
     .add(
       "--export-prefix",
       "",

src/tools/wasm-split/split-options.h

@@ -50,7 +50,6 @@ struct WasmSplitOptions : ToolOptions {
   bool emitBinary = true;
   bool symbolMap = false;
   bool placeholderMap = false;
-  bool jspi = false;
   bool stripDebug = false;
 
   // TODO: Remove this. See the comment in wasm-binary.h.

src/tools/wasm-split/wasm-split.cpp

@@ -308,12 +308,6 @@ void splitModule(const WasmSplitOptions& options) {
     std::cerr << "warning: not keeping any functions in the primary module\n";
   }
 
-  if (options.jspi) {
-    // The load secondary module function must be kept in the main module.
-    keepFuncs.insert(ModuleSplitting::LOAD_SECONDARY_MODULE);
-    splitFuncs.erase(ModuleSplitting::LOAD_SECONDARY_MODULE);
-  }
-
   // If warnings are enabled, check that any functions are being split out.
   if (!options.quiet && splitFuncs.size() == 0) {
     std::cerr
@@ -352,7 +346,6 @@ void splitModule(const WasmSplitOptions& options) {
   setCommonSplitConfigs(config, options);
   config.secondaryFuncs.push_back(std::move(splitFuncs));
   config.secondaryNames.push_back("deferred");
-  config.jspi = options.jspi;
   auto splitResults = ModuleSplitting::splitFunctions(wasm, config);
   auto& secondary = *splitResults.secondaries.begin();
 

test/lit/help/wasm-split.test

@@ -94,11 +94,6 @@
 ;; CHECK-NEXT:   --placeholder-namespace              [split, multi-split] The same as
 ;; CHECK-NEXT:                                        --placeholder-namespace-prefix.
 ;; CHECK-NEXT:
-;; CHECK-NEXT:   --jspi                               [split] Transform the module to support
-;; CHECK-NEXT:                                        asynchronously loading the secondary
-;; CHECK-NEXT:                                        module before any placeholder functions
-;; CHECK-NEXT:                                        have been called.
-;; CHECK-NEXT:
 ;; CHECK-NEXT:   --export-prefix                      [split, multi-split] An identifying
 ;; CHECK-NEXT:                                        prefix to prepend to new export names
 ;; CHECK-NEXT:                                        created by module splitting.