1 files changed, 211 insertions, 0 deletions
diff --git a/src/passes/LegalizeJSInterface.cpp b/src/passes/LegalizeJSInterface.cpp
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+++ b/src/passes/LegalizeJSInterface.cpp
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+/*
+ * Copyright 2016 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// i64 values are not valid in JS, and must be handled in some other
+// way. This pass transforms all i64s in params and results in imports
+// and exports into pairs of i32, i32 (low, high). If JS on the outside
+// calls with that ABI, then everything should then just work, using
+// stub methods added in this pass, that thunk i64s into i32, i32 and
+// vice versa as necessary.
+//
+
+#include <wasm.h>
+#include <pass.h>
+#include <wasm-builder.h>
+#include <ast_utils.h>
+
+namespace wasm {
+
+Name TEMP_RET_0("tempRet0");
+
+struct LegalizeJSInterface : public Pass {
+  void run(PassRunner* runner, Module* module) override {
+    // for each illegal export, we must export a legalized stub instead
+    for (auto& ex : module->exports) {
+      if (ex->kind == Export::Function) {
+        // if it's an import, ignore it
+        if (auto* func = module->checkFunction(ex->value)) {
+          if (isIllegal(func)) {
+            auto legalName = makeLegalStub(func, module);
+            ex->value = legalName;
+          }
+        }
+      }
+    }
+    // for each illegal import, we must call a legalized stub instead
+    std::vector<Import*> newImports; // add them at the end, to not invalidate the iter
+    for (auto& im : module->imports) {
+      if (im->kind == Import::Function && isIllegal(im->functionType)) {
+        Name funcName;
+        auto* legal = makeLegalStub(im.get(), module, funcName);
+        illegalToLegal[im->name] = funcName;
+        newImports.push_back(legal);
+      }
+    }
+    if (illegalToLegal.size() > 0) {
+      for (auto* im : newImports) {
+        module->addImport(im);
+      }
+
+      // fix up imports: call_import of an illegal must be turned to a call of a legal
+
+      struct FixImports : public WalkerPass<PostWalker<FixImports, Visitor<FixImports>>> {
+        bool isFunctionParallel() override { return true; }
+
+        Pass* create() override { return new FixImports(illegalToLegal); }
+
+        std::map<Name, Name>* illegalToLegal;
+
+        FixImports(std::map<Name, Name>* illegalToLegal) : illegalToLegal(illegalToLegal) {}
+
+        void visitCallImport(CallImport* curr) {
+          auto iter = illegalToLegal->find(curr->target);
+          if (iter == illegalToLegal->end()) return;
+
+          if (iter->second == getFunction()->name) return; // inside the stub function itself, is the one safe place to do the call
+          replaceCurrent(Builder(*getModule()).makeCall(iter->second, curr->operands, curr->type));
+        }
+      };
+
+      PassRunner passRunner(module);
+      passRunner.add<FixImports>(&illegalToLegal);
+      passRunner.run();
+    }
+  }
+
+private:
+  // map of illegal to legal names for imports
+  std::map<Name, Name> illegalToLegal;
+
+  template<typename T>
+  bool isIllegal(T* t) {
+    for (auto param : t->params) {
+      if (param == i64) return true;
+    }
+    if (t->result == i64) return true;
+    return false;
+  }
+
+  // JS calls the export, so it must call a legal stub that calls the actual wasm function
+  Name makeLegalStub(Function* func, Module* module) {
+    Builder builder(*module);
+    auto* legal = new Function();
+    legal->name = Name(std::string("legalstub$") + func->name.str);
+
+    auto* call = module->allocator.alloc<Call>();
+    call->target = func->name;
+    call->type = func->result;
+
+    for (auto param : func->params) {
+      if (param == i64) {
+        call->operands.push_back(I64Utilities::recreateI64(builder, legal->params.size(), legal->params.size() + 1));
+        legal->params.push_back(i32);
+        legal->params.push_back(i32);
+      } else {
+        call->operands.push_back(builder.makeGetLocal(legal->params.size(), param));
+        legal->params.push_back(param);
+      }
+    }
+
+    if (func->result == i64) {
+      legal->result = i32;
+      auto index = builder.addVar(legal, Name(), i64);
+      auto* block = builder.makeBlock();
+      block->list.push_back(builder.makeSetLocal(index, call));
+      if (module->checkGlobal(TEMP_RET_0)) {
+        block->list.push_back(builder.makeSetGlobal(
+          TEMP_RET_0,
+          I64Utilities::getI64High(builder, index)
+        ));
+      } else {
+        block->list.push_back(builder.makeUnreachable()); // no way to emit the high bits :(
+      }
+      block->list.push_back(I64Utilities::getI64Low(builder, index));
+      block->finalize();
+      legal->body = block;
+    } else {
+      legal->result = func->result;
+      legal->body = call;
+    }
+
+    // a method may be exported multiple times
+    if (!module->checkFunction(legal->name)) {
+      module->addFunction(legal);
+    }
+    return legal->name;
+  }
+
+  // wasm calls the import, so it must call a stub that calls the actual legal JS import
+  Import* makeLegalStub(Import* im, Module* module, Name& funcName) {
+    Builder builder(*module);
+    auto* type = new FunctionType();
+    type->name =  Name(std::string("legaltype$") + im->name.str);
+    auto* legal = new Import();
+    legal->name = Name(std::string("legalimport$") + im->name.str);
+    legal->module = im->module;
+    legal->base = im->base;
+    legal->kind = Import::Function;
+    legal->functionType = type;
+    auto* func = new Function();
+    func->name = Name(std::string("legalfunc$") + im->name.str);
+    funcName = func->name;
+
+    auto* call = module->allocator.alloc<CallImport>();
+    call->target = legal->name;
+
+    for (auto param : im->functionType->params) {
+      if (param == i64) {
+        call->operands.push_back(I64Utilities::getI64Low(builder, func->params.size()));
+        call->operands.push_back(I64Utilities::getI64High(builder, func->params.size()));
+        type->params.push_back(i32);
+        type->params.push_back(i32);
+      } else {
+        call->operands.push_back(builder.makeGetLocal(func->params.size(), param));
+        type->params.push_back(param);
+      }
+      func->params.push_back(param);
+    }
+
+    if (im->functionType->result == i64) {
+      call->type = i32;
+      Expression* get;
+      if (module->checkGlobal(TEMP_RET_0)) {
+        get = builder.makeGetGlobal(TEMP_RET_0, i32);
+      } else {
+        get = builder.makeUnreachable(); // no way to emit the high bits :(
+      }
+      func->body = I64Utilities::recreateI64(builder, call, get);
+      type->result = i32;
+    } else {
+      call->type = im->functionType->result;
+      func->body = call;
+      type->result = im->functionType->result;
+    }
+    func->result = im->functionType->result;
+
+    module->addFunction(func);
+    module->addFunctionType(type);
+    return legal;
+  }
+};
+
+Pass *createLegalizeJSInterfacePass() {
+  return new LegalizeJSInterface();
+}
+
+} // namespace wasm
+