1 files changed, 77 insertions, 0 deletions
diff --git a/src/passes/LogExecution.cpp b/src/passes/LogExecution.cpp
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+++ b/src/passes/LogExecution.cpp
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+/*
+ * Copyright 2017 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.
+ */
+
+//
+// Instruments the build with code to log execution at each function
+// entry and loop header. This can be useful in debugging, to log out
+// a trace, and diff it to another (running in another browser, to
+// check for bugs, for example).
+//
+// The logging is performed by calling an ffi with an id for each
+// call site. You need to provide that import on the JS side.
+//
+
+#include <wasm.h>
+#include <wasm-builder.h>
+#include <pass.h>
+#include "shared-constants.h"
+#include "asmjs/shared-constants.h"
+#include "asm_v_wasm.h"
+
+namespace wasm {
+
+Name LOGGER("log_execution");
+
+struct LogExecution : public WalkerPass<PostWalker<LogExecution>> {
+  void visitLoop(Loop* curr) {
+    curr->body = makeLogCall(curr->body);
+  }
+
+  void visitFunction(Function* curr) {
+    curr->body = makeLogCall(curr->body);
+  }
+
+  void visitModule(Module *curr) {
+    // Add the import
+    auto import = new Import;
+    import->name = LOGGER;
+    import->module = ENV;
+    import->base = LOGGER;
+    import->functionType = ensureFunctionType("vi", curr)->name;
+    import->kind = ExternalKind::Function;
+    curr->addImport(import);
+  }
+
+private:
+  Expression* makeLogCall(Expression* curr) {
+    static Index id = 0;
+    Builder builder(*getModule());
+    return builder.makeSequence(
+      builder.makeCallImport(
+        LOGGER,
+        { builder.makeConst(Literal(int32_t(id++))) },
+        none
+      ),
+      curr
+    );
+  }
+};
+
+Pass *createLogExecutionPass() {
+  return new LogExecution();
+}
+
+} // namespace wasm