Rename `wasm2asm` to `wasm2js`, emit ESM by default (#1642)

* Rename the `wasm2asm` tool to `wasm2js`

This commit performs a relatively simple rename of the `wasm2asm` tool to
`wasm2js`. The functionality of the tool doesn't change just yet but it's
intended that we'll start generating an ES module instead of just an `asm.js`
function soon.

* wasm2js: Support `*.wasm` input files

Previously `wasm2js` only supported `*.wast` files but to make it a bit easier
to use in tooling pipelines this commit adds support for reading in a `*.wasm`
file directly. Determining which parser to use depends on the input filename,
where the binary parser is used with `*.wasm` files and the wast parser is used
for all other files.

* wasm2js: Emit ESM imports/exports by default

This commit alters the default behavior of `wasm2js` to emit an ESM by default,
either importing items from the environment or exporting. Items like
initialization of memory are also handled here.

1 files changed, 122 insertions, 0 deletions

diff --git a/src/tools/wasm2js.cpp b/src/tools/wasm2js.cpp
new file mode 100644
index 000000000..8a57a5a1a
--- /dev/null
+++ b/src/tools/wasm2js.cpp
@@ -0,0 +1,122 @@
+/*
+ * Copyright 2015 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.
+ */
+
+//
+// wasm2js console tool
+//
+
+#include "support/colors.h"
+#include "support/command-line.h"
+#include "support/file.h"
+#include "wasm-s-parser.h"
+#include "wasm2js.h"
+
+using namespace cashew;
+using namespace wasm;
+
+int main(int argc, const char *argv[]) {
+  Wasm2JSBuilder::Flags builderFlags;
+  Options options("wasm2js", "Transform .wasm/.wast files to asm.js");
+  options
+      .add("--output", "-o", "Output file (stdout if not specified)",
+           Options::Arguments::One,
+           [](Options* o, const std::string& argument) {
+             o->extra["output"] = argument;
+             Colors::disable();
+           })
+      .add("--allow-asserts", "", "Allow compilation of .wast testing asserts",
+           Options::Arguments::Zero,
+           [&](Options* o, const std::string& argument) {
+             builderFlags.allowAsserts = true;
+             o->extra["asserts"] = "1";
+           })
+      .add("--pedantic", "", "Emulate WebAssembly trapping behavior",
+           Options::Arguments::Zero,
+           [&](Options* o, const std::string& argument) {
+             builderFlags.pedantic = true;
+           })
+      .add_positional("INFILE", Options::Arguments::One,
+                      [](Options *o, const std::string& argument) {
+                        o->extra["infile"] = argument;
+                      });
+  options.parse(argc, argv);
+  if (options.debug) builderFlags.debug = true;
+
+  Element* root;
+  Module wasm;
+  Ref asmjs;
+
+  try {
+    // If the input filename ends in `.wasm`, then parse it in binary form,
+    // otherwise assume it's a `*.wast` file and go from there.
+    //
+    // Note that we're not using the built-in `ModuleReader` which will also do
+    // similar logic here because when testing JS files we use the
+    // `--allow-asserts` flag which means we need to parse the extra
+    // s-expressions that come at the end of the `*.wast` file after the module
+    // is defined.
+    auto &input = options.extra["infile"];
+    std::string suffix(".wasm");
+    if (input.size() >= suffix.size() &&
+        input.compare(input.size() - suffix.size(), suffix.size(), suffix) == 0) {
+      ModuleReader reader;
+      reader.setDebug(options.debug);
+      reader.read(input, wasm, "");
+
+      if (options.debug) std::cerr << "asming..." << std::endl;
+      Wasm2JSBuilder wasm2js(builderFlags);
+      asmjs = wasm2js.processWasm(&wasm);
+
+    } else {
+      auto input(
+          read_file<std::vector<char>>(options.extra["infile"], Flags::Text, options.debug ? Flags::Debug : Flags::Release));
+      if (options.debug) std::cerr << "s-parsing..." << std::endl;
+      SExpressionParser parser(input.data());
+      root = parser.root;
+
+      if (options.debug) std::cerr << "w-parsing..." << std::endl;
+      SExpressionWasmBuilder builder(wasm, *(*root)[0]);
+
+      if (options.debug) std::cerr << "asming..." << std::endl;
+      Wasm2JSBuilder wasm2js(builderFlags);
+      asmjs = wasm2js.processWasm(&wasm);
+
+      if (options.extra["asserts"] == "1") {
+        if (options.debug) std::cerr << "asserting..." << std::endl;
+        flattenAppend(asmjs, wasm2js.processAsserts(&wasm, *root, builder));
+      }
+    }
+  } catch (ParseException& p) {
+    p.dump(std::cerr);
+    Fatal() << "error in parsing input";
+  } catch (std::bad_alloc&) {
+    Fatal() << "error in building module, std::bad_alloc (possibly invalid request for silly amounts of memory)";
+  }
+
+  if (options.debug) {
+    std::cerr << "a-printing..." << std::endl;
+    asmjs->stringify(std::cout, true);
+    std::cout << '\n';
+  }
+
+  if (options.debug) std::cerr << "j-printing..." << std::endl;
+  JSPrinter jser(true, true, asmjs);
+  jser.printAst();
+  Output output(options.extra["output"], Flags::Text, options.debug ? Flags::Debug : Flags::Release);
+  output << jser.buffer << std::endl;
+
+  if (options.debug) std::cerr << "done." << std::endl;
+}