Add feature options to emscripten metadata (#1982)

Emscripten runs wasm-emscripten-finalize before running wasm-opt, so the target features section is stripped out before optimizations are run. One option would have been to add another wasm-opt invocation at the very end to strip the target features section, but dumping the features as metadata avoids the extra tool invocation. In the long run, it would be nice to have only as single binaryen invocation to do all the work that needs doing.

src/tools/tool-options.h

@@ -60,19 +60,12 @@ struct ToolOptions : public Options {
                disabledFeatures.makeMVP();
              });
     (*this)
-        .addFeature("sign-ext", "sign extension operations",
-                    FeatureSet::SignExt)
-        .addFeature("threads", "atomic operations",
-                    FeatureSet::Atomics)
-        .addFeature("mutable-globals", "mutable globals",
-                    FeatureSet::MutableGlobals)
-        .addFeature("nontrapping-float-to-int",
-                    "nontrapping float-to-int operations",
-                    FeatureSet::TruncSat)
-        .addFeature("simd", "SIMD operations and types",
-                    FeatureSet::SIMD)
-        .addFeature("bulk-memory", "bulk memory operations",
-                    FeatureSet::BulkMemory)
+        .addFeature(FeatureSet::SignExt, "sign extension operations")
+        .addFeature(FeatureSet::Atomics, "atomic operations")
+        .addFeature(FeatureSet::MutableGlobals, "mutable globals")
+        .addFeature(FeatureSet::TruncSat, "nontrapping float-to-int operations")
+        .addFeature(FeatureSet::SIMD, "SIMD operations and types")
+        .addFeature(FeatureSet::BulkMemory, "bulk memory operations")
         .add("--no-validation", "-n",
              "Disables validation, assumes inputs are correct",
              Options::Arguments::Zero,
@@ -81,11 +74,11 @@ struct ToolOptions : public Options {
              });
   }
 
-  ToolOptions& addFeature(const std::string& name,
-                          const std::string& description,
-                          FeatureSet::Feature feature) {
+  ToolOptions& addFeature(FeatureSet::Feature feature,
+                          const std::string& description) {
+
     (*this)
-        .add(std::string("--enable-") + name, "",
+        .add(std::string("--enable-") + FeatureSet::toString(feature), "",
              std::string("Enable ") + description, Arguments::Zero,
              [=](Options*, const std::string&) {
                hasFeatureOptions = true;
@@ -94,7 +87,7 @@ struct ToolOptions : public Options {
                disabledFeatures.set(feature, false);
              })
 
-        .add(std::string("--disable-") + name, "",
+        .add(std::string("--disable-") + FeatureSet::toString(feature), "",
              std::string("Disable ") + description, Arguments::Zero,
              [=](Options*, const std::string&) {
                hasFeatureOptions = true;

src/tools/wasm-emscripten-finalize.cpp

@@ -23,8 +23,8 @@
 
 #include "ir/trapping.h"
 #include "support/colors.h"
-#include "support/command-line.h"
 #include "support/file.h"
+#include "tool-options.h"
 #include "wasm-binary.h"
 #include "wasm-emscripten.h"
 #include "wasm-io.h"
@@ -50,8 +50,8 @@ int main(int argc, const char *argv[]) {
   bool legalizeJavaScriptFFI = true;
   uint64_t globalBase = INVALID_BASE;
   uint64_t initialStackPointer = INVALID_BASE;
-  Options options("wasm-emscripten-finalize",
-                  "Performs Emscripten-specific transforms on .wasm files");
+  ToolOptions options("wasm-emscripten-finalize",
+                      "Performs Emscripten-specific transforms on .wasm files");
   options
       .add("--output", "-o", "Output file",
            Options::Arguments::One,
@@ -130,6 +130,8 @@ int main(int argc, const char *argv[]) {
     Fatal() << "error in parsing wasm source map";
   }
 
+  options.calculateFeatures(wasm);
+
   if (options.debug) {
     std::cerr << "Module before:\n";
     WasmPrinter::printModule(&wasm, std::cerr);
@@ -204,12 +206,11 @@ int main(int argc, const char *argv[]) {
       legalizeJavaScriptFFI ? ABI::LegalizationLevel::Full
                             : ABI::LegalizationLevel::Minimal
     ));
-    passRunner.add("strip-target-features");
     passRunner.run();
   }
 
   // Substantial changes to the wasm are done, enough to create the metadata.
-  std::string metadata = generator.generateEmscriptenMetadata(dataSize, initializerFunctions);
+  std::string metadata = generator.generateEmscriptenMetadata(dataSize, initializerFunctions, options.passOptions.features);
 
   // Finally, separate out data segments if relevant (they may have been needed
   // for metadata).
@@ -226,6 +227,13 @@ int main(int argc, const char *argv[]) {
     WasmPrinter::printModule(&wasm, std::cerr);
   }
 
+  // Strip target features section (its information is in the metadata)
+  {
+    PassRunner passRunner(&wasm);
+    passRunner.add("strip-target-features");
+    passRunner.run();
+  }
+
   auto outputBinaryFlag = emitBinary ? Flags::Binary : Flags::Text;
   Output output(outfile, outputBinaryFlag, Flags::Release);
   ModuleWriter writer;

src/wasm-emscripten.h

@@ -49,7 +49,8 @@ class EmscriptenGlueGenerator {
   void replaceStackPointerGlobal();
 
   std::string generateEmscriptenMetadata(
-    Address staticBump, std::vector<Name> const& initializerFunctions);
+    Address staticBump, std::vector<Name> const& initializerFunctions,
+    FeatureSet features);
 
   void fixInvokeFunctionNames();
 

src/wasm-features.h

@@ -18,6 +18,9 @@
 #define wasm_features_h
 
 #include <stdint.h>
+#include <string>
+
+#include "compiler-support.h"
 
 struct FeatureSet {
   enum Feature : uint32_t {
@@ -31,6 +34,18 @@ struct FeatureSet {
     All = Atomics | MutableGlobals | TruncSat | SIMD | BulkMemory | SignExt
   };
 
+  static std::string toString(Feature f) {
+    switch (f) {
+      case Atomics: return "threads";
+      case MutableGlobals: return "mutable-globals";
+      case TruncSat: return "nontrapping-float-to-int";
+      case SIMD: return "simd";
+      case BulkMemory: return "bulk-memory";
+      case SignExt: return "sign-ext";
+      default: WASM_UNREACHABLE();
+    }
+  }
+
   FeatureSet() : features(MVP) {}
   FeatureSet(uint32_t features) : features(features) {}
 
@@ -59,6 +74,16 @@ struct FeatureSet {
     features = features & ~other.features & All;
   }
 
+  template<typename F>
+  void iterFeatures(F f) {
+    if (hasAtomics()) f(Atomics);
+    if (hasMutableGlobals()) f(MutableGlobals);
+    if (hasTruncSat()) f(TruncSat);
+    if (hasSIMD()) f(SIMD);
+    if (hasBulkMemory()) f(BulkMemory);
+    if (hasSignExt()) f(SignExt);
+  }
+
   bool operator<=(const FeatureSet& other) {
     return !(features & ~other.features);
   }

src/wasm/wasm-emscripten.cpp

@@ -789,7 +789,8 @@ void printSet(std::ostream& o, C& c) {
 }
 
 std::string EmscriptenGlueGenerator::generateEmscriptenMetadata(
-    Address staticBump, std::vector<Name> const& initializerFunctions) {
+    Address staticBump, std::vector<Name> const& initializerFunctions,
+    FeatureSet features) {
   bool commaFirst;
   auto nextElement = [&commaFirst]() {
     if (commaFirst) {
@@ -926,6 +927,15 @@ std::string EmscriptenGlueGenerator::generateEmscriptenMetadata(
     }
   });
   meta << "\n  ]\n";
+
+  meta << "  \"features\": [";
+  commaFirst = true;
+  meta << nextElement() << "\"--mvp-features\"";
+  features.iterFeatures([&](FeatureSet::Feature f) {
+    meta << nextElement() << "\"--enable-" << FeatureSet::toString(f) << '"';
+  });
+  meta << "\n  ]\n";
+
   meta << "}\n";
 
   return meta.str();

test/lld/duplicate_imports.wast.out

@@ -137,6 +137,15 @@
   "invokeFuncs": [
     "invoke_ffd"
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/em_asm.wast.mem.out

@@ -261,6 +261,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/em_asm.wast.out

@@ -262,6 +262,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/em_asm_O0.wast.out

@@ -122,6 +122,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/em_asm_table.wast.out

@@ -92,6 +92,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/em_js_O0.wast.out

@@ -72,6 +72,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/hello_world.wast.mem.out

@@ -97,6 +97,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/hello_world.wast.out

@@ -98,6 +98,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/init.wast.out

@@ -109,6 +109,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/recursive.wast.out

@@ -155,6 +155,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/reserved_func_ptr.wast.out

@@ -192,6 +192,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)

test/lld/shared.wast.out

@@ -72,6 +72,15 @@
   },
   "invokeFuncs": [
   ]
+  "features": [
+    "--mvp-features",
+    "--enable-threads",
+    "--enable-mutable-globals",
+    "--enable-nontrapping-float-to-int",
+    "--enable-simd",
+    "--enable-bulk-memory",
+    "--enable-sign-ext"
+  ]
 }
 -- END METADATA --
 ;)