add an option to not fuzz memory (#1915)

Author: kripken

src/tools/fuzzing.h

@@ -131,8 +131,14 @@ class TranslateToFuzzReader {
     allowNaNs = allowNaNs_;
   }
 
+  void setAllowMemory(bool allowMemory_) {
+    allowMemory = allowMemory_;
+  }
+
   void build() {
-    setupMemory();
+    if (allowMemory) {
+      setupMemory();
+    }
     setupTable();
     setupGlobals();
     addImportLoggingSupport();
@@ -187,6 +193,9 @@ class TranslateToFuzzReader {
   // TODO: de-NaN SIMD values
   bool allowNaNs = true;
 
+  // Whether to emit memory operations like loads and stores.
+  bool allowMemory = true;
+
   // Features allowed to be emitted
   FeatureSet features = FeatureSet::All;
 
@@ -1137,6 +1146,7 @@ class TranslateToFuzzReader {
   }
 
   Expression* makeLoad(Type type) {
+    if (!allowMemory) return makeTrivial(type);
     auto* ret = makeNonAtomicLoad(type);
     if (type != i32 && type != i64) return ret;
     if (!features.hasAtomics() || oneIn(2)) return ret;
@@ -1208,6 +1218,7 @@ class TranslateToFuzzReader {
   }
 
   Expression* makeStore(Type type) {
+    if (!allowMemory) return makeTrivial(type);
     auto* ret = makeNonAtomicStore(type);
     auto* store = ret->dynCast<Store>();
     if (!store) return ret;
@@ -1595,6 +1606,7 @@ class TranslateToFuzzReader {
 
   Expression* makeAtomic(Type type) {
     assert(features.hasAtomics());
+    if (!allowMemory) return makeTrivial(type);
     wasm.memory.shared = true;
     if (type == i32 && oneIn(2)) {
       if (ATOMIC_WAITS && oneIn(2)) {
@@ -1732,6 +1744,7 @@ class TranslateToFuzzReader {
   }
 
   Expression* makeBulkMemory(Type type) {
+    if (!allowMemory) return makeTrivial(type);
     assert(features.hasBulkMemory());
     assert(type == none);
     switch (upTo(4)) {
@@ -1744,6 +1757,7 @@ class TranslateToFuzzReader {
   }
 
   Expression* makeMemoryInit() {
+    if (!allowMemory) return makeTrivial(none);
     auto segment = uint32_t(get32());
     Expression* dest = make(i32);
     Expression* offset = make(i32);
@@ -1752,17 +1766,20 @@ class TranslateToFuzzReader {
   }
 
   Expression* makeDataDrop() {
+    if (!allowMemory) return makeTrivial(none);
     return builder.makeDataDrop(get32());
   }
 
   Expression* makeMemoryCopy() {
+    if (!allowMemory) return makeTrivial(none);
     Expression* dest = make(i32);
     Expression* source = make(i32);
     Expression* size = make(i32);
     return builder.makeMemoryCopy(dest, source, size);
   }
 
   Expression* makeMemoryFill() {
+    if (!allowMemory) return makeTrivial(none);
     Expression* dest = make(i32);
     Expression* value = make(i32);
     Expression* size = make(i32);

src/tools/wasm-opt.cpp

@@ -72,6 +72,7 @@ int main(int argc, const char* argv[]) {
   bool translateToFuzz = false;
   bool fuzzPasses = false;
   bool fuzzNaNs = true;
+  bool fuzzMemory = true;
   std::string emitJSWrapper;
   std::string emitSpecWrapper;
   std::string inputSourceMapFilename;
@@ -116,6 +117,9 @@ int main(int argc, const char* argv[]) {
       .add("--no-fuzz-nans", "", "don't emit NaNs when fuzzing, and remove them at runtime as well (helps avoid nondeterminism between VMs)",
            Options::Arguments::Zero,
            [&](Options *o, const std::string& arguments) { fuzzNaNs = false; })
+      .add("--no-fuzz-memory", "", "don't emit memory ops when fuzzing",
+           Options::Arguments::Zero,
+           [&](Options *o, const std::string& arguments) { fuzzMemory = false; })
       .add("--emit-js-wrapper", "-ejw", "Emit a JavaScript wrapper file that can run the wasm with some test values, useful for fuzzing",
            Options::Arguments::One,
            [&](Options *o, const std::string& arguments) { emitJSWrapper = arguments; })
@@ -172,6 +176,7 @@ int main(int argc, const char* argv[]) {
     }
     reader.setFeatures(options.getFeatures());
     reader.setAllowNaNs(fuzzNaNs);
+    reader.setAllowMemory(fuzzMemory);
     reader.build();
     if (options.passOptions.validate) {
       if (!WasmValidator().validate(wasm, options.getFeatures())) {