Bug 1329019 - Baldr: Only compute bytecode hash in debug mode (r=yury)

MozReview-Commit-ID: GKxQzBznHJh

js/src/jit-test/tests/debug/wasm-12.js

@@ -5,6 +5,7 @@ if (!wasmDebuggingIsSupported())
   quit();
 
 var g = newGlobal();
+var dbg = new Debugger(g);
 g.eval(`
 function initWasm(s) { return new WebAssembly.Instance(new WebAssembly.Module(wasmTextToBinary(s))); }
 o1 = initWasm('(module (func) (export "" 0))');
@@ -19,7 +20,6 @@ function isValidWasmURL(url) {
    return /^wasm:(?:[^:]*:)*?[0-9a-f]{16}$/.test(url);
 }
 
-var dbg = new Debugger(g);
 var foundScripts = dbg.findScripts().filter(isWasm);
 assertEq(foundScripts.length, 2);
 assertEq(isValidWasmURL(foundScripts[0].source.url), true);

js/src/wasm/WasmCode.cpp

@@ -559,8 +559,7 @@ Metadata::serializedSize() const
            SerializedPodVectorSize(tables) +
            SerializedPodVectorSize(funcNames) +
            SerializedPodVectorSize(customSections) +
-           filename.serializedSize() +
-           sizeof(hash);
+           filename.serializedSize();
 }
 
 size_t
@@ -592,7 +591,6 @@ Metadata::serialize(uint8_t* cursor) const
     cursor = SerializePodVector(cursor, funcNames);
     cursor = SerializePodVector(cursor, customSections);
     cursor = filename.serialize(cursor);
-    cursor = WriteBytes(cursor, hash, sizeof(hash));
     return cursor;
 }
 
@@ -606,8 +604,7 @@ Metadata::deserialize(const uint8_t* cursor)
     (cursor = DeserializePodVector(cursor, &tables)) &&
     (cursor = DeserializePodVector(cursor, &funcNames)) &&
     (cursor = DeserializePodVector(cursor, &customSections)) &&
-    (cursor = filename.deserialize(cursor)) &&
-    (cursor = ReadBytes(cursor, hash, sizeof(hash)));
+    (cursor = filename.deserialize(cursor));
     debugEnabled = false;
     debugFuncArgTypes.clear();
     debugFuncReturnTypes.clear();

js/src/wasm/WasmCode.h

@@ -379,7 +379,8 @@ class Metadata : public ShareableBase<Metadata>, public MetadataCacheablePod
     explicit Metadata(UniqueMetadataTier tier, ModuleKind kind = ModuleKind::Wasm)
       : MetadataCacheablePod(kind),
         metadata1_(Move(tier)),
-        debugEnabled(false)
+        debugEnabled(false),
+        debugHash()
     {}
     virtual ~Metadata() {}
 
@@ -406,12 +407,12 @@ class Metadata : public ShareableBase<Metadata>, public MetadataCacheablePod
     NameInBytecodeVector  funcNames;
     CustomSectionVector   customSections;
     CacheableChars        filename;
-    ModuleHash            hash;
 
     // Debug-enabled code is not serialized.
     bool                  debugEnabled;
     FuncArgTypesVector    debugFuncArgTypes;
     FuncReturnTypesVector debugFuncReturnTypes;
+    ModuleHash            debugHash;
 
     bool usesMemory() const { return UsesMemory(memoryUsage); }
     bool hasSharedMemory() const { return memoryUsage == MemoryUsage::Shared; }

js/src/wasm/WasmDebug.cpp

@@ -612,9 +612,11 @@ DebugState::debugDisplayURL(JSContext* cx) const
     // - "wasm:" as protocol;
     // - URI encoded filename from metadata (if can be encoded), plus ":";
     // - 64-bit hash of the module bytes (as hex dump).
+
     js::StringBuffer result(cx);
     if (!result.append("wasm:"))
         return nullptr;
+
     if (const char* filename = metadata().filename.get()) {
         js::StringBuffer filenamePrefix(cx);
         // EncodeURI returns false due to invalid chars or OOM -- fail only
@@ -623,12 +625,16 @@ DebugState::debugDisplayURL(JSContext* cx) const
             if (!cx->isExceptionPending())
                 return nullptr;
             cx->clearPendingException(); // ignore invalid URI
-        } else if (!result.append(filenamePrefix.finishString()) || !result.append(":")) {
+        } else if (!result.append(filenamePrefix.finishString())) {
             return nullptr;
         }
     }
 
-    const ModuleHash& hash = metadata().hash;
+    if (metadata().debugEnabled) {
+        if (!result.append(":"))
+            return nullptr;
+
+        const ModuleHash& hash = metadata().debugHash;
         for (size_t i = 0; i < sizeof(ModuleHash); i++) {
             char digit1 = hash[i] / 16, digit2 = hash[i] % 16;
             if (!result.append((char)(digit1 < 10 ? digit1 + '0' : digit1 + 'a' - 10)))
@@ -636,6 +642,8 @@ DebugState::debugDisplayURL(JSContext* cx) const
             if (!result.append((char)(digit2 < 10 ? digit2 + '0' : digit2 + 'a' - 10)))
                 return nullptr;
         }
+    }
+
     return result.finishString();
 }
 

js/src/wasm/WasmGenerator.cpp

@@ -1100,11 +1100,14 @@ static_assert(sizeof(ModuleHash) <= sizeof(mozilla::SHA1Sum::Hash),
 void
 ModuleGenerator::generateBytecodeHash(const ShareableBytes& bytecode)
 {
+    if (!env_->debugEnabled())
+        return;
+
     mozilla::SHA1Sum::Hash hash;
     mozilla::SHA1Sum sha1Sum;
     sha1Sum.update(bytecode.begin(), bytecode.length());
     sha1Sum.finish(hash);
-    memcpy(metadata_->hash, hash, sizeof(ModuleHash));
+    memcpy(metadata_->debugHash, hash, sizeof(ModuleHash));
 }
 
 bool