Bug 1698127 - wasm: Use range-based for loops. r=lth

clang static-analysis prefers to use range-based for loops whenever
it is possible. Some of the replacements are obvious improvements,
while others are a bit murky. Open to discussion on whether these
all make sense.

Differential Revision: https://phabricator.services.mozilla.com/D108204

js/src/wasm/WasmBaselineCompile.cpp

@@ -3356,8 +3356,7 @@ class BaseCompiler final : public BaseCompilerInterface {
   }
 
   [[nodiscard]] bool generateOutOfLineCode() {
-    for (uint32_t i = 0; i < outOfLine_.length(); i++) {
-      OutOfLineCode* ool = outOfLine_[i];
+    for (auto ool : outOfLine_) {
       ool->bind(&fr, &masm);
       ool->generate(&masm);
     }
@@ -5443,8 +5442,7 @@ class BaseCompiler final : public BaseCompilerInterface {
   // Call this between opcodes.
   void performRegisterLeakCheck() {
     BaseRegAlloc::LeakCheck check(ra);
-    for (size_t i = 0; i < stk_.length(); i++) {
-      Stk& item = stk_[i];
+    for (auto& item : stk_) {
       switch (item.kind_) {
         case Stk::RegisterI32:
           check.addKnownI32(item.i32reg());
@@ -6291,10 +6289,10 @@ class BaseCompiler final : public BaseCompilerInterface {
 #endif
     masm.bind(theTable);
 
-    for (uint32_t i = 0; i < labels.length(); i++) {
+    for (const auto& label : labels) {
       CodeLabel cl;
       masm.writeCodePointer(&cl);
-      cl.target()->bind(labels[i].offset());
+      cl.target()->bind(label.offset());
       masm.addCodeLabel(cl);
     }
   }

js/src/wasm/WasmCode.cpp

@@ -1151,10 +1151,9 @@ const wasm::WasmTryNote* CodeTier::lookupWasmTryNote(const void* pc) const {
 
   // We find the first hit (there may be multiple) to obtain the innermost
   // handler, which is why we cannot binary search here.
-  for (size_t i = 0; i < tryNotes.length(); i++) {
-    const WasmTryNote& tn = tryNotes[i];
-    if (target >= tn.begin && target < tn.end) {
-      return &tryNotes[i];
+  for (const auto& tryNote : tryNotes) {
+    if (target >= tryNote.begin && target < tryNote.end) {
+      return &tryNote;
     }
   }
 

js/src/wasm/WasmGC.h

@@ -184,9 +184,9 @@ class StackMaps {
  public:
   StackMaps() : sorted_(false) {}
   ~StackMaps() {
-    for (size_t i = 0; i < mapping_.length(); i++) {
-      mapping_[i].map->destroy();
-      mapping_[i].map = nullptr;
+    for (auto& maplet : mapping_) {
+      maplet.map->destroy();
+      maplet.map = nullptr;
     }
   }
   [[nodiscard]] bool add(uint8_t* nextInsnAddr, StackMap* map) {
@@ -197,9 +197,9 @@ class StackMaps {
     return add(maplet.nextInsnAddr, maplet.map);
   }
   void clear() {
-    for (size_t i = 0; i < mapping_.length(); i++) {
-      mapping_[i].nextInsnAddr = nullptr;
-      mapping_[i].map = nullptr;
+    for (auto& maplet : mapping_) {
+      maplet.nextInsnAddr = nullptr;
+      maplet.map = nullptr;
     }
     mapping_.clear();
   }
@@ -213,7 +213,7 @@ class StackMaps {
     return m;
   }
   void offsetBy(uintptr_t delta) {
-    for (size_t i = 0; i < mapping_.length(); i++) mapping_[i].offsetBy(delta);
+    for (auto& maplet : mapping_) maplet.offsetBy(delta);
   }
   void sort() {
     MOZ_ASSERT(!sorted_);

js/src/wasm/WasmInstance.cpp

@@ -1381,9 +1381,7 @@ bool Instance::init(JSContext* cx, const JSFunctionVector& funcImports,
     ExclusiveData<FuncTypeIdSet>::Guard lockedFuncTypeIdSet =
         funcTypeIdSet.lock();
 
-    for (uint32_t typeIndex = 0; typeIndex < metadata().types.length();
-         typeIndex++) {
-      const TypeDefWithId& typeDef = metadata().types[typeIndex];
+    for (const TypeDefWithId& typeDef : metadata().types) {
       switch (typeDef.kind()) {
         case TypeDefKind::Func: {
           const FuncType& funcType = typeDef.funcType();
@@ -2145,8 +2143,8 @@ JSString* Instance::createDisplayURL(JSContext* cx) {
     }
 
     const ModuleHash& hash = metadata().debugHash;
-    for (size_t i = 0; i < sizeof(ModuleHash); i++) {
-      char digit1 = hash[i] / 16, digit2 = hash[i] % 16;
+    for (unsigned char byte : hash) {
+      char digit1 = byte / 16, digit2 = byte % 16;
       if (!result.append(
               (char)(digit1 < 10 ? digit1 + '0' : digit1 + 'a' - 10))) {
         return nullptr;

js/src/wasm/WasmJS.cpp

@@ -3694,8 +3694,8 @@ WasmExceptionObject* WasmExceptionObject::create(JSContext* cx,
                    MemoryUse::WasmExceptionTag);
 
   wasm::ValTypeVector* newValueTypes = js_new<ValTypeVector>();
-  for (uint32_t i = 0; i < type.length(); i++) {
-    if (!newValueTypes->append(type[i])) {
+  for (auto t : type) {
+    if (!newValueTypes->append(t)) {
       return nullptr;
     }
   }

js/src/wasm/WasmOpIter.h

@@ -3146,7 +3146,7 @@ inline bool OpIter<Policy>::readVectorShuffle(Value* v1, Value* v2,
                                               V128* selectMask) {
   MOZ_ASSERT(Classify(op_) == OpKind::VectorShuffle);
 
-  for (unsigned i = 0; i < 16; i++) {
+  for (unsigned char& byte : selectMask->bytes) {
     uint8_t tmp;
     if (!readFixedU8(&tmp)) {
       return fail("unable to read shuffle index");
@@ -3154,7 +3154,7 @@ inline bool OpIter<Policy>::readVectorShuffle(Value* v1, Value* v2,
     if (tmp > 31) {
       return fail("shuffle index out of range");
     }
-    selectMask->bytes[i] = tmp;
+    byte = tmp;
   }
 
   if (!popWithType(ValType::V128, v2)) {
@@ -3174,8 +3174,8 @@ template <typename Policy>
 inline bool OpIter<Policy>::readV128Const(V128* value) {
   MOZ_ASSERT(Classify(op_) == OpKind::V128);
 
-  for (unsigned i = 0; i < 16; i++) {
-    if (!readFixedU8(&value->bytes[i])) {
+  for (unsigned char& byte : value->bytes) {
+    if (!readFixedU8(&byte)) {
       return fail("unable to read V128 constant");
     }
   }

js/src/wasm/WasmValidate.cpp

@@ -2215,8 +2215,8 @@ static bool DecodeMemoryLimits(Decoder& d, ModuleEnvironment* env) {
 
 #ifdef ENABLE_WASM_EXCEPTIONS
 static bool EventIsJSCompatible(Decoder& d, const ValTypeVector& type) {
-  for (uint32_t i = 0; i < type.length(); i++) {
-    if (type[i].isTypeIndex()) {
+  for (auto t : type) {
+    if (t.isTypeIndex()) {
       return d.fail("cannot expose indexed reference type");
     }
   }