[vm/compiler] Speed up the compiler part which deals with kernel reading up in DEBUG mode

This reduces our AOT compiler's time - gen_snapshot -  by half in DEBUG mode.

Issue dart-lang/sdk#32603

Change-Id: I235afc40acba32036d4127c31c93f3b22f522314
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/103441
Commit-Queue: Martin Kustermann <[email protected]>
Reviewed-by: Alexander Aprelev <[email protected]>

Author: mkustermann

runtime/vm/kernel_binary.h

@@ -177,15 +177,7 @@ class Reader : public ValueObject {
         offset_(0) {
     // The reader expects that the actual data is external, though allows
     // having a view into this external typed data.
-#if defined(DEBUG)
-    if (typed_data_->IsTypedDataView()) {
-      const auto& backing_store =
-          TypedDataBase::Handle(TypedDataView::Cast(*typed_data_).typed_data());
-      ASSERT(backing_store.IsExternalTypedData());
-    } else {
-      ASSERT(typed_data_->IsExternalTypedData());
-    }
-#endif
+    DEBUG_ASSERT(typed_data_->IsBackedByExternalTypedData());
   }
 
   uint32_t ReadFromIndex(intptr_t end_offset,
@@ -199,10 +191,15 @@ class Reader : public ValueObject {
     return result;
   }
 
-  uint32_t ReadUInt32At(intptr_t offset) const {
-    ASSERT((size_ >= 4) && (offset >= 0) && (offset <= size_ - 4));
-    uint32_t value;
-    value = typed_data_->GetUint32(offset);
+  DART_FORCE_INLINE uint32_t ReadUInt32At(intptr_t offset) const {
+    ASSERT(size_ >= 4 && offset >= 0 && (offset <= size_ - 4));
+    // We validated in the [Reader] constructor that we have either an
+    // ExternalTypedData or a view on top of an ExternalTypedData.
+    //
+    // This means the data pointer will not change and we can use
+    // [DataAddrUnsafe].
+    const uint32_t value =
+        *static_cast<uint32_t*>(typed_data_->DataAddrUnsafe(offset));
     return Utils::BigEndianToHost32(value);
   }
 
@@ -358,9 +355,13 @@ class Reader : public ValueObject {
   }
 
  private:
-  const uint8_t* buffer() const {
-    NoSafepointScope no_safepoint(thread_);
-    return reinterpret_cast<uint8_t*>(typed_data_->DataAddr(0));
+  DART_FORCE_INLINE const uint8_t* buffer() const {
+    // We validated in the [Reader] constructor that we have either an
+    // ExternalTypedData or a view on top of an ExternalTypedData.
+    //
+    // This means the data pointer will not change and we can use
+    // [DataAddrUnsafe].
+    return reinterpret_cast<uint8_t*>(typed_data_->DataAddrUnsafe(0));
   }
 
   Thread* thread_;

runtime/vm/object.cc

@@ -21169,6 +21169,19 @@ RawTypedDataView* TypedDataBase::CreateUint8View(intptr_t offset_in_bytes,
                             offset_in_bytes, length_in_bytes, space);
 }
 
+#if defined(DEBUG)
+bool TypedDataBase::IsBackedByExternalTypedData() const {
+  if (IsExternalTypedData()) {
+    return true;
+  }
+  if (IsTypedDataView()) {
+    const auto& view = TypedDataView::Cast(*this);
+    return TypedDataBase::Handle(view.typed_data()).IsExternalTypedData();
+  }
+  return false;
+}
+#endif
+
 const char* TypedDataView::ToCString() const {
   auto zone = Thread::Current()->zone();
   return OS::SCreate(zone, "TypedDataView(cid: %" Pd ")", GetClassId());

runtime/vm/object.h

@@ -8410,6 +8410,13 @@ class TypedDataBase : public Instance {
 #if defined(DEBUG)
     ValidateInvariant();
 #endif
+    return DataAddrUnsafe(byte_offset);
+  }
+
+  // To speed up debug mode (e.g. for kernel reading - which uses typed data
+  // for kernel buffers) we expose the data pointer without asserts for bounds
+  // checks and invariants.
+  DART_FORCE_INLINE void* DataAddrUnsafe(intptr_t byte_offset) const {
     return reinterpret_cast<void*>(raw_ptr()->data_ + byte_offset);
   }
 
@@ -8471,6 +8478,10 @@ class TypedDataBase : public Instance {
 
 #undef TYPED_GETTER_SETTER
 
+#if defined(DEBUG)
+  bool IsBackedByExternalTypedData() const;
+#endif
+
  protected:
   void SetLength(intptr_t value) const {
     ASSERT(value <= Smi::kMaxValue);