diff --git a/AK/Bitmap.h b/AK/Bitmap.h
index 493abe7d5a..aaaa46e6bc 100644
--- a/AK/Bitmap.h
+++ b/AK/Bitmap.h
@@ -112,7 +112,7 @@ public:
         fill(default_value);
 
         if (previous_data != nullptr) {
-            memcpy(m_data, previous_data, previous_size_bytes);
+            __builtin_memcpy(m_data, previous_data, previous_size_bytes);
 
             if ((previous_size % 8) != 0) {
                 if (default_value)
@@ -127,7 +127,7 @@ public:
 
     void fill(bool value)
     {
-        memset(m_data, value ? 0xff : 0x00, size_in_bytes());
+        __builtin_memset(m_data, value ? 0xff : 0x00, size_in_bytes());
     }
 
     Optional<size_t> find_first_set() const
diff --git a/AK/ByteBuffer.h b/AK/ByteBuffer.h
index 23684f9820..179cba936c 100644
--- a/AK/ByteBuffer.h
+++ b/AK/ByteBuffer.h
@@ -213,7 +213,7 @@ public:
     {
         int old_size = size();
         grow(size() + data_size);
-        memcpy(this->data() + old_size, data, data_size);
+        __builtin_memcpy(this->data() + old_size, data, data_size);
     }
 
 private:
@@ -237,7 +237,7 @@ inline ByteBufferImpl::ByteBufferImpl(const void* data, size_t size, Constructio
 {
     ASSERT(mode == Copy);
     m_data = static_cast<u8*>(kmalloc(size));
-    memcpy(m_data, data, size);
+    __builtin_memcpy(m_data, data, size);
     m_owned = true;
 }
 
@@ -257,7 +257,7 @@ inline void ByteBufferImpl::grow(size_t size)
     ASSERT(size > m_size);
     ASSERT(m_owned);
     u8* new_data = static_cast<u8*>(kmalloc(size));
-    memcpy(new_data, m_data, m_size);
+    __builtin_memcpy(new_data, m_data, m_size);
     u8* old_data = m_data;
     m_data = new_data;
     m_size = size;
@@ -272,7 +272,7 @@ inline NonnullRefPtr<ByteBufferImpl> ByteBufferImpl::create_uninitialized(size_t
 inline NonnullRefPtr<ByteBufferImpl> ByteBufferImpl::create_zeroed(size_t size)
 {
     auto buffer = ::adopt(*new ByteBufferImpl(size));
-    memset(buffer->data(), 0, size);
+    __builtin_memset(buffer->data(), 0, size);
     return buffer;
 }
 
diff --git a/AK/Optional.h b/AK/Optional.h
index c135440013..7686bfdd5d 100644
--- a/AK/Optional.h
+++ b/AK/Optional.h
@@ -157,7 +157,7 @@ private:
         ASSERT(m_has_value);
         return *reinterpret_cast<const T*>(&m_storage);
     }
-    u8 m_storage[sizeof(T)] { 0 };
+    unsigned char m_storage[sizeof(T)] { 0 };
     bool m_has_value { false };
 };
 
diff --git a/AK/String.h b/AK/String.h
index d1851fabf0..0158adb223 100644
--- a/AK/String.h
+++ b/AK/String.h
@@ -177,7 +177,7 @@ public:
             return !cstring;
         if (!cstring)
             return false;
-        return !strcmp(characters(), cstring);
+        return !__builtin_strcmp(characters(), cstring);
     }
 
     bool operator!=(const char* cstring) const
@@ -273,7 +273,7 @@ inline bool operator<(const char* characters, const String& string)
     if (string.is_null())
         return false;
 
-    return strcmp(characters, string.characters()) < 0;
+    return __builtin_strcmp(characters, string.characters()) < 0;
 }
 
 inline bool operator>=(const char* characters, const String& string)
@@ -289,7 +289,7 @@ inline bool operator>(const char* characters, const String& string)
     if (string.is_null())
         return false;
 
-    return strcmp(characters, string.characters()) > 0;
+    return __builtin_strcmp(characters, string.characters()) > 0;
 }
 
 inline bool operator<=(const char* characters, const String& string)
diff --git a/AK/Vector.h b/AK/Vector.h
index 8512d3014a..735d45e157 100644
--- a/AK/Vector.h
+++ b/AK/Vector.h
@@ -96,7 +96,7 @@ public:
         if (!count)
             return;
         if constexpr (Traits<T>::is_trivial()) {
-            memmove(destination, source, count * sizeof(T));
+            __builtin_memmove(destination, source, count * sizeof(T));
             return;
         }
         for (size_t i = 0; i < count; ++i)
@@ -108,7 +108,7 @@ public:
         if (!count)
             return;
         if constexpr (Traits<T>::is_trivial()) {
-            memmove(destination, source, count * sizeof(T));
+            __builtin_memmove(destination, source, count * sizeof(T));
             return;
         }
         for (size_t i = 0; i < count; ++i)
@@ -121,7 +121,7 @@ public:
             return true;
 
         if constexpr (Traits<T>::is_trivial())
-            return !memcmp(a, b, count * sizeof(T));
+            return !__builtin_memcmp(a, b, count * sizeof(T));
 
         for (size_t i = 0; i < count; ++i) {
             if (a[i] != b[i])
@@ -641,7 +641,7 @@ private:
     size_t m_size { 0 };
     size_t m_capacity { 0 };
 
-    alignas(T) u8 m_inline_buffer_storage[sizeof(T) * inline_capacity];
+    alignas(T) unsigned char m_inline_buffer_storage[sizeof(T) * inline_capacity];
     T* m_outline_buffer { nullptr };
 };