Improve Debug test speed.

Removed some very expensive debug checks off the fast path
of deallocation.

src/ds/address.h

@@ -61,7 +61,7 @@ namespace snmalloc
    * power of two.
    */
   template<size_t alignment, typename T = void>
-  inline T* pointer_align_down(void* p)
+  SNMALLOC_FAST_PATH T* pointer_align_down(void* p)
   {
     static_assert(alignment > 0);
     static_assert(bits::next_pow2_const(alignment) == alignment);

src/ds/bits.h

@@ -54,7 +54,7 @@ namespace snmalloc
 
     static constexpr size_t ADDRESS_BITS = is64() ? 48 : 32;
 
-    inline size_t clz(size_t x)
+    SNMALLOC_FAST_PATH size_t clz(size_t x)
     {
 #if defined(_MSC_VER)
 #  ifdef USE_LZCNT
@@ -193,7 +193,7 @@ namespace snmalloc
 #endif
     }
 
-    inline size_t next_pow2(size_t x)
+    SNMALLOC_FAST_PATH size_t next_pow2(size_t x)
     {
       // Correct for numbers [0..MAX_SIZE >> 1).
       // Returns 1 for x > (MAX_SIZE >> 1).
@@ -223,7 +223,7 @@ namespace snmalloc
       return BITS - clz_const(x - 1);
     }
 
-    static inline size_t align_down(size_t value, size_t alignment)
+    static SNMALLOC_FAST_PATH size_t align_down(size_t value, size_t alignment)
     {
       assert(next_pow2(alignment) == alignment);
 

src/mem/slab.h

@@ -45,6 +45,7 @@ namespace snmalloc
       assert(rsize == sizeclass_to_size(meta.sizeclass));
       assert(sl.get_head() == (SlabLink*)pointer_offset(this, meta.link));
       assert(!meta.is_full());
+      meta.debug_slab_invariant(this);
 
       void* p = nullptr;
       bool p_has_value = false;
@@ -156,7 +157,6 @@ namespace snmalloc
       if (meta.is_unused())
         error("Detected potential double free.");
 #endif
-      meta.debug_slab_invariant(this);
 
       if (unlikely(meta.return_object()))
         return false;
@@ -170,7 +170,7 @@ namespace snmalloc
 
       // Set the next pointer to the previous head.
       Metaslab::store_next(p, head);
-      meta.debug_slab_invariant(this);
+
       return true;
     }
 
@@ -182,6 +182,7 @@ namespace snmalloc
     dealloc_slow(SlabList* sl, Superslab* super, void* p)
     {
       Metaslab& meta = super->get_meta(this);
+      meta.debug_slab_invariant(this);
 
       if (meta.is_full())
       {