Cycles: Solve possible issues with running out of stack memory allocator

Policy here is a bit more complicated, if tree becomes too deep we're
forced to create a leaf node and size of that leaf wouldn't be so well
predicted, which means it's quite tricky to use single stack array for
that.

Made it more official feature that StackAllocator will fall-back to
heap when running out of stack memory.

It's still much better than always using heap allocator.

1 files changed, 16 insertions, 9 deletions

diff --git a/intern/cycles/util/util_stack_allocator.h b/intern/cycles/util/util_stack_allocator.h
index 85edd8061ee..29260888eef 100644
--- a/intern/cycles/util/util_stack_allocator.h
+++ b/intern/cycles/util/util_stack_allocator.h
@@ -54,28 +54,35 @@ public:
 	T *allocate(size_t n, const void *hint = 0)
 	{
 		(void)hint;
+		if(n == 0) {
+			return NULL;
+		}
 		if(pointer_ + n >= SIZE) {
-			assert(!"Stack allocator overallocated");
-			/* NOTE: This is just a safety feature for the release builds, so
-			 * we fallback to a less efficient allocation but preventing crash
-			 * from happening.
-			 */
-			return (T*)malloc(n * sizeof(T));
+			size_t size = n * sizeof(T);
+			util_guarded_mem_alloc(size);
+#ifdef WITH_BLENDER_GUARDEDALLOC
+			return (T*)MEM_mallocN_aligned(size, 16, "Cycles Alloc");
+#else
+			return (T*)malloc(size);
+#endif
 		}
 		T *mem = &data_[pointer_];
 		pointer_ += n;
 		return mem;
 	}
 
-	void deallocate(T *p, size_t /*n*/)
+	void deallocate(T *p, size_t n)
 	{
 		if(p == NULL) {
 			return;
 		}
 		if(p < data_ || p >= data_ + SIZE) {
-			/* Again this is just a safety feature for the release builds. */
-			assert(!"Should never happen");
+			util_guarded_mem_free(n * sizeof(T));
+#ifdef WITH_BLENDER_GUARDEDALLOC
+			MEM_freeN(p);
+#else
 			free(p);
+#endif
 			return;
 		}
 		/* We don't support memory free for the stack allocator. */