Attempt to make CI faster.

- Don't run an expensive functionality test in debug builds.
- Don't run the different cache configurations (they're probably going
  away soon because they help only in synthetic benchmarks).

src/test/func/release-rounding/rounding.cc

@@ -0,0 +1,33 @@
+#include <snmalloc.h>
+
+using namespace snmalloc;
+
+// Check for all sizeclass that we correctly round every offset within
+// a superslab to the correct value, by comparing with the standard
+// unoptimised version using division.
+// Also check we correctly determine multiples using optimized check.
+
+int main(int argc, char** argv)
+{
+  UNUSED(argc);
+  UNUSED(argv);
+
+  for (size_t size_class = 0; size_class < NUM_SIZECLASSES; size_class++)
+  {
+    size_t rsize = sizeclass_to_size((uint8_t)size_class);
+    for (size_t offset = 0; offset < SUPERSLAB_SIZE; offset++)
+    {
+      size_t rounded = (offset / rsize) * rsize;
+      bool mod_0 = (offset % rsize) == 0;
+
+      size_t opt_rounded = round_by_sizeclass(rsize, offset);
+      if (rounded != opt_rounded)
+        abort();
+
+      bool opt_mod_0 = is_multiple_of_sizeclass(rsize, offset);
+      if (opt_mod_0 != mod_0)
+        abort();
+    }
+  }
+  return 0;
+}