Fixes to ctz on Windows Clang.

src/test/func/bits/bits.cc

@@ -0,0 +1,43 @@
+/**
+ * Unit tests for operations in bits.h
+ */
+
+#include <iostream>
+#include <test/setup.h>
+#include <ds/bits.h>
+
+void
+test_ctz()
+{
+  for (size_t i = 0; i < sizeof(size_t) * 8; i++)
+    if (snmalloc::bits::ctz(snmalloc::bits::one_at_bit(i)) != i)
+    {
+      std::cout << "Failed with ctz(one_at_bit(i)) != i for i=" << i << std::endl;
+      abort();
+    }
+}
+
+
+void
+test_clz()
+{
+  const size_t PTRSIZE_LOG = sizeof(size_t) * 8;
+
+  for (size_t i = 0; i < sizeof(size_t) * 8; i++)
+    if (snmalloc::bits::clz(snmalloc::bits::one_at_bit(i)) != (PTRSIZE_LOG - i - 1))
+    {
+      std::cout << "Failed with clz(one_at_bit(i)) != (PTRSIZE_LOG - i - 1) for i=" << i << std::endl;
+      abort();
+    }
+}
+
+int main(int argc, char** argv)
+{
+  UNUSED(argc);
+  UNUSED(argv);
+
+  setup();
+
+  test_clz();
+  test_ctz();
+}