Refactor/consolidate legacy Bloom implementation details (#5784)

Summary:
Refactoring to consolidate implementation details of legacy
Bloom filters. This helps to organize and document some related,
obscure code.

Also added make/cpp var TEST_CACHE_LINE_SIZE so that it's easy to
compile and run unit tests for non-native cache line size. (Fixed a
related test failure in db_properties_test.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5784

Test Plan:
make check, including Recently added Bloom schema unit tests
(in ./plain_table_db_test && ./bloom_test), and including with
TEST_CACHE_LINE_SIZE=128U and TEST_CACHE_LINE_SIZE=256U. Tested the
schema tests with temporary fault injection into new implementations.

Some performance testing with modified unit tests suggest a small to moderate
improvement in speed.

Differential Revision: D17381384

Pulled By: pdillinger

fbshipit-source-id: ee42586da996798910fc45ac0b6289147f16d8df

1 files changed, 28 insertions, 0 deletions

diff --git a/third-party/folly/folly/ConstexprMath.h b/third-party/folly/folly/ConstexprMath.h
index b125c5f42..f09167e0d 100644
--- a/third-party/folly/folly/ConstexprMath.h
+++ b/third-party/folly/folly/ConstexprMath.h
@@ -14,4 +14,32 @@ template <typename T, typename... Ts>
 constexpr T constexpr_max(T a, T b, Ts... ts) {
   return b < a ? constexpr_max(a, ts...) : constexpr_max(b, ts...);
 }
+
+namespace detail {
+template <typename T>
+constexpr T constexpr_log2_(T a, T e) {
+  return e == T(1) ? a : constexpr_log2_(a + T(1), e / T(2));
+}
+
+template <typename T>
+constexpr T constexpr_log2_ceil_(T l2, T t) {
+  return l2 + T(T(1) << l2 < t ? 1 : 0);
+}
+
+template <typename T>
+constexpr T constexpr_square_(T t) {
+  return t * t;
+}
+}  // namespace detail
+
+template <typename T>
+constexpr T constexpr_log2(T t) {
+  return detail::constexpr_log2_(T(0), t);
+}
+
+template <typename T>
+constexpr T constexpr_log2_ceil(T t) {
+  return detail::constexpr_log2_ceil_(constexpr_log2(t), t);
+}
+
 } // namespace folly