Move AlignedSysAllocator computation of max

Summary: [Folly] Move `AlignedSysAllocator` computation of max value over input alignment values from two places to a single place.

Differential Revision: D19229096

fbshipit-source-id: 4e95c7b7e0afe99c37116150184eb180683c7d13

folly/Memory.h

@@ -434,8 +434,8 @@ class DefaultAlign {
     assert(!(align_ < sizeof(void*)) && bool("bad align: too small"));
     assert(!(align_ & (align_ - 1)) && bool("bad align: not power-of-two"));
   }
-  std::size_t operator()(std::size_t align) const noexcept {
-    return align_ < align ? align : align_;
+  std::size_t operator()() const noexcept {
+    return align_;
   }
 
   friend bool operator==(Self const& a, Self const& b) noexcept {
@@ -454,8 +454,8 @@ class FixedAlign {
   using Self = FixedAlign<Align>;
 
  public:
-  constexpr std::size_t operator()(std::size_t align) const noexcept {
-    return Align < align ? align : Align;
+  constexpr std::size_t operator()() const noexcept {
+    return Align;
   }
 
   friend bool operator==(Self const&, Self const&) noexcept {
@@ -496,7 +496,7 @@ class AlignedSysAllocator : private Align {
 
  public:
   static_assert(std::is_nothrow_copy_constructible<Align>::value, "");
-  static_assert(is_nothrow_invocable_r_v<std::size_t, Align, std::size_t>, "");
+  static_assert(is_nothrow_invocable_r_v<std::size_t, Align>, "");
 
   using value_type = T;
 
@@ -521,7 +521,7 @@ class AlignedSysAllocator : private Align {
 
   T* allocate(size_t count) {
     using lifted = typename detail::lift_void_to_char<T>::type;
-    auto const a = align()(alignof(lifted));
+    auto const a = align()() < alignof(lifted) ? alignof(lifted) : align()();
     auto const p = aligned_malloc(sizeof(lifted) * count, a);
     if (!p) {
       if (FOLLY_UNLIKELY(errno != ENOMEM)) {