commit a7fe7eb75957872935b934633ca3e614ed0944c5
author Dominik Laskowski <domlaskowski@google.com> Wed Feb 16 10:44:28 2022 -0800
committer Dominik Laskowski <domlaskowski@google.com> Wed Mar 23 15:44:03 2022 -0700
tree 5a7fddd078b910b646ec0f66f4840edd5c2492b6
parent af5fa6bf7519e780e017cd1af87ed0a4b3dcb5b8

FTL: Remove libutils dependency of Flags

Also, fix the __builtin type suffix in flag_string to avoid truncation
of upper bits for 64-bit flags on platforms with 32-bit unsigned long.

Bug: 185536303
Test: ftl_test
Change-Id: I1719255cc4dd60ec3203e111c37d6851471c631d

include/ftl/Flags.h

diff --git a/include/ftl/Flags.h b/include/ftl/Flags.h
index 708eaf5..db3d9ea 100644
--- a/include/ftl/Flags.h
+++ b/include/ftl/Flags.h
@@ -19,13 +19,12 @@
 #include <ftl/enum.h>
 #include <ftl/string.h>
 
+#include <bitset>
 #include <cstdint>
 #include <iterator>
 #include <string>
 #include <type_traits>
 
-#include "utils/BitSet.h"
-
 // TODO(b/185536303): Align with FTL style and namespace.
 
 namespace android {
@@ -56,21 +55,22 @@
           : mFlags(t) {}
 
     class Iterator {
-        // The type can't be larger than 64-bits otherwise it won't fit in BitSet64.
-        static_assert(sizeof(U) <= sizeof(uint64_t));
+        using Bits = std::uint64_t;
+        static_assert(sizeof(U) <= sizeof(Bits));
 
     public:
+        constexpr Iterator() = default;
         Iterator(Flags<F> flags) : mRemainingFlags(flags.mFlags) { (*this)++; }
-        Iterator() : mRemainingFlags(0), mCurrFlag(static_cast<F>(0)) {}
 
         // Pre-fix ++
         Iterator& operator++() {
-            if (mRemainingFlags.isEmpty()) {
-                mCurrFlag = static_cast<F>(0);
+            if (mRemainingFlags.none()) {
+                mCurrFlag = 0;
             } else {
-                uint64_t bit = mRemainingFlags.clearLastMarkedBit(); // counts from left
-                const U flag = 1 << (64 - bit - 1);
-                mCurrFlag = static_cast<F>(flag);
+                // TODO: Replace with std::countr_zero in C++20.
+                const Bits bit = static_cast<Bits>(__builtin_ctzll(mRemainingFlags.to_ullong()));
+                mRemainingFlags.reset(static_cast<std::size_t>(bit));
+                mCurrFlag = static_cast<U>(static_cast<Bits>(1) << bit);
             }
             return *this;
         }
@@ -88,7 +88,7 @@
 
         bool operator!=(Iterator other) const { return !(*this == other); }
 
-        F operator*() { return mCurrFlag; }
+        F operator*() const { return F{mCurrFlag}; }
 
         // iterator traits
 
@@ -107,8 +107,8 @@
         using pointer = void;
 
     private:
-        BitSet64 mRemainingFlags;
-        F mCurrFlag;
+        std::bitset<sizeof(Bits) * 8> mRemainingFlags;
+        U mCurrFlag = 0;
     };
 
     /*

include/ftl/enum.h

diff --git a/include/ftl/enum.h b/include/ftl/enum.h
index 5234c05..82af1d6 100644
--- a/include/ftl/enum.h
+++ b/include/ftl/enum.h
@@ -261,10 +261,10 @@
   const auto value = to_underlying(v);
 
   // TODO: Replace with std::popcount and std::countr_zero in C++20.
-  if (__builtin_popcountl(value) != 1) return {};
+  if (__builtin_popcountll(value) != 1) return {};
 
   constexpr auto kRange = details::EnumRange<E, details::FlagName>{};
-  return kRange.values[__builtin_ctzl(value)];
+  return kRange.values[__builtin_ctzll(value)];
 }
 
 // Returns a stringified enumerator, or its integral value if not named.