Introduce `Group::MaskNonFull` without usage.

It can be used instead of `MaskEmptyOrDeleted` in case of inserting to empty table.
`MaskNonFull` requires less operations, in particular it eliminates `_mm_set1_epi8` and `_mm_cmpgt_epi8` operations.

PiperOrigin-RevId: 607587394
Change-Id: Ia48f922d1ca6de38cc91e7ab0d608c45f8f2c446

3 files changed, 68 insertions, 0 deletions

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index d6950e61..cef042e7 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -657,6 +657,14 @@ struct GroupSse2Impl {
         static_cast<uint16_t>(_mm_movemask_epi8(ctrl) ^ 0xffff));
   }
 
+  // Returns a bitmask representing the positions of non full slots.
+  // Note: this includes: kEmpty, kDeleted, kSentinel.
+  // It is useful in contexts when kSentinel is not present.
+  auto MaskNonFull() const {
+    return BitMask<uint16_t, kWidth>(
+        static_cast<uint16_t>(_mm_movemask_epi8(ctrl)));
+  }
+
   // Returns a bitmask representing the positions of empty or deleted slots.
   NonIterableBitMask<uint16_t, kWidth> MaskEmptyOrDeleted() const {
     auto special = _mm_set1_epi8(static_cast<char>(ctrl_t::kSentinel));
@@ -725,6 +733,18 @@ struct GroupAArch64Impl {
                    /*NullifyBitsOnIteration=*/true>(mask);
   }
 
+  // Returns a bitmask representing the positions of non full slots.
+  // Note: this includes: kEmpty, kDeleted, kSentinel.
+  // It is useful in contexts when kSentinel is not present.
+  auto MaskNonFull() const {
+    uint64_t mask = vget_lane_u64(
+        vreinterpret_u64_u8(vclt_s8(vreinterpret_s8_u8(ctrl),
+                                    vdup_n_s8(static_cast<int8_t>(0)))),
+        0);
+    return BitMask<uint64_t, kWidth, /*Shift=*/3,
+                   /*NullifyBitsOnIteration=*/true>(mask);
+  }
+
   NonIterableBitMask<uint64_t, kWidth, 3> MaskEmptyOrDeleted() const {
     uint64_t mask =
         vget_lane_u64(vreinterpret_u64_u8(vcgt_s8(
@@ -797,6 +817,13 @@ struct GroupPortableImpl {
     return BitMask<uint64_t, kWidth, 3>((ctrl ^ kMsbs8Bytes) & kMsbs8Bytes);
   }
 
+  // Returns a bitmask representing the positions of non full slots.
+  // Note: this includes: kEmpty, kDeleted, kSentinel.
+  // It is useful in contexts when kSentinel is not present.
+  auto MaskNonFull() const {
+    return BitMask<uint64_t, kWidth, 3>(ctrl  & kMsbs8Bytes);
+  }
+
   NonIterableBitMask<uint64_t, kWidth, 3> MaskEmptyOrDeleted() const {
     return NonIterableBitMask<uint64_t, kWidth, 3>((ctrl & ~(ctrl << 7)) &
                                                    kMsbs8Bytes);
diff --git a/absl/container/internal/raw_hash_set_benchmark.cc b/absl/container/internal/raw_hash_set_benchmark.cc
index bc8184d4..8cd43fb5 100644
--- a/absl/container/internal/raw_hash_set_benchmark.cc
+++ b/absl/container/internal/raw_hash_set_benchmark.cc
@@ -479,6 +479,17 @@ void BM_Group_MaskEmptyOrDeleted(benchmark::State& state) {
 }
 BENCHMARK(BM_Group_MaskEmptyOrDeleted);
 
+void BM_Group_MaskNonFull(benchmark::State& state) {
+  std::array<ctrl_t, Group::kWidth> group;
+  Iota(group.begin(), group.end(), -4);
+  Group g{group.data()};
+  for (auto _ : state) {
+    ::benchmark::DoNotOptimize(g);
+    ::benchmark::DoNotOptimize(g.MaskNonFull());
+  }
+}
+BENCHMARK(BM_Group_MaskNonFull);
+
 void BM_Group_CountLeadingEmptyOrDeleted(benchmark::State& state) {
   std::array<ctrl_t, Group::kWidth> group;
   Iota(group.begin(), group.end(), -2);
@@ -501,6 +512,17 @@ void BM_Group_MatchFirstEmptyOrDeleted(benchmark::State& state) {
 }
 BENCHMARK(BM_Group_MatchFirstEmptyOrDeleted);
 
+void BM_Group_MatchFirstNonFull(benchmark::State& state) {
+  std::array<ctrl_t, Group::kWidth> group;
+  Iota(group.begin(), group.end(), -2);
+  Group g{group.data()};
+  for (auto _ : state) {
+    ::benchmark::DoNotOptimize(g);
+    ::benchmark::DoNotOptimize(g.MaskNonFull().LowestBitSet());
+  }
+}
+BENCHMARK(BM_Group_MatchFirstNonFull);
+
 void BM_DropDeletes(benchmark::State& state) {
   constexpr size_t capacity = (1 << 20) - 1;
   std::vector<ctrl_t> ctrl(capacity + 1 + Group::kWidth);
diff --git a/absl/container/internal/raw_hash_set_test.cc b/absl/container/internal/raw_hash_set_test.cc
index 1c428ea7..8e196fdf 100644
--- a/absl/container/internal/raw_hash_set_test.cc
+++ b/absl/container/internal/raw_hash_set_test.cc
@@ -307,6 +307,25 @@ TEST(Group, MaskFull) {
   }
 }
 
+TEST(Group, MaskNonFull) {
+  if (Group::kWidth == 16) {
+    ctrl_t group[] = {
+        ctrl_t::kEmpty, CtrlT(1),          ctrl_t::kDeleted,  CtrlT(3),
+        ctrl_t::kEmpty, CtrlT(5),          ctrl_t::kSentinel, CtrlT(7),
+        CtrlT(7),       CtrlT(5),          ctrl_t::kDeleted,  CtrlT(1),
+        CtrlT(1),       ctrl_t::kSentinel, ctrl_t::kEmpty,    CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskNonFull(),
+                ElementsAre(0, 2, 4, 6, 10, 13, 14));
+  } else if (Group::kWidth == 8) {
+    ctrl_t group[] = {ctrl_t::kEmpty,    CtrlT(1), ctrl_t::kEmpty,
+                      ctrl_t::kDeleted,  CtrlT(2), ctrl_t::kSentinel,
+                      ctrl_t::kSentinel, CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskNonFull(), ElementsAre(0, 2, 3, 5, 6));
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
+}
+
 TEST(Group, MaskEmptyOrDeleted) {
   if (Group::kWidth == 16) {
     ctrl_t group[] = {ctrl_t::kEmpty,   CtrlT(1), ctrl_t::kEmpty,    CtrlT(3),