From 0f35765048ea9b9fce70dc7c7781bed3321d99cd Mon Sep 17 00:00:00 2001 From: Connal de Souza Date: Thu, 23 Feb 2023 09:52:08 -0800 Subject: Optimize ConvertSpecialToEmptyAndFullToDeleted on Arm MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit BM_DropDeletes 73.4µs ± 0% 68.9µs ± 1% -6.22% (p=0.008 n=5+5) PiperOrigin-RevId: 511813266 Change-Id: Id28cece454d583e2dfe060e27cfc4720f987f009 --- absl/container/internal/raw_hash_set.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'absl/container') diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h index e5306a4f..f4de2d65 100644 --- a/absl/container/internal/raw_hash_set.h +++ b/absl/container/internal/raw_hash_set.h @@ -675,9 +675,10 @@ struct GroupAArch64Impl { void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const { uint64_t mask = vget_lane_u64(vreinterpret_u64_u8(ctrl), 0); constexpr uint64_t msbs = 0x8080808080808080ULL; - constexpr uint64_t lsbs = 0x0101010101010101ULL; - auto x = mask & msbs; - auto res = (~x + (x >> 7)) & ~lsbs; + constexpr uint64_t slsbs = 0x0202020202020202ULL; + constexpr uint64_t midbs = 0x7e7e7e7e7e7e7e7eULL; + auto x = slsbs & (mask >> 6); + auto res = (x + midbs) | msbs; little_endian::Store64(dst, res); } -- cgit v1.2.3