From 58e042da9210710dc4ac3b320e48b54e2449521e Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Fri, 2 Jul 2021 20:42:20 -0700 Subject: Export of internal Abseil changes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit -- 1620e8ffaa93ef24510ca60c7fff2a07248ac9f6 by Abseil Team : Update comment. PiperOrigin-RevId: 382858259 -- 20db116f28469149d10e0f7f8b976cb903dd4879 by Gennadiy Rozental : Add benchmark running on multiple flags. Update size_tester to include cost of absl::GetFlag call. Add size_tester invocation for bool flag. New benchmark better represent GetFlag usage. PiperOrigin-RevId: 382820341 -- 2e097ad3811c4e329f75b98877a5e74c1d3d84fd by Abseil Team : Avoid 64x64->128 multiplication in absl::Hash's mix on AArch64 On AArch64, calculating a 128-bit product is inefficient, because it requires a sequence of two instructions to calculate the upper and lower halves of the result. So calculate a 64-bit product instead. Making MultType 64-bits means the upper 32 bits of the result do not participate in shift/xor, but the add/multiply gives us sufficient mixing. PiperOrigin-RevId: 382625931 -- f3ae3f32cb53168c8dc91b766f2932dc87cec503 by Abseil Team : Remove homegrown Round implementation absl/time/duration.cc defined a Round implementation to accommodate old versions of MSVC that lacked std::round(long double). Abseil no longer supports those MSVCs, so we don’t need the homegrown implementation anymore. Remove it, and replace calls to it with std::rint. PiperOrigin-RevId: 382605191 -- a13631c91bf5478289e1a512ce215c85501a26f7 by Martijn Vels : Move the Consume() conversion functions out of cord_rep_ring into cord_rep_consume. This makes these functions generic, so we can repurpose these for the new Btree conversion functions. PiperOrigin-RevId: 382594902 -- 7394c737500c2d8371fcf913b21ad1b321ba499d by Benjamin Barenblat : Remove homegrown Round implementation absl/time/duration.cc defined a Round implementation to accommodate old versions of MSVC that lacked std::round(long double). Abseil no longer supports those MSVCs, so we don’t need the homegrown implementation anymore. Remove it, and replace calls to it with std::rint. PiperOrigin-RevId: 382569900 -- d72a761f43dc5c9b9510c3a1363177ed26646b5d by Abseil Team : Prefer `getentropy` for Emscripten. It needs a different header, so I've separated it out from the GLIBC check above. PiperOrigin-RevId: 382332475 -- 74e261dbb467741b2ddd8b490e04c531fdd2f559 by Martijn Vels : Add BTREE tag for CordRepNode implementing a Btree cord. This change only forward declared the CordRepBtree class (not implemented yet) and defines the enum value BTREE. While RING and BTREE should never co-exist, we define a new value for BTREE so as not to make transitioning between RING and BTREE harder than it needs to be. This changes shifts the FLAT value / computation from FLAT = 4 to FLAT =5 PiperOrigin-RevId: 382326710 GitOrigin-RevId: 1620e8ffaa93ef24510ca60c7fff2a07248ac9f6 Change-Id: Ia8f99dde3874808f56062bd37ab3e63764099734 --- absl/hash/internal/hash.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'absl/hash') diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h index 69dbbc6b..90627e00 100644 --- a/absl/hash/internal/hash.h +++ b/absl/hash/internal/hash.h @@ -856,8 +856,15 @@ class ABSL_DLL MixingHashState : public HashStateBase { } ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Mix(uint64_t state, uint64_t v) { +#if defined(__aarch64__) + // On AArch64, calculating a 128-bit product is inefficient, because it + // requires a sequence of two instructions to calculate the upper and lower + // halves of the result. + using MultType = uint64_t; +#else using MultType = absl::conditional_t; +#endif // We do the addition in 64-bit space to make sure the 128-bit // multiplication is fast. If we were to do it as MultType the compiler has // to assume that the high word is non-zero and needs to perform 2 -- cgit v1.2.3