mirror of https://github.com/grpc/grpc.git
Merge pull request #18910 from arjunroy/slice_eq_static
Added slice equality when static fastpath.pull/19014/head
Arjun Roy
6 years ago
committed by
GitHub
commit
50e16f6d3a
23 changed files with 198 additions and 105 deletions
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/*
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* |
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* Copyright 2019 gRPC authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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* |
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*/ |
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#ifndef GRPC_CORE_LIB_SLICE_SLICE_UTILS_H |
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#define GRPC_CORE_LIB_SLICE_SLICE_UTILS_H |
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#include <grpc/support/port_platform.h> |
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#include <grpc/slice.h> |
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// When we compare two slices, and we know the latter is not inlined, we can
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// short circuit our comparison operator. We specifically use differs()
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// semantics instead of equals() semantics due to more favourable code
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// generation when using differs(). Specifically, we may use the output of
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// grpc_slice_differs_refcounted for control flow. If we use differs()
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// semantics, we end with a tailcall to memcmp(). If we use equals() semantics,
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// we need to invert the result that memcmp provides us, which costs several
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// instructions to do so. If we're using the result for control flow (i.e.
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// branching based on the output) then we're just performing the extra
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// operations to invert the result pointlessly. Concretely, we save 6 ops on
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// x86-64/clang with differs().
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int grpc_slice_differs_refcounted(const grpc_slice& a, |
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const grpc_slice& b_not_inline); |
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// When we compare two slices, and we *know* that one of them is static or
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// interned, we can short circuit our slice equality function. The second slice
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// here must be static or interned; slice a can be any slice, inlined or not.
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inline bool grpc_slice_eq_static_interned(const grpc_slice& a, |
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const grpc_slice& b_static_interned) { |
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if (a.refcount == b_static_interned.refcount) { |
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return true; |
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} |
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return !grpc_slice_differs_refcounted(a, b_static_interned); |
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} |
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#endif /* GRPC_CORE_LIB_SLICE_SLICE_UTILS_H */ |
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