commit 24f810e5c79c02a20890467e8ae25ab6b064d9a7
author Mitchell Kember <mkember@fuchsia.infra.roller.google.com> Wed May 25 19:42:28 2022 +0000
committer Copybara-Service <copybara-worker@google.com> Wed May 25 12:44:00 2022 -0700
tree 237735ed3cd79b90796b82d220381bd746980922
parent adf6a68171b6fa84c953955c365ec2b3cd8cbd6e

[roll] Roll fuchsia [rust][fidl] Elide more bounds checks in release mode

This CL changes most `self.buf[i]` array accesses to use `get_unchecked`
or `get_unchecked_mut`, moving bounds checks to `debug_assert!` instead.
This was already how most of the encoding/decoding logic worked. There
was no particular reason to keep the bounds checks in these helpers.

Note that I did not mark these functions unsafe because "the caller does
bounds checks" is an assumption throughout this file. For example,
calling field.encode(...) or field.decode(...) works the same way and
requires equal scrutiny. For more context on these decisions, see
Id4c9e44b21d94e9c7994696808db7eac3c7baac7.

Benchmark results:

Test case                                               Improve/regress?  Factor change  Mean before          Mean after
------------------------------------------------------  ----------------  -------------  -------------------  --------------------
LLCPP/Decode/HandleArray/Plain/64/Steps.Setup/WallTime  faster            0.992-1.000    76727 +/- 205 ns     76404 +/- 88 ns
Rust/Builder/DatagramSocket/RecvMsg/Request/WallTime    faster            0.466-0.684    2.10 +/- 0.39 ns     1.1629 +/- 0.0029 ns
Rust/Decode/ByteArray/16/WallTime                       faster            0.465-0.834    18.5 +/- 2.3 ns      11.6 +/- 1.9 ns
Rust/Decode/ByteVector/16/WallTime                      slower            1.009-1.034    119.57 +/- 0.32 ns   122.2 +/- 1.2 ns
Rust/Decode/Table/AllSet/63/WallTime                    faster            0.809-0.881    560.5 +/- 6.1 ns     473 +/- 15 ns
Rust/Decode/Table/SingleSet/16_of_63/WallTime           faster            0.837-0.957    99.2 +/- 4.6 ns      88.7 +/- 1.8 ns
Rust/Decode/Union/LastSet/1/WallTime                    faster            0.911-0.966    20.82 +/- 0.35 ns    19.53 +/- 0.25 ns
Rust/Decode/Union/LastSet/16/WallTime                   faster            0.829-1.000    27.9 +/- 2.1 ns      25.38 +/- 0.49 ns
Rust/Encode/ByteVector/16/WallTime                      faster            0.861-0.916    45.66 +/- 0.96 ns    40.56 +/- 0.40 ns
Rust/Encode/DatagramSocket/RecvMsg/Request/WallTime     faster            0.920-0.944    23.468 +/- 0.099 ns  21.86 +/- 0.19 ns
Rust/Encode/DatagramSocket/SendMsg2/Result/WallTime     faster            0.962-0.991    39.25 +/- 0.21 ns    38.32 +/- 0.37 ns
Rust/Encode/EmptyStruct/WallTime                        faster            0.916-0.939    22.12 +/- 0.15 ns    20.52 +/- 0.11 ns
Rust/Encode/EnumArray/NonDense/256/WallTime             faster            0.924-0.961    877.6 +/- 9.3 ns     827.1 +/- 7.5 ns
Rust/Encode/ErrorSyntaxResult_Failure/WallTime          faster            0.925-0.976    38.71 +/- 0.78 ns    36.79 +/- 0.24 ns
Rust/Encode/HandleArray/Event/64/WallTime               slower            1.010-1.037    1755 +/- 12 ns       1796 +/- 12 ns
Rust/Encode/String/16/WallTime                          faster            0.951-0.998    45.08 +/- 0.75 ns    43.92 +/- 0.32 ns
Rust/Encode/StructField/16/WallTime                     faster            0.958-0.975    21.917 +/- 0.100 ns  21.179 +/- 0.086 ns
Rust/Encode/Table/AllSet/63/WallTime                    faster            0.947-0.989    1127.2 +/- 1.5 ns    1091 +/- 22 ns
Rust/Encode/Table/LastSetOthersReserved/16/WallTime     slower            1.007-1.014    62.73 +/- 0.14 ns    63.408 +/- 0.081 ns
Rust/Encode/Table/LastSetOthersReserved/63/WallTime     slower            1.000-1.102    68.13 +/- 0.13 ns    71.6 +/- 3.3 ns
Rust/Encode/Table/SingleSet/16_of_63/WallTime           faster            0.934-0.949    246.21 +/- 0.81 ns   231.8 +/- 1.0 ns
Rust/Encode/Table/SingleSet/63_of_63/WallTime           faster            0.928-0.936    777.7 +/- 1.8 ns     724.8 +/- 1.3 ns
Rust/Encode/Union/LastSet/1/WallTime                    faster            0.944-0.959    40.121 +/- 0.062 ns  38.18 +/- 0.24 ns
Rust/Encode/Union/LastSet/16/WallTime                   slower            1.011-1.018    38.584 +/- 0.060 ns  39.153 +/- 0.069 ns
Rust/Encode/Union/LastSet/256/WallTime                  faster            0.962-0.971    41.686 +/- 0.081 ns  40.30 +/- 0.11 ns

Test: fx test fidl_rust_conformance_tests
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/683140
Original-Revision: 500af410225fde728cd0975b8a43f8f9aaf7b458
GitOrigin-RevId: 195d15879c9ca0c40a233317b59e8315ebea8b4d
Change-Id: I058b5bd5378f16e4f0448b7d02ac001ddf2dc3ac