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Sebastian Pop 9070500633 improve performance of string::find
string::find used to call the generic algorithm ::find.  The patch special
case string::find such that it ultimately gets converted to calls to memchr
and memcmp.

The patch improves the performance of the string::find routine by about 20x.

Without the patch, the performance on an x86_64-linux 3400 MHz machine is:

Benchmark                           Time           CPU Iterations
-----------------------------------------------------------------
BM_StringFindNoMatch/10             4 ns          4 ns  166421326
BM_StringFindNoMatch/64            37 ns         37 ns   18754392
BM_StringFindNoMatch/512          268 ns        268 ns    2586060
BM_StringFindNoMatch/4k          2143 ns       2144 ns     328342
BM_StringFindNoMatch/32k        16910 ns      16917 ns      40623
BM_StringFindNoMatch/128k       67577 ns      67602 ns      10138
BM_StringFindAllMatch/1             3 ns          3 ns  265163471
BM_StringFindAllMatch/8             6 ns          6 ns  112582467
BM_StringFindAllMatch/64           36 ns         36 ns   19566457
BM_StringFindAllMatch/512         209 ns        209 ns    3318893
BM_StringFindAllMatch/4k         1618 ns       1618 ns     432963
BM_StringFindAllMatch/32k       12909 ns      12914 ns      54317
BM_StringFindAllMatch/128k      48342 ns      48361 ns      13922
BM_StringFindMatch1/1           33777 ns      33790 ns      20698
BM_StringFindMatch1/8           33940 ns      33953 ns      20619
BM_StringFindMatch1/64          34038 ns      34051 ns      20571
BM_StringFindMatch1/512         34217 ns      34230 ns      20480
BM_StringFindMatch1/4k          35510 ns      35524 ns      19752
BM_StringFindMatch1/32k         46438 ns      46456 ns      15030
BM_StringFindMatch2/1           33839 ns      33852 ns      20648
BM_StringFindMatch2/8           33950 ns      33963 ns      20594
BM_StringFindMatch2/64          33846 ns      33859 ns      20668
BM_StringFindMatch2/512         34023 ns      34036 ns      20279
BM_StringFindMatch2/4k          35422 ns      35436 ns      19716
BM_StringFindMatch2/32k         46570 ns      46588 ns      15027

With the patch applied

Benchmark                           Time           CPU Iterations
-----------------------------------------------------------------
BM_StringFindNoMatch/10             5 ns          5 ns  133724346
BM_StringFindNoMatch/64             6 ns          6 ns  119312184
BM_StringFindNoMatch/512           13 ns         13 ns   51539628
BM_StringFindNoMatch/4k            77 ns         77 ns    8935934
BM_StringFindNoMatch/32k          551 ns        551 ns    1222808
BM_StringFindNoMatch/128k        2684 ns       2685 ns     259957
BM_StringFindAllMatch/1             7 ns          7 ns   98017959
BM_StringFindAllMatch/8             7 ns          7 ns   91466911
BM_StringFindAllMatch/64            8 ns          8 ns   85707392
BM_StringFindAllMatch/512          20 ns         20 ns   34490895
BM_StringFindAllMatch/4k           93 ns         93 ns    7360375
BM_StringFindAllMatch/32k         827 ns        828 ns     829944
BM_StringFindAllMatch/128k       3593 ns       3594 ns     195815
BM_StringFindMatch1/1            1332 ns       1332 ns     516354
BM_StringFindMatch1/8            1336 ns       1336 ns     495876
BM_StringFindMatch1/64           1338 ns       1339 ns     516656
BM_StringFindMatch1/512          1357 ns       1357 ns     510717
BM_StringFindMatch1/4k           1485 ns       1486 ns     461228
BM_StringFindMatch1/32k          2235 ns       2236 ns     318253
BM_StringFindMatch2/1            1335 ns       1335 ns     517105
BM_StringFindMatch2/8            1336 ns       1337 ns     518004
BM_StringFindMatch2/64           1344 ns       1345 ns     511751
BM_StringFindMatch2/512          1361 ns       1361 ns     508150
BM_StringFindMatch2/4k           1611 ns       1611 ns     463388
BM_StringFindMatch2/32k          2187 ns       2187 ns     317532

Patch written by Aditya Kumar and Sebastian Pop.

Differential Revision: https://reviews.llvm.org/D27068

llvm-svn: 290761
2016-12-30 18:01:36 +00:00
clang Allow lexer to handle string_view literals. Patch from Anton Bikineev. 2016-12-30 04:51:10 +00:00
clang-tools-extra [clang-tidy] google-explicit-constructor: ignore macros 2016-12-30 15:15:14 +00:00
compiler-rt Decrease kLargeMalloc block size in ASAN unit tests. 2016-12-28 21:57:51 +00:00
debuginfo-tests New round of fixes for "Always compile debuginfo-tests for the host triple" 2014-10-18 23:47:59 +00:00
libclc Fix build since r286752. 2016-11-14 16:06:33 +00:00
libcxx improve performance of string::find 2016-12-30 18:01:36 +00:00
libcxxabi add cxa_demangle_fuzzer 2016-12-28 03:28:29 +00:00
libunwind EHABI: mark some functions as exported 2016-11-17 23:53:35 +00:00
lld [ELF] - Fix mistype in comment. NFC. 2016-12-25 06:49:17 +00:00
lldb Fix the variable view in the "gui" curses mode so that variables whose children change will update correctly. Previously the variable view would update the children once and not change. If you were stepping through code where the dynamic type of a variable would change the value and its children, or a synthetic type (like say for a std::vector<int>), the variable view wouldn't update. Now it caches the children and uses the process stop ID to tell when the children need to be updated. 2016-12-28 21:22:37 +00:00
llgo [llgo] Remove support for LLVM attributes 2016-12-06 19:22:04 +00:00
llvm [CVP] Adjust iteration order to reduce the amount of work required 2016-12-30 18:00:55 +00:00
openmp Fix for the __kmpc_global_num_threads function to return the value of the __kmp_all_nth global var. 2016-12-21 21:20:20 +00:00
parallel-libs [Axccel] Remove -Wno-missing-braces in build 2016-12-19 21:34:07 +00:00
polly Update to isl-0.18-28-gccb9f33 2016-12-28 19:35:49 +00:00