llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Mark de Wever (mordante)
<details>
<summary>Changes</summary>
The formatter specializations for _CharT* and const _CharT* typically write all
elements in a loop. This format's internal functions are optimized for larger
writes.
Instead of writing one element at a time conversion the range to a
basic_string_view and write that instead.
For C string of 6 characters this is a bit slower, but for 60 characters it's
faster. The improvements for back_inserter<std::list<_CharT>> are
not as great as the others; it just gets as slow as
basic_string_view<_CharT>.
Before
---------------------------------------------------------------------------------------------------------------
Benchmark
Time CPU Iterations
---------------------------------------------------------------------------------------------------------------
BM_sprintf/C string len = 6 4.81
ns 4.80 ns 145890280
BM_format/C string len = 6 52.6
ns 52.4 ns 13252327
BM_format_to_back_inserter<std::string>/C string len = 6
53.0 ns 52.8 ns 13262680
BM_format_to_back_inserter<std::vector<char>>/C string len = 6
69.7 ns 69.6 ns 10045636
BM_format_to_back_inserter<std::deque<char>>/C string len = 6
148 ns 148 ns 4729368
BM_format_to_back_inserter<std::list<char>>/C string len = 6
127 ns 126 ns 5538441
BM_format_to_iterator/<std::array> C string len = 6
42.9 ns 42.8 ns 16367158
BM_format_to_iterator/<std::string> C string len = 6
43.5 ns 43.4 ns 16141644
BM_format_to_iterator/<std::vector> C string len = 6
42.9 ns 42.8 ns 16366718
BM_format_to_iterator/<std::deque> C string len = 6
47.8 ns 47.7 ns 14686488
BM_format/string len = 6 55.3
ns 55.2 ns 12696889
BM_format_to_back_inserter<std::string>/string len = 6
55.4 ns 55.2 ns 12660731
BM_format_to_back_inserter<std::vector<char>>/string len = 6
70.7 ns 70.5 ns 9927313
BM_format_to_back_inserter<std::deque<char>>/string len = 6
153 ns 153 ns 4573936
BM_format_to_back_inserter<std::list<char>>/string len = 6
128 ns 128 ns 5486033
BM_format_to_iterator/<std::array> string len = 6
44.6 ns 44.5 ns 15758122
BM_format_to_iterator/<std::string> string len = 6
44.7 ns 44.6 ns 15690226
BM_format_to_iterator/<std::vector> string len = 6
44.3 ns 44.2 ns 15715898
BM_format_to_iterator/<std::deque> string len = 6
50.3 ns 50.1 ns 13958635
BM_format/string_view len = 6 54.2
ns 54.1 ns 12929525
BM_format_to_back_inserter<std::string>/string_view len = 6
54.3 ns 54.1 ns 12929219
BM_format_to_back_inserter<std::vector<char>>/string_view len = 6
70.0 ns 69.8 ns 10022355
BM_format_to_back_inserter<std::deque<char>>/string_view len = 6
153 ns 152 ns 4585749
BM_format_to_back_inserter<std::list<char>>/string_view len = 6
128 ns 128 ns 5489760
BM_format_to_iterator/<std::array> string_view len = 6
44.2 ns 44.1 ns 15884839
BM_format_to_iterator/<std::string> string_view len = 6
44.8 ns 44.6 ns 15664278
BM_format_to_iterator/<std::vector> string_view len = 6
44.7 ns 44.6 ns 15716983
BM_format_to_iterator/<std::deque> string_view len = 6
50.3 ns 50.2 ns 13936091
BM_sprintf/C string len = 60 4.16
ns 4.15 ns 168764227
BM_format/C string len = 60 169
ns 169 ns 4144060
BM_format_to_back_inserter<std::string>/C string len = 60
167 ns 167 ns 4203915
BM_format_to_back_inserter<std::vector<char>>/C string len = 60
177 ns 176 ns 3965619
BM_format_to_back_inserter<std::deque<char>>/C string len = 60
383 ns 382 ns 1832531
BM_format_to_back_inserter<std::list<char>>/C string len = 60
1270 ns 1267 ns 552686
BM_format_to_iterator/<std::array> C string len = 60
141 ns 140 ns 4988441
BM_format_to_iterator/<std::string> C string len = 60
141 ns 141 ns 4956101
BM_format_to_iterator/<std::vector> C string len = 60
141 ns 141 ns 4963443
BM_format_to_iterator/<std::deque> C string len = 60
144 ns 143 ns 4893139
BM_format/string len = 60 73.4
ns 73.2 ns 9548455
BM_format_to_back_inserter<std::string>/string len = 60
73.2 ns 73.0 ns 9524524
BM_format_to_back_inserter<std::vector<char>>/string len = 60
81.6 ns 81.4 ns 8584033
BM_format_to_back_inserter<std::deque<char>>/string len = 60
279 ns 279 ns 2515146
BM_format_to_back_inserter<std::list<char>>/string len = 60
1177 ns 1174 ns 597172
BM_format_to_iterator/<std::array> string len = 60
44.5 ns 44.4 ns 15753131
BM_format_to_iterator/<std::string> string len = 60
44.7 ns 44.6 ns 15692630
BM_format_to_iterator/<std::vector> string len = 60
44.8 ns 44.7 ns 15664689
BM_format_to_iterator/<std::deque> string len = 60
50.6 ns 50.5 ns 13838617
BM_format/string_view len = 60 72.8
ns 72.6 ns 9674007
BM_format_to_back_inserter<std::string>/string_view len = 60
72.7 ns 72.6 ns 9638209
BM_format_to_back_inserter<std::vector<char>>/string_view len = 60
82.6 ns 82.4 ns 8496602
BM_format_to_back_inserter<std::deque<char>>/string_view len = 60
280 ns 280 ns 2508982
BM_format_to_back_inserter<std::list<char>>/string_view len = 60
1176 ns 1173 ns 597714
BM_format_to_iterator/<std::array> string_view len = 60
44.2 ns 44.1 ns 15896934
BM_format_to_iterator/<std::string> string_view len = 60
44.7 ns 44.6 ns 15695427
BM_format_to_iterator/<std::vector> string_view len = 60
44.7 ns 44.6 ns 15680899
BM_format_to_iterator/<std::deque> string_view len = 60
50.3 ns 50.1 ns 13962755
BM_sprintf/C string len = 6000 114
ns 114 ns 6170153
BM_format/C string len = 6000 11792
ns 11763 ns 59619
BM_format_to_back_inserter<std::string>/C string len = 6000
11778 ns 11746 ns 59572
BM_format_to_back_inserter<std::vector<char>>/C string len = 6000
11715 ns 11686 ns 60053
BM_format_to_back_inserter<std::deque<char>>/C string len = 6000
25464 ns 25403 ns 27538
BM_format_to_back_inserter<std::list<char>>/C string len = 6000
126044 ns 125726 ns 5572
BM_format_to_iterator/<std::array> C string len = 6000
10792 ns 10766 ns 64943
BM_format_to_iterator/<std::string> C string len = 6000
10791 ns 10761 ns 64918
BM_format_to_iterator/<std::vector> C string len = 6000
10775 ns 10750 ns 65149
BM_format_to_iterator/<std::deque> C string len = 6000
11242 ns 11215 ns 62542
BM_format/string len = 6000 919
ns 917 ns 763961
BM_format_to_back_inserter<std::string>/string len = 6000
920 ns 917 ns 763094
BM_format_to_back_inserter<std::vector<char>>/string len = 6000
888 ns 886 ns 793468
BM_format_to_back_inserter<std::deque<char>>/string len = 6000
14999 ns 14963 ns 46758
BM_format_to_back_inserter<std::list<char>>/string len = 6000
114504 ns 114213 ns 6130
BM_format_to_iterator/<std::array> string len = 6000
120 ns 120 ns 5823426
BM_format_to_iterator/<std::string> string len = 6000
106 ns 106 ns 6609299
BM_format_to_iterator/<std::vector> string len = 6000
106 ns 106 ns 6613867
BM_format_to_iterator/<std::deque> string len = 6000
367 ns 366 ns 1912818
BM_format/string_view len = 6000 910
ns 907 ns 771491
BM_format_to_back_inserter<std::string>/string_view len = 6000
911 ns 909 ns 770065
BM_format_to_back_inserter<std::vector<char>>/string_view len =
6000 878 ns 876 ns 794976
BM_format_to_back_inserter<std::deque<char>>/string_view len = 6000
15031 ns 14994 ns 46651
BM_format_to_back_inserter<std::list<char>>/string_view len = 6000
114510 ns 114219 ns 6130
BM_format_to_iterator/<std::array> string_view len = 6000
121 ns 120 ns 5814249
BM_format_to_iterator/<std::string> string_view len = 6000
116 ns 115 ns 6072315
BM_format_to_iterator/<std::vector> string_view len = 6000
115 ns 115 ns 6095762
BM_format_to_iterator/<std::deque> string_view len = 6000
351 ns 350 ns 2002175
After
---------------------------------------------------------------------------------------------------------------
Benchmark
Time CPU Iterations
---------------------------------------------------------------------------------------------------------------
BM_sprintf/C string len = 6 4.83
ns 4.83 ns 145502957
BM_format/C string len = 6 55.1
ns 55.1 ns 12687656
BM_format_to_back_inserter<std::string>/C string len = 6
55.1 ns 55.1 ns 12691642
BM_format_to_back_inserter<std::vector<char>>/C string len = 6
71.2 ns 71.3 ns 9819560
BM_format_to_back_inserter<std::deque<char>>/C string len = 6
154 ns 154 ns 4548709
BM_format_to_back_inserter<std::list<char>>/C string len = 6
131 ns 131 ns 5338318
BM_format_to_iterator/<std::array> C string len = 6
45.0 ns 45.0 ns 15569429
BM_format_to_iterator/<std::string> C string len = 6
45.9 ns 45.9 ns 15240594
BM_format_to_iterator/<std::vector> C string len = 6
44.4 ns 44.4 ns 15768343
BM_format_to_iterator/<std::deque> C string len = 6
50.1 ns 50.1 ns 13995837
BM_format/string len = 6 54.8
ns 54.8 ns 12738209
BM_format_to_back_inserter<std::string>/string len = 6
55.4 ns 55.4 ns 12634483
BM_format_to_back_inserter<std::vector<char>>/string len = 6
70.4 ns 70.4 ns 9948288
BM_format_to_back_inserter<std::deque<char>>/string len = 6
154 ns 154 ns 4531741
BM_format_to_back_inserter<std::list<char>>/string len = 6
132 ns 132 ns 5289798
BM_format_to_iterator/<std::array> string len = 6
44.5 ns 44.5 ns 15743437
BM_format_to_iterator/<std::string> string len = 6
44.9 ns 44.9 ns 15591961
BM_format_to_iterator/<std::vector> string len = 6
45.0 ns 45.0 ns 15541308
BM_format_to_iterator/<std::deque> string len = 6
50.5 ns 50.5 ns 13837884
BM_format/string_view len = 6 54.5
ns 54.5 ns 12833591
BM_format_to_back_inserter<std::string>/string_view len = 6
54.6 ns 54.6 ns 12818233
BM_format_to_back_inserter<std::vector<char>>/string_view len = 6
69.9 ns 69.9 ns 10018025
BM_format_to_back_inserter<std::deque<char>>/string_view len = 6
154 ns 154 ns 4534215
BM_format_to_back_inserter<std::list<char>>/string_view len = 6
131 ns 131 ns 5337938
BM_format_to_iterator/<std::array> string_view len = 6
44.2 ns 44.2 ns 15854695
BM_format_to_iterator/<std::string> string_view len = 6
45.0 ns 45.0 ns 15551054
BM_format_to_iterator/<std::vector> string_view len = 6
45.0 ns 45.0 ns 15567905
BM_format_to_iterator/<std::deque> string_view len = 6
50.5 ns 50.5 ns 13858261
BM_sprintf/C string len = 60 4.16
ns 4.16 ns 168066307
BM_format/C string len = 60 73.8
ns 73.8 ns 9487364
BM_format_to_back_inserter<std::string>/C string len = 60
73.7 ns 73.7 ns 9492371
BM_format_to_back_inserter<std::vector<char>>/C string len = 60
83.1 ns 83.1 ns 8399017
BM_format_to_back_inserter<std::deque<char>>/C string len = 60
284 ns 284 ns 2466510
BM_format_to_back_inserter<std::list<char>>/C string len = 60
1177 ns 1177 ns 592514
BM_format_to_iterator/<std::array> C string len = 60
44.9 ns 44.9 ns 15558172
BM_format_to_iterator/<std::string> C string len = 60
45.8 ns 45.8 ns 15283103
BM_format_to_iterator/<std::vector> C string len = 60
44.6 ns 44.6 ns 15678967
BM_format_to_iterator/<std::deque> C string len = 60
50.5 ns 50.5 ns 13839524
BM_format/string len = 60 72.2
ns 72.2 ns 9687634
BM_format_to_back_inserter<std::string>/string len = 60
72.0 ns 72.1 ns 9695746
BM_format_to_back_inserter<std::vector<char>>/string len = 60
82.3 ns 82.3 ns 8509528
BM_format_to_back_inserter<std::deque<char>>/string len = 60
279 ns 279 ns 2506108
BM_format_to_back_inserter<std::list<char>>/string len = 60
1180 ns 1180 ns 592963
BM_format_to_iterator/<std::array> string len = 60
44.7 ns 44.7 ns 15657865
BM_format_to_iterator/<std::string> string len = 60
45.0 ns 45.0 ns 15569049
BM_format_to_iterator/<std::vector> string len = 60
44.9 ns 44.9 ns 15576187
BM_format_to_iterator/<std::deque> string len = 60
50.7 ns 50.7 ns 13803188
BM_format/string_view len = 60 72.4
ns 72.4 ns 9663061
BM_format_to_back_inserter<std::string>/string_view len = 60
72.8 ns 72.8 ns 9638941
BM_format_to_back_inserter<std::vector<char>>/string_view len = 60
81.9 ns 81.9 ns 8529931
BM_format_to_back_inserter<std::deque<char>>/string_view len = 60
283 ns 283 ns 2471522
BM_format_to_back_inserter<std::list<char>>/string_view len = 60
1177 ns 1177 ns 594752
BM_format_to_iterator/<std::array> string_view len = 60
44.2 ns 44.2 ns 15841413
BM_format_to_iterator/<std::string> string_view len = 60
45.1 ns 45.1 ns 15546279
BM_format_to_iterator/<std::vector> string_view len = 60
45.0 ns 45.0 ns 15555756
BM_format_to_iterator/<std::deque> string_view len = 60
50.1 ns 50.1 ns 10000000
BM_sprintf/C string len = 6000 344
ns 344 ns 2037753
BM_format/C string len = 6000 980
ns 980 ns 713341
BM_format_to_back_inserter<std::string>/C string len = 6000
979 ns 979 ns 709571
BM_format_to_back_inserter<std::vector<char>>/C string len = 6000
944 ns 944 ns 744518
BM_format_to_back_inserter<std::deque<char>>/C string len = 6000
14916 ns 14915 ns 46875
BM_format_to_back_inserter<std::list<char>>/C string len = 6000
114686 ns 114688 ns 6110
BM_format_to_iterator/<std::array> C string len = 6000
159 ns 159 ns 4394506
BM_format_to_iterator/<std::string> C string len = 6000
159 ns 159 ns 4384577
BM_format_to_iterator/<std::vector> C string len = 6000
159 ns 159 ns 4393225
BM_format_to_iterator/<std::deque> C string len = 6000
437 ns 437 ns 1601253
BM_format/string len = 6000 929
ns 929 ns 751889
BM_format_to_back_inserter<std::string>/string len = 6000
933 ns 933 ns 752042
BM_format_to_back_inserter<std::vector<char>>/string len = 6000
892 ns 892 ns 785064
BM_format_to_back_inserter<std::deque<char>>/string len = 6000
14840 ns 14839 ns 47177
BM_format_to_back_inserter<std::list<char>>/string len = 6000
114940 ns 114942 ns 6095
BM_format_to_iterator/<std::array> string len = 6000
144 ns 144 ns 4859849
BM_format_to_iterator/<std::string> string len = 6000
106 ns 106 ns 6565564
BM_format_to_iterator/<std::vector> string len = 6000
107 ns 107 ns 6584152
BM_format_to_iterator/<std::deque> string len = 6000
368 ns 368 ns 1904727
BM_format/string_view len = 6000 919
ns 919 ns 760401
BM_format_to_back_inserter<std::string>/string_view len = 6000
917 ns 917 ns 760934
BM_format_to_back_inserter<std::vector<char>>/string_view len =
6000 880 ns 880 ns 796244
BM_format_to_back_inserter<std::deque<char>>/string_view len = 6000
14854 ns 14853 ns 47101
BM_format_to_back_inserter<std::list<char>>/string_view len = 6000
114963 ns 114967 ns 6086
BM_format_to_iterator/<std::array> string_view len = 6000
117 ns 117 ns 5974080
BM_format_to_iterator/<std::string> string_view len = 6000
116 ns 116 ns 6016080
BM_format_to_iterator/<std::vector> string_view len = 6000
116 ns 116 ns 6053780
BM_format_to_iterator/<std::deque> string_view len = 6000
351 ns 351 ns 1993879
Comparing libcxx/benchmarks/1/write_string_comparison.bench.out to
libcxx/benchmarks/2/write_string_comparison.bench.out
Benchmark
Time CPU Time Old Time New CPU Old CPU
New
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
BM_sprintf/C string len = 6
+0.0034 +0.0058 5 5 5
5
BM_format/C string len = 6
+0.0484 +0.0508 53 55 52
55
BM_format_to_back_inserter<std::string>/C string len = 6
+0.0395 +0.0424 53 55 53
55
BM_format_to_back_inserter<std::vector<char>>/C string len = 6
+0.0220 +0.0244 70 71
70 71
BM_format_to_back_inserter<std::deque<char>>/C string len = 6
+0.0399 +0.0424 148 154
148 154
BM_format_to_back_inserter<std::list<char>>/C string len = 6
+0.0339 +0.0365 127 131
126 131
BM_format_to_iterator/<std::array> C string len = 6
+0.0494 +0.0520 43 45 43
45
BM_format_to_iterator/<std::string> C string len = 6
+0.0539 +0.0568 44 46 43
46
BM_format_to_iterator/<std::vector> C string len = 6
+0.0359 +0.0384 43 44 43
44
BM_format_to_iterator/<std::deque> C string len = 6
+0.0488 +0.0513 48 50 48
50
BM_format/string len = 6
-0.0105 -0.0081 55 55 55
55
BM_format_to_back_inserter<std::string>/string len = 6
+0.0008 +0.0036 55 55 55
55
BM_format_to_back_inserter<std::vector<char>>/string len = 6
-0.0046 -0.0021 71 70
71 70
BM_format_to_back_inserter<std::deque<char>>/string len = 6
+0.0066 +0.0091 153 154
153 154
BM_format_to_back_inserter<std::list<char>>/string len = 6
+0.0291 +0.0316 128 132
128 132
BM_format_to_iterator/<std::array> string len = 6
-0.0030 -0.0006 45 44 44
44
BM_format_to_iterator/<std::string> string len = 6
+0.0045 +0.0069 45 45 45
45
BM_format_to_iterator/<std::vector> string len = 6
+0.0150 +0.0177 44 45 44
45
BM_format_to_iterator/<std::deque> string len = 6
+0.0059 +0.0084 50 51 50
51
BM_format/string_view len = 6
+0.0050 +0.0075 54 55 54
55
BM_format_to_back_inserter<std::string>/string_view len = 6
+0.0052 +0.0081 54 55 54
55
BM_format_to_back_inserter<std::vector<char>>/string_view len = 6
-0.0017 +0.0008 70 70
70 70
BM_format_to_back_inserter<std::deque<char>>/string_view len = 6
+0.0113 +0.0137 153 154
152 154
BM_format_to_back_inserter<std::list<char>>/string_view len = 6
+0.0260 +0.0286 128 131
128 131
BM_format_to_iterator/<std::array> string_view len = 6
-0.0006 +0.0021 44 44 44
44
BM_format_to_iterator/<std::string> string_view len = 6
+0.0059 +0.0084 45 45 45
45
BM_format_to_iterator/<std::vector> string_view len = 6
+0.0083 +0.0108 45 45 45
45
BM_format_to_iterator/<std::deque> string_view len = 6
+0.0048 +0.0073 50 51 50
51
BM_sprintf/C string len = 60
+0.0002 +0.0029 4 4 4
4
BM_format/C string len = 60
-0.5640 -0.5629 169 74 169
74
BM_format_to_back_inserter<std::string>/C string len = 60
-0.5592 -0.5582 167 74 167
74
BM_format_to_back_inserter<std::vector<char>>/C string len = 60
-0.5294 -0.5282 177 83
176 83
BM_format_to_back_inserter<std::deque<char>>/C string len = 60
-0.2591 -0.2570 383 284
382 284
BM_format_to_back_inserter<std::list<char>>/C string len = 60
-0.0730 -0.0707 1270 1177
1267 1177
BM_format_to_iterator/<std::array> C string len = 60
-0.6804 -0.6797 141 45 140
45
BM_format_to_iterator/<std::string> C string len = 60
-0.6759 -0.6750 141 46 141
46
BM_format_to_iterator/<std::vector> C string len = 60
-0.6849 -0.6841 141 45 141
45
BM_format_to_iterator/<std::deque> C string len = 60
-0.6481 -0.6471 144 51 143
51
BM_format/string len = 60
-0.0167 -0.0142 73 72 73
72
BM_format_to_back_inserter<std::string>/string len = 60
-0.0151 -0.0127 73 72 73
72
BM_format_to_back_inserter<std::vector<char>>/string len = 60
+0.0093 +0.0118 82 82
81 82
BM_format_to_back_inserter<std::deque<char>>/string len = 60
-0.0003 +0.0023 279 279
279 279
BM_format_to_back_inserter<std::list<char>>/string len = 60
+0.0025 +0.0050 1177 1180
1174 1180
BM_format_to_iterator/<std::array> string len = 60
+0.0046 +0.0070 45 45 44
45
BM_format_to_iterator/<std::string> string len = 60
+0.0050 +0.0075 45 45 45
45
BM_format_to_iterator/<std::vector> string len = 60
+0.0025 +0.0051 45 45 45
45
BM_format_to_iterator/<std::deque> string len = 60
+0.0031 +0.0056 51 51 50
51
BM_format/string_view len = 60
-0.0054 -0.0030 73 72 73
72
BM_format_to_back_inserter<std::string>/string_view len = 60
+0.0001 +0.0026 73 73 73
73
BM_format_to_back_inserter<std::vector<char>>/string_view len = 60
-0.0090 -0.0066 83 82
82 82
BM_format_to_back_inserter<std::deque<char>>/string_view len = 60
+0.0097 +0.0126 280 283
280 283
BM_format_to_back_inserter<std::list<char>>/string_view len = 60
+0.0011 +0.0036 1176 1177
1173 1177
BM_format_to_iterator/<std::array> string_view len = 60
+0.0001 +0.0026 44 44 44
44
BM_format_to_iterator/<std::string> string_view len = 60
+0.0083 +0.0107 45 45 45
45
BM_format_to_iterator/<std::vector> string_view len = 60
+0.0068 +0.0093 45 45 45
45
BM_format_to_iterator/<std::deque> string_view len = 60
-0.0038 -0.0014 50 50 50
50
BM_sprintf/C string len = 6000
+2.0230 +2.0305 114 344 114
344
BM_format/C string len = 6000
-0.9169 -0.9167 11792 980 11763
980
BM_format_to_back_inserter<std::string>/C string len = 6000
-0.9169 -0.9166 11778 979 11746
979
BM_format_to_back_inserter<std::vector<char>>/C string len = 6000
-0.9194 -0.9192 11715 944
11686 944
BM_format_to_back_inserter<std::deque<char>>/C string len = 6000
-0.4143 -0.4129 25464 14916
25403 14915
BM_format_to_back_inserter<std::list<char>>/C string len = 6000
-0.0901 -0.0878 126044 114686
125726 114688
BM_format_to_iterator/<std::array> C string len = 6000
-0.9852 -0.9852 10792 159 10766
159
BM_format_to_iterator/<std::string> C string len = 6000
-0.9852 -0.9852 10791 159 10761
159
BM_format_to_iterator/<std::vector> C string len = 6000
-0.9852 -0.9852 10775 159 10750
159
BM_format_to_iterator/<std::deque> C string len = 6000
-0.9611 -0.9610 11242 437 11215
437
BM_format/string len = 6000
+0.0108 +0.0133 919 929 917
929
BM_format_to_back_inserter<std::string>/string len = 6000
+0.0138 +0.0167 920 933 917
933
BM_format_to_back_inserter<std::vector<char>>/string len = 6000
+0.0041 +0.0064 888 892
886 892
BM_format_to_back_inserter<std::deque<char>>/string len = 6000
-0.0107 -0.0082 14999 14840
14963 14839
BM_format_to_back_inserter<std::list<char>>/string len = 6000
+0.0038 +0.0064 114504 114940
114213 114942
BM_format_to_iterator/<std::array> string len = 6000
+0.2011 +0.2040 120 144 120
144
BM_format_to_iterator/<std::string> string len = 6000
+0.0032 +0.0057 106 106 106
106
BM_format_to_iterator/<std::vector> string len = 6000
+0.0057 +0.0085 106 107 106
107
BM_format_to_iterator/<std::deque> string len = 6000
+0.0011 +0.0036 367 368 366
368
BM_format/string_view len = 6000
+0.0105 +0.0130 910 919 907
919
BM_format_to_back_inserter<std::string>/string_view len = 6000
+0.0057 +0.0081 911 917 909
917
BM_format_to_back_inserter<std::vector<char>>/string_view len =
6000 +0.0023 +0.0050 878 880
876 880
BM_format_to_back_inserter<std::deque<char>>/string_view len = 6000
-0.0118 -0.0094 15031 14854
14994 14853
BM_format_to_back_inserter<std::list<char>>/string_view len = 6000
+0.0040 +0.0065 114510 114963
114219 114967
BM_format_to_iterator/<std::array> string_view len = 6000
-0.0299 -0.0275 121 117 120
117
BM_format_to_iterator/<std::string> string_view len = 6000
+0.0062 +0.0086 116 116 115
116
BM_format_to_iterator/<std::vector> string_view len = 6000
+0.0034 +0.0062 115 116 115
116
BM_format_to_iterator/<std::deque> string_view len = 6000
+0.0011 +0.0035 351 351 350
351
OVERALL_GEOMEAN
-0.2959 -0.2941 0 0 0
0
---
Full diff: https://github.com/llvm/llvm-project/pull/101805.diff
1 Files Affected:
- (modified) libcxx/include/__format/formatter_string.h (+7-25)
``````````diff
diff --git a/libcxx/include/__format/formatter_string.h
b/libcxx/include/__format/formatter_string.h
index dee2b3ad073a5..a30e563992ece 100644
--- a/libcxx/include/__format/formatter_string.h
+++ b/libcxx/include/__format/formatter_string.h
@@ -64,32 +64,14 @@ struct _LIBCPP_TEMPLATE_VIS formatter<const _CharT*,
_CharT> : public __formatte
template <class _FormatContext>
_LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(const _CharT*
__str, _FormatContext& __ctx) const {
_LIBCPP_ASSERT_INTERNAL(__str, "The basic_format_arg constructor should
have prevented an invalid pointer.");
-
- __format_spec::__parsed_specifications<_CharT> __specs =
_Base::__parser_.__get_parsed_std_specifications(__ctx);
-# if _LIBCPP_STD_VER >= 23
- if (_Base::__parser_.__type_ == __format_spec::__type::__debug)
- return
__formatter::__format_escaped_string(basic_string_view<_CharT>{__str},
__ctx.out(), __specs);
-# endif
-
- // When using a center or right alignment and the width option the length
- // of __str must be known to add the padding upfront. This case is handled
- // by the base class by converting the argument to a basic_string_view.
+ // Converting the input to a basic_string_view means the data is looped
over twice;
+ // - once to determine the lenght, and
+ // - once to process the data.
//
- // When using left alignment and the width option the padding is added
- // after outputting __str so the length can be determined while outputting
- // __str. The same holds true for the precision, during outputting __str it
- // can be validated whether the precision threshold has been reached. For
- // now these optimizations aren't implemented. Instead the base class
- // handles these options.
- // TODO FMT Implement these improvements.
- if (__specs.__has_width() || __specs.__has_precision())
- return __formatter::__write_string(basic_string_view<_CharT>{__str},
__ctx.out(), __specs);
-
- // No formatting required, copy the string to the output.
- auto __out_it = __ctx.out();
- while (*__str)
- *__out_it++ = *__str++;
- return __out_it;
+ // This sounds slower than writing the output directly. However internally
+ // the output algorithms have optimizations for "bulk" operations. This
+ // means processing the data twice is faster than processing it once.
+ return _Base::format(basic_string_view<_CharT>(__str), __ctx);
}
};
``````````
</details>
https://github.com/llvm/llvm-project/pull/101805
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