bors ffdf18d144 Auto merge of #88788 - falk-hueffner:speedup-int-log10-branchless, r=joshtriplett ... Speedup int log10 branchless This is achieved with a branchless bit-twiddling implementation of the case x < 100_000, and using this as building block. Benchmark on an Intel i7-8700K (Coffee Lake): ``` name old ns/iter new ns/iter diff ns/iter diff % speedup num::int_log::u8_log10_predictable 165 169 4 2.42% x 0.98 num::int_log::u8_log10_random 438 423 -15 -3.42% x 1.04 num::int_log::u8_log10_random_small 438 423 -15 -3.42% x 1.04 num::int_log::u16_log10_predictable 633 417 -216 -34.12% x 1.52 num::int_log::u16_log10_random 908 471 -437 -48.13% x 1.93 num::int_log::u16_log10_random_small 945 471 -474 -50.16% x 2.01 num::int_log::u32_log10_predictable 1,496 1,340 -156 -10.43% x 1.12 num::int_log::u32_log10_random 1,076 873 -203 -18.87% x 1.23 num::int_log::u32_log10_random_small 1,145 874 -271 -23.67% x 1.31 num::int_log::u64_log10_predictable 4,005 3,171 -834 -20.82% x 1.26 num::int_log::u64_log10_random 1,247 1,021 -226 -18.12% x 1.22 num::int_log::u64_log10_random_small 1,265 921 -344 -27.19% x 1.37 num::int_log::u128_log10_predictable 39,667 39,579 -88 -0.22% x 1.00 num::int_log::u128_log10_random 6,456 6,696 240 3.72% x 0.96 num::int_log::u128_log10_random_small 4,108 3,903 -205 -4.99% x 1.05 ``` Benchmark on an M1 Mac Mini: ``` name old ns/iter new ns/iter diff ns/iter diff % speedup num::int_log::u8_log10_predictable 143 130 -13 -9.09% x 1.10 num::int_log::u8_log10_random 375 325 -50 -13.33% x 1.15 num::int_log::u8_log10_random_small 376 325 -51 -13.56% x 1.16 num::int_log::u16_log10_predictable 500 322 -178 -35.60% x 1.55 num::int_log::u16_log10_random 794 405 -389 -48.99% x 1.96 num::int_log::u16_log10_random_small 1,035 405 -630 -60.87% x 2.56 num::int_log::u32_log10_predictable 1,144 894 -250 -21.85% x 1.28 num::int_log::u32_log10_random 832 786 -46 -5.53% x 1.06 num::int_log::u32_log10_random_small 832 787 -45 -5.41% x 1.06 num::int_log::u64_log10_predictable 2,681 2,057 -624 -23.27% x 1.30 num::int_log::u64_log10_random 1,015 806 -209 -20.59% x 1.26 num::int_log::u64_log10_random_small 1,004 795 -209 -20.82% x 1.26 num::int_log::u128_log10_predictable 56,825 56,526 -299 -0.53% x 1.01 num::int_log::u128_log10_random 9,056 8,861 -195 -2.15% x 1.02 num::int_log::u128_log10_random_small 1,528 1,527 -1 -0.07% x 1.00 ``` The 128 bit case remains ridiculously slow because llvm fails to optimize division by a constant 128-bit value to multiplications. This could be worked around but it seems preferable to fix this in llvm. From u32 up, table lookup (like suggested [here](https://github.com/rust-lang/rust/issues/70887#issuecomment-881099813)) is still faster, but requires a hardware `leading_zeros` to be viable, and might clog up the cache.		2021-10-12 03:18:54 +00:00
..
fmt	Use a test value that doesn't depend on the handling of even/odd rounding	2021-10-03 20:15:12 -07:00
hash	move object safety test to library/core	2021-08-15 13:00:25 -04:00
iter	implement advance_(back_)_by on more iterators	2021-09-30 21:23:28 +02:00
num	Auto merge of #88788 - falk-hueffner:speedup-int-log10-branchless, r=joshtriplett	2021-10-12 03:18:54 +00:00
ops	Expand the docs for ops::ControlFlow a bit	2021-02-06 22:36:05 -08:00
alloc.rs	mv std libs to library/	2020-07-27 19:51:13 -05:00
any.rs	Add test for issue 84666.	2021-06-03 16:13:45 +02:00
array.rs	Also cfg flag auxiliar function	2021-10-08 06:40:24 -03:00
ascii.rs	Make ui test that are run-pass and do not test the compiler itself library tests	2020-11-30 02:47:32 +01:00
atomic.rs	enable atomic_min/max tests in Miri	2021-03-02 19:58:55 +01:00
bool.rs	Make ui test that are run-pass and do not test the compiler itself library tests	2020-11-30 02:47:32 +01:00
cell.rs	Add a few tests for UnsafeCell	2021-08-31 16:32:01 -07:00
char.rs	Further simplification of to_digit	2021-06-10 20:16:35 +01:00
clone.rs	Fix borrow and deref	2021-03-03 11:23:29 +01:00
cmp.rs	Make ui test that are run-pass and do not test the compiler itself library tests	2020-11-30 02:47:32 +01:00
const_ptr.rs	Revert "Revert tests added by PR 81167."	2021-06-27 12:05:17 +02:00
intrinsics.rs	move test to intergrated test in library/core	2020-09-24 14:46:57 +00:00
lazy.rs	Make OnceCell<T> transparent to dropck	2020-08-18 00:34:54 +02:00
lib.rs	Rollup merge of #75644 - c410-f3r:array, r=yaahc	2021-10-09 17:08:38 +02:00
macros.rs	Allow leading pipe in matches!() patterns.	2021-07-15 22:05:45 +03:00
manually_drop.rs	Test ManuallyDrop::clone_from.	2021-07-05 11:55:45 +00:00
mem.rs	Remove the deprecated core::raw and std::raw module.	2021-07-03 14:03:27 +08:00
nonzero.rs	Added impl Rem<NonZeroU{0}> for u{0} which cannot panic	2020-12-17 18:42:19 +02:00
ops.rs	Expand the docs for ops::ControlFlow a bit	2021-02-06 22:36:05 -08:00
option.rs	const fn for option copied, take & replace + tests	2021-08-29 13:19:17 +02:00
pattern.rs	mv std libs to library/	2020-07-27 19:51:13 -05:00
pin.rs	Make some methods of Pin<&mut T> unstable const	2020-09-18 19:23:50 +02:00
ptr.rs	Bump cfgs	2021-04-04 14:57:05 -04:00
result.rs	Update to new bootstrap compiler	2021-06-28 11:30:49 -04:00
slice.rs	Move to the top of file	2021-08-31 08:28:51 -07:00
str_lossy.rs	mv std libs to library/	2020-07-27 19:51:13 -05:00
str.rs	mv std libs to library/	2020-07-27 19:51:13 -05:00
task.rs	Move const tests for Poll to library\core	2020-09-04 01:04:34 +02:00
time.rs	Make Duration's Debug format pad to width	2021-09-16 03:09:31 +02:00
tuple.rs	mv std libs to library/	2020-07-27 19:51:13 -05:00
unicode.rs	Make ui test that are run-pass and do not test the compiler itself library tests	2020-11-30 02:47:32 +01:00