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Add max and min to Ord
Pursuant to issue #25663, this PR adds max and min methods with default implementations to std::cmp::Ord. It also modifies std::cmp::max|min to internally alias to Ord::max|min, so that any overrides of the default implementations are automatically used by std::cmp::max|min.
Closes #25663
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Add overflow checking for `str::get` with inclusive ranges
Fixes https://github.com/rust-lang/rust/issues/42401
Two commits here:
1. The first makes `str::index` just call `SliceIndex<str>::index`. It's intended to have no behavior change, except where the two methods were inconsistent.
2. The second actually adds the overflow checking to `get(_mut)` (and tests for it)
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Fixes #42618
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See #42629 and #42630.
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Add dedicated docstrings to Sum/Product impl of Result
(and fix a minor grammar typo below)
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(and fix a minor grammar typo below)
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core: allow messages in unimplemented!() macro
This makes `unimplemented!()` match `unreachable!()`, allowing a message and possible formatting to be provided to better explain what and/or why something is not implemented.
I've used this myself in hyper for a while, include the type and method name, to better help while prototyping new modules, like `unimplemented!("Conn::poll_complete")`, or `unimplemented!("Conn::poll; state={:?}", state)`.
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speed up mem::swap
I would have thought that the mem::swap code didn't need an intermediate variable precisely because the pointers are guaranteed never to alias. And.. it doesn't! It seems that llvm will also auto-vectorize this case for large structs, but alas it doesn't seem to have all the aliasing info it needs and so will add redundant checks (and even not bother with autovectorizing for small types). Looks like a lot of performance could still be gained here, so this might be a good test case for future optimizer improvements.
Here are the current benchmarks for the simd version of mem::swap; the timings are in cycles (code below) measured with 10 iterations. The timings for sizes > 32 which are not a multiple of 8 tend to be ever so slightly faster in the old code, but not always. For large struct sizes (> 1024) the new code shows a marked improvement.
\* = latest commit
† = subtracted from other measurements
| arr_length | noop<sup>†</sup> | rust_stdlib | simd_u64x4\* | simd_u64x8
|------------------|------------|-------------------|-------------------|-------------------
8|80|90|90|90
16|72|177|177|177
24|32|76|76|76
32|68|188|112|188
40|32|80|60|80
48|32|84|56|84
56|32|108|72|108
64|32|108|72|76
72|80|350|220|230
80|80|350|220|230
88|80|420|270|270
96|80|420|270|270
104|80|500|320|320
112|80|490|320|320
120|72|528|342|342
128|48|360|234|234
136|72|987|387|387
144|80|1070|420|420
152|64|856|376|376
160|68|804|400|400
168|80|1060|520|520
176|80|1070|520|520
184|32|464|228|228
192|32|504|228|228
200|32|440|248|248
208|72|987|573|573
216|80|1464|220|220
224|48|852|450|450
232|72|1182|666|666
240|32|428|288|288
248|32|428|308|308
256|80|860|770|770
264|80|1130|820|820
272|80|1340|820|820
280|80|1220|870|870
288|72|1227|804|804
296|72|1356|849|849
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Simplify FromIterator example of Result
The previous version may be clearer for newcomers, but this is how you'd write it idiomaticly.
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Get LLVM to stop generating dead assembly in next_power_of_two
It turns out that LLVM can turn `@llvm.ctlz.i64(_, true)` into `@llvm.ctlz.i64(_, false)` ([`ctlz`](http://llvm.org/docs/LangRef.html#llvm-ctlz-intrinsic)) where valuable, but never does the opposite. That leads to some silly assembly getting generated in certain cases.
A contrived-but-clear example https://is.gd/VAIKuC:
```rust
fn foo(x:u64) -> u32 {
if x == 0 { return !0; }
x.leading_zeros()
}
```
Generates
```asm
testq %rdi, %rdi
je .LBB0_1
je .LBB0_3 ; <-- wha?
bsrq %rdi, %rax
xorq $63, %rax
retq
.LBB0_1:
movl $-1, %eax
retq
.LBB0_3:
movl $64, %eax ; <-- dead
retq
```
I noticed this in `next_power_of_two`, which without this PR generates the following:
```asm
cmpq $2, %rcx
jae .LBB1_2
movl $1, %eax
retq
.LBB1_2:
decq %rcx
je .LBB1_3
bsrq %rcx, %rcx
xorq $63, %rcx
jmp .LBB1_5
.LBB1_3:
movl $64, %ecx ; <-- dead
.LBB1_5:
movq $-1, %rax
shrq %cl, %rax
incq %rax
retq
```
And with this PR becomes
```asm
cmpq $2, %rcx
jae .LBB0_2
movl $1, %eax
retq
.LBB0_2:
decq %rcx
bsrq %rcx, %rcx
xorl $63, %ecx
movq $-1, %rax
shrq %cl, %rax
incq %rax
retq
```
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LLVM currently doesn't remove the "bypass if argument is zero" assembly inside branches where the value is known to be non-zero, pessimizing code that uses uN::leading_zeros
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By having the left and right strings above and below on the same line it helps spot the difference between the two. E.g.
thread 'tests::test_safe_filename' panicked at 'assertion failed: `(left == right)`
left: `"-aandb--S123.html"`
right: `"-aandb-S123.html"`',
When the strings are both on the same line it take a lot longer to spot the difference. It is a small change but the small time savings add up with repetition. This helps Rust be an excellent language to write tests in.
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Rollup of 5 pull requests
- Successful merges: #42470, #42490, #42497, #42510, #42512
- Failed merges:
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Improve documentation of next_power_of_two
Clarify overflow behavior of `next_power_of_two`.
Related Issue: #18604
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Pursuant to issue #25663, this commit adds the max and min functions to the Ord trait, enabling items that implement Ord to use UFCS (ex. 1.max(2)) instead of the longer std::cmp::max(1,2) format.
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Doc changes for assert macros
See #29381
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See #29381
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Fixes #42401
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Move any extra logic that the former had into the latter, so they're consistent.
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Change for-loop desugar to not borrow the iterator during the loop
This is enables the use of suspend points inside for-loops in movable generators. This is illegal in the current desugaring as `iter` is borrowed across the body.
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Deprecate range-specific `step_by`
Deprecation attributes and test updates only.
Was replaced by an any-iterator version in https://github.com/rust-lang/rust/pull/41439
Last follow-up (this release) to https://github.com/rust-lang/rust/pull/42110#issuecomment-303210138
r? @alexcrichton
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Add an in-place rotate method for slices to libcore
A helpful primitive for moving chunks of data around inside a slice.
For example, if you have a range selected and are drag-and-dropping it somewhere else (Example from [Sean Parent's talk](https://youtu.be/qH6sSOr-yk8?t=560)).
(If this should be an RFC instead of a PR, please let me know.)
Edit: changed example
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Adding support for the llvm `prefetch` intrinsic
Optimize `slice::binary_search` by using prefetching.
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Related to #37251
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Only exposed as DeprecatedStepBy (as of PR 41439)
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Changed all the tests except test_range_step to use Iterator::step_by.
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