`findScalarPos` might do repetitive work, even if using simd. For
example, when searching the string `/abcde/fghijk/lm` for the character
`/`, a 16-byte wide search would yield `1000001000000100` but would only
count the first `1` and re-search the remaining of the string.
When testing locally, the difference was quite significative:
```
count scalar
5737 iterations 522.83us per iterations
0 bytes per iteration
worst: 2370us median: 512us stddev: 107.64us
count v2
38333 iterations 78.03us per iterations
0 bytes per iteration
worst: 713us median: 76us stddev: 10.62us
count scalar v2
99565 iterations 29.80us per iterations
0 bytes per iteration
worst: 41us median: 29us stddev: 1.04us
```
Note that `count v2` is a simpler string search, similar to the
remaining version of the simd approach:
```
pub fn countV2(comptime T: type, haystack: []const T, needle: T) usize {
const n = haystack.len;
if (n < 1) return 0;
var count: usize = 0;
for (haystack[0..n]) |item| {
count += @intFromBool(item == needle);
}
return count;
}
```
Which implies the compiler yields some optimized code for a simpler loop
that is more performant than the `findScalarPos`-based approach, hence
the usage of iterative approach for the remaining of the haystack.
Co-authored-by: StAlKeR7779 <stalkek7779@yandex.ru>
Moving towards our function naming convention of having one word per
concept and constructing function names out of concatenated concepts.
In `std.mem` the concepts are:
* "find" - return index of substring
* "pos" - starting index parameter
* "last" - search from the end
* "linear" - simple for loop rather than fancy algo
* "scalar" - substring is a single element
* Document std.mem.* functions
Functions in std.mem are essential for virtually all applications,
yet many of them lacked documentation.
Co-authored-by: Andrew Kelley <andrew@ziglang.org>
Basically everything that has a direct replacement or no uses left.
Notable omissions:
- std.ArrayHashMap: Too much fallout, needs a separate cleanup.
- std.debug.runtime_safety: Too much fallout.
- std.heap.GeneralPurposeAllocator: Lots of references to it remain, not
a simple find and replace as "debug allocator" is not equivalent to
"general purpose allocator".
- std.io.Reader: Is being reworked at the moment.
- std.unicode.utf8Decode(): No replacement, needs a new API first.
- Manifest backwards compat options: Removal would break test data used
by TestFetchBuilder.
- panic handler needs to be a namespace: Many tests still rely on it
being a function, needs a separate cleanup.
Nothing interesting here; literally just the bare minimum so I can work on this
on and off in a branch without worrying about merge conflicts in the non-backend
code.
* fix merge conflicts
* rename the declarations
* reword documentation
* extract FixedBufferAllocator to separate file
* take advantage of locals
* remove the assertion about max alignment in Allocator API, leaving it
Allocator implementation defined
* fix non-inline function call in start logic
The GeneralPurposeAllocator implementation is totally broken because it
uses global state but I didn't address that in this commit.
heap.zig: define new default page sizes
heap.zig: add min/max_page_size and their options
lib/std/c: add miscellaneous declarations
heap.zig: add pageSize() and its options
switch to new page sizes, especially in GPA/stdlib
mem.zig: remove page_size
This was done by regex substitution with `sed`. I then manually went
over the entire diff and fixed any incorrect changes.
This diff also changes a lot of `callconv(.C)` to `callconv(.c)`, since
my regex happened to also trigger here. I opted to leave these changes
in, since they *are* a correct migration, even if they're not the one I
was trying to do!
The `if (@sizeOf(T) == 0) return true;` check simply doesn't work for a number
of cases so that is removed and changed into `@sizeOf(T) != 0` and then
used in the `eqlBytes` check chain to make comparing `enum{}`s possible.
The rest special-cases for comptime-only types and undefined to make
those comparisons possible as well.
Fixes#19929
I was just bitten by this footgun, where I actually wanted
`sliceAsBytes` but unintentionally used `asBytes`, which in practice
ignored all but the first element. Just add a comptime assertion to
trigger a compile error in this case.
The compiler actually doesn't need any functional changes for this: Sema
does reification based on the tag indices of `std.builtin.Type` already!
So, no zig1.wasm update is necessary.
This change is necessary to disallow name clashes between fields and
decls on a type, which is a prerequisite of #9938.
