Add sincosf function

[daurnimator]

Fixes #7260

@MasterQ32 I have no idea how to test this, you didn't leave a reproducer.

[ikskuh]

@MasterQ32 I have no idea how to test this, you didn't leave a reproducer.

Me neither. It just happens somewhere in > 5000 LOC where code uses a lot of sin and cos

[LemonBoy]

Here's the man page, some tests are needed to make sure this implementation matches the libc one (wrt nan/infinity inputs, the errno part should be honored too?).

Adding the sincos variant is trivial.

[daurnimator]

the errno part should be honored too?

great question. At first I thought so, but then I saw that e.g. sinf doesn't....
What is the correct behaviour here?
The fact that LLVM optimises to things that require errno doesn't sit well with me.

[LemonBoy]

The fact that LLVM optimises to things that require errno doesn't sit well with me.

Calm your tits, LLVM is smart. The optimization kicks in iff sin/cos are marked with readnone meaning they don't touch errno at all.
Check out this gcc ticket for more info, the errno clause is specified in the sacred POSIX texts.

[LemonBoy]

Reproducer:

const std = @import("std");

extern var foo: f32;

pub fn main() !void {
    var y = @sin(foo);
    var z = @cos(foo);
    std.mem.doNotOptimizeAway(y);
    std.mem.doNotOptimizeAway(z);
}

Compile with: zig build-exe -target native-linux-gnu -OReleaseFast

[daurnimator]

Tested with

const std = @import("std");

export fn myfunc(foo: f32) f32 {
    var y = @sin(foo);
    var z = @cos(foo);
    return y + z;
}

zig build-lib -dynamic -target native-linux-gnu -OReleaseFast sincosf.zig
objdump --disassemble libsincosf.so

and looks correct.... will re-kick CI because error message is gone now.