gu: Add clang-friendly codepath

[Beyley]

Clang refuses to assemble the asm macro, stating the instruction is "unavailable with your current feature set", and im not sure why, ive tried enabling a bunch of features, and nothing seems to make it happy. So i enabled the non-accelerated codepath on clang, which makes it compile, and allows most of gu (at least all thats needed for a cube sample) to be compiled using the LLVM/Clang 16 shipped with the Zig compiler

[IridescentRose]

Can you not use __builtin_clz()?

Edit: Since you're using zig you could just export the zig-ified version of this function and use the @clz() builtin

[Beyley]

Can you not use __builtin_clz()?

Edit: Since you're using zig you could just export the zig-ified version of this function and use the @clz() builtin

I was able to use __builtin_clz yes, good catch

And my zig PSP SDK is trying to re-use as much of the C SDK as possible (since i dont have nearly as much time/resources/experience). Which is why im re-using the pspsdk C implementations of gu and gum (and calling into those using the standard C headers with @cImport), rather than using the Zig implementations provided by zpsp-dev/zig-psp, since those ports are outdated and would have been a large effort to bring up to Zig 0.12.0-dev
So id rather reuse the C implementations of this, since __builtin_clz and @clz will compile down to the same LLVM IR anyway

[fjtrujy]

@davidgfnet could you take a look at this change?

[davidgfnet]

Can you please use __builtin_clz for both gcc and clang? gcc should generate the CLZ instruction natively. clang won't since it doesn't support it (AFAIK). In any case, should work for most compilers and gcc should still emit the faster asm.

[sharkwouter]

@Beyley are you still planning on updating this with the feedback given? I'd like to be able to merge this.

[Beyley]

@Beyley are you still planning on updating this with the feedback given? I'd like to be able to merge this.

My bad, i got busy and completely forgot! I'll switch it to use __builtin_clz on GCC aswell

[Beyley]

Done

[sharkwouter]

Thanks, if the ci passes I'll merge this.