tests: debuginfo: Work around or disable broken tests on powerpc

[Gelbpunkt]

f16 support for PowerPC has issues in LLVM, therefore we need a small workaround to prevent LLVM from emitting symbols that don't exist for PowerPC yet.

It also appears that #128973 applies to PowerPC targets as well, though I've only tested 64-bit Linux targets.

[rustbot]

r? @oli-obk

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[rustbot]

Some changes occurred in src/tools/compiletest

cc @jieyouxu

[workingjubilee]

I feel that we really should not have types that must be ignored in the same file as other types.

[Gelbpunkt]

So would you suggest splitting off the f16 parts into a f16-globals-metadata test and disabling that on the affected targets?

[workingjubilee]

Yes, I think that would be preferable. If it's powerpc, then it's likely going to be others.

[Gelbpunkt]

Amazing, pulling f16 into its own test suddenly makes the test pass. I'm not too sure what part of the old vs new code is responsible for LLVM emitting the symbol vs not emitting it.

[Gelbpunkt]

Okay, fairly simple it turns out:

This emits __gnu_h2f_ieee

static mut F16: f16 = 1.5;
static mut F32: f16 = 2.5;

fn main() {
    _zzz(); // #break

    let a = unsafe { (F16, F32) };
}

fn _zzz() {()}

This doesn't

static mut F16: f16 = 1.5;

fn main() {
    _zzz(); // #break

    let a = unsafe { (F16,) };
}

fn _zzz() {()}

[Gelbpunkt]

I included a workaround instead of disabling the tests.

[workingjubilee]

...huh.

[workingjubilee]

my guess is that it tries to convert the f16 to the f32 due to rules about how we represent the tuple layout

[oli-obk]

@bors r+

[bors]

📌 Commit e1b6cfe has been approved by oli-obk

It is now in the queue for this repository.