3.2_f32 formatted as 0 on powerpc64le

[NobodyXu]

In my PR ParkMyCar/compact_str#16 , when formatting 3.2 using std, it gives me 0 on target powerpc64le instead of 3.2 (it works on all other target).

P.S. ryu also format it as 0.0 on it dtolnay/ryu#47

[mbartlett21]

Did you mean dtolnay/ryu#47 for the ryu issue?

@rustbot label +O-PowerPC

[NobodyXu]

Did you mean dtolnay/ryu#47 for the ryu issue?

Oh yes, thank you for pointing this out

[NobodyXu]

I just tried to reproduce this on my own x86_64 linux box by running:

cross +nightly test --release --all-features --manifest-path=compact_str/Cargo.toml --target powerpc-unknown-linux-gnu

however, all tests passed without problem...

But the test running on github action still failed on powerpc64le

[nagisa]

Marked this as I-unsound though I don’t really have a definite culprit here. Historically these sorts of problems have been caused by calling convention mismatches, codegen failures or some other similarly scary and “has potential to cause other code to break much more terribly” problem.

[nagisa]

I just tried to reproduce this on my own x86_64 linux box by running:

You used a 32-bit PPC target here. Does this reproduce with a powerpc64le target?

cross +nightly test --release --all-features --manifest-path=compact_str/Cargo.toml --target powerpc64le-unknown-linux-gnu

[NobodyXu]

cross +nightly test --release --all-features --manifest-path=compact_str/Cargo.toml --target powerpc64le-unknown-linux-gnu

Thanks for pointing this out again!

With the updated command, I was able to reproduce that.

[NobodyXu]

Now I was also able to reproduce it using this:

fn main() {
    println!("{}", 3.2_f32);
}

And it gives me 0 using cross +nightly run --release --target powerpc64le-unknown-linux-gnu (the --release flag can be omitted).

[NobodyXu]

This is the assembly I get:

0000000000008d50 <tests::main>:
    8d50: 09 00 4c 3c  	addis 2, 12, 9
    8d54: b0 f1 42 38  	addi 2, 2, -3664
    8d58: a6 02 08 7c  	mflr 0
    8d5c: 10 00 01 f8  	std 0, 16(1)
    8d60: 51 ff 21 f8  	stdu 1, -176(1)
    8d64: fd ff 62 3c  	addis 3, 2, -3
    8d68: 6c c4 63 38  	addi 3, 3, -15252
    8d6c: 4d fb ff 4b  	bl 0x88b8
    8d70: 00 00 00 60  	nop
    8d74: 60 00 81 f8  	std 4, 96(1)
    8d78: 68 00 61 f8  	std 3, 104(1)
    8d7c: 60 00 61 e8  	ld 3, 96(1)
    8d80: 68 00 81 e8  	ld 4, 104(1)
    8d84: a0 00 81 f8  	std 4, 160(1)
    8d88: a8 00 61 f8  	std 3, 168(1)
    8d8c: a0 00 c1 38  	addi 6, 1, 160
    8d90: ff ff 62 3c  	addis 3, 2, -1
    8d94: c0 48 83 38  	addi 4, 3, 18624
    8d98: 70 00 61 38  	addi 3, 1, 112
    8d9c: 02 00 a0 38  	li 5, 2
    8da0: 01 00 e0 38  	li 7, 1
    8da4: c5 fd ff 4b  	bl 0x8b68
    8da8: 00 00 00 60  	nop
    8dac: 70 00 61 38  	addi 3, 1, 112
    8db0: 59 77 01 48  	bl 0x20508
    8db4: 00 00 00 60  	nop
    8db8: b0 00 21 38  	addi 1, 1, 176
    8dbc: 10 00 01 e8  	ld 0, 16(1)
    8dc0: a6 03 08 7c  	mtlr 0
    8dc4: 20 00 80 4e  	blr
		...
    8dd4: 00 00 00 60  	nop
    8dd8: 00 00 00 60  	nop
    8ddc: 00 00 00 60  	nop