Re: [PATCH 2/8] x86/irq: Track if IRQ was found in PIR during initial loop (to load PIR vals)

[Thomas Gleixner]

On Mon, Mar 17 2025 at 09:53, Sean Christopherson wrote:
> On Mon, Mar 17, 2025, Thomas Gleixner wrote:
>> > -	for (i = 0; i < 4; i++)
>> > +	for (i = 0; i < 4; i++) {
>> >  		pir_copy[i] = READ_ONCE(pir[i]);
>> > +		if (pir_copy[i])
>> > +			found_irq = true;
>> > +	}
>> 
>> That's four extra conditional branches. You can avoid them completely. See
>> delta patch below.
>
> Huh.  gcc elides the conditional branches when computing found_irq regardless of
> the approach; the JEs in the changelog are from skipping the XCHG.
>
> But clang-14 does not.  I'll slot this in.

Neither does GCC 12. That's why I noticed.