[PATCH 09/15] irq: arm: perform irqentry in entry code

[Marc Zyngier]

On 2021-11-30 08:49, Vladimir Murzin wrote:

> One month and a week later...
> 
> I observe that in terms of performance
> 
>    MRS       r0, ipsr
> 
> is equivalent to readl_relaxed(BASEADDR_V7M_SCB + V7M_SCB_ICSR)
> 
>    MOV.W   r3, #3758153728
>    LDR.W   r0, [r3, #3332]
> 
> Old compilers can produce less performant sequence like
> 
>    LDR      r3,0xbcc0
>    ADD.W    r3,r3,#0xaf00
>    LDR      r0,[r3,#0]
> 
> So, what would be your preference?

If there is no significant overhead to reading the MMIO register
and that you see a benefit in enabling COMPILE_TEST, then this
probably is the way to go.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...