Hi Chris,

On Wed, 25 Oct 2000, Chris Gilbert wrote:
> I've been trying to build an arm32 kernel with the -mcpu=strongarm 
> -mtune=strongarm.

Oh ok

> The problem I've had is that the podulebus doesn't get devices attaching 
> properly. Anyway, after doing some rummaging around in the .s files from a 
> kernel with and without the above options it seems that it's doing the 
> following optimsation:
> turning:
> ldr r3, [r5, #6]
> mov r0, r3, lsr #16
> into
> ldrh r0, [r5, #4]
> 
> This occurs at about line 289/290 of sys/arch/arm32/podulebus/podulebus.c
> I believe it should actually produce:
> ldrh r0, [r5, #8]

Well i chalenge that :)

Lets say the memory is represented as follows from r5 :

    7 6 5 4 | 3 2 1 0

ldr r3, [r5, #6]
   r3 <- [5476]    // (in)famous rotating
mov r0, r3, lsr # 16
   r0 <- [--54]    // with the `-' zero

The optimalisation implemented is :
ldrh r0, [r5, #4]
   r0 <- [--54]    // the same

Your sequence
ldrh r0, [r5, #8]

would read bytes outside the 8 bytes even....

Cheers !!,
Reinoud