@h = high order 16 bits
@l = low order 16 bits
@ha = high order 16 bits adjusted so that, when you add the sign-extended
low order 16 bits, the value comes out to the right number
Example of @ha:
lis r3, 0x0000FFFF@ha /* r3 = 0x0001oooo */
addi r3, r3, 0x0000FFFF@l /* r3 = 0x0001oooo + 0xffffFFFF =
0x0000FFFF */
will actually load 0x00010000 into r3 in the first instruction because the
second instruction (addi) sign-extends the 0x0000FFFF to become
0xFFFFFFFF. After the addi, r3 will have the proper value 0x0000FFFF.
ori does not sign extend the immediate value, so it does not have this
quirk and therefore you would use @h and @l:
lis r3, 0x0000FFFF@h /* r3 = 0x00000000 */
ori r3, r3, 0x0000FFFF@l /* r3 = 0x0000oooo | 0xooooFFFF =
0x0000FFFF */
I've never figured out why someone would want to use addi instead of ori in
the second instruction of the load sequence.
gvb
At 11:32 AM 5/8/2003 -0400, okisoftxman(a)hotmail.com wrote:
>In u-boot/cpu/mpc8xx/start.S,I usually find this symbol "@",such as
>followed:
>
>_start:
> lis r3, CFG_IMMR@h /* position IMMR */
> mtspr 638, r3
> li r21, BOOTFLAG_COLD /* Normal Power-On: Boot from FLASH */
> b boot_cold
>
>what does it means? Thank you!
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