https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85669
--- Comment #32 from Wilco <wdijkstr at arm dot com> ---
(In reply to Segher Boessenkool from comment #29)
> It aligns the stack to 16:
>
> # r3 is size, at entry
> addi r3,r3,18
> ...
> rlwinm r3,r3,0,0,27
> ...
> neg r3,r3
> ...
> lwz r2,0(r1)
> ...
> stwux r2,r1,r3
>
> (the rlwinm is r3 &= ~15; )
So this rounds up the size but also adds an extra 16 bytes to the requested
allocation. The alloca blocks don't get correctly aligned since
STACK_DYNAMIC_OFFSET returns 72 (which is not a multiple of 16):
t1_a4
addi r2,r1,72 -> 72 % 16 != 0 (correct value would be 64)
stw r6,60(r1)
stw r2,56(r1)
This also shows in t1/t2_a32:
addi r2,r1,103 -> 31 + 72 = 103 (correct value would be 80+31)
stw r6,64(r1)
rlwinm r2,r2,0,0,26
So this proves STACK_DYNAMIC_OFFSET is incorrect indeed. If there are still
failures with that fixed then the stack pointer must also be unaligned.
